DATAMONGO-1535 - Release version 2.0 M2 (Kay).

And add snapshot profile for 3.5.0.

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,9 +1,12 @@
+<!--
+
 Thank you for proposing a pull request. This template will guide you through the essential steps necessary for a pull request.
 Make sure that:
 
+-->
+
 - [ ] You have read the [Spring Data contribution guidelines](https://github.com/spring-projects/spring-data-build/blob/master/CONTRIBUTING.adoc).
 - [ ] There is a ticket in the bug tracker for the project in our [JIRA](https://jira.spring.io/browse/DATAMONGO).
 - [ ] You use the code formatters provided [here](https://github.com/spring-projects/spring-data-build/tree/master/etc/ide) and have them applied to your changes. Don’t submit any formatting related changes.
 - [ ] You submit test cases (unit or integration tests) that back your changes.
 - [ ] You added yourself as author in the headers of the classes you touched. Amend the date range in the Apache license header if needed. For new types, add the license header (copy from another file and set the current year only).
-- [ ] You provide your full name and an email address registered with your GitHub account. If you’re a first-time submitter, make sure you have completed the [Contributor’s License Agreement form](https://support.springsource.com/spring_committer_signup).

.travis.yml

@@ -9,22 +9,19 @@ before_script:
 env:
   matrix:
     - PROFILE=ci
-    - PROFILE=mongo3
-    - PROFILE=mongo3-next
-    - PROFILE=mongo31
-    - PROFILE=mongo32
-    - PROFILE=mongo33
     - PROFILE=mongo34-next
+    - PROFILE=mongo35-next
 
 # Current MongoDB version is 2.4.2 as of 2016-04, see https://github.com/travis-ci/travis-ci/issues/3694
 # apt-get starts a MongoDB instance so it's not started using before_script
 addons:
   apt:
     sources:
-    - mongodb-3.2-precise
+    - mongodb-3.4-precise
     packages:
     - mongodb-org-server
     - mongodb-org-shell
+    - oracle-java8-installer
 
 sudo: false
 

README.md

@@ -143,8 +143,8 @@ public class MyService {
 Here are some ways for you to get involved in the community:
 
 * Get involved with the Spring community on Stackoverflow and help out on the [spring-data-mongodb](http://stackoverflow.com/questions/tagged/spring-data-mongodb) tag by responding to questions and joining the debate.
-* Create [JIRA](https://jira.springframework.org/browse/DATADOC) tickets for bugs and new features and comment and vote on the ones that you are interested in.  
+* Create [JIRA](https://jira.spring.io/browse/DATAMONGO) tickets for bugs and new features and comment and vote on the ones that you are interested in.  
 * Github is for social coding: if you want to write code, we encourage contributions through pull requests from [forks of this repository](http://help.github.com/forking/). If you want to contribute code this way, please reference a JIRA ticket as well covering the specific issue you are addressing.
 * Watch for upcoming articles on Spring by [subscribing](http://spring.io/blog) to spring.io.
 
-Before we accept a non-trivial patch or pull request we will need you to sign the [contributor's agreement](https://support.springsource.com/spring_committer_signup).  Signing the contributor's agreement does not grant anyone commit rights to the main repository, but it does mean that we can accept your contributions, and you will get an author credit if we do.  Active contributors might be asked to join the core team, and given the ability to merge pull requests.
+Before we accept a non-trivial patch or pull request we will need you to [sign the Contributor License Agreement](https://cla.pivotal.io/sign/spring). Signing the contributor’s agreement does not grant anyone commit rights to the main repository, but it does mean that we can accept your contributions, and you will get an author credit if we do. If you forget to do so, you'll be reminded when you submit a pull request. Active contributors might be asked to join the core team, and given the ability to merge pull requests.

etc/formatting.xml

@@ -1,291 +0,0 @@
-<?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<profiles version="12">
-<profile kind="CodeFormatterProfile" name="Spring Data" version="12">
-<setting id="org.eclipse.jdt.core.formatter.comment.insert_new_line_before_root_tags" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.disabling_tag" value="@formatter:off"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_annotation" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_comma_in_type_parameters" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_brace_in_type_declaration" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_type_arguments" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.brace_position_for_anonymous_type_declaration" value="end_of_line"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_colon_in_case" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_brace_in_array_initializer" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.comment.new_lines_at_block_boundaries" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_in_empty_annotation_declaration" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_before_closing_brace_in_array_initializer" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_paren_in_annotation" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.blank_lines_before_field" value="0"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_paren_in_while" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.use_on_off_tags" value="false"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_between_empty_parens_in_annotation_type_member_declaration" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_before_else_in_if_statement" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_prefix_operator" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.keep_else_statement_on_same_line" value="false"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_ellipsis" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.comment.insert_new_line_for_parameter" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_brace_in_annotation_type_declaration" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.indent_breaks_compare_to_cases" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_at_in_annotation" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_multiple_fields" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_expressions_in_array_initializer" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_conditional_expression" value="80"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_paren_in_for" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_binary_operator" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_question_in_wildcard" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.brace_position_for_array_initializer" value="end_of_line"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_between_empty_parens_in_enum_constant" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_before_finally_in_try_statement" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_after_annotation_on_local_variable" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_before_catch_in_try_statement" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_paren_in_while" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.blank_lines_after_package" value="1"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_type_parameters" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.continuation_indentation" value="2"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_postfix_operator" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_arguments_in_method_invocation" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_closing_angle_bracket_in_type_arguments" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_comma_in_superinterfaces" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.blank_lines_before_new_chunk" value="1"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_binary_operator" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.blank_lines_before_package" value="0"/>
-<setting id="org.eclipse.jdt.core.compiler.source" value="1.7"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_enum_constant_arguments" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_paren_in_constructor_declaration" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.comment.format_line_comments" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_closing_angle_bracket_in_type_arguments" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_enum_declarations" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.join_wrapped_lines" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_brace_in_block" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_arguments_in_explicit_constructor_call" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_comma_in_method_invocation_arguments" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.blank_lines_before_member_type" value="1"/>
-<setting id="org.eclipse.jdt.core.formatter.align_type_members_on_columns" value="false"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_paren_in_enum_constant" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_paren_in_for" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_brace_in_method_declaration" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_selector_in_method_invocation" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_paren_in_switch" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_unary_operator" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_colon_in_case" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.comment.indent_parameter_description" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_closing_paren_in_method_declaration" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_closing_paren_in_switch" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_brace_in_enum_declaration" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_angle_bracket_in_type_parameters" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.comment.clear_blank_lines_in_block_comment" value="false"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_in_empty_type_declaration" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.lineSplit" value="120"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_paren_in_if" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_between_brackets_in_array_type_reference" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_paren_in_parenthesized_expression" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_comma_in_explicitconstructorcall_arguments" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_brace_in_constructor_declaration" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.blank_lines_before_first_class_body_declaration" value="0"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_after_annotation_on_method" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.indentation.size" value="2"/>
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-<setting id="org.eclipse.jdt.core.formatter.enabling_tag" value="@formatter:on"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_paren_in_enum_constant" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_superclass_in_type_declaration" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_assignment" value="0"/>
-<setting id="org.eclipse.jdt.core.compiler.problem.assertIdentifier" value="error"/>
-<setting id="org.eclipse.jdt.core.formatter.tabulation.char" value="tab"/>
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-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_colon_in_labeled_statement" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_comma_in_parameterized_type_reference" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_superinterfaces_in_type_declaration" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_binary_expression" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.brace_position_for_enum_declaration" value="end_of_line"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_after_annotation_on_type" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_closing_paren_in_while" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.compiler.codegen.inlineJsrBytecode" value="enabled"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_paren_in_try" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.put_empty_statement_on_new_line" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_after_label" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_after_annotation_on_parameter" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_angle_bracket_in_type_parameters" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_between_empty_parens_in_method_invocation" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_before_while_in_do_statement" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_arguments_in_enum_constant" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.comment.format_javadoc_comments" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.comment.line_length" value="120"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_after_annotation_on_package" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.blank_lines_between_import_groups" value="1"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_comma_in_enum_constant_arguments" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_semicolon" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.brace_position_for_constructor_declaration" value="end_of_line"/>
-<setting id="org.eclipse.jdt.core.formatter.number_of_blank_lines_at_beginning_of_method_body" value="0"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_colon_in_conditional" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.indent_body_declarations_compare_to_type_header" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_paren_in_annotation_type_member_declaration" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.wrap_before_binary_operator" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.indent_body_declarations_compare_to_enum_declaration_header" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.blank_lines_between_type_declarations" value="1"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_closing_paren_in_synchronized" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.indent_statements_compare_to_block" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_superinterfaces_in_enum_declaration" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.join_lines_in_comments" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_question_in_conditional" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_comma_in_multiple_field_declarations" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_compact_if" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_for_inits" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.indent_switchstatements_compare_to_cases" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_array_initializer" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_colon_in_default" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_and_in_type_parameter" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_between_empty_parens_in_constructor_declaration" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.blank_lines_before_imports" value="1"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_colon_in_assert" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.comment.format_html" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_throws_clause_in_method_declaration" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_closing_angle_bracket_in_type_parameters" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_bracket_in_array_allocation_expression" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_in_empty_anonymous_type_declaration" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_colon_in_conditional" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_angle_bracket_in_parameterized_type_reference" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_closing_paren_in_for" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_postfix_operator" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.comment.format_source_code" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_paren_in_synchronized" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_allocation_expression" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_constructor_declaration_throws" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_parameters_in_method_declaration" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_closing_brace_in_array_initializer" value="insert"/>
-<setting id="org.eclipse.jdt.core.compiler.codegen.targetPlatform" value="1.7"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_resources_in_try" value="80"/>
-<setting id="org.eclipse.jdt.core.formatter.use_tabs_only_for_leading_indentations" value="false"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_arguments_in_annotation" value="16"/>
-<setting id="org.eclipse.jdt.core.formatter.comment.format_header" value="false"/>
-<setting id="org.eclipse.jdt.core.formatter.comment.format_block_comments" value="false"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_closing_paren_in_enum_constant" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.alignment_for_enum_constants" value="0"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_new_line_in_empty_block" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.indent_body_declarations_compare_to_annotation_declaration_header" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_closing_paren_in_parenthesized_expression" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_paren_in_parenthesized_expression" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_closing_paren_in_catch" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_comma_in_multiple_local_declarations" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_paren_in_switch" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_comma_in_for_increments" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_paren_in_method_invocation" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_colon_in_assert" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.brace_position_for_type_declaration" value="end_of_line"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_brace_in_array_initializer" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_between_empty_braces_in_array_initializer" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_opening_paren_in_method_declaration" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_semicolon_in_for" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_paren_in_catch" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_angle_bracket_in_parameterized_type_reference" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_multiple_field_declarations" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_closing_paren_in_annotation" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_parameterized_type_reference" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_method_invocation_arguments" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.comment.new_lines_at_javadoc_boundaries" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.blank_lines_after_imports" value="1"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_comma_in_multiple_local_declarations" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.indent_body_declarations_compare_to_enum_constant_header" value="true"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_after_semicolon_in_for" value="insert"/>
-<setting id="org.eclipse.jdt.core.formatter.never_indent_line_comments_on_first_column" value="false"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_semicolon_in_try_resources" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.insert_space_before_opening_angle_bracket_in_type_arguments" value="do not insert"/>
-<setting id="org.eclipse.jdt.core.formatter.never_indent_block_comments_on_first_column" value="false"/>
-<setting id="org.eclipse.jdt.core.formatter.keep_then_statement_on_same_line" value="false"/>
-</profile>
-</profiles>

pom.xml

@@ -5,7 +5,7 @@
 
 	<groupId>org.springframework.data</groupId>
 	<artifactId>spring-data-mongodb-parent</artifactId>
-	<version>2.0.0.M1</version>
+	<version>2.0.0.M2</version>
 	<packaging>pom</packaging>
 
 	<name>Spring Data MongoDB</name>
@@ -15,7 +15,7 @@
 	<parent>
 		<groupId>org.springframework.data.build</groupId>
 		<artifactId>spring-data-parent</artifactId>
-		<version>2.0.0.M1</version>
+		<version>2.0.0.M2</version>
 	</parent>
 
 	<modules>
@@ -28,9 +28,9 @@
 	<properties>
 		<project.type>multi</project.type>
 		<dist.id>spring-data-mongodb</dist.id>
-		<springdata.commons>2.0.0.M1</springdata.commons>
-		<mongo>3.2.2</mongo>
-		<mongo.reactivestreams>1.2.0</mongo.reactivestreams>
+		<springdata.commons>2.0.0.M2</springdata.commons>
+		<mongo>3.4.2</mongo>
+		<mongo.reactivestreams>1.3.0</mongo.reactivestreams>
 	</properties>
 
 	<developers>
@@ -114,70 +114,28 @@
 	</developers>
 
 	<profiles>
-		<profile>
-
-			<id>mongo3</id>
-			<properties>
-				<mongo>3.0.4</mongo>
-			</properties>
-
-		</profile>
-
-		<profile>
-
-			<id>mongo3-next</id>
-			<properties>
-				<mongo>3.0.5-SNAPSHOT</mongo>
-			</properties>
-
-			<repositories>
-				<repository>
-					<id>mongo-snapshots</id>
-					<url>https://oss.sonatype.org/content/repositories/snapshots</url>
-				</repository>
-			</repositories>
-
-		</profile>
-
-		<profile>
-
-			<id>mongo31</id>
-			<properties>
-				<mongo>3.1.1</mongo>
-			</properties>
-
-		</profile>
-
-		<profile>
-
-			<id>mongo32</id>
-			<properties>
-				<mongo>3.2.2</mongo>
-			</properties>
-
-		</profile>
-
-		<profile>
-
-			<id>mongo33</id>
-			<properties>
-				<mongo>3.3.0</mongo>
-			</properties>
-
-			<repositories>
-				<repository>
-					<id>mongo-snapshots</id>
-					<url>https://oss.sonatype.org/content/repositories/snapshots</url>
-				</repository>
-			</repositories>
-
-		</profile>
 
 		<profile>
 
 			<id>mongo34-next</id>
 			<properties>
-				<mongo>3.4.0-SNAPSHOT</mongo>
+				<mongo>3.4.3-SNAPSHOT</mongo>
+			</properties>
+
+			<repositories>
+				<repository>
+					<id>mongo-snapshots</id>
+					<url>https://oss.sonatype.org/content/repositories/snapshots</url>
+				</repository>
+			</repositories>
+
+		</profile>
+
+		<profile>
+
+			<id>mongo35-next</id>
+			<properties>
+				<mongo>3.5.0-SNAPSHOT</mongo>
 			</properties>
 
 			<repositories>

spring-data-mongodb-cross-store/pom.xml

@@ -6,7 +6,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>2.0.0.M1</version>
+		<version>2.0.0.M2</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 
@@ -48,7 +48,7 @@
 		<dependency>
 			<groupId>org.springframework.data</groupId>
 			<artifactId>spring-data-mongodb</artifactId>
-			<version>2.0.0.M1</version>
+			<version>2.0.0.M2</version>
 		</dependency>
 
 		<!-- reactive -->

spring-data-mongodb-cross-store/src/test/resources/META-INF/spring/applicationContext.xml

@@ -20,13 +20,13 @@
   <mongo:mapping-converter/>
   
   <!--  Mongo config -->
-  <bean id="mongo" class="org.springframework.data.mongodb.core.MongoClientFactoryBean">
+  <bean id="mongoClient" class="org.springframework.data.mongodb.core.MongoClientFactoryBean">
     <property name="host" value="localhost"/>
     <property name="port" value="27017"/>
   </bean>
 
   <bean id="mongoDbFactory" class="org.springframework.data.mongodb.core.SimpleMongoDbFactory">
-  	<constructor-arg name="mongo" ref="mongo"/>
+  	<constructor-arg name="mongoClient" ref="mongoClient"/>
   	<constructor-arg name="databaseName" value="database"/>
   </bean>
 

spring-data-mongodb-distribution/pom.xml

@@ -13,7 +13,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>2.0.0.M1</version>
+		<version>2.0.0.M2</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb-log4j/pom.xml

@@ -5,7 +5,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>2.0.0.M1</version>
+		<version>2.0.0.M2</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb-log4j/src/main/java/org/springframework/data/mongodb/log4j/MongoLog4jAppender.java

@@ -18,6 +18,8 @@ package org.springframework.data.mongodb.log4j;
 import java.net.UnknownHostException;
 import java.util.Arrays;
 import java.util.Calendar;
+import java.util.Collections;
+import java.util.List;
 import java.util.Map;
 
 import org.apache.log4j.AppenderSkeleton;
@@ -31,14 +33,17 @@ import com.mongodb.BasicDBObject;
 import com.mongodb.DB;
 import com.mongodb.Mongo;
 import com.mongodb.MongoClient;
+import com.mongodb.MongoCredential;
+import com.mongodb.ServerAddress;
 import com.mongodb.WriteConcern;
 
 /**
  * Log4j appender writing log entries into a MongoDB instance.
- * 
+ *
  * @author Jon Brisbin
  * @author Oliver Gierke
- * @auhtor Christoph Strobl
+ * @author Christoph Strobl
+ * @author Ricardo Espirito Santo
  */
 public class MongoLog4jAppender extends AppenderSkeleton {
 
@@ -56,6 +61,9 @@ public class MongoLog4jAppender extends AppenderSkeleton {
 
 	protected String host = "localhost";
 	protected int port = 27017;
+	protected String username;
+	protected String password;
+	protected String authenticationDatabase;
 	protected String database = "logs";
 	protected String collectionPattern = "%c";
 	protected PatternLayout collectionLayout = new PatternLayout(collectionPattern);
@@ -65,8 +73,7 @@ public class MongoLog4jAppender extends AppenderSkeleton {
 	protected Mongo mongo;
 	protected DB db;
 
-	public MongoLog4jAppender() {
-	}
+	public MongoLog4jAppender() {}
 
 	public MongoLog4jAppender(boolean isActive) {
 		super(isActive);
@@ -88,6 +95,53 @@ public class MongoLog4jAppender extends AppenderSkeleton {
 		this.port = port;
 	}
 
+	/**
+	 * @return
+	 * @since 1.10
+	 */
+	public String getUsername() {
+		return username;
+	}
+
+	/**
+	 * @param username may be {@literal null} for unauthenticated access.
+	 * @since 1.10
+	 */
+	public void setUsername(String username) {
+		this.username = username;
+	}
+
+	/**
+	 * @return
+	 * @since 1.10
+	 */
+	public String getPassword() {
+		return password;
+	}
+
+	/**
+	 * @param password may be {@literal null} for unauthenticated access.
+	 * @since 1.10
+	 */
+	public void setPassword(String password) {
+		this.password = password;
+	}
+
+	/**
+	 * @return
+	 */
+	public String getAuthenticationDatabase() {
+		return authenticationDatabase;
+	}
+
+	/**
+	 * @param authenticationDatabase may be {@literal null} to use {@link #getDatabase()} as authentication database.
+	 * @since 1.10
+	 */
+	public void setAuthenticationDatabase(String authenticationDatabase) {
+		this.authenticationDatabase = authenticationDatabase;
+	}
+
 	public String getDatabase() {
 		return database;
 	}
@@ -113,14 +167,14 @@ public class MongoLog4jAppender extends AppenderSkeleton {
 		this.applicationId = applicationId;
 	}
 
-	public void setWarnOrHigherWriteConcern(String wc) {
-		this.warnOrHigherWriteConcern = WriteConcern.valueOf(wc);
-	}
-
 	public String getWarnOrHigherWriteConcern() {
 		return warnOrHigherWriteConcern.toString();
 	}
 
+	public void setWarnOrHigherWriteConcern(String wc) {
+		this.warnOrHigherWriteConcern = WriteConcern.valueOf(wc);
+	}
+
 	public String getInfoOrLowerWriteConcern() {
 		return infoOrLowerWriteConcern.toString();
 	}
@@ -130,10 +184,26 @@ public class MongoLog4jAppender extends AppenderSkeleton {
 	}
 
 	protected void connectToMongo() throws UnknownHostException {
-		this.mongo = new MongoClient(host, port);
+
+		this.mongo = createMongoClient();
 		this.db = mongo.getDB(database);
 	}
 
+	private MongoClient createMongoClient() throws UnknownHostException {
+
+		ServerAddress serverAddress = new ServerAddress(host, port);
+
+		if (null == password || null == username) {
+			return new MongoClient(serverAddress);
+		}
+
+		String authenticationDatabaseToUse = authenticationDatabase == null ? this.database : authenticationDatabase;
+		MongoCredential mongoCredential = MongoCredential.createCredential(username,
+				authenticationDatabaseToUse, password.toCharArray());
+		List<MongoCredential> credentials = Collections.singletonList(mongoCredential);
+		return new MongoClient(serverAddress, credentials);
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.apache.log4j.AppenderSkeleton#append(org.apache.log4j.spi.LoggingEvent)

spring-data-mongodb-log4j/src/test/java/org/springframework/data/mongodb/log4j/MongoLog4jAppenderAuthenticationIntegrationTests.java

@@ -0,0 +1,114 @@
+/*
+ * Copyright 2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.log4j;
+
+import static org.hamcrest.Matchers.*;
+import static org.junit.Assert.*;
+
+import java.util.Calendar;
+import java.util.Collections;
+
+import org.apache.log4j.LogManager;
+import org.apache.log4j.Logger;
+import org.apache.log4j.MDC;
+import org.apache.log4j.PropertyConfigurator;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.mongodb.BasicDBList;
+import com.mongodb.BasicDBObject;
+import com.mongodb.BasicDBObjectBuilder;
+import com.mongodb.DB;
+import com.mongodb.DBCursor;
+import com.mongodb.MongoClient;
+import com.mongodb.MongoCredential;
+import com.mongodb.ServerAddress;
+
+/**
+ * Integration tests for {@link MongoLog4jAppender} using authentication.
+ *
+ * @author Mark Paluch
+ */
+public class MongoLog4jAppenderAuthenticationIntegrationTests {
+
+	private final static String username = "admin";
+	private final static String password = "test";
+	private final static String authenticationDatabase = "logs";
+
+	MongoClient mongo;
+	DB db;
+	String collection;
+	ServerAddress serverLocation;
+
+	Logger log;
+
+	@Before
+	public void setUp() throws Exception {
+
+		serverLocation = new ServerAddress("localhost", 27017);
+
+		mongo = new MongoClient(serverLocation);
+		db = mongo.getDB("logs");
+
+		BasicDBList roles = new BasicDBList();
+		roles.add("dbOwner");
+		db.command(new BasicDBObjectBuilder().add("createUser", username).add("pwd", password).add("roles", roles).get());
+		mongo.close();
+
+		mongo = new MongoClient(serverLocation, Collections
+				.singletonList(MongoCredential.createCredential(username, authenticationDatabase, password.toCharArray())));
+		db = mongo.getDB("logs");
+
+		Calendar now = Calendar.getInstance();
+		collection = String.valueOf(now.get(Calendar.YEAR)) + String.format("%1$02d", now.get(Calendar.MONTH) + 1);
+
+		LogManager.resetConfiguration();
+		PropertyConfigurator.configure(getClass().getResource("/log4j-with-authentication.properties"));
+
+		log = Logger.getLogger(MongoLog4jAppenderIntegrationTests.class.getName());
+	}
+
+	@After
+	public void tearDown() {
+
+		if (db != null) {
+			db.getCollection(collection).remove(new BasicDBObject());
+			db.command(new BasicDBObject("dropUser", username));
+		}
+
+		LogManager.resetConfiguration();
+		PropertyConfigurator.configure(getClass().getResource("/log4j.properties"));
+	}
+
+	@Test
+	public void testLogging() {
+
+		log.debug("DEBUG message");
+		log.info("INFO message");
+		log.warn("WARN message");
+		log.error("ERROR message");
+
+		DBCursor msgs = db.getCollection(collection).find();
+		assertThat(msgs.count(), is(4));
+	}
+
+	@Test
+	public void testProperties() {
+		MDC.put("property", "one");
+		log.debug("DEBUG message");
+	}
+}

spring-data-mongodb-log4j/src/test/java/org/springframework/data/mongodb/log4j/MongoLog4jAppenderIntegrationTests.java

@@ -20,8 +20,10 @@ import static org.junit.Assert.*;
 
 import java.util.Calendar;
 
+import org.apache.log4j.LogManager;
 import org.apache.log4j.Logger;
 import org.apache.log4j.MDC;
+import org.apache.log4j.PropertyConfigurator;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
@@ -30,31 +32,34 @@ import com.mongodb.BasicDBObject;
 import com.mongodb.DB;
 import com.mongodb.DBCursor;
 import com.mongodb.MongoClient;
+import com.mongodb.ServerAddress;
 
 /**
  * Integration tests for {@link MongoLog4jAppender}.
- * 
+ *
  * @author Jon Brisbin
  * @author Oliver Gierke
  * @author Christoph Strobl
  */
 public class MongoLog4jAppenderIntegrationTests {
 
-	static final String NAME = MongoLog4jAppenderIntegrationTests.class.getName();
-
-	private static final Logger log = Logger.getLogger(NAME);
 	MongoClient mongo;
 	DB db;
 	String collection;
+	ServerAddress serverLocation;
+	Logger log;
 
 	@Before
 	public void setUp() throws Exception {
+		serverLocation = new ServerAddress("localhost", 27017);
 
-		mongo = new MongoClient("localhost", 27017);
+		mongo = new MongoClient(serverLocation);
 		db = mongo.getDB("logs");
 
 		Calendar now = Calendar.getInstance();
 		collection = String.valueOf(now.get(Calendar.YEAR)) + String.format("%1$02d", now.get(Calendar.MONTH) + 1);
+
+		log = Logger.getLogger(MongoLog4jAppenderIntegrationTests.class.getName());
 	}
 
 	@After
@@ -76,7 +81,6 @@ public class MongoLog4jAppenderIntegrationTests {
 
 	@Test
 	public void testProperties() {
-
 		MDC.put("property", "one");
 		log.debug("DEBUG message");
 	}

spring-data-mongodb-log4j/src/test/java/org/springframework/data/mongodb/log4j/MongoLog4jAppenderUnitTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,10 +24,7 @@ import org.junit.Test;
  */
 public class MongoLog4jAppenderUnitTests {
 
-	/**
-	 * @see DATAMONGO-641
-	 */
-	@Test
+	@Test // DATAMONGO-641
 	public void closesWithoutMongoInstancePresent() {
 		new MongoLog4jAppender().close();
 	}

spring-data-mongodb-log4j/src/test/resources/log4j-with-authentication.properties

@@ -0,0 +1,16 @@
+log4j.rootCategory=INFO, mongo
+
+log4j.appender.mongo=org.springframework.data.mongodb.log4j.MongoLog4jAppender
+log4j.appender.mongo.layout=org.apache.log4j.PatternLayout
+log4j.appender.mongo.layout.ConversionPattern=%d %p [%c] - <%m>%n
+log4j.appender.mongo.host = localhost
+log4j.appender.mongo.port = 27017
+log4j.appender.mongo.database = logs
+log4j.appender.mongo.username = admin
+log4j.appender.mongo.password = test
+log4j.appender.mongo.authenticationDatabase = logs
+log4j.appender.mongo.collectionPattern = %X{year}%X{month}
+log4j.appender.mongo.applicationId = my.application
+log4j.appender.mongo.warnOrHigherWriteConcern = FSYNC_SAFE
+
+log4j.category.org.springframework.data.mongodb=DEBUG

spring-data-mongodb-log4j/src/test/resources/log4j.properties

@@ -1,13 +1,13 @@
-log4j.rootCategory=INFO, stdout
+log4j.rootCategory=INFO, mongo
 
-log4j.appender.stdout=org.springframework.data.mongodb.log4j.MongoLog4jAppender
-log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
-log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - <%m>%n
-log4j.appender.stdout.host = localhost
-log4j.appender.stdout.port = 27017
-log4j.appender.stdout.database = logs
-log4j.appender.stdout.collectionPattern = %X{year}%X{month}
-log4j.appender.stdout.applicationId = my.application
-log4j.appender.stdout.warnOrHigherWriteConcern = FSYNC_SAFE
+log4j.appender.mongo=org.springframework.data.mongodb.log4j.MongoLog4jAppender
+log4j.appender.mongo.layout=org.apache.log4j.PatternLayout
+log4j.appender.mongo.layout.ConversionPattern=%d %p [%c] - <%m>%n
+log4j.appender.mongo.host = localhost
+log4j.appender.mongo.port = 27017
+log4j.appender.mongo.database = logs
+log4j.appender.mongo.collectionPattern = %X{year}%X{month}
+log4j.appender.mongo.applicationId = my.application
+log4j.appender.mongo.warnOrHigherWriteConcern = FSYNC_SAFE
 
 log4j.category.org.springframework.data.mongodb=DEBUG

spring-data-mongodb/pom.xml

@@ -11,14 +11,13 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>2.0.0.M1</version>
+		<version>2.0.0.M2</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 
 	<properties>
 		<objenesis>1.3</objenesis>
 		<equalsverifier>1.5</equalsverifier>
-		<mongo>3.3.0</mongo>
 	</properties>
 
 	<dependencies>
@@ -111,6 +110,13 @@
 			<optional>true</optional>
 		</dependency>
 
+		<dependency>
+		 	<groupId>io.projectreactor.addons</groupId>
+			<artifactId>reactor-test</artifactId>
+			<version>${reactor}</version>
+			<optional>true</optional>
+		</dependency>
+
 		<dependency>
 		 	<groupId>io.reactivex</groupId>
 			<artifactId>rxjava</artifactId>
@@ -125,6 +131,13 @@
 			<optional>true</optional>
 		</dependency>
 
+		<dependency>
+			<groupId>io.reactivex.rxjava2</groupId>
+			<artifactId>rxjava</artifactId>
+			<version>${rxjava2}</version>
+			<optional>true</optional>
+		</dependency>
+
 		<!-- CDI -->
 		<dependency>
 			<groupId>javax.enterprise</groupId>

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/config/AbstractMongoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2016 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,7 +17,6 @@ package org.springframework.data.mongodb.config;
 
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.data.authentication.UserCredentials;
 import org.springframework.data.mongodb.MongoDbFactory;
 import org.springframework.data.mongodb.core.MongoTemplate;
 import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
@@ -26,12 +25,11 @@ import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver;
 import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
 import org.springframework.data.mongodb.core.mapping.Document;
 
-import com.mongodb.Mongo;
 import com.mongodb.MongoClient;
 
 /**
  * Base class for Spring Data MongoDB configuration using JavaConfig.
- * 
+ *
  * @author Mark Pollack
  * @author Oliver Gierke
  * @author Thomas Darimont
@@ -41,35 +39,21 @@ import com.mongodb.MongoClient;
  * @see MongoConfigurationSupport
  */
 @Configuration
-public abstract class AbstractMongoConfiguration extends MongoConfigurationSupport {
+public abstract class
+AbstractMongoConfiguration extends MongoConfigurationSupport {
 
 	/**
-	 * Return the name of the authentication database to use. Defaults to {@literal null} and will turn into the value
-	 * returned by {@link #getDatabaseName()} later on effectively.
-	 * 
+	 * Return the {@link MongoClient} instance to connect to. Annotate with {@link Bean} in case you want to expose a
+	 * {@link MongoClient} instance to the {@link org.springframework.context.ApplicationContext}.
+	 *
 	 * @return
-	 * @deprecated since 1.7. {@link MongoClient} should hold authentication data within
-	 *             {@link MongoClient#getCredentialsList()}
 	 */
-	@Deprecated
-	protected String getAuthenticationDatabaseName() {
-		return null;
-	}
-
-	/**
-	 * Return the {@link Mongo} instance to connect to. Annotate with {@link Bean} in case you want to expose a
-	 * {@link Mongo} instance to the {@link org.springframework.context.ApplicationContext}.
-	 * 
-	 * @return
-	 * @throws Exception
-	 */
-	public abstract Mongo mongo() throws Exception;
+	public abstract MongoClient mongoClient();
 
 	/**
 	 * Creates a {@link MongoTemplate}.
-	 * 
+	 *
 	 * @return
-	 * @throws Exception
 	 */
 	@Bean
 	public MongoTemplate mongoTemplate() throws Exception {
@@ -77,17 +61,16 @@ public abstract class AbstractMongoConfiguration extends MongoConfigurationSuppo
 	}
 
 	/**
-	 * Creates a {@link SimpleMongoDbFactory} to be used by the {@link MongoTemplate}. Will use the {@link Mongo} instance
-	 * configured in {@link #mongo()}.
-	 * 
-	 * @see #mongo()
+	 * Creates a {@link SimpleMongoDbFactory} to be used by the {@link MongoTemplate}. Will use the {@link MongoClient}
+	 * instance configured in {@link #mongo()}.
+	 *
+	 * @see #mongoClient()
 	 * @see #mongoTemplate()
 	 * @return
-	 * @throws Exception
 	 */
 	@Bean
-	public MongoDbFactory mongoDbFactory() throws Exception {
-		return new SimpleMongoDbFactory(mongo(), getDatabaseName(), getUserCredentials(), getAuthenticationDatabaseName());
+	public MongoDbFactory mongoDbFactory() {
+		return new SimpleMongoDbFactory(mongoClient(), getDatabaseName());
 	}
 
 	/**
@@ -107,23 +90,10 @@ public abstract class AbstractMongoConfiguration extends MongoConfigurationSuppo
 		return mappingBasePackage == null ? null : mappingBasePackage.getName();
 	}
 
-	/**
-	 * Return {@link UserCredentials} to be used when connecting to the MongoDB instance or {@literal null} if none shall
-	 * be used.
-	 * 
-	 * @return
-	 * @deprecated since 1.7. {@link MongoClient} should hold authentication data within
-	 *             {@link MongoClient#getCredentialsList()}
-	 */
-	@Deprecated
-	protected UserCredentials getUserCredentials() {
-		return null;
-	}
-
 	/**
 	 * Creates a {@link MappingMongoConverter} using the configured {@link #mongoDbFactory()} and
 	 * {@link #mongoMappingContext()}. Will get {@link #customConversions()} applied.
-	 * 
+	 *
 	 * @see #customConversions()
 	 * @see #mongoMappingContext()
 	 * @see #mongoDbFactory()

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/config/BeanNames.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2014 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,13 +21,14 @@ package org.springframework.data.mongodb.config;
  * @author Jon Brisbin
  * @author Oliver Gierke
  * @author Martin Baumgartner
+ * @author Christoph Strobl
  */
 public abstract class BeanNames {
 
 	public static final String MAPPING_CONTEXT_BEAN_NAME = "mongoMappingContext";
 
 	static final String INDEX_HELPER_BEAN_NAME = "indexCreationHelper";
-	static final String MONGO_BEAN_NAME = "mongo";
+	static final String MONGO_BEAN_NAME = "mongoClient";
 	static final String DB_FACTORY_BEAN_NAME = "mongoDbFactory";
 	static final String VALIDATING_EVENT_LISTENER_BEAN_NAME = "validatingMongoEventListener";
 	static final String IS_NEW_STRATEGY_FACTORY_BEAN_NAME = "isNewStrategyFactory";

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/config/MappingMongoConverterParser.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2016 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -55,6 +55,7 @@ import org.springframework.data.mapping.context.MappingContextIsNewStrategyFacto
 import org.springframework.data.mapping.model.CamelCaseAbbreviatingFieldNamingStrategy;
 import org.springframework.data.mongodb.core.convert.CustomConversions;
 import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
+import org.springframework.data.mongodb.core.convert.QueryMapper;
 import org.springframework.data.mongodb.core.index.MongoPersistentEntityIndexCreator;
 import org.springframework.data.mongodb.core.mapping.Document;
 import org.springframework.data.mongodb.core.mapping.MongoMappingContext;
@@ -125,6 +126,7 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 
 			BeanDefinitionBuilder indexOperationsProviderBuilder = BeanDefinitionBuilder.genericBeanDefinition("org.springframework.data.mongodb.core.DefaultIndexOperationsProvider");
 			indexOperationsProviderBuilder.addConstructorArgReference(dbFactoryRef);
+			indexOperationsProviderBuilder.addConstructorArgValue(BeanDefinitionBuilder.genericBeanDefinition(QueryMapper.class).addConstructorArgReference(id).getBeanDefinition());
 			parserContext.registerBeanComponent(new BeanComponentDefinition(indexOperationsProviderBuilder.getBeanDefinition(), "indexOperationsProvider"));
 		}
 
@@ -367,7 +369,9 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 		 * @param filters
 		 */
 		public NegatingFilter(TypeFilter... filters) {
-			Assert.notNull(filters);
+
+			Assert.notNull(filters, "TypeFilters must not be null");
+
 			this.delegates = new HashSet<TypeFilter>(Arrays.asList(filters));
 		}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/config/MongoConfigurationSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -62,7 +62,7 @@ public abstract class MongoConfigurationSupport {
 
 	/**
 	 * Return the name of the database to connect to.
-	 * 
+	 *
 	 * @return must not be {@literal null}.
 	 */
 	protected abstract String getDatabaseName();
@@ -72,7 +72,7 @@ public abstract class MongoConfigurationSupport {
 	 * configuration class' (the concrete class, not this one here) by default. So if you have a
 	 * {@code com.acme.AppConfig} extending {@link MongoConfigurationSupport} the base package will be considered
 	 * {@code com.acme} unless the method is overridden to implement alternate behavior.
-	 * 
+	 *
 	 * @return the base packages to scan for mapped {@link Document} classes or an empty collection to not enable scanning
 	 *         for entities.
 	 * @since 1.10
@@ -85,8 +85,8 @@ public abstract class MongoConfigurationSupport {
 
 	/**
 	 * Creates a {@link MongoMappingContext} equipped with entity classes scanned from the mapping base package.
-	 * 
-	 * @see #getMappingBasePackage()
+	 *
+	 * @see #getMappingBasePackages()
 	 * @return
 	 * @throws ClassNotFoundException
 	 */

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/config/MongoDbFactoryParser.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2015 by the original author(s).
+ * Copyright 2011-2017 by the original author(s).
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,7 +30,6 @@ import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.xml.AbstractBeanDefinitionParser;
 import org.springframework.beans.factory.xml.BeanDefinitionParser;
 import org.springframework.beans.factory.xml.ParserContext;
-import org.springframework.data.authentication.UserCredentials;
 import org.springframework.data.config.BeanComponentDefinitionBuilder;
 import org.springframework.data.mongodb.core.MongoClientFactoryBean;
 import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
@@ -99,8 +98,6 @@ public class MongoDbFactoryParser extends AbstractBeanDefinitionParser {
 		String mongoRef = element.getAttribute("mongo-ref");
 		String dbname = element.getAttribute("dbname");
 
-		BeanDefinition userCredentials = getUserCredentialsBeanDefinition(element, parserContext);
-
 		// Defaulting
 		if (StringUtils.hasText(mongoRef)) {
 			dbFactoryBuilder.addConstructorArgReference(mongoRef);
@@ -109,8 +106,6 @@ public class MongoDbFactoryParser extends AbstractBeanDefinitionParser {
 		}
 
 		dbFactoryBuilder.addConstructorArgValue(StringUtils.hasText(dbname) ? dbname : "db");
-		dbFactoryBuilder.addConstructorArgValue(userCredentials);
-		dbFactoryBuilder.addConstructorArgValue(element.getAttribute("authentication-dbname"));
 
 		BeanDefinitionBuilder writeConcernPropertyEditorBuilder = getWriteConcernPropertyEditorBuilder();
 
@@ -138,28 +133,6 @@ public class MongoDbFactoryParser extends AbstractBeanDefinitionParser {
 		return getSourceBeanDefinition(mongoBuilder, parserContext, element);
 	}
 
-	/**
-	 * Returns a {@link BeanDefinition} for a {@link UserCredentials} object.
-	 * 
-	 * @param element
-	 * @return the {@link BeanDefinition} or {@literal null} if neither username nor password given.
-	 */
-	private BeanDefinition getUserCredentialsBeanDefinition(Element element, ParserContext context) {
-
-		String username = element.getAttribute("username");
-		String password = element.getAttribute("password");
-
-		if (!StringUtils.hasText(username) && !StringUtils.hasText(password)) {
-			return null;
-		}
-
-		BeanDefinitionBuilder userCredentialsBuilder = BeanDefinitionBuilder.genericBeanDefinition(UserCredentials.class);
-		userCredentialsBuilder.addConstructorArgValue(StringUtils.hasText(username) ? username : null);
-		userCredentialsBuilder.addConstructorArgValue(StringUtils.hasText(password) ? password : null);
-
-		return getSourceBeanDefinition(userCredentialsBuilder, context, element);
-	}
-
 	/**
 	 * Creates a {@link BeanDefinition} for a {@link MongoURI} or {@link MongoClientURI} depending on configured
 	 * attributes. <br />
@@ -193,7 +166,7 @@ public class MongoDbFactoryParser extends AbstractBeanDefinitionParser {
 					parserContext.extractSource(element));
 		}
 
-		Class<?> type = hasClientUri ? MongoClientURI.class : MongoURI.class;
+		Class<?> type = MongoClientURI.class;
 		String uri = hasClientUri ? element.getAttribute("client-uri") : element.getAttribute("uri");
 
 		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(type);

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/config/MongoJmxParser.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,12 +26,19 @@ import org.springframework.data.mongodb.monitor.*;
 import org.springframework.util.StringUtils;
 import org.w3c.dom.Element;
 
+/**
+ * @author Mark Pollack
+ * @author Thomas Risberg
+ * @author John Brisbin
+ * @author Oliver Gierke
+ * @author Christoph Strobl
+ */
 public class MongoJmxParser implements BeanDefinitionParser {
 
 	public BeanDefinition parse(Element element, ParserContext parserContext) {
 		String name = element.getAttribute("mongo-ref");
 		if (!StringUtils.hasText(name)) {
-			name = "mongo";
+			name = BeanNames.MONGO_BEAN_NAME;
 		}
 		registerJmxComponents(name, element, parserContext);
 		return null;

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/config/MongoNamespaceHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2015 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -33,7 +33,6 @@ public class MongoNamespaceHandler extends NamespaceHandlerSupport {
 	public void init() {
 
 		registerBeanDefinitionParser("mapping-converter", new MappingMongoConverterParser());
-		registerBeanDefinitionParser("mongo", new MongoParser());
 		registerBeanDefinitionParser("mongo-client", new MongoClientParser());
 		registerBeanDefinitionParser("db-factory", new MongoDbFactoryParser());
 		registerBeanDefinitionParser("jmx", new MongoJmxParser());

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/config/MongoParser.java

@@ -1,76 +0,0 @@
-/*
- * Copyright 2011-2015 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.config;
-
-import org.springframework.beans.factory.config.BeanDefinition;
-import org.springframework.beans.factory.parsing.BeanComponentDefinition;
-import org.springframework.beans.factory.parsing.CompositeComponentDefinition;
-import org.springframework.beans.factory.support.BeanDefinitionBuilder;
-import org.springframework.beans.factory.xml.BeanDefinitionParser;
-import org.springframework.beans.factory.xml.ParserContext;
-import org.springframework.data.config.BeanComponentDefinitionBuilder;
-import org.springframework.data.config.ParsingUtils;
-import org.springframework.data.mongodb.core.MongoFactoryBean;
-import org.springframework.util.StringUtils;
-import org.w3c.dom.Element;
-
-/**
- * Parser for <mongo;gt; definitions.
- * 
- * @author Mark Pollack
- * @author Oliver Gierke
- * @author Christoph Strobl
- */
-public class MongoParser implements BeanDefinitionParser {
-
-	/* 
-	 * (non-Javadoc)
-	 * @see org.springframework.beans.factory.xml.BeanDefinitionParser#parse(org.w3c.dom.Element, org.springframework.beans.factory.xml.ParserContext)
-	 */
-	public BeanDefinition parse(Element element, ParserContext parserContext) {
-
-		Object source = parserContext.extractSource(element);
-		String id = element.getAttribute("id");
-
-		BeanComponentDefinitionBuilder helper = new BeanComponentDefinitionBuilder(element, parserContext);
-
-		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(MongoFactoryBean.class);
-		ParsingUtils.setPropertyValue(builder, element, "port", "port");
-		ParsingUtils.setPropertyValue(builder, element, "host", "host");
-		ParsingUtils.setPropertyValue(builder, element, "write-concern", "writeConcern");
-
-		MongoParsingUtils.parseMongoOptions(element, builder);
-		MongoParsingUtils.parseReplicaSet(element, builder);
-
-		String defaultedId = StringUtils.hasText(id) ? id : BeanNames.MONGO_BEAN_NAME;
-
-		parserContext.pushContainingComponent(new CompositeComponentDefinition("Mongo", source));
-
-		BeanComponentDefinition mongoComponent = helper.getComponent(builder, defaultedId);
-		parserContext.registerBeanComponent(mongoComponent);
-		BeanComponentDefinition serverAddressPropertyEditor = helper.getComponent(MongoParsingUtils
-				.getServerAddressPropertyEditorBuilder());
-		parserContext.registerBeanComponent(serverAddressPropertyEditor);
-		BeanComponentDefinition writeConcernPropertyEditor = helper.getComponent(MongoParsingUtils
-				.getWriteConcernPropertyEditorBuilder());
-		parserContext.registerBeanComponent(writeConcernPropertyEditor);
-
-		parserContext.popAndRegisterContainingComponent();
-
-		return mongoComponent.getBeanDefinition();
-	}
-
-}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/config/MongoParsingUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2015 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,7 +25,6 @@ import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.support.ManagedMap;
 import org.springframework.beans.factory.xml.BeanDefinitionParser;
 import org.springframework.data.mongodb.core.MongoClientOptionsFactoryBean;
-import org.springframework.data.mongodb.core.MongoOptionsFactoryBean;
 import org.springframework.util.xml.DomUtils;
 import org.w3c.dom.Element;
 
@@ -54,42 +53,6 @@ abstract class MongoParsingUtils {
 		setPropertyValue(mongoBuilder, element, "replica-set", "replicaSetSeeds");
 	}
 
-	/**
-	 * Parses the {@code mongo:options} sub-element. Populates the given attribute factory with the proper attributes.
-	 * 
-	 * @return true if parsing actually occured, {@literal false} otherwise
-	 */
-	static boolean parseMongoOptions(Element element, BeanDefinitionBuilder mongoBuilder) {
-
-		Element optionsElement = DomUtils.getChildElementByTagName(element, "options");
-
-		if (optionsElement == null) {
-			return false;
-		}
-
-		BeanDefinitionBuilder optionsDefBuilder = BeanDefinitionBuilder
-				.genericBeanDefinition(MongoOptionsFactoryBean.class);
-
-		setPropertyValue(optionsDefBuilder, optionsElement, "connections-per-host", "connectionsPerHost");
-		setPropertyValue(optionsDefBuilder, optionsElement, "threads-allowed-to-block-for-connection-multiplier",
-				"threadsAllowedToBlockForConnectionMultiplier");
-		setPropertyValue(optionsDefBuilder, optionsElement, "max-wait-time", "maxWaitTime");
-		setPropertyValue(optionsDefBuilder, optionsElement, "connect-timeout", "connectTimeout");
-		setPropertyValue(optionsDefBuilder, optionsElement, "socket-timeout", "socketTimeout");
-		setPropertyValue(optionsDefBuilder, optionsElement, "socket-keep-alive", "socketKeepAlive");
-		setPropertyValue(optionsDefBuilder, optionsElement, "auto-connect-retry", "autoConnectRetry");
-		setPropertyValue(optionsDefBuilder, optionsElement, "max-auto-connect-retry-time", "maxAutoConnectRetryTime");
-		setPropertyValue(optionsDefBuilder, optionsElement, "write-number", "writeNumber");
-		setPropertyValue(optionsDefBuilder, optionsElement, "write-timeout", "writeTimeout");
-		setPropertyValue(optionsDefBuilder, optionsElement, "write-fsync", "writeFsync");
-		setPropertyValue(optionsDefBuilder, optionsElement, "slave-ok", "slaveOk");
-		setPropertyValue(optionsDefBuilder, optionsElement, "ssl", "ssl");
-		setPropertyReference(optionsDefBuilder, optionsElement, "ssl-socket-factory-ref", "sslSocketFactory");
-
-		mongoBuilder.addPropertyValue("mongoOptions", optionsDefBuilder.getBeanDefinition());
-		return true;
-	}
-
 	/**
 	 * Parses the {@code mongo:client-options} sub-element. Populates the given attribute factory with the proper
 	 * attributes.
@@ -129,6 +92,7 @@ abstract class MongoParsingUtils {
 		setPropertyValue(clientOptionsDefBuilder, optionsElement, "heartbeat-socket-timeout", "heartbeatSocketTimeout");
 		setPropertyValue(clientOptionsDefBuilder, optionsElement, "ssl", "ssl");
 		setPropertyReference(clientOptionsDefBuilder, optionsElement, "ssl-socket-factory-ref", "sslSocketFactory");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "server-selection-timeout", "serverSelectionTimeout");
 
 		mongoClientBuilder.addPropertyValue("mongoClientOptions", clientOptionsDefBuilder.getBeanDefinition());
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/DefaultBulkOperations.java

@@ -123,7 +123,16 @@ class DefaultBulkOperations implements BulkOperations {
 
 		Assert.notNull(document, "Document must not be null!");
 
-		models.add(new InsertOneModel<Document>((Document) mongoOperations.getConverter().convertToMongoType(document)));
+		if (document instanceof Document) {
+
+			models.add(new InsertOneModel<>((Document) document));
+			return this;
+		}
+
+		Document sink = new Document();
+		mongoOperations.getConverter().write(document, sink);
+
+		models.add(new InsertOneModel<>(sink));
 		return this;
 	}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/DefaultIndexOperations.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2016 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,13 +18,16 @@ package org.springframework.data.mongodb.core;
 import static org.springframework.data.mongodb.core.MongoTemplate.*;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
 
 import org.bson.Document;
 import org.springframework.dao.DataAccessException;
+import org.springframework.data.mongodb.core.convert.QueryMapper;
 import org.springframework.data.mongodb.MongoDbFactory;
 import org.springframework.data.mongodb.core.index.IndexDefinition;
 import org.springframework.data.mongodb.core.index.IndexInfo;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.util.Assert;
 
 import com.mongodb.MongoException;
@@ -43,22 +46,45 @@ import com.mongodb.client.model.IndexOptions;
  */
 public class DefaultIndexOperations implements IndexOperations {
 
+	private static final String PARTIAL_FILTER_EXPRESSION_KEY = "partialFilterExpression";
+
 	private final MongoDbFactory mongoDbFactory;
 	private final String collectionName;
+	private final QueryMapper mapper;
+	private final Class<?> type;
 
 	/**
 	 * Creates a new {@link DefaultIndexOperations}.
 	 * 
 	 * @param mongoDbFactory must not be {@literal null}.
 	 * @param collectionName must not be {@literal null}.
+	 * @param queryMapper must not be {@literal null}.
 	 */
-	public DefaultIndexOperations(MongoDbFactory mongoDbFactory, String collectionName) {
+	public DefaultIndexOperations(MongoDbFactory mongoDbFactory, String collectionName, QueryMapper queryMapper) {
+
+		this(mongoDbFactory, collectionName, queryMapper, null);
+	}
+
+	/**
+	 * Creates a new {@link DefaultIndexOperations}.
+	 *
+	 * @param mongoDbFactory must not be {@literal null}.
+	 * @param collectionName must not be {@literal null}.
+	 * @param queryMapper must not be {@literal null}.
+	 * @param type Type used for mapping potential partial index filter expression. Can be {@literal null}.
+	 * @since 1.10
+	 */
+	public DefaultIndexOperations(MongoDbFactory mongoDbFactory, String collectionName, QueryMapper queryMapper,
+			Class<?> type) {
 
 		Assert.notNull(mongoDbFactory, "MongoDbFactory must not be null!");
 		Assert.notNull(collectionName, "Collection name can not be null!");
+		Assert.notNull(queryMapper, "QueryMapper must not be null!");
 
 		this.mongoDbFactory = mongoDbFactory;
 		this.collectionName = collectionName;
+		this.mapper = queryMapper;
+		this.type = type;
 	}
 
 	/*
@@ -74,10 +100,38 @@ public class DefaultIndexOperations implements IndexOperations {
 			if (indexOptions != null) {
 
 				IndexOptions ops = IndexConverters.indexDefinitionToIndexOptionsConverter().convert(indexDefinition);
+
+				if (indexOptions.containsKey(PARTIAL_FILTER_EXPRESSION_KEY)) {
+
+					Assert.isInstanceOf(Document.class, indexOptions.get(PARTIAL_FILTER_EXPRESSION_KEY));
+
+					ops.partialFilterExpression( mapper.getMappedObject(
+							(Document) indexOptions.get(PARTIAL_FILTER_EXPRESSION_KEY), lookupPersistentEntity(type, collectionName)));
+				}
+
 				return collection.createIndex(indexDefinition.getIndexKeys(), ops);
 			}
 			return collection.createIndex(indexDefinition.getIndexKeys());
-		});
+		}
+
+		);
+	}
+
+	private MongoPersistentEntity<?> lookupPersistentEntity(Class<?> entityType, String collection) {
+
+		if (entityType != null) {
+			return mapper.getMappingContext().getRequiredPersistentEntity(entityType);
+		}
+
+		Collection<? extends MongoPersistentEntity<?>> entities = mapper.getMappingContext().getPersistentEntities();
+
+		for (MongoPersistentEntity<?> entity : entities) {
+			if (entity.getCollection().equals(collection)) {
+				return entity;
+			}
+		}
+
+		return null;
 	}
 
 	/*
@@ -134,7 +188,7 @@ public class DefaultIndexOperations implements IndexOperations {
 
 	public <T> T execute(CollectionCallback<T> callback) {
 
-		Assert.notNull(callback);
+		Assert.notNull(callback, "CollectionCallback must not be null!");
 
 		try {
 			MongoCollection<Document> collection = mongoDbFactory.getDb().getCollection(collectionName);

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/DefaultIndexOperationsProvider.java

@@ -16,6 +16,7 @@
 package org.springframework.data.mongodb.core;
 
 import org.springframework.data.mongodb.MongoDbFactory;
+import org.springframework.data.mongodb.core.convert.QueryMapper;
 
 /**
  * {@link IndexOperationsProvider} to obtain {@link IndexOperations} from a given {@link MongoDbFactory}. TODO: Review
@@ -27,12 +28,13 @@ import org.springframework.data.mongodb.MongoDbFactory;
 class DefaultIndexOperationsProvider implements IndexOperationsProvider {
 
 	private final MongoDbFactory mongoDbFactory;
+	private final QueryMapper mapper;
 
 	/**
 	 * @param mongoDbFactory must not be {@literal null}.
 	 */
-	DefaultIndexOperationsProvider(MongoDbFactory mongoDbFactory) {
-		this.mongoDbFactory = mongoDbFactory;
+	DefaultIndexOperationsProvider(MongoDbFactory mongoDbFactory, QueryMapper mapper) {
+		this.mongoDbFactory = mongoDbFactory; this.mapper = mapper;
 	}
 
 	/* (non-Javadoc)
@@ -40,6 +42,6 @@ class DefaultIndexOperationsProvider implements IndexOperationsProvider {
 	 */
 	@Override
 	public IndexOperations indexOps(String collectionName) {
-		return new DefaultIndexOperations(mongoDbFactory, collectionName);
+		return new DefaultIndexOperations(mongoDbFactory, collectionName, mapper);
 	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/GeoCommandStatistics.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -62,7 +62,7 @@ class GeoCommandStatistics {
 	 * didn't return any result introduced in MongoDB 3.2 RC1.
 	 * 
 	 * @return
-	 * @see https://jira.mongodb.org/browse/SERVER-21024
+	 * @see <a href="https://jira.mongodb.org/browse/SERVER-21024">MongoDB Jira SERVER-21024</a>
 	 */
 	public double getAverageDistance() {
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/GeoJsonConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015 the original author or authors.
+ * Copyright 2015-2016 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,15 +17,14 @@ package org.springframework.data.mongodb.core;
 
 import org.springframework.context.annotation.Bean;
 import org.springframework.data.mongodb.core.geo.GeoJsonModule;
-import org.springframework.data.web.config.SpringDataWebConfigurationMixin;
+import org.springframework.data.web.config.SpringDataJacksonModules;
 
 /**
  * Configuration class to expose {@link GeoJsonModule} as a Spring bean.
  * 
  * @author Oliver Gierke
  */
-@SpringDataWebConfigurationMixin
-public class GeoJsonConfiguration {
+public class GeoJsonConfiguration implements SpringDataJacksonModules {
 
 	@Bean
 	public GeoJsonModule geoJsonModule() {

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/IndexConverters.java

@@ -117,6 +117,10 @@ abstract class IndexConverters {
 				}
 			}
 
+			if(indexOptions.containsKey("partialFilterExpression")) {
+				ops = ops.partialFilterExpression((org.bson.Document)indexOptions.get("partialFilterExpression"));
+			}
+
 			return ops;
 		};
 	}
@@ -124,43 +128,7 @@ abstract class IndexConverters {
 	private static Converter<Document, IndexInfo> getDocumentIndexInfoConverter() {
 
 		return ix -> {
-			Document keyDocument = (Document) ix.get("key");
-			int numberOfElements = keyDocument.keySet().size();
-
-			List<IndexField> indexFields = new ArrayList<IndexField>(numberOfElements);
-
-			for (String key : keyDocument.keySet()) {
-
-				Object value = keyDocument.get(key);
-
-				if (TWO_D_IDENTIFIERS.contains(value)) {
-					indexFields.add(IndexField.geo(key));
-				} else if ("text".equals(value)) {
-
-					Document weights = (Document) ix.get("weights");
-					for (String fieldName : weights.keySet()) {
-						indexFields.add(IndexField.text(fieldName, Float.valueOf(weights.get(fieldName).toString())));
-					}
-
-				} else {
-
-					Double keyValue = new Double(value.toString());
-
-					if (ONE.equals(keyValue)) {
-						indexFields.add(IndexField.create(key, ASC));
-					} else if (MINUS_ONE.equals(keyValue)) {
-						indexFields.add(IndexField.create(key, DESC));
-					}
-				}
-			}
-
-			String name = ix.get("name").toString();
-
-			boolean unique = ix.containsKey("unique") ? (Boolean) ix.get("unique") : false;
-			boolean sparse = ix.containsKey("sparse") ? (Boolean) ix.get("sparse") : false;
-
-			String language = ix.containsKey("default_language") ? (String) ix.get("default_language") : "";
-			return new IndexInfo(indexFields, name, unique, sparse, language);
+			return IndexInfo.indexInfoOf(ix);
 		};
 	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/IndexOperationsProvider.java

@@ -16,6 +16,8 @@
 
 package org.springframework.data.mongodb.core;
 
+import org.springframework.data.mongodb.core.convert.QueryMapper;
+
 /**
  * TODO: Revisit for a better pattern.
  * @author Mark Paluch

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoAdmin.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2013 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,31 +15,30 @@
  */
 package org.springframework.data.mongodb.core;
 
-import org.springframework.data.authentication.UserCredentials;
+import com.mongodb.MongoClient;
+import com.mongodb.client.MongoDatabase;
+import org.bson.Document;
 import org.springframework.jmx.export.annotation.ManagedOperation;
 import org.springframework.jmx.export.annotation.ManagedResource;
 import org.springframework.util.Assert;
 
-import com.mongodb.DB;
-import com.mongodb.Mongo;
-
 /**
  * Mongo server administration exposed via JMX annotations
  * 
  * @author Mark Pollack
- * @author Thomas Darimont
+ * @author Thomas Darimont
+ * @author Mark Paluch
+ * @author Christoph Strobl
  */
 @ManagedResource(description = "Mongo Admin Operations")
 public class MongoAdmin implements MongoAdminOperations {
 
-	private final Mongo mongo;
-	private String username;
-	private String password;
-	private String authenticationDatabaseName;
+	private final MongoClient mongoClient;
 
-	public MongoAdmin(Mongo mongo) {
-		Assert.notNull(mongo);
-		this.mongo = mongo;
+	public MongoAdmin(MongoClient mongoClient) {
+
+		Assert.notNull(mongoClient, "MongoClient must not be null!");
+		this.mongoClient = mongoClient;
 	}
 
 	/* (non-Javadoc)
@@ -47,7 +46,7 @@ public class MongoAdmin implements MongoAdminOperations {
 	  */
 	@ManagedOperation
 	public void dropDatabase(String databaseName) {
-		getDB(databaseName).dropDatabase();
+		getDB(databaseName).drop();
 	}
 
 	/* (non-Javadoc)
@@ -63,37 +62,16 @@ public class MongoAdmin implements MongoAdminOperations {
 	  */
 	@ManagedOperation
 	public String getDatabaseStats(String databaseName) {
-		return getDB(databaseName).getStats().toString();
+		return getDB(databaseName).runCommand(new Document("dbStats", 1).append("scale" , 1024)).toJson();
 	}
 
-	/**
-	 * Sets the username to use to connect to the Mongo database
-	 * 
-	 * @param username The username to use
-	 */
-	public void setUsername(String username) {
-		this.username = username;
+	@ManagedOperation
+	public String getServerStatus() {
+		return getDB("admin").runCommand(new Document("serverStatus", 1).append("rangeDeleter", 1).append("repl", 1)).toJson();
 	}
 
-	/**
-	 * Sets the password to use to authenticate with the Mongo database.
-	 * 
-	 * @param password The password to use
-	 */
-	public void setPassword(String password) {
-		this.password = password;
-	}
 
-	/**
-	 * Sets the authenticationDatabaseName to use to authenticate with the Mongo database.
-	 * 
-	 * @param authenticationDatabaseName The authenticationDatabaseName to use.
-	 */
-	public void setAuthenticationDatabaseName(String authenticationDatabaseName) {
-		this.authenticationDatabaseName = authenticationDatabaseName;
-	}
-
-	DB getDB(String databaseName) {
-		return MongoDbUtils.getDB(mongo, databaseName, new UserCredentials(username, password), authenticationDatabaseName);
+	MongoDatabase getDB(String databaseName) {
+		return mongoClient.getDatabase(databaseName);
 	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoClientFactoryBean.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015 the original author or authors.
+ * Copyright 2015-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,7 +26,6 @@ import org.springframework.dao.support.PersistenceExceptionTranslator;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.StringUtils;
 
-import com.mongodb.Mongo;
 import com.mongodb.MongoClient;
 import com.mongodb.MongoClientOptions;
 import com.mongodb.MongoCredential;
@@ -38,7 +37,7 @@ import com.mongodb.ServerAddress;
  * @author Christoph Strobl
  * @since 1.7
  */
-public class MongoClientFactoryBean extends AbstractFactoryBean<Mongo> implements PersistenceExceptionTranslator {
+public class MongoClientFactoryBean extends AbstractFactoryBean<MongoClient> implements PersistenceExceptionTranslator {
 
 	private static final PersistenceExceptionTranslator DEFAULT_EXCEPTION_TRANSLATOR = new MongoExceptionTranslator();
 
@@ -108,8 +107,8 @@ public class MongoClientFactoryBean extends AbstractFactoryBean<Mongo> implement
 	 * (non-Javadoc)
 	 * @see org.springframework.beans.factory.FactoryBean#getObjectType()
 	 */
-	public Class<? extends Mongo> getObjectType() {
-		return Mongo.class;
+	public Class<? extends MongoClient> getObjectType() {
+		return MongoClient.class;
 	}
 
 	/*
@@ -125,7 +124,7 @@ public class MongoClientFactoryBean extends AbstractFactoryBean<Mongo> implement
 	 * @see org.springframework.beans.factory.config.AbstractFactoryBean#createInstance()
 	 */
 	@Override
-	protected Mongo createInstance() throws Exception {
+	protected MongoClient createInstance() throws Exception {
 
 		if (mongoClientOptions == null) {
 			mongoClientOptions = MongoClientOptions.builder().build();
@@ -143,7 +142,7 @@ public class MongoClientFactoryBean extends AbstractFactoryBean<Mongo> implement
 	 * @see org.springframework.beans.factory.config.AbstractFactoryBean#destroyInstance(java.lang.Object)
 	 */
 	@Override
-	protected void destroyInstance(Mongo instance) throws Exception {
+	protected void destroyInstance(MongoClient instance) throws Exception {
 		instance.close();
 	}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoClientOptionsFactoryBean.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015 the original author or authors.
+ * Copyright 2015-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -30,9 +30,10 @@ import com.mongodb.WriteConcern;
 
 /**
  * A factory bean for construction of a {@link MongoClientOptions} instance.
- * 
+ *
  * @author Christoph Strobl
  * @author Oliver Gierke
+ * @author Mark Paluch
  * @since 1.7
  */
 public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClientOptions> {
@@ -62,13 +63,14 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 	private int heartbeatConnectTimeout = DEFAULT_MONGO_OPTIONS.getHeartbeatConnectTimeout();
 	private int heartbeatSocketTimeout = DEFAULT_MONGO_OPTIONS.getHeartbeatSocketTimeout();
 	private String requiredReplicaSetName = DEFAULT_MONGO_OPTIONS.getRequiredReplicaSetName();
+	private int serverSelectionTimeout = DEFAULT_MONGO_OPTIONS.getServerSelectionTimeout();
 
 	private boolean ssl;
 	private SSLSocketFactory sslSocketFactory;
 
 	/**
 	 * Set the {@link MongoClient} description.
-	 * 
+	 *
 	 * @param description
 	 */
 	public void setDescription(String description) {
@@ -77,7 +79,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the minimum number of connections per host.
-	 * 
+	 *
 	 * @param minConnectionsPerHost
 	 */
 	public void setMinConnectionsPerHost(int minConnectionsPerHost) {
@@ -87,7 +89,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 	/**
 	 * Set the number of connections allowed per host. Will block if run out. Default is 10. System property
 	 * {@code MONGO.POOLSIZE} can override
-	 * 
+	 *
 	 * @param connectionsPerHost
 	 */
 	public void setConnectionsPerHost(int connectionsPerHost) {
@@ -98,7 +100,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 	 * Set the multiplier for connectionsPerHost for # of threads that can block. Default is 5. If connectionsPerHost is
 	 * 10, and threadsAllowedToBlockForConnectionMultiplier is 5, then 50 threads can block more than that and an
 	 * exception will be thrown.
-	 * 
+	 *
 	 * @param threadsAllowedToBlockForConnectionMultiplier
 	 */
 	public void setThreadsAllowedToBlockForConnectionMultiplier(int threadsAllowedToBlockForConnectionMultiplier) {
@@ -107,7 +109,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the max wait time of a blocking thread for a connection. Default is 12000 ms (2 minutes)
-	 * 
+	 *
 	 * @param maxWaitTime
 	 */
 	public void setMaxWaitTime(int maxWaitTime) {
@@ -116,7 +118,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * The maximum idle time for a pooled connection.
-	 * 
+	 *
 	 * @param maxConnectionIdleTime
 	 */
 	public void setMaxConnectionIdleTime(int maxConnectionIdleTime) {
@@ -125,7 +127,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the maximum life time for a pooled connection.
-	 * 
+	 *
 	 * @param maxConnectionLifeTime
 	 */
 	public void setMaxConnectionLifeTime(int maxConnectionLifeTime) {
@@ -134,7 +136,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the connect timeout in milliseconds. 0 is default and infinite.
-	 * 
+	 *
 	 * @param connectTimeout
 	 */
 	public void setConnectTimeout(int connectTimeout) {
@@ -143,7 +145,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the socket timeout. 0 is default and infinite.
-	 * 
+	 *
 	 * @param socketTimeout
 	 */
 	public void setSocketTimeout(int socketTimeout) {
@@ -152,7 +154,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the keep alive flag, controls whether or not to have socket keep alive timeout. Defaults to false.
-	 * 
+	 *
 	 * @param socketKeepAlive
 	 */
 	public void setSocketKeepAlive(boolean socketKeepAlive) {
@@ -161,7 +163,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the {@link ReadPreference}.
-	 * 
+	 *
 	 * @param readPreference
 	 */
 	public void setReadPreference(ReadPreference readPreference) {
@@ -171,7 +173,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 	/**
 	 * Set the {@link WriteConcern} that will be the default value used when asking the {@link MongoDbFactory} for a DB
 	 * object.
-	 * 
+	 *
 	 * @param writeConcern
 	 */
 	public void setWriteConcern(WriteConcern writeConcern) {
@@ -187,7 +189,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the frequency that the driver will attempt to determine the current state of each server in the cluster.
-	 * 
+	 *
 	 * @param heartbeatFrequency
 	 */
 	public void setHeartbeatFrequency(int heartbeatFrequency) {
@@ -197,7 +199,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 	/**
 	 * In the event that the driver has to frequently re-check a server's availability, it will wait at least this long
 	 * since the previous check to avoid wasted effort.
-	 * 
+	 *
 	 * @param minHeartbeatFrequency
 	 */
 	public void setMinHeartbeatFrequency(int minHeartbeatFrequency) {
@@ -206,7 +208,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the connect timeout for connections used for the cluster heartbeat.
-	 * 
+	 *
 	 * @param heartbeatConnectTimeout
 	 */
 	public void setHeartbeatConnectTimeout(int heartbeatConnectTimeout) {
@@ -215,7 +217,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the socket timeout for connections used for the cluster heartbeat.
-	 * 
+	 *
 	 * @param heartbeatSocketTimeout
 	 */
 	public void setHeartbeatSocketTimeout(int heartbeatSocketTimeout) {
@@ -224,7 +226,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Configures the name of the replica set.
-	 * 
+	 *
 	 * @param requiredReplicaSetName
 	 */
 	public void setRequiredReplicaSetName(String requiredReplicaSetName) {
@@ -233,7 +235,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * This controls if the driver should us an SSL connection. Defaults to |@literal false}.
-	 * 
+	 *
 	 * @param ssl
 	 */
 	public void setSsl(boolean ssl) {
@@ -243,22 +245,35 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 	/**
 	 * Set the {@link SSLSocketFactory} to use for the {@literal SSL} connection. If none is configured here,
 	 * {@link SSLSocketFactory#getDefault()} will be used.
-	 * 
+	 *
 	 * @param sslSocketFactory
 	 */
 	public void setSslSocketFactory(SSLSocketFactory sslSocketFactory) {
+
 		this.sslSocketFactory = sslSocketFactory;
+		this.ssl = sslSocketFactory != null;
 	}
 
-	/* 
+	/**
+	 * Set the {@literal server selection timeout} in msec for a 3.x MongoDB Java driver. If not set the default value of
+	 * 30 sec will be used. A value of 0 means that it will timeout immediately if no server is available. A negative
+	 * value means to wait indefinitely.
+	 *
+	 * @param serverSelectionTimeout in msec.
+	 */
+	public void setServerSelectionTimeout(int serverSelectionTimeout) {
+		this.serverSelectionTimeout = serverSelectionTimeout;
+	}
+
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.beans.factory.config.AbstractFactoryBean#createInstance()
 	 */
 	@Override
 	protected MongoClientOptions createInstance() throws Exception {
 
-		SocketFactory socketFactoryToUse = ssl ? (sslSocketFactory != null ? sslSocketFactory : SSLSocketFactory
-				.getDefault()) : this.socketFactory;
+		SocketFactory socketFactoryToUse = ssl
+				? (sslSocketFactory != null ? sslSocketFactory : SSLSocketFactory.getDefault()) : this.socketFactory;
 
 		return MongoClientOptions.builder() //
 				.alwaysUseMBeans(this.alwaysUseMBeans) //
@@ -278,6 +293,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 				.minHeartbeatFrequency(minHeartbeatFrequency) //
 				.readPreference(readPreference) //
 				.requiredReplicaSetName(requiredReplicaSetName) //
+				.serverSelectionTimeout(serverSelectionTimeout) //
 				.socketFactory(socketFactoryToUse) //
 				.socketKeepAlive(socketKeepAlive) //
 				.socketTimeout(socketTimeout) //

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoDbUtils.java

@@ -1,216 +0,0 @@
-/*
- * Copyright 2010-2015 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-import org.springframework.data.authentication.UserCredentials;
-import org.springframework.data.mongodb.util.MongoClientVersion;
-import org.springframework.transaction.support.TransactionSynchronizationManager;
-import org.springframework.util.Assert;
-
-import com.mongodb.DB;
-import com.mongodb.Mongo;
-import com.mongodb.MongoClient;
-
-/**
- * Helper class featuring helper methods for internal MongoDb classes. Mainly intended for internal use within the
- * framework.
- * 
- * @author Thomas Risberg
- * @author Graeme Rocher
- * @author Oliver Gierke
- * @author Randy Watler
- * @author Thomas Darimont
- * @author Christoph Strobl
- * @since 1.0
- */
-public abstract class MongoDbUtils {
-
-	private static final Logger LOGGER = LoggerFactory.getLogger(MongoDbUtils.class);
-
-	/**
-	 * Private constructor to prevent instantiation.
-	 */
-	private MongoDbUtils() {}
-
-	/**
-	 * Obtains a {@link DB} connection for the given {@link Mongo} instance and database name
-	 * 
-	 * @param mongo the {@link Mongo} instance, must not be {@literal null}.
-	 * @param databaseName the database name, must not be {@literal null} or empty.
-	 * @return the {@link DB} connection
-	 */
-	public static DB getDB(Mongo mongo, String databaseName) {
-		return doGetDB(mongo, databaseName, UserCredentials.NO_CREDENTIALS, true, databaseName);
-	}
-
-	/**
-	 * Obtains a {@link DB} connection for the given {@link Mongo} instance and database name
-	 * 
-	 * @param mongo the {@link Mongo} instance, must not be {@literal null}.
-	 * @param databaseName the database name, must not be {@literal null} or empty.
-	 * @param credentials the credentials to use, must not be {@literal null}.
-	 * @return the {@link DB} connection
-	 * @deprecated since 1.7. The {@link MongoClient} itself should hold credentials within
-	 *             {@link MongoClient#getCredentialsList()}.
-	 */
-	@Deprecated
-	public static DB getDB(Mongo mongo, String databaseName, UserCredentials credentials) {
-		return getDB(mongo, databaseName, credentials, databaseName);
-	}
-
-	/**
-	 * @param mongo
-	 * @param databaseName
-	 * @param credentials
-	 * @param authenticationDatabaseName
-	 * @return
-	 * @deprecated since 1.7. The {@link MongoClient} itself should hold credentials within
-	 *             {@link MongoClient#getCredentialsList()}.
-	 */
-	@Deprecated
-	public static DB getDB(Mongo mongo, String databaseName, UserCredentials credentials,
-			String authenticationDatabaseName) {
-
-		Assert.notNull(mongo, "No Mongo instance specified!");
-		Assert.hasText(databaseName, "Database name must be given!");
-		Assert.notNull(credentials, "Credentials must not be null, use UserCredentials.NO_CREDENTIALS!");
-		Assert.hasText(authenticationDatabaseName, "Authentication database name must not be null or empty!");
-
-		return doGetDB(mongo, databaseName, credentials, true, authenticationDatabaseName);
-	}
-
-	private static DB doGetDB(Mongo mongo, String databaseName, UserCredentials credentials, boolean allowCreate,
-			String authenticationDatabaseName) {
-
-		DbHolder dbHolder = (DbHolder) TransactionSynchronizationManager.getResource(mongo);
-
-		// Do we have a populated holder and TX sync active?
-		if (dbHolder != null && !dbHolder.isEmpty() && TransactionSynchronizationManager.isSynchronizationActive()) {
-
-			DB db = dbHolder.getDB(databaseName);
-
-			// DB found but not yet synchronized
-			if (db != null && !dbHolder.isSynchronizedWithTransaction()) {
-
-				LOGGER.debug("Registering Spring transaction synchronization for existing MongoDB {}.", databaseName);
-
-				TransactionSynchronizationManager.registerSynchronization(new MongoSynchronization(dbHolder, mongo));
-				dbHolder.setSynchronizedWithTransaction(true);
-			}
-
-			if (db != null) {
-				return db;
-			}
-		}
-
-		// Lookup fresh database instance
-		LOGGER.debug("Getting Mongo Database name=[{}]", databaseName);
-
-		DB db = mongo.getDB(databaseName);
-
-		if (!(mongo instanceof MongoClient) && requiresAuthDbAuthentication(credentials)) {
-			ReflectiveDbInvoker.authenticate(mongo, db, credentials, authenticationDatabaseName);
-		}
-
-		// TX sync active, bind new database to thread
-		if (TransactionSynchronizationManager.isSynchronizationActive()) {
-
-			LOGGER.debug("Registering Spring transaction synchronization for MongoDB instance {}.", databaseName);
-
-			DbHolder holderToUse = dbHolder;
-
-			if (holderToUse == null) {
-				holderToUse = new DbHolder(databaseName, db);
-			} else {
-				holderToUse.addDB(databaseName, db);
-			}
-
-			// synchronize holder only if not yet synchronized
-			if (!holderToUse.isSynchronizedWithTransaction()) {
-				TransactionSynchronizationManager.registerSynchronization(new MongoSynchronization(holderToUse, mongo));
-				holderToUse.setSynchronizedWithTransaction(true);
-			}
-
-			if (holderToUse != dbHolder) {
-				TransactionSynchronizationManager.bindResource(mongo, holderToUse);
-			}
-		}
-
-		// Check whether we are allowed to return the DB.
-		if (!allowCreate && !isDBTransactional(db, mongo)) {
-			throw new IllegalStateException("No Mongo DB bound to thread, "
-					+ "and configuration does not allow creation of non-transactional one here");
-		}
-
-		return db;
-	}
-
-	/**
-	 * Return whether the given DB instance is transactional, that is, bound to the current thread by Spring's transaction
-	 * facilities.
-	 * 
-	 * @param db the DB to check
-	 * @param mongo the Mongo instance that the DB was created with (may be <code>null</code>)
-	 * @return whether the DB is transactional
-	 */
-	public static boolean isDBTransactional(DB db, Mongo mongo) {
-
-		if (mongo == null) {
-			return false;
-		}
-		DbHolder dbHolder = (DbHolder) TransactionSynchronizationManager.getResource(mongo);
-		return dbHolder != null && dbHolder.containsDB(db);
-	}
-
-	/**
-	 * Perform actual closing of the Mongo DB object, catching and logging any cleanup exceptions thrown.
-	 * 
-	 * @param db the DB to close (may be <code>null</code>)
-	 * @deprecated since 1.7. The main use case for this method is to ensure that applications can read their own
-	 *             unacknowledged writes, but this is no longer so prevalent since the MongoDB Java driver version 3
-	 *             started defaulting to acknowledged writes.
-	 */
-	@Deprecated
-	public static void closeDB(DB db) {
-
-		if (db != null) {
-			LOGGER.debug("Closing Mongo DB object");
-			try {
-				ReflectiveDbInvoker.requestDone(db);
-			} catch (Throwable ex) {
-				LOGGER.debug("Unexpected exception on closing Mongo DB object", ex);
-			}
-		}
-	}
-
-	/**
-	 * Check if credentials present. In case we're using a mongo-java-driver version 3 or above we do not have the need
-	 * for authentication as the auth data has to be provided within the MongoClient
-	 * 
-	 * @param credentials
-	 * @return
-	 */
-	private static boolean requiresAuthDbAuthentication(UserCredentials credentials) {
-
-		if (credentials == null || !credentials.hasUsername()) {
-			return false;
-		}
-
-		return !MongoClientVersion.isMongo3Driver();
-	}
-}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoFactoryBean.java

@@ -1,199 +0,0 @@
-/*
- * Copyright 2010-2015 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.List;
-
-import org.springframework.beans.factory.config.AbstractFactoryBean;
-import org.springframework.dao.DataAccessException;
-import org.springframework.dao.support.PersistenceExceptionTranslator;
-import org.springframework.data.mongodb.CannotGetMongoDbConnectionException;
-import org.springframework.util.StringUtils;
-
-import com.mongodb.Mongo;
-import com.mongodb.MongoOptions;
-import com.mongodb.ServerAddress;
-import com.mongodb.WriteConcern;
-
-/**
- * Convenient factory for configuring MongoDB.
- * 
- * @author Thomas Risberg
- * @author Graeme Rocher
- * @author Oliver Gierke
- * @author Thomas Darimont
- * @author Christoph Strobl
- * @since 1.0
- * @deprecated since 1.7. Please use {@link MongoClientFactoryBean} instead.
- */
-@Deprecated
-public class MongoFactoryBean extends AbstractFactoryBean<Mongo> implements PersistenceExceptionTranslator {
-
-	private static final PersistenceExceptionTranslator DEFAULT_EXCEPTION_TRANSLATOR = new MongoExceptionTranslator();
-
-	private MongoOptions mongoOptions;
-	private String host;
-	private Integer port;
-	private WriteConcern writeConcern;
-	private List<ServerAddress> replicaSetSeeds;
-	private List<ServerAddress> replicaPair;
-	private PersistenceExceptionTranslator exceptionTranslator = DEFAULT_EXCEPTION_TRANSLATOR;
-
-	/**
-	 * @param mongoOptions
-	 */
-	public void setMongoOptions(MongoOptions mongoOptions) {
-		this.mongoOptions = mongoOptions;
-	}
-
-	public void setReplicaSetSeeds(ServerAddress[] replicaSetSeeds) {
-		this.replicaSetSeeds = filterNonNullElementsAsList(replicaSetSeeds);
-	}
-
-	/**
-	 * @deprecated use {@link #setReplicaSetSeeds(ServerAddress[])} instead
-	 * @param replicaPair
-	 */
-	@Deprecated
-	public void setReplicaPair(ServerAddress[] replicaPair) {
-		this.replicaPair = filterNonNullElementsAsList(replicaPair);
-	}
-
-	/**
-	 * Configures the host to connect to.
-	 * 
-	 * @param host
-	 */
-	public void setHost(String host) {
-		this.host = host;
-	}
-
-	/**
-	 * Configures the port to connect to.
-	 * 
-	 * @param port
-	 */
-	public void setPort(int port) {
-		this.port = port;
-	}
-
-	/**
-	 * Sets the {@link WriteConcern} to be configured for the {@link Mongo} instance to be created.
-	 * 
-	 * @param writeConcern
-	 */
-	public void setWriteConcern(WriteConcern writeConcern) {
-		this.writeConcern = writeConcern;
-	}
-
-	/**
-	 * Configures the {@link PersistenceExceptionTranslator} to use.
-	 * 
-	 * @param exceptionTranslator can be {@literal null}.
-	 */
-	public void setExceptionTranslator(PersistenceExceptionTranslator exceptionTranslator) {
-		this.exceptionTranslator = exceptionTranslator == null ? DEFAULT_EXCEPTION_TRANSLATOR : exceptionTranslator;
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.beans.factory.FactoryBean#getObjectType()
-	 */
-	public Class<? extends Mongo> getObjectType() {
-		return Mongo.class;
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.dao.support.PersistenceExceptionTranslator#translateExceptionIfPossible(java.lang.RuntimeException)
-	 */
-	public DataAccessException translateExceptionIfPossible(RuntimeException ex) {
-		return exceptionTranslator.translateExceptionIfPossible(ex);
-	}
-
-	/* 
-	 * (non-Javadoc)
-	 * @see org.springframework.beans.factory.config.AbstractFactoryBean#createInstance()
-	 */
-	@Override
-	protected Mongo createInstance() throws Exception {
-
-		Mongo mongo;
-		ServerAddress defaultOptions = new ServerAddress();
-
-		if (mongoOptions == null) {
-			mongoOptions = new MongoOptions();
-		}
-
-		if (!isNullOrEmpty(replicaPair)) {
-			if (replicaPair.size() < 2) {
-				throw new CannotGetMongoDbConnectionException("A replica pair must have two server entries");
-			}
-			mongo = new Mongo(replicaPair.get(0), replicaPair.get(1), mongoOptions);
-		} else if (!isNullOrEmpty(replicaSetSeeds)) {
-			mongo = new Mongo(replicaSetSeeds, mongoOptions);
-		} else {
-			String mongoHost = StringUtils.hasText(host) ? host : defaultOptions.getHost();
-			mongo = port != null ? new Mongo(new ServerAddress(mongoHost, port), mongoOptions) : new Mongo(mongoHost,
-					mongoOptions);
-		}
-
-		if (writeConcern != null) {
-			mongo.setWriteConcern(writeConcern);
-		}
-
-		return mongo;
-	}
-
-	/* 
-	 * (non-Javadoc)
-	 * @see org.springframework.beans.factory.config.AbstractFactoryBean#destroyInstance(java.lang.Object)
-	 */
-	@Override
-	protected void destroyInstance(Mongo mongo) throws Exception {
-		mongo.close();
-	}
-
-	private static boolean isNullOrEmpty(Collection<?> elements) {
-		return elements == null || elements.isEmpty();
-	}
-
-	/**
-	 * Returns the given array as {@link List} with all {@literal null} elements removed.
-	 * 
-	 * @param elements the elements to filter <T>
-	 * @return a new unmodifiable {@link List#} from the given elements without nulls
-	 */
-	private static <T> List<T> filterNonNullElementsAsList(T[] elements) {
-
-		if (elements == null) {
-			return Collections.emptyList();
-		}
-
-		List<T> candidateElements = new ArrayList<T>();
-
-		for (T element : elements) {
-			if (element != null) {
-				candidateElements.add(element);
-			}
-		}
-
-		return Collections.unmodifiableList(candidateElements);
-	}
-}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoOperations.java

@@ -1,6 +1,6 @@
 /*
- * Copyright 2011-2016 the original author or authors.
- * 
+ * Copyright 2011-2017 the original author or authors.
+ *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
@@ -23,6 +23,7 @@ import org.bson.Document;
 import org.springframework.data.geo.GeoResults;
 import org.springframework.data.mongodb.core.BulkOperations.BulkMode;
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
+import org.springframework.data.mongodb.core.aggregation.AggregationOptions;
 import org.springframework.data.mongodb.core.aggregation.AggregationResults;
 import org.springframework.data.mongodb.core.aggregation.TypedAggregation;
 import org.springframework.data.mongodb.core.convert.MongoConverter;
@@ -38,7 +39,6 @@ import org.springframework.data.mongodb.core.query.Update;
 import org.springframework.data.util.CloseableIterator;
 
 import com.mongodb.Cursor;
-import com.mongodb.DB;
 import com.mongodb.ReadPreference;
 import com.mongodb.client.MongoCollection;
 import com.mongodb.client.result.DeleteResult;
@@ -48,7 +48,7 @@ import com.mongodb.client.result.UpdateResult;
  * Interface that specifies a basic set of MongoDB operations. Implemented by {@link MongoTemplate}. Not often used but
  * a useful option for extensibility and testability (as it can be easily mocked, stubbed, or be the target of a JDK
  * proxy).
- * 
+ *
  * @author Thomas Risberg
  * @author Mark Pollack
  * @author Oliver Gierke
@@ -56,12 +56,13 @@ import com.mongodb.client.result.UpdateResult;
  * @author Chuong Ngo
  * @author Christoph Strobl
  * @author Thomas Darimont
+ * @author Maninder Singh
  */
 public interface MongoOperations {
 
 	/**
 	 * The collection name used for the specified class by this template.
-	 * 
+	 *
 	 * @param entityClass must not be {@literal null}.
 	 * @return
 	 */
@@ -71,7 +72,7 @@ public interface MongoOperations {
 	 * Execute the a MongoDB command expressed as a JSON string. This will call the method JSON.parse that is part of the
 	 * MongoDB driver to convert the JSON string to a Document. Any errors that result from executing this command will be
 	 * converted into Spring's DAO exception hierarchy.
-	 * 
+	 *
 	 * @param jsonCommand a MongoDB command expressed as a JSON string.
 	 */
 	Document executeCommand(String jsonCommand);
@@ -79,7 +80,7 @@ public interface MongoOperations {
 	/**
 	 * Execute a MongoDB command. Any errors that result from executing this command will be converted into Spring's DAO
 	 * exception hierarchy.
-	 * 
+	 *
 	 * @param command a MongoDB command
 	 */
 	Document executeCommand(Document command);
@@ -87,7 +88,7 @@ public interface MongoOperations {
 	/**
 	 * Execute a MongoDB command. Any errors that result from executing this command will be converted into Spring's data
 	 * access exception hierarchy.
-	 * 
+	 *
 	 * @param command a MongoDB command, must not be {@literal null}.
 	 * @param readPreference read preferences to use, can be {@literal null}.
 	 * @return
@@ -97,7 +98,7 @@ public interface MongoOperations {
 
 	/**
 	 * Execute a MongoDB query and iterate over the query results on a per-document basis with a DocumentCallbackHandler.
-	 * 
+	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
 	 *          specification
 	 * @param collectionName name of the collection to retrieve the objects from
@@ -109,7 +110,7 @@ public interface MongoOperations {
 	 * Executes a {@link DbCallback} translating any exceptions as necessary.
 	 * <p/>
 	 * Allows for returning a result object, that is a domain object or a collection of domain objects.
-	 * 
+	 *
 	 * @param <T> return type
 	 * @param action callback object that specifies the MongoDB actions to perform on the passed in DB instance.
 	 * @return a result object returned by the action or <tt>null</tt>
@@ -120,7 +121,7 @@ public interface MongoOperations {
 	 * Executes the given {@link CollectionCallback} on the entity collection of the specified class.
 	 * <p/>
 	 * Allows for returning a result object, that is a domain object or a collection of domain objects.
-	 * 
+	 *
 	 * @param entityClass class that determines the collection to use
 	 * @param <T> return type
 	 * @param action callback object that specifies the MongoDB action
@@ -132,7 +133,7 @@ public interface MongoOperations {
 	 * Executes the given {@link CollectionCallback} on the collection of the given name.
 	 * <p/>
 	 * Allows for returning a result object, that is a domain object or a collection of domain objects.
-	 * 
+	 *
 	 * @param <T> return type
 	 * @param collectionName the name of the collection that specifies which DBCollection instance will be passed into
 	 * @param action callback object that specifies the MongoDB action the callback action.
@@ -145,7 +146,7 @@ public interface MongoOperations {
 	 * {@link Cursor}.
 	 * <p>
 	 * Returns a {@link CloseableIterator} that wraps the a Mongo DB {@link Cursor} that needs to be closed.
-	 * 
+	 *
 	 * @param <T> element return type
 	 * @param query must not be {@literal null}.
 	 * @param entityType must not be {@literal null}.
@@ -159,7 +160,7 @@ public interface MongoOperations {
 	 * by a Mongo DB {@link Cursor}.
 	 * <p>
 	 * Returns a {@link CloseableIterator} that wraps the a Mongo DB {@link Cursor} that needs to be closed.
-	 * 
+	 *
 	 * @param <T> element return type
 	 * @param query must not be {@literal null}.
 	 * @param entityType must not be {@literal null}.
@@ -171,7 +172,7 @@ public interface MongoOperations {
 
 	/**
 	 * Create an uncapped collection with a name based on the provided entity class.
-	 * 
+	 *
 	 * @param entityClass class that determines the collection to create
 	 * @return the created collection
 	 */
@@ -179,7 +180,7 @@ public interface MongoOperations {
 
 	/**
 	 * Create a collection with a name based on the provided entity class using the options.
-	 * 
+	 *
 	 * @param entityClass class that determines the collection to create
 	 * @param collectionOptions options to use when creating the collection.
 	 * @return the created collection
@@ -188,7 +189,7 @@ public interface MongoOperations {
 
 	/**
 	 * Create an uncapped collection with the provided name.
-	 * 
+	 *
 	 * @param collectionName name of the collection
 	 * @return the created collection
 	 */
@@ -196,7 +197,7 @@ public interface MongoOperations {
 
 	/**
 	 * Create a collection with the provided name and options.
-	 * 
+	 *
 	 * @param collectionName name of the collection
 	 * @param collectionOptions options to use when creating the collection.
 	 * @return the created collection
@@ -205,7 +206,7 @@ public interface MongoOperations {
 
 	/**
 	 * A set of collection names.
-	 * 
+	 *
 	 * @return list of collection names
 	 */
 	Set<String> getCollectionNames();
@@ -214,7 +215,7 @@ public interface MongoOperations {
 	 * Get a collection by name, creating it if it doesn't exist.
 	 * <p/>
 	 * Translate any exceptions as necessary.
-	 * 
+	 *
 	 * @param collectionName name of the collection
 	 * @return an existing collection or a newly created one.
 	 */
@@ -224,7 +225,7 @@ public interface MongoOperations {
 	 * Check to see if a collection with a name indicated by the entity class exists.
 	 * <p/>
 	 * Translate any exceptions as necessary.
-	 * 
+	 *
 	 * @param entityClass class that determines the name of the collection
 	 * @return true if a collection with the given name is found, false otherwise.
 	 */
@@ -234,7 +235,7 @@ public interface MongoOperations {
 	 * Check to see if a collection with a given name exists.
 	 * <p/>
 	 * Translate any exceptions as necessary.
-	 * 
+	 *
 	 * @param collectionName name of the collection
 	 * @return true if a collection with the given name is found, false otherwise.
 	 */
@@ -244,7 +245,7 @@ public interface MongoOperations {
 	 * Drop the collection with the name indicated by the entity class.
 	 * <p/>
 	 * Translate any exceptions as necessary.
-	 * 
+	 *
 	 * @param entityClass class that determines the collection to drop/delete.
 	 */
 	<T> void dropCollection(Class<T> entityClass);
@@ -253,28 +254,28 @@ public interface MongoOperations {
 	 * Drop the collection with the given name.
 	 * <p/>
 	 * Translate any exceptions as necessary.
-	 * 
+	 *
 	 * @param collectionName name of the collection to drop/delete.
 	 */
 	void dropCollection(String collectionName);
 
 	/**
 	 * Returns the operations that can be performed on indexes
-	 * 
+	 *
 	 * @return index operations on the named collection
 	 */
 	IndexOperations indexOps(String collectionName);
 
 	/**
 	 * Returns the operations that can be performed on indexes
-	 * 
+	 *
 	 * @return index operations on the named collection associated with the given entity class
 	 */
 	IndexOperations indexOps(Class<?> entityClass);
 
 	/**
 	 * Returns the {@link ScriptOperations} that can be performed on {@link com.mongodb.DB} level.
-	 * 
+	 *
 	 * @return
 	 * @since 1.7
 	 */
@@ -282,7 +283,7 @@ public interface MongoOperations {
 
 	/**
 	 * Returns a new {@link BulkOperations} for the given collection.
-	 * 
+	 *
 	 * @param mode the {@link BulkMode} to use for bulk operations, must not be {@literal null}.
 	 * @param collectionName the name of the collection to work on, must not be {@literal null} or empty.
 	 * @return {@link BulkOperations} on the named collection
@@ -291,7 +292,7 @@ public interface MongoOperations {
 
 	/**
 	 * Returns a new {@link BulkOperations} for the given entity type.
-	 * 
+	 *
 	 * @param mode the {@link BulkMode} to use for bulk operations, must not be {@literal null}.
 	 * @param entityType the name of the entity class, must not be {@literal null}.
 	 * @return {@link BulkOperations} on the named collection associated of the given entity class.
@@ -300,7 +301,7 @@ public interface MongoOperations {
 
 	/**
 	 * Returns a new {@link BulkOperations} for the given entity type and collection name.
-	 * 
+	 *
 	 * @param mode the {@link BulkMode} to use for bulk operations, must not be {@literal null}.
 	 * @param entityClass the name of the entity class, must not be {@literal null}.
 	 * @param collectionName the name of the collection to work on, must not be {@literal null} or empty.
@@ -316,7 +317,7 @@ public interface MongoOperations {
 	 * <p/>
 	 * If your collection does not contain a homogeneous collection of types, this operation will not be an efficient way
 	 * to map objects since the test for class type is done in the client and not on the server.
-	 * 
+	 *
 	 * @param entityClass the parameterized type of the returned list
 	 * @return the converted collection
 	 */
@@ -330,7 +331,7 @@ public interface MongoOperations {
 	 * <p/>
 	 * If your collection does not contain a homogeneous collection of types, this operation will not be an efficient way
 	 * to map objects since the test for class type is done in the client and not on the server.
-	 * 
+	 *
 	 * @param entityClass the parameterized type of the returned list.
 	 * @param collectionName name of the collection to retrieve the objects from
 	 * @return the converted collection
@@ -340,7 +341,7 @@ public interface MongoOperations {
 	/**
 	 * Execute a group operation over the entire collection. The group operation entity class should match the 'shape' of
 	 * the returned object that takes int account the initial document structure as well as any finalize functions.
-	 * 
+	 *
 	 * @param criteria The criteria that restricts the row that are considered for grouping. If not specified all rows are
 	 *          considered.
 	 * @param inputCollectionName the collection where the group operation will read from
@@ -355,7 +356,7 @@ public interface MongoOperations {
 	 * Execute a group operation restricting the rows to those which match the provided Criteria. The group operation
 	 * entity class should match the 'shape' of the returned object that takes int account the initial document structure
 	 * as well as any finalize functions.
-	 * 
+	 *
 	 * @param criteria The criteria that restricts the row that are considered for grouping. If not specified all rows are
 	 *          considered.
 	 * @param inputCollectionName the collection where the group operation will read from
@@ -369,7 +370,7 @@ public interface MongoOperations {
 	/**
 	 * Execute an aggregation operation. The raw results will be mapped to the given entity class. The name of the
 	 * inputCollection is derived from the inputType of the aggregation.
-	 * 
+	 *
 	 * @param aggregation The {@link TypedAggregation} specification holding the aggregation operations, must not be
 	 *          {@literal null}.
 	 * @param collectionName The name of the input collection to use for the aggreation.
@@ -382,7 +383,7 @@ public interface MongoOperations {
 	/**
 	 * Execute an aggregation operation. The raw results will be mapped to the given entity class. The name of the
 	 * inputCollection is derived from the inputType of the aggregation.
-	 * 
+	 *
 	 * @param aggregation The {@link TypedAggregation} specification holding the aggregation operations, must not be
 	 *          {@literal null}.
 	 * @param outputType The parameterized type of the returned list, must not be {@literal null}.
@@ -393,7 +394,7 @@ public interface MongoOperations {
 
 	/**
 	 * Execute an aggregation operation. The raw results will be mapped to the given entity class.
-	 * 
+	 *
 	 * @param aggregation The {@link Aggregation} specification holding the aggregation operations, must not be
 	 *          {@literal null}.
 	 * @param inputType the inputType where the aggregation operation will read from, must not be {@literal null} or
@@ -406,7 +407,7 @@ public interface MongoOperations {
 
 	/**
 	 * Execute an aggregation operation. The raw results will be mapped to the given entity class.
-	 * 
+	 *
 	 * @param aggregation The {@link Aggregation} specification holding the aggregation operations, must not be
 	 *          {@literal null}.
 	 * @param collectionName the collection where the aggregation operation will read from, must not be {@literal null} or
@@ -417,9 +418,84 @@ public interface MongoOperations {
 	 */
 	<O> AggregationResults<O> aggregate(Aggregation aggregation, String collectionName, Class<O> outputType);
 
+	/**
+	 * Execute an aggregation operation backed by a Mongo DB {@link Cursor}.
+	 * <p>
+	 * Returns a {@link CloseableIterator} that wraps the a Mongo DB {@link Cursor} that needs to be closed. The raw
+	 * results will be mapped to the given entity class. The name of the inputCollection is derived from the inputType of
+	 * the aggregation.
+	 * <p>
+	 * Aggregation streaming can't be used with {@link AggregationOptions#isExplain() aggregation explain}. Enabling
+	 * explanation mode will throw an {@link IllegalArgumentException}.
+	 *
+	 * @param aggregation The {@link TypedAggregation} specification holding the aggregation operations, must not be
+	 *          {@literal null}.
+	 * @param collectionName The name of the input collection to use for the aggreation.
+	 * @param outputType The parameterized type of the returned list, must not be {@literal null}.
+	 * @return The results of the aggregation operation.
+	 * @since 2.0
+	 */
+	<O> CloseableIterator<O> aggregateStream(TypedAggregation<?> aggregation, String collectionName, Class<O> outputType);
+
+	/**
+	 * Execute an aggregation operation backed by a Mongo DB {@link Cursor}.
+	 * <p/>
+	 * Returns a {@link CloseableIterator} that wraps the a Mongo DB {@link Cursor} that needs to be closed. The raw
+	 * results will be mapped to the given entity class and are returned as stream. The name of the inputCollection is
+	 * derived from the inputType of the aggregation.
+	 * <p/>
+	 * Aggregation streaming can't be used with {@link AggregationOptions#isExplain() aggregation explain}. Enabling
+	 * explanation mode will throw an {@link IllegalArgumentException}.
+	 *
+	 * @param aggregation The {@link TypedAggregation} specification holding the aggregation operations, must not be
+	 *          {@literal null}.
+	 * @param outputType The parameterized type of the returned list, must not be {@literal null}.
+	 * @return The results of the aggregation operation.
+	 * @since 2.0
+	 */
+	<O> CloseableIterator<O> aggregateStream(TypedAggregation<?> aggregation, Class<O> outputType);
+
+	/**
+	 * Execute an aggregation operation backed by a Mongo DB {@link Cursor}.
+	 * <p/>
+	 * Returns a {@link CloseableIterator} that wraps the a Mongo DB {@link Cursor} that needs to be closed. The raw
+	 * results will be mapped to the given entity class.
+	 * <p/>
+	 * Aggregation streaming can't be used with {@link AggregationOptions#isExplain() aggregation explain}. Enabling
+	 * explanation mode will throw an {@link IllegalArgumentException}.
+	 *
+	 * @param aggregation The {@link Aggregation} specification holding the aggregation operations, must not be
+	 *          {@literal null}.
+	 * @param inputType the inputType where the aggregation operation will read from, must not be {@literal null} or
+	 *          empty.
+	 * @param outputType The parameterized type of the returned list, must not be {@literal null}.
+	 * @return The results of the aggregation operation.
+	 * @since 2.0
+	 */
+	<O> CloseableIterator<O> aggregateStream(Aggregation aggregation, Class<?> inputType, Class<O> outputType);
+
+	/**
+	 * Execute an aggregation operation backed by a Mongo DB {@link Cursor}.
+	 * <p/>
+	 * Returns a {@link CloseableIterator} that wraps the a Mongo DB {@link Cursor} that needs to be closed. The raw
+	 * results will be mapped to the given entity class.
+	 * <p/>
+	 * Aggregation streaming can't be used with {@link AggregationOptions#isExplain() aggregation explain}. Enabling
+	 * explanation mode will throw an {@link IllegalArgumentException}.
+	 *
+	 * @param aggregation The {@link Aggregation} specification holding the aggregation operations, must not be
+	 *          {@literal null}.
+	 * @param collectionName the collection where the aggregation operation will read from, must not be {@literal null} or
+	 *          empty.
+	 * @param outputType The parameterized type of the returned list, must not be {@literal null}.
+	 * @return The results of the aggregation operation.
+	 * @since 2.0
+	 */
+	<O> CloseableIterator<O> aggregateStream(Aggregation aggregation, String collectionName, Class<O> outputType);
+
 	/**
 	 * Execute a map-reduce operation. The map-reduce operation will be formed with an output type of INLINE
-	 * 
+	 *
 	 * @param inputCollectionName the collection where the map-reduce will read from
 	 * @param mapFunction The JavaScript map function
 	 * @param reduceFunction The JavaScript reduce function
@@ -432,7 +508,7 @@ public interface MongoOperations {
 
 	/**
 	 * Execute a map-reduce operation that takes additional map-reduce options.
-	 * 
+	 *
 	 * @param inputCollectionName the collection where the map-reduce will read from
 	 * @param mapFunction The JavaScript map function
 	 * @param reduceFunction The JavaScript reduce function
@@ -446,7 +522,7 @@ public interface MongoOperations {
 	/**
 	 * Execute a map-reduce operation that takes a query. The map-reduce operation will be formed with an output type of
 	 * INLINE
-	 * 
+	 *
 	 * @param query The query to use to select the data for the map phase
 	 * @param inputCollectionName the collection where the map-reduce will read from
 	 * @param mapFunction The JavaScript map function
@@ -460,7 +536,7 @@ public interface MongoOperations {
 
 	/**
 	 * Execute a map-reduce operation that takes a query and additional map-reduce options
-	 * 
+	 *
 	 * @param query The query to use to select the data for the map phase
 	 * @param inputCollectionName the collection where the map-reduce will read from
 	 * @param mapFunction The JavaScript map function
@@ -477,7 +553,7 @@ public interface MongoOperations {
 	 * information to determine the collection the query is ran against. Note, that MongoDB limits the number of results
 	 * by default. Make sure to add an explicit limit to the {@link NearQuery} if you expect a particular number of
 	 * results.
-	 * 
+	 *
 	 * @param near must not be {@literal null}.
 	 * @param entityClass must not be {@literal null}.
 	 * @return
@@ -488,7 +564,7 @@ public interface MongoOperations {
 	 * Returns {@link GeoResults} for all entities matching the given {@link NearQuery}. Note, that MongoDB limits the
 	 * number of results by default. Make sure to add an explicit limit to the {@link NearQuery} if you expect a
 	 * particular number of results.
-	 * 
+	 *
 	 * @param near must not be {@literal null}.
 	 * @param entityClass must not be {@literal null}.
 	 * @param collectionName the collection to trigger the query against. If no collection name is given the entity class
@@ -506,7 +582,7 @@ public interface MongoOperations {
 	 * <p/>
 	 * The query is specified as a {@link Query} which can be created either using the {@link BasicQuery} or the more
 	 * feature rich {@link Query}.
-	 * 
+	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
 	 *          specification
 	 * @param entityClass the parameterized type of the returned list.
@@ -523,7 +599,7 @@ public interface MongoOperations {
 	 * <p/>
 	 * The query is specified as a {@link Query} which can be created either using the {@link BasicQuery} or the more
 	 * feature rich {@link Query}.
-	 * 
+	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
 	 *          specification
 	 * @param entityClass the parameterized type of the returned list.
@@ -534,7 +610,7 @@ public interface MongoOperations {
 
 	/**
 	 * Determine result of given {@link Query} contains at least one element.
-	 * 
+	 *
 	 * @param query the {@link Query} class that specifies the criteria used to find a record.
 	 * @param collectionName name of the collection to check for objects.
 	 * @return
@@ -543,7 +619,7 @@ public interface MongoOperations {
 
 	/**
 	 * Determine result of given {@link Query} contains at least one element.
-	 * 
+	 *
 	 * @param query the {@link Query} class that specifies the criteria used to find a record.
 	 * @param entityClass the parameterized type.
 	 * @return
@@ -552,7 +628,7 @@ public interface MongoOperations {
 
 	/**
 	 * Determine result of given {@link Query} contains at least one element.
-	 * 
+	 *
 	 * @param query the {@link Query} class that specifies the criteria used to find a record.
 	 * @param entityClass the parameterized type.
 	 * @param collectionName name of the collection to check for objects.
@@ -568,7 +644,7 @@ public interface MongoOperations {
 	 * <p/>
 	 * The query is specified as a {@link Query} which can be created either using the {@link BasicQuery} or the more
 	 * feature rich {@link Query}.
-	 * 
+	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
 	 *          specification
 	 * @param entityClass the parameterized type of the returned list.
@@ -584,7 +660,7 @@ public interface MongoOperations {
 	 * <p/>
 	 * The query is specified as a {@link Query} which can be created either using the {@link BasicQuery} or the more
 	 * feature rich {@link Query}.
-	 * 
+	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
 	 *          specification
 	 * @param entityClass the parameterized type of the returned list.
@@ -596,7 +672,7 @@ public interface MongoOperations {
 	/**
 	 * Returns a document with the given id mapped onto the given class. The collection the query is ran against will be
 	 * derived from the given target class as well.
-	 * 
+	 *
 	 * @param <T>
 	 * @param id the id of the document to return.
 	 * @param entityClass the type the document shall be converted into.
@@ -606,7 +682,7 @@ public interface MongoOperations {
 
 	/**
 	 * Returns the document with the given id from the given collection mapped onto the given target class.
-	 * 
+	 *
 	 * @param id the id of the document to return
 	 * @param entityClass the type to convert the document to
 	 * @param collectionName the collection to query for the document
@@ -616,9 +692,9 @@ public interface MongoOperations {
 	<T> T findById(Object id, Class<T> entityClass, String collectionName);
 
 	/**
-	 * Triggers <a href="http://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify
-	 * <a/> to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query}.
-	 * 
+	 * Triggers <a href="http://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
+	 * to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query}.
+	 *
 	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
 	 *          fields specification.
 	 * @param update the {@link Update} to apply on matching documents.
@@ -628,9 +704,9 @@ public interface MongoOperations {
 	<T> T findAndModify(Query query, Update update, Class<T> entityClass);
 
 	/**
-	 * Triggers <a href="http://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify
-	 * <a/> to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query}.
-	 * 
+	 * Triggers <a href="http://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
+	 * to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query}.
+	 *
 	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
 	 *          fields specification.
 	 * @param update the {@link Update} to apply on matching documents.
@@ -641,10 +717,10 @@ public interface MongoOperations {
 	<T> T findAndModify(Query query, Update update, Class<T> entityClass, String collectionName);
 
 	/**
-	 * Triggers <a href="http://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify
-	 * <a/> to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query} taking
+	 * Triggers <a href="http://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
+	 * to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query} taking
 	 * {@link FindAndModifyOptions} into account.
-	 * 
+	 *
 	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
 	 *          fields specification.
 	 * @param update the {@link Update} to apply on matching documents.
@@ -655,10 +731,10 @@ public interface MongoOperations {
 	<T> T findAndModify(Query query, Update update, FindAndModifyOptions options, Class<T> entityClass);
 
 	/**
-	 * Triggers <a href="http://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify
-	 * <a/> to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query} taking
+	 * Triggers <a href="http://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
+	 * to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query} taking
 	 * {@link FindAndModifyOptions} into account.
-	 * 
+	 *
 	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
 	 *          fields specification.
 	 * @param update the {@link Update} to apply on matching documents.
@@ -679,7 +755,7 @@ public interface MongoOperations {
 	 * <p/>
 	 * The query is specified as a {@link Query} which can be created either using the {@link BasicQuery} or the more
 	 * feature rich {@link Query}.
-	 * 
+	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
 	 *          specification
 	 * @param entityClass the parameterized type of the returned list.
@@ -696,7 +772,7 @@ public interface MongoOperations {
 	 * <p/>
 	 * The query is specified as a {@link Query} which can be created either using the {@link BasicQuery} or the more
 	 * feature rich {@link Query}.
-	 * 
+	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
 	 *          specification
 	 * @param entityClass the parameterized type of the returned list.
@@ -707,7 +783,7 @@ public interface MongoOperations {
 
 	/**
 	 * Returns the number of documents for the given {@link Query} by querying the collection of the given entity class.
-	 * 
+	 *
 	 * @param query
 	 * @param entityClass must not be {@literal null}.
 	 * @return
@@ -718,7 +794,7 @@ public interface MongoOperations {
 	 * Returns the number of documents for the given {@link Query} querying the given collection. The given {@link Query}
 	 * must solely consist of document field references as we lack type information to map potential property references
 	 * onto document fields. TO make sure the query gets mapped, use {@link #count(Query, Class, String)}.
-	 * 
+	 *
 	 * @param query
 	 * @param collectionName must not be {@literal null} or empty.
 	 * @return
@@ -729,7 +805,7 @@ public interface MongoOperations {
 	/**
 	 * Returns the number of documents for the given {@link Query} by querying the given collection using the given entity
 	 * class to map the given {@link Query}.
-	 * 
+	 *
 	 * @param query
 	 * @param entityClass must not be {@literal null}.
 	 * @param collectionName must not be {@literal null} or empty.
@@ -750,7 +826,7 @@ public interface MongoOperations {
 	 * <p/>
 	 * <p/>
 	 * Insert is used to initially store the object into the database. To update an existing object use the save method.
-	 * 
+	 *
 	 * @param objectToSave the object to store in the collection.
 	 */
 	void insert(Object objectToSave);
@@ -762,7 +838,7 @@ public interface MongoOperations {
 	 * configured otherwise, an instance of MappingMongoConverter will be used.
 	 * <p/>
 	 * Insert is used to initially store the object into the database. To update an existing object use the save method.
-	 * 
+	 *
 	 * @param objectToSave the object to store in the collection
 	 * @param collectionName name of the collection to store the object in
 	 */
@@ -770,7 +846,7 @@ public interface MongoOperations {
 
 	/**
 	 * Insert a Collection of objects into a collection in a single batch write to the database.
-	 * 
+	 *
 	 * @param batchToSave the list of objects to save.
 	 * @param entityClass class that determines the collection to use
 	 */
@@ -778,7 +854,7 @@ public interface MongoOperations {
 
 	/**
 	 * Insert a list of objects into the specified collection in a single batch write to the database.
-	 * 
+	 *
 	 * @param batchToSave the list of objects to save.
 	 * @param collectionName name of the collection to store the object in
 	 */
@@ -787,7 +863,7 @@ public interface MongoOperations {
 	/**
 	 * Insert a mixed Collection of objects into a database collection determining the collection name to use based on the
 	 * class.
-	 * 
+	 *
 	 * @param collectionToSave the list of objects to save.
 	 */
 	void insertAll(Collection<? extends Object> objectsToSave);
@@ -804,7 +880,7 @@ public interface MongoOperations {
 	 * property type will be handled by Spring's BeanWrapper class that leverages Type Conversion API. See
 	 * <a href="http://docs.spring.io/spring/docs/current/spring-framework-reference/html/validation.html#core-convert" >
 	 * Spring's Type Conversion"</a> for more details.
-	 * 
+	 *
 	 * @param objectToSave the object to store in the collection
 	 */
 	void save(Object objectToSave);
@@ -821,7 +897,7 @@ public interface MongoOperations {
 	 * property type will be handled by Spring's BeanWrapper class that leverages Type Cobnversion API. See <a
 	 * http://docs.spring.io/spring/docs/current/spring-framework-reference/html/validation.html#core-convert">Spring's
 	 * Type Conversion"</a> for more details.
-	 * 
+	 *
 	 * @param objectToSave the object to store in the collection
 	 * @param collectionName name of the collection to store the object in
 	 */
@@ -830,7 +906,7 @@ public interface MongoOperations {
 	/**
 	 * Performs an upsert. If no document is found that matches the query, a new document is created and inserted by
 	 * combining the query document and the update document.
-	 * 
+	 *
 	 * @param query the query document that specifies the criteria used to select a record to be upserted
 	 * @param update the update document that contains the updated object or $ operators to manipulate the existing object
 	 * @param entityClass class that determines the collection to use
@@ -841,7 +917,7 @@ public interface MongoOperations {
 	/**
 	 * Performs an upsert. If no document is found that matches the query, a new document is created and inserted by
 	 * combining the query document and the update document.
-	 * 
+	 *
 	 * @param query the query document that specifies the criteria used to select a record to be updated
 	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
 	 *          object.
@@ -853,7 +929,7 @@ public interface MongoOperations {
 	/**
 	 * Performs an upsert. If no document is found that matches the query, a new document is created and inserted by
 	 * combining the query document and the update document.
-	 * 
+	 *
 	 * @param query the query document that specifies the criteria used to select a record to be upserted
 	 * @param update the update document that contains the updated object or $ operators to manipulate the existing object
 	 * @param entityClass class of the pojo to be operated on
@@ -865,7 +941,7 @@ public interface MongoOperations {
 	/**
 	 * Updates the first object that is found in the collection of the entity class that matches the query document with
 	 * the provided update document.
-	 * 
+	 *
 	 * @param query the query document that specifies the criteria used to select a record to be updated
 	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
 	 *          object.
@@ -877,7 +953,7 @@ public interface MongoOperations {
 	/**
 	 * Updates the first object that is found in the specified collection that matches the query document criteria with
 	 * the provided updated document.
-	 * 
+	 *
 	 * @param query the query document that specifies the criteria used to select a record to be updated
 	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
 	 *          object.
@@ -889,7 +965,7 @@ public interface MongoOperations {
 	/**
 	 * Updates the first object that is found in the specified collection that matches the query document criteria with
 	 * the provided updated document.
-	 * 
+	 *
 	 * @param query the query document that specifies the criteria used to select a record to be updated
 	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
 	 *          object.
@@ -902,7 +978,7 @@ public interface MongoOperations {
 	/**
 	 * Updates all objects that are found in the collection for the entity class that matches the query document criteria
 	 * with the provided updated document.
-	 * 
+	 *
 	 * @param query the query document that specifies the criteria used to select a record to be updated
 	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
 	 *          object.
@@ -914,7 +990,7 @@ public interface MongoOperations {
 	/**
 	 * Updates all objects that are found in the specified collection that matches the query document criteria with the
 	 * provided updated document.
-	 * 
+	 *
 	 * @param query the query document that specifies the criteria used to select a record to be updated
 	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
 	 *          object.
@@ -926,7 +1002,7 @@ public interface MongoOperations {
 	/**
 	 * Updates all objects that are found in the collection for the entity class that matches the query document criteria
 	 * with the provided updated document.
-	 * 
+	 *
 	 * @param query the query document that specifies the criteria used to select a record to be updated
 	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
 	 *          object.
@@ -938,14 +1014,14 @@ public interface MongoOperations {
 
 	/**
 	 * Remove the given object from the collection by id.
-	 * 
+	 *
 	 * @param object
 	 */
 	DeleteResult remove(Object object);
 
 	/**
 	 * Removes the given object from the given collection.
-	 * 
+	 *
 	 * @param object
 	 * @param collection must not be {@literal null} or empty.
 	 */
@@ -954,7 +1030,7 @@ public interface MongoOperations {
 	/**
 	 * Remove all documents that match the provided query document criteria from the the collection used to store the
 	 * entityClass. The Class parameter is also used to help convert the Id of the object if it is present in the query.
-	 * 
+	 *
 	 * @param query
 	 * @param entityClass
 	 */
@@ -963,7 +1039,7 @@ public interface MongoOperations {
 	/**
 	 * Remove all documents that match the provided query document criteria from the the collection used to store the
 	 * entityClass. The Class parameter is also used to help convert the Id of the object if it is present in the query.
-	 * 
+	 *
 	 * @param query
 	 * @param entityClass
 	 * @param collectionName
@@ -973,7 +1049,7 @@ public interface MongoOperations {
 	/**
 	 * Remove all documents from the specified collection that match the provided query document criteria. There is no
 	 * conversion/mapping done for any criteria using the id field.
-	 * 
+	 *
 	 * @param query the query document that specifies the criteria used to remove a record
 	 * @param collectionName name of the collection where the objects will removed
 	 */
@@ -981,7 +1057,7 @@ public interface MongoOperations {
 
 	/**
 	 * Returns and removes all documents form the specified collection that match the provided query.
-	 * 
+	 *
 	 * @param query
 	 * @param collectionName
 	 * @return
@@ -991,7 +1067,7 @@ public interface MongoOperations {
 
 	/**
 	 * Returns and removes all documents matching the given query form the collection used to store the entityClass.
-	 * 
+	 *
 	 * @param query
 	 * @param entityClass
 	 * @return
@@ -1003,7 +1079,7 @@ public interface MongoOperations {
 	 * Returns and removes all documents that match the provided query document criteria from the the collection used to
 	 * store the entityClass. The Class parameter is also used to help convert the Id of the object if it is present in
 	 * the query.
-	 * 
+	 *
 	 * @param query
 	 * @param entityClass
 	 * @param collectionName
@@ -1014,7 +1090,7 @@ public interface MongoOperations {
 
 	/**
 	 * Returns the underlying {@link MongoConverter}.
-	 * 
+	 *
 	 * @return
 	 */
 	MongoConverter getConverter();

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoOptionsFactoryBean.java

@@ -1,255 +0,0 @@
-/*
- * Copyright 2010-2015 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import javax.net.ssl.SSLSocketFactory;
-
-import org.springframework.beans.factory.config.AbstractFactoryBean;
-import org.springframework.data.mongodb.util.MongoClientVersion;
-
-import com.mongodb.MongoOptions;
-
-/**
- * A factory bean for construction of a {@link MongoOptions} instance. In case used with MongoDB Java driver version 3
- * porperties not suppprted by the driver will be ignored.
- *
- * @author Graeme Rocher
- * @author Mark Pollack
- * @author Mike Saavedra
- * @author Thomas Darimont
- * @author Christoph Strobl
- * @deprecated since 1.7. Please use {@link MongoClientOptionsFactoryBean} instead.
- */
-@Deprecated
-public class MongoOptionsFactoryBean extends AbstractFactoryBean<MongoOptions> {
-
-	private static final MongoOptions DEFAULT_MONGO_OPTIONS = new MongoOptions();
-
-	private int connectionsPerHost = DEFAULT_MONGO_OPTIONS.getConnectionsPerHost();
-	private int threadsAllowedToBlockForConnectionMultiplier = DEFAULT_MONGO_OPTIONS
-			.getThreadsAllowedToBlockForConnectionMultiplier();
-	private int maxWaitTime = DEFAULT_MONGO_OPTIONS.getMaxWaitTime();
-	private int connectTimeout = DEFAULT_MONGO_OPTIONS.getConnectTimeout();
-	private int socketTimeout = DEFAULT_MONGO_OPTIONS.getSocketTimeout();
-	private boolean socketKeepAlive = DEFAULT_MONGO_OPTIONS.isSocketKeepAlive();
-	private int writeNumber = DEFAULT_MONGO_OPTIONS.getW();
-	private int writeTimeout = DEFAULT_MONGO_OPTIONS.getWtimeout();
-	private boolean writeFsync = DEFAULT_MONGO_OPTIONS.isFsync();
-
-	private boolean autoConnectRetry = !MongoClientVersion.isMongo3Driver() ? ReflectiveMongoOptionsInvoker
-			.getAutoConnectRetry(DEFAULT_MONGO_OPTIONS) : false;
-	private long maxAutoConnectRetryTime = !MongoClientVersion.isMongo3Driver() ? ReflectiveMongoOptionsInvoker
-			.getMaxAutoConnectRetryTime(DEFAULT_MONGO_OPTIONS) : -1;
-	private boolean slaveOk = !MongoClientVersion.isMongo3Driver() ? ReflectiveMongoOptionsInvoker
-			.getSlaveOk(DEFAULT_MONGO_OPTIONS) : false;
-
-	private boolean ssl;
-	private SSLSocketFactory sslSocketFactory;
-
-	/**
-	 * Configures the maximum number of connections allowed per host until we will block.
-	 * 
-	 * @param connectionsPerHost
-	 */
-	public void setConnectionsPerHost(int connectionsPerHost) {
-		this.connectionsPerHost = connectionsPerHost;
-	}
-
-	/**
-	 * A multiplier for connectionsPerHost for # of threads that can block a connection. If connectionsPerHost is 10, and
-	 * threadsAllowedToBlockForConnectionMultiplier is 5, then 50 threads can block. If more threads try to block an
-	 * exception will be thrown.
-	 * 
-	 * @param threadsAllowedToBlockForConnectionMultiplier
-	 */
-	public void setThreadsAllowedToBlockForConnectionMultiplier(int threadsAllowedToBlockForConnectionMultiplier) {
-		this.threadsAllowedToBlockForConnectionMultiplier = threadsAllowedToBlockForConnectionMultiplier;
-	}
-
-	/**
-	 * Max wait time of a blocking thread for a connection.
-	 * 
-	 * @param maxWaitTime
-	 */
-	public void setMaxWaitTime(int maxWaitTime) {
-		this.maxWaitTime = maxWaitTime;
-	}
-
-	/**
-	 * Configures the connect timeout in milliseconds. Defaults to 0 (infinite time).
-	 * 
-	 * @param connectTimeout
-	 */
-	public void setConnectTimeout(int connectTimeout) {
-		this.connectTimeout = connectTimeout;
-	}
-
-	/**
-	 * Configures the socket timeout. Defaults to 0 (infinite time).
-	 * 
-	 * @param socketTimeout
-	 */
-	public void setSocketTimeout(int socketTimeout) {
-		this.socketTimeout = socketTimeout;
-	}
-
-	/**
-	 * Configures whether or not to have socket keep alive turned on (SO_KEEPALIVE). Defaults to {@literal false}.
-	 * 
-	 * @param socketKeepAlive
-	 */
-	public void setSocketKeepAlive(boolean socketKeepAlive) {
-		this.socketKeepAlive = socketKeepAlive;
-	}
-
-	/**
-	 * This specifies the number of servers to wait for on the write operation, and exception raising behavior. The 'w'
-	 * option to the getlasterror command. Defaults to 0.
-	 * <ul>
-	 * <li>-1 = don't even report network errors</li>
-	 * <li>0 = default, don't call getLastError by default</li>
-	 * <li>1 = basic, call getLastError, but don't wait for slaves</li>
-	 * <li>2 += wait for slaves</li>
-	 * </ul>
-	 * 
-	 * @param writeNumber the number of servers to wait for on the write operation, and exception raising behavior.
-	 */
-	public void setWriteNumber(int writeNumber) {
-		this.writeNumber = writeNumber;
-	}
-
-	/**
-	 * Configures the timeout for write operations in milliseconds. This defaults to {@literal 0} (indefinite).
-	 * 
-	 * @param writeTimeout
-	 */
-	public void setWriteTimeout(int writeTimeout) {
-		this.writeTimeout = writeTimeout;
-	}
-
-	/**
-	 * Configures whether or not to fsync. The 'fsync' option to the getlasterror command. Defaults to {@literal false}.
-	 * 
-	 * @param writeFsync to fsync on <code>write (true)<code>, otherwise {@literal false}.
-	 */
-	public void setWriteFsync(boolean writeFsync) {
-		this.writeFsync = writeFsync;
-	}
-
-	/**
-	 * Configures whether or not the system retries automatically on a failed connect. This defaults to {@literal false}.
-	 * 
-	 * @deprecated since 1.7.
-	 */
-	@Deprecated
-	public void setAutoConnectRetry(boolean autoConnectRetry) {
-		this.autoConnectRetry = autoConnectRetry;
-	}
-
-	/**
-	 * Configures the maximum amount of time in millisecons to spend retrying to open connection to the same server. This
-	 * defaults to {@literal 0}, which means to use the default {@literal 15s} if {@link #autoConnectRetry} is on.
-	 * 
-	 * @param maxAutoConnectRetryTime the maxAutoConnectRetryTime to set
-	 * @deprecated since 1.7
-	 */
-	@Deprecated
-	public void setMaxAutoConnectRetryTime(long maxAutoConnectRetryTime) {
-		this.maxAutoConnectRetryTime = maxAutoConnectRetryTime;
-	}
-
-	/**
-	 * Specifies if the driver is allowed to read from secondaries or slaves. Defaults to {@literal false}.
-	 * 
-	 * @param slaveOk true if the driver should read from secondaries or slaves.
-	 * @deprecated since 1.7
-	 */
-	@Deprecated
-	public void setSlaveOk(boolean slaveOk) {
-		this.slaveOk = slaveOk;
-	}
-
-	/**
-	 * Specifies if the driver should use an SSL connection to Mongo. This defaults to {@literal false}. By default
-	 * {@link SSLSocketFactory#getDefault()} will be used. See {@link #setSslSocketFactory(SSLSocketFactory)} if you want
-	 * to configure a custom factory.
-	 * 
-	 * @param ssl true if the driver should use an SSL connection.
-	 * @see #setSslSocketFactory(SSLSocketFactory)
-	 */
-	public void setSsl(boolean ssl) {
-		this.ssl = ssl;
-	}
-
-	/**
-	 * Specifies the {@link SSLSocketFactory} to use for creating SSL connections to Mongo. Defaults to
-	 * {@link SSLSocketFactory#getDefault()}. Implicitly activates {@link #setSsl(boolean)} if a non-{@literal null} value
-	 * is given.
-	 * 
-	 * @param sslSocketFactory the sslSocketFactory to use.
-	 * @see #setSsl(boolean)
-	 */
-	public void setSslSocketFactory(SSLSocketFactory sslSocketFactory) {
-
-		setSsl(sslSocketFactory != null);
-		this.sslSocketFactory = sslSocketFactory;
-	}
-
-	/* 
-	 * (non-Javadoc)
-	 * @see org.springframework.beans.factory.config.AbstractFactoryBean#createInstance()
-	 */
-	@Override
-	protected MongoOptions createInstance() throws Exception {
-
-		if (MongoClientVersion.isMongo3Driver()) {
-			throw new IllegalArgumentException(
-					String
-							.format("Usage of 'mongo-options' is no longer supported for MongoDB Java driver version 3 and above. Please use 'mongo-client-options' and refer to chapter 'MongoDB 3.0 Support' for details."));
-		}
-
-		MongoOptions options = new MongoOptions();
-
-		options.setConnectionsPerHost(connectionsPerHost);
-		options.setThreadsAllowedToBlockForConnectionMultiplier(threadsAllowedToBlockForConnectionMultiplier);
-		options.setMaxWaitTime(maxWaitTime);
-		options.setConnectTimeout(connectTimeout);
-		options.setSocketTimeout(socketTimeout);
-		options.setSocketKeepAlive(socketKeepAlive);
-
-		options.setW(writeNumber);
-		options.setWtimeout(writeTimeout);
-		options.setFsync(writeFsync);
-
-		if (ssl) {
-			options.setSocketFactory(sslSocketFactory != null ? sslSocketFactory : SSLSocketFactory.getDefault());
-		}
-
-		ReflectiveMongoOptionsInvoker.setAutoConnectRetry(options, autoConnectRetry);
-		ReflectiveMongoOptionsInvoker.setMaxAutoConnectRetryTime(options, maxAutoConnectRetryTime);
-		ReflectiveMongoOptionsInvoker.setSlaveOk(options, slaveOk);
-
-		return options;
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.beans.factory.FactoryBean#getObjectType()
-	 */
-	public Class<?> getObjectType() {
-		return MongoOptions.class;
-	}
-}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoTemplate.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2016 the original author or authors.
+ * Copyright 2010-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,23 +17,13 @@ package org.springframework.data.mongodb.core;
 
 import static org.springframework.data.mongodb.core.query.Criteria.*;
 import static org.springframework.data.mongodb.core.query.SerializationUtils.*;
+import static org.springframework.data.util.Optionals.*;
 
 import java.io.IOException;
-import java.util.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.LinkedHashSet;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 import java.util.Map.Entry;
-import java.util.Scanner;
-import java.util.Set;
 import java.util.concurrent.TimeUnit;
 
-import com.mongodb.*;
 import org.bson.Document;
 import org.bson.conversions.Bson;
 import org.bson.types.ObjectId;
@@ -54,7 +44,6 @@ import org.springframework.dao.InvalidDataAccessApiUsageException;
 import org.springframework.dao.OptimisticLockingFailureException;
 import org.springframework.dao.support.PersistenceExceptionTranslator;
 import org.springframework.data.annotation.Id;
-import org.springframework.data.authentication.UserCredentials;
 import org.springframework.data.convert.EntityReader;
 import org.springframework.data.geo.Distance;
 import org.springframework.data.geo.GeoResult;
@@ -68,6 +57,7 @@ import org.springframework.data.mongodb.MongoDbFactory;
 import org.springframework.data.mongodb.core.BulkOperations.BulkMode;
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
 import org.springframework.data.mongodb.core.aggregation.AggregationOperationContext;
+import org.springframework.data.mongodb.core.aggregation.AggregationOptions;
 import org.springframework.data.mongodb.core.aggregation.AggregationResults;
 import org.springframework.data.mongodb.core.aggregation.Fields;
 import org.springframework.data.mongodb.core.aggregation.TypeBasedAggregationOperationContext;
@@ -104,6 +94,8 @@ import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.data.mongodb.core.query.Update;
 import org.springframework.data.mongodb.util.MongoClientVersion;
 import org.springframework.data.util.CloseableIterator;
+import org.springframework.data.util.Optionals;
+import org.springframework.data.util.Pair;
 import org.springframework.jca.cci.core.ConnectionCallback;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
@@ -111,6 +103,15 @@ import org.springframework.util.ObjectUtils;
 import org.springframework.util.ResourceUtils;
 import org.springframework.util.StringUtils;
 
+import com.mongodb.Cursor;
+import com.mongodb.DBCollection;
+import com.mongodb.DBCursor;
+import com.mongodb.Mongo;
+import com.mongodb.MongoClient;
+import com.mongodb.MongoException;
+import com.mongodb.ReadPreference;
+import com.mongodb.WriteConcern;
+import com.mongodb.client.AggregateIterable;
 import com.mongodb.client.FindIterable;
 import com.mongodb.client.MapReduceIterable;
 import com.mongodb.client.MongoCollection;
@@ -143,6 +144,8 @@ import com.mongodb.util.JSONParseException;
  * @author Doménique Tilleuil
  * @author Niko Schmuck
  * @author Mark Paluch
+ * @author Laszlo Csontos
+ * @author Maninder Singh
  */
 @SuppressWarnings("deprecation")
 public class MongoTemplate implements MongoOperations, ApplicationContextAware, IndexOperationsProvider {
@@ -177,28 +180,14 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	private ResourceLoader resourceLoader;
 	private MongoPersistentEntityIndexCreator indexCreator;
 
-	private Mongo mongo;
-
 	/**
 	 * Constructor used for a basic template configuration
 	 *
-	 * @param mongo must not be {@literal null}.
+	 * @param mongoClient must not be {@literal null}.
 	 * @param databaseName must not be {@literal null} or empty.
 	 */
-	public MongoTemplate(Mongo mongo, String databaseName) {
-		this(new SimpleMongoDbFactory(mongo, databaseName), null);
-	}
-
-	/**
-	 * Constructor used for a template configuration with user credentials in the form of
-	 * {@link org.springframework.data.authentication.UserCredentials}
-	 *
-	 * @param mongo must not be {@literal null}.
-	 * @param databaseName must not be {@literal null} or empty.
-	 * @param userCredentials
-	 */
-	public MongoTemplate(Mongo mongo, String databaseName, UserCredentials userCredentials) {
-		this(new SimpleMongoDbFactory(mongo, databaseName, userCredentials));
+	public MongoTemplate(MongoClient mongoClient, String databaseName) {
+		this(new SimpleMongoDbFactory(mongoClient, databaseName), null);
 	}
 
 	/**
@@ -218,7 +207,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	 */
 	public MongoTemplate(MongoDbFactory mongoDbFactory, MongoConverter mongoConverter) {
 
-		Assert.notNull(mongoDbFactory);
+		Assert.notNull(mongoDbFactory, "MongoDbFactory must not be null!");
 
 		this.mongoDbFactory = mongoDbFactory;
 		this.exceptionTranslator = mongoDbFactory.getExceptionTranslator();
@@ -240,7 +229,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 
 	/**
 	 * Configures the {@link WriteResultChecking} to be used with the template. Setting {@literal null} will reset the
-	 * default of {@value #DEFAULT_WRITE_RESULT_CHECKING}.
+	 * default of {@link #DEFAULT_WRITE_RESULT_CHECKING}.
 	 *
 	 * @param resultChecking
 	 */
@@ -269,8 +258,8 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	}
 
 	/**
-	 * Used by @{link {@link #prepareCollection(DBCollection)} to set the {@link ReadPreference} before any operations are
-	 * performed.
+	 * Used by @{link {@link #prepareCollection(MongoCollection)} to set the {@link ReadPreference} before any operations
+	 * are performed.
 	 *
 	 * @param readPreference
 	 */
@@ -318,7 +307,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	}
 
 	/**
-	 * Returns the default {@link org.springframework.data.mongodb.core.core.convert.MongoConverter}.
+	 * Returns the default {@link org.springframework.data.mongodb.core.convert.MongoConverter}.
 	 *
 	 * @return
 	 */
@@ -353,7 +342,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 			public CloseableIterator<T> doInCollection(MongoCollection<Document> collection)
 					throws MongoException, DataAccessException {
 
-				MongoPersistentEntity<?> persistentEntity = mappingContext.getPersistentEntity(entityType);
+				MongoPersistentEntity<?> persistentEntity = mappingContext.getRequiredPersistentEntity(entityType);
 
 				Document mappedFields = queryMapper.getMappedFields(query.getFieldsObject(), persistentEntity);
 				Document mappedQuery = queryMapper.getMappedObject(query.getQueryObject(), persistentEntity);
@@ -361,8 +350,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 				FindIterable<Document> cursor = collection.find(mappedQuery).projection(mappedFields);
 				QueryCursorPreparer cursorPreparer = new QueryCursorPreparer(query, entityType);
 
-				ReadDocumentCallback<T> readCallback = new ReadDocumentCallback<T>(mongoConverter, entityType,
-						collectionName);
+				ReadDocumentCallback<T> readCallback = new ReadDocumentCallback<T>(mongoConverter, entityType, collectionName);
 
 				return new CloseableIterableCursorAdapter<T>(cursorPreparer.prepare(cursor), exceptionTranslator, readCallback);
 			}
@@ -411,15 +399,6 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		return result;
 	}
 
-	protected void logCommandExecutionError(final Document command, CommandResult result) {
-
-		String error = result.getErrorMessage();
-
-		if (error != null) {
-			LOGGER.warn("Command execution of {} failed: {}", command.toString(), error);
-		}
-	}
-
 	public void executeQuery(Query query, String collectionName, DocumentCallbackHandler dch) {
 		executeQuery(query, collectionName, dch, new QueryCursorPreparer(query, null));
 	}
@@ -438,9 +417,9 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	protected void executeQuery(Query query, String collectionName, DocumentCallbackHandler dch,
 			CursorPreparer preparer) {
 
-		Assert.notNull(query);
+		Assert.notNull(query, "Query must not be null!");
 
-		Document queryObject = queryMapper.getMappedObject(query.getQueryObject(), null);
+		Document queryObject = queryMapper.getMappedObject(query.getQueryObject(), Optional.empty());
 		Document sortObject = query.getSortObject();
 		Document fieldsObject = query.getFieldsObject();
 
@@ -454,7 +433,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 
 	public <T> T execute(DbCallback<T> action) {
 
-		Assert.notNull(action);
+		Assert.notNull(action, "DbCallbackmust not be null!");
 
 		try {
 			MongoDatabase db = this.getDb();
@@ -470,7 +449,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 
 	public <T> T execute(String collectionName, CollectionCallback<T> callback) {
 
-		Assert.notNull(callback);
+		Assert.notNull(callback, "CollectionCallback must not be null!");
 
 		try {
 			MongoCollection<Document> collection = getAndPrepareCollection(getDb(), collectionName);
@@ -539,11 +518,11 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	}
 
 	public IndexOperations indexOps(String collectionName) {
-		return new DefaultIndexOperations(getMongoDbFactory(), collectionName);
+		return new DefaultIndexOperations(getMongoDbFactory(), collectionName, queryMapper);
 	}
 
 	public IndexOperations indexOps(Class<?> entityClass) {
-		return new DefaultIndexOperations(getMongoDbFactory(), determineCollectionName(entityClass));
+		return new DefaultIndexOperations(getMongoDbFactory(), determineCollectionName(entityClass), queryMapper);
 	}
 
 	public BulkOperations bulkOps(BulkMode bulkMode, String collectionName) {
@@ -632,9 +611,11 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	}
 
 	public <T> T findById(Object id, Class<T> entityClass, String collectionName) {
-		MongoPersistentEntity<?> persistentEntity = mappingContext.getPersistentEntity(entityClass);
-		MongoPersistentProperty idProperty = persistentEntity == null ? null : persistentEntity.getIdProperty();
-		String idKey = idProperty == null ? ID_FIELD : idProperty.getName();
+
+		String idKey = mappingContext.getPersistentEntity(entityClass)//
+				.flatMap(it -> it.getIdProperty())//
+				.map(it -> it.getName()).orElse(ID_FIELD);
+
 		return doFindOne(collectionName, new Document(idKey, id), null, entityClass);
 	}
 
@@ -678,7 +659,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		List<GeoResult<T>> result = new ArrayList<GeoResult<T>>(results.size());
 
 		int index = 0;
-		int elementsToSkip = near.getSkip() != null ? near.getSkip() : 0;
+		long elementsToSkip = near.getSkip() != null ? near.getSkip() : 0;
 
 		for (Object element : results) {
 
@@ -686,7 +667,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 			 * As MongoDB currently (2.4.4) doesn't support the skipping of elements in near queries
 			 * we skip the elements ourselves to avoid at least the document 2 object mapping overhead.
 			 *
-			 * @see https://jira.mongodb.org/browse/SERVER-3925
+			 * @see <a href="https://jira.mongodb.org/browse/SERVER-3925">MongoDB Jira: SERVER-3925</a>
 			 */
 			if (index >= elementsToSkip) {
 				result.add(callback.doWith((Document) element));
@@ -735,7 +716,8 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	}
 
 	public long count(Query query, Class<?> entityClass) {
-		Assert.notNull(entityClass);
+
+		Assert.notNull(entityClass, "Entity class must not be null!");
 		return count(query, entityClass, determineCollectionName(entityClass));
 	}
 
@@ -749,16 +731,13 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	 */
 	public long count(Query query, Class<?> entityClass, String collectionName) {
 
-		Assert.hasText(collectionName);
+		Assert.hasText(collectionName, "Collection name must not be null or empty!");
+
 		final Document document = query == null ? null
 				: queryMapper.getMappedObject(query.getQueryObject(),
-						entityClass == null ? null : mappingContext.getPersistentEntity(entityClass));
+						Optional.ofNullable(entityClass).flatMap(it -> mappingContext.getPersistentEntity(entityClass)));
 
-		return execute(collectionName, new CollectionCallback<Long>() {
-			public Long doInCollection(MongoCollection<Document> collection) throws MongoException, DataAccessException {
-				return collection.count(document);
-			}
-		});
+		return execute(collectionName, (CollectionCallback<Long>) collection -> collection.count(document));
 	}
 
 	/*
@@ -830,11 +809,9 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 
 	protected <T> void doInsert(String collectionName, T objectToSave, MongoWriter<T> writer) {
 
-		assertUpdateableIdIfNotSet(objectToSave);
-
 		initializeVersionProperty(objectToSave);
-
 		maybeEmitEvent(new BeforeConvertEvent<T>(objectToSave, collectionName));
+		assertUpdateableIdIfNotSet(objectToSave);
 
 		Document dbDoc = toDocument(objectToSave, writer);
 
@@ -877,13 +854,13 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 
 	private void initializeVersionProperty(Object entity) {
 
-		MongoPersistentEntity<?> mongoPersistentEntity = getPersistentEntity(entity.getClass());
+		Optional<? extends MongoPersistentEntity<?>> persistentEntity = getPersistentEntity(entity.getClass());
 
-		if (mongoPersistentEntity != null && mongoPersistentEntity.hasVersionProperty()) {
-			ConvertingPropertyAccessor accessor = new ConvertingPropertyAccessor(
-					mongoPersistentEntity.getPropertyAccessor(entity), mongoConverter.getConversionService());
-			accessor.setProperty(mongoPersistentEntity.getVersionProperty(), 0);
-		}
+		ifAllPresent(persistentEntity, persistentEntity.flatMap(it -> it.getVersionProperty()), (l, r) -> {
+			ConvertingPropertyAccessor accessor = new ConvertingPropertyAccessor(l.getPropertyAccessor(entity),
+					mongoConverter.getConversionService());
+			accessor.setProperty(r, Optional.of(0));
+		});
 	}
 
 	public void insert(Collection<? extends Object> batchToSave, Class<?> entityClass) {
@@ -908,11 +885,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 				continue;
 			}
 
-			MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(element.getClass());
-
-			if (entity == null) {
-				throw new InvalidDataAccessApiUsageException("No PersistentEntity information found for " + element.getClass());
-			}
+			MongoPersistentEntity<?> entity = mappingContext.getRequiredPersistentEntity(element.getClass());
 
 			String collection = entity.getCollection();
 			List<T> collectionElements = elementsByCollection.get(collection);
@@ -932,14 +905,14 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 
 	protected <T> void doInsertBatch(String collectionName, Collection<? extends T> batchToSave, MongoWriter<T> writer) {
 
-		Assert.notNull(writer);
+		Assert.notNull(writer, "MongoWriter must not be null!");
 
 		List<Document> documentList = new ArrayList<Document>();
 		for (T o : batchToSave) {
 
 			initializeVersionProperty(o);
-
 			maybeEmitEvent(new BeforeConvertEvent<T>(o, collectionName));
+
 			Document document = toDocument(o, writer);
 
 			maybeEmitEvent(new BeforeSaveEvent<T>(o, document, collectionName));
@@ -960,59 +933,51 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 
 	public void save(Object objectToSave) {
 
-		Assert.notNull(objectToSave);
+		Assert.notNull(objectToSave, "Object to save must not be null!");
 		save(objectToSave, determineEntityCollectionName(objectToSave));
 	}
 
 	public void save(Object objectToSave, String collectionName) {
 
-		Assert.notNull(objectToSave);
-		Assert.hasText(collectionName);
+		Assert.notNull(objectToSave, "Object to save must not be null!");
+		Assert.hasText(collectionName, "Collection name must not be null or empty!");
 
-		MongoPersistentEntity<?> mongoPersistentEntity = getPersistentEntity(objectToSave.getClass());
+		Optional<? extends MongoPersistentEntity<?>> entity = getPersistentEntity(objectToSave.getClass());
+		Optional<MongoPersistentProperty> versionProperty = entity.flatMap(it -> it.getVersionProperty());
 
-		// No optimistic locking -> simple save
-		if (mongoPersistentEntity == null || !mongoPersistentEntity.hasVersionProperty()) {
-			doSave(collectionName, objectToSave, this.mongoConverter);
-			return;
-		}
-
-		doSaveVersioned(objectToSave, mongoPersistentEntity, collectionName);
+		mapIfAllPresent(entity, versionProperty, //
+				(l, r) -> doSaveVersioned(objectToSave, l, collectionName))//
+						.orElseGet(() -> doSave(collectionName, objectToSave, this.mongoConverter));
 	}
 
-	private <T> void doSaveVersioned(T objectToSave, MongoPersistentEntity<?> entity, String collectionName) {
+	private <T> T doSaveVersioned(T objectToSave, MongoPersistentEntity<?> entity, String collectionName) {
 
 		ConvertingPropertyAccessor convertingAccessor = new ConvertingPropertyAccessor(
 				entity.getPropertyAccessor(objectToSave), mongoConverter.getConversionService());
 
-		MongoPersistentProperty idProperty = entity.getIdProperty();
-		MongoPersistentProperty versionProperty = entity.getVersionProperty();
+		Optional<MongoPersistentProperty> versionProperty = entity.getVersionProperty();
+		Optional<Number> versionNumber = versionProperty.flatMap(it -> convertingAccessor.getProperty(it, Number.class));
 
-		Object version = convertingAccessor.getProperty(versionProperty);
-		Number versionNumber = convertingAccessor.getProperty(versionProperty, Number.class);
-
-		// Fresh instance -> initialize version property
-		if (version == null) {
-			doInsert(collectionName, objectToSave, this.mongoConverter);
-		} else {
-
-			assertUpdateableIdIfNotSet(objectToSave);
-
-			// Create query for entity with the id and old version
-			Object id = convertingAccessor.getProperty(idProperty);
-			Query query = new Query(Criteria.where(idProperty.getName()).is(id).and(versionProperty.getName()).is(version));
+		return mapIfAllPresent(versionProperty, versionNumber, (property, number) -> {
 
 			// Bump version number
-			convertingAccessor.setProperty(versionProperty, versionNumber.longValue() + 1);
+			convertingAccessor.setProperty(property, Optional.of(number.longValue() + 1));
+
+			maybeEmitEvent(new BeforeConvertEvent<T>(objectToSave, collectionName));
+			assertUpdateableIdIfNotSet(objectToSave);
 
 			Document document = new Document();
 
-			maybeEmitEvent(new BeforeConvertEvent<T>(objectToSave, collectionName));
 			this.mongoConverter.write(objectToSave, document);
 
 			maybeEmitEvent(new BeforeSaveEvent<T>(objectToSave, document, collectionName));
 			Update update = Update.fromDocument(document, ID_FIELD);
 
+			// Create query for entity with the id and old version
+			MongoPersistentProperty idProperty = entity.getRequiredIdProperty();
+			Object id = entity.getIdentifierAccessor(objectToSave).getRequiredIdentifier();
+			Query query = new Query(Criteria.where(idProperty.getName()).is(id).and(property.getName()).is(number));
+
 			UpdateResult result = doUpdate(collectionName, query, update, objectToSave.getClass(), false, false);
 
 			if (result.getModifiedCount() == 0) {
@@ -1021,14 +986,19 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 								versionNumber, collectionName));
 			}
 			maybeEmitEvent(new AfterSaveEvent<T>(objectToSave, document, collectionName));
-		}
+
+			return objectToSave;
+
+		}).orElseGet(() -> {
+			doInsert(collectionName, objectToSave, this.mongoConverter);
+			return objectToSave;
+		});
 	}
 
-	protected <T> void doSave(String collectionName, T objectToSave, MongoWriter<T> writer) {
-
-		assertUpdateableIdIfNotSet(objectToSave);
+	protected <T> T doSave(String collectionName, T objectToSave, MongoWriter<T> writer) {
 
 		maybeEmitEvent(new BeforeConvertEvent<T>(objectToSave, collectionName));
+		assertUpdateableIdIfNotSet(objectToSave);
 
 		Document dbDoc = toDocument(objectToSave, writer);
 
@@ -1037,6 +1007,8 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 
 		populateIdIfNecessary(objectToSave, id);
 		maybeEmitEvent(new AfterSaveEvent<T>(objectToSave, dbDoc, collectionName));
+
+		return objectToSave;
 	}
 
 	protected Object insertDocument(final String collectionName, final Document document, final Class<?> entityClass) {
@@ -1174,7 +1146,8 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 			public UpdateResult doInCollection(MongoCollection<Document> collection)
 					throws MongoException, DataAccessException {
 
-				MongoPersistentEntity<?> entity = entityClass == null ? null : getPersistentEntity(entityClass);
+				Optional<? extends MongoPersistentEntity<?>> entity = entityClass == null ? Optional.empty()
+						: getPersistentEntity(entityClass);
 
 				increaseVersionForUpdateIfNecessary(entity, update);
 
@@ -1183,6 +1156,10 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 				Document updateObj = update == null ? new Document()
 						: updateMapper.getMappedObject(update.getUpdateObject(), entity);
 
+				if (multi && update.isIsolated() && !queryObj.containsKey("$isolated")) {
+					queryObj.put("$isolated", 1);
+				}
+
 				if (LOGGER.isDebugEnabled()) {
 					LOGGER.debug("Calling update using query: {} and update: {} in collection: {}",
 							serializeToJsonSafely(queryObj), serializeToJsonSafely(updateObj), collectionName);
@@ -1210,23 +1187,23 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		});
 	}
 
-	private void increaseVersionForUpdateIfNecessary(MongoPersistentEntity<?> persistentEntity, Update update) {
+	private void increaseVersionForUpdateIfNecessary(Optional<? extends MongoPersistentEntity<?>> persistentEntity,
+			Update update) {
 
-		if (persistentEntity != null && persistentEntity.hasVersionProperty()) {
-			String versionFieldName = persistentEntity.getVersionProperty().getFieldName();
+		ifAllPresent(persistentEntity, persistentEntity.flatMap(it -> it.getVersionProperty()), (entity, property) -> {
+			String versionFieldName = property.getFieldName();
 			if (!update.modifies(versionFieldName)) {
 				update.inc(versionFieldName, 1L);
 			}
-		}
+		});
 	}
 
-	private boolean documentContainsVersionProperty(Document document, MongoPersistentEntity<?> persistentEntity) {
+	private boolean documentContainsVersionProperty(Document document,
+			Optional<? extends MongoPersistentEntity<?>> persistentEntity) {
 
-		if (persistentEntity == null || !persistentEntity.hasVersionProperty()) {
-			return false;
-		}
-
-		return document.containsKey(persistentEntity.getVersionProperty().getFieldName());
+		return mapIfAllPresent(persistentEntity, persistentEntity.flatMap(it -> it.getVersionProperty()), //
+				(entity, property) -> document.containsKey(property.getFieldName()))//
+						.orElse(false);
 	}
 
 	public DeleteResult remove(Object object) {
@@ -1240,7 +1217,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 
 	public DeleteResult remove(Object object, String collection) {
 
-		Assert.hasText(collection);
+		Assert.hasText(collection, "Collection name must not be null or empty!");
 
 		if (object == null) {
 			return null;
@@ -1256,25 +1233,21 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	 * @param object
 	 * @return
 	 */
-	private Entry<String, Object> extractIdPropertyAndValue(Object object) {
+	private Pair<String, Optional<Object>> extractIdPropertyAndValue(Object object) {
 
 		Assert.notNull(object, "Id cannot be extracted from 'null'.");
 
 		Class<?> objectType = object.getClass();
 
 		if (object instanceof Document) {
-			return Collections.singletonMap(ID_FIELD, ((Document) object).get(ID_FIELD)).entrySet().iterator().next();
+			return Pair.of(ID_FIELD, Optional.ofNullable(((Document) object).get(ID_FIELD)));
 		}
 
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(objectType);
-		MongoPersistentProperty idProp = entity == null ? null : entity.getIdProperty();
+		Optional<? extends MongoPersistentEntity<?>> entity = mappingContext.getPersistentEntity(objectType);
+		return mapIfAllPresent(entity, entity.flatMap(it -> it.getIdProperty()), //
 
-		if (idProp == null || entity == null) {
-			throw new MappingException("No id property found for object of type " + objectType);
-		}
-
-		Object idValue = entity.getPropertyAccessor(object).getProperty(idProp);
-		return Collections.singletonMap(idProp.getFieldName(), idValue).entrySet().iterator().next();
+				(l, r) -> Pair.of(r.getFieldName(), l.getPropertyAccessor(object).getProperty(r)))//
+						.orElseThrow(() -> new MappingException("No id property found for object of type " + objectType));
 	}
 
 	/**
@@ -1285,8 +1258,8 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	 */
 	private Query getIdQueryFor(Object object) {
 
-		Entry<String, Object> id = extractIdPropertyAndValue(object);
-		return new Query(where(id.getKey()).is(id.getValue()));
+		Pair<String, Optional<Object>> id = extractIdPropertyAndValue(object);
+		return new Query(where(id.getFirst()).is(id.getSecond().orElse(null)));
 	}
 
 	/**
@@ -1300,34 +1273,38 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		Assert.notEmpty(objects, "Cannot create Query for empty collection.");
 
 		Iterator<?> it = objects.iterator();
-		Entry<String, Object> firstEntry = extractIdPropertyAndValue(it.next());
+		Pair<String, Optional<Object>> pair = extractIdPropertyAndValue(it.next());
 
 		ArrayList<Object> ids = new ArrayList<Object>(objects.size());
-		ids.add(firstEntry.getValue());
+		ids.add(pair.getSecond().orElse(null));
 
 		while (it.hasNext()) {
-			ids.add(extractIdPropertyAndValue(it.next()).getValue());
+			ids.add(extractIdPropertyAndValue(it.next()).getSecond().orElse(null));
 		}
 
-		return new Query(where(firstEntry.getKey()).in(ids));
+		return new Query(where(pair.getFirst()).in(ids));
 	}
 
-	private void assertUpdateableIdIfNotSet(Object entity) {
+	private void assertUpdateableIdIfNotSet(Object value) {
 
-		MongoPersistentEntity<?> persistentEntity = mappingContext.getPersistentEntity(entity.getClass());
-		MongoPersistentProperty idProperty = persistentEntity == null ? null : persistentEntity.getIdProperty();
+		Optional<? extends MongoPersistentEntity<?>> persistentEntity = mappingContext
+				.getPersistentEntity(value.getClass());
+		Optional<MongoPersistentProperty> idProperty = persistentEntity.flatMap(it -> it.getIdProperty());
 
-		if (idProperty == null || persistentEntity == null) {
-			return;
-		}
+		Optionals.ifAllPresent(persistentEntity, idProperty, (entity, property) -> {
 
-		Object idValue = persistentEntity.getPropertyAccessor(entity).getProperty(idProperty);
+			Optional<Object> propertyValue = entity.getPropertyAccessor(value).getProperty(property);
 
-		if (idValue == null && !MongoSimpleTypes.AUTOGENERATED_ID_TYPES.contains(idProperty.getType())) {
-			throw new InvalidDataAccessApiUsageException(
-					String.format("Cannot autogenerate id of type %s for entity of type %s!", idProperty.getType().getName(),
-							entity.getClass().getName()));
-		}
+			if (propertyValue.isPresent()) {
+				return;
+			}
+
+			if (!MongoSimpleTypes.AUTOGENERATED_ID_TYPES.contains(property.getType())) {
+				throw new InvalidDataAccessApiUsageException(
+						String.format("Cannot autogenerate id of type %s for entity of type %s!", property.getType().getName(),
+								value.getClass().getName()));
+			}
+		});
 	}
 
 	public DeleteResult remove(Query query, String collectionName) {
@@ -1351,7 +1328,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		Assert.hasText(collectionName, "Collection name must not be null or empty!");
 
 		final Document queryObject = query.getQueryObject();
-		final MongoPersistentEntity<?> entity = getPersistentEntity(entityClass);
+		final Optional<? extends MongoPersistentEntity<?>> entity = getPersistentEntity(entityClass);
 
 		return execute(collectionName, new CollectionCallback<DeleteResult>() {
 			public DeleteResult doInCollection(MongoCollection<Document> collection)
@@ -1431,7 +1408,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 				result = result.sort(query.getSortObject());
 			}
 
-			result = result.filter(queryMapper.getMappedObject(query.getQueryObject(), null));
+			result = result.filter(queryMapper.getMappedObject(query.getQueryObject(), Optional.empty()));
 		}
 
 		if (mapReduceOptions != null) {
@@ -1477,7 +1454,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		if (criteria == null) {
 			document.put("cond", null);
 		} else {
-			document.put("cond", queryMapper.getMappedObject(criteria.getCriteriaObject(), null));
+			document.put("cond", queryMapper.getMappedObject(criteria.getCriteriaObject(), Optional.empty()));
 		}
 		// If initial document was a JavaScript string, potentially loaded by Spring's Resource abstraction, load it and
 		// convert to Document
@@ -1524,11 +1501,17 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		return new GroupByResults<T>(mappedResults, commandResult);
 	}
 
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.MongoOperations#aggregate(org.springframework.data.mongodb.core.aggregation.TypedAggregation, java.lang.Class)
+	 */
 	@Override
 	public <O> AggregationResults<O> aggregate(TypedAggregation<?> aggregation, Class<O> outputType) {
 		return aggregate(aggregation, determineCollectionName(aggregation.getInputType()), outputType);
 	}
 
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.MongoOperations#aggregate(org.springframework.data.mongodb.core.aggregation.TypedAggregation, java.lang.String, java.lang.Class)
+	 */
 	@Override
 	public <O> AggregationResults<O> aggregate(TypedAggregation<?> aggregation, String inputCollectionName,
 			Class<O> outputType) {
@@ -1540,6 +1523,9 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		return aggregate(aggregation, inputCollectionName, outputType, context);
 	}
 
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.MongoOperations#aggregate(org.springframework.data.mongodb.core.aggregation.Aggregation, java.lang.Class, java.lang.Class)
+	 */
 	@Override
 	public <O> AggregationResults<O> aggregate(Aggregation aggregation, Class<?> inputType, Class<O> outputType) {
 
@@ -1547,11 +1533,54 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 				new TypeBasedAggregationOperationContext(inputType, mappingContext, queryMapper));
 	}
 
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.MongoOperations#aggregate(org.springframework.data.mongodb.core.aggregation.Aggregation, java.lang.String, java.lang.Class)
+	 */
 	@Override
 	public <O> AggregationResults<O> aggregate(Aggregation aggregation, String collectionName, Class<O> outputType) {
 		return aggregate(aggregation, collectionName, outputType, null);
 	}
 
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.MongoOperations#aggregateStream(org.springframework.data.mongodb.core.aggregation.TypedAggregation, java.lang.String, java.lang.Class)
+	 */
+	@Override
+	public <O> CloseableIterator<O> aggregateStream(TypedAggregation<?> aggregation, String inputCollectionName,
+			Class<O> outputType) {
+
+		Assert.notNull(aggregation, "Aggregation pipeline must not be null!");
+
+		AggregationOperationContext context = new TypeBasedAggregationOperationContext(aggregation.getInputType(),
+				mappingContext, queryMapper);
+		return aggregateStream(aggregation, inputCollectionName, outputType, context);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.MongoOperations#aggregateStream(org.springframework.data.mongodb.core.aggregation.TypedAggregation, java.lang.Class)
+	 */
+	@Override
+	public <O> CloseableIterator<O> aggregateStream(TypedAggregation<?> aggregation, Class<O> outputType) {
+		return aggregateStream(aggregation, determineCollectionName(aggregation.getInputType()), outputType);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.MongoOperations#aggregateStream(org.springframework.data.mongodb.core.aggregation.Aggregation, java.lang.Class, java.lang.Class)
+	 */
+	@Override
+	public <O> CloseableIterator<O> aggregateStream(Aggregation aggregation, Class<?> inputType, Class<O> outputType) {
+
+		return aggregateStream(aggregation, determineCollectionName(inputType), outputType,
+				new TypeBasedAggregationOperationContext(inputType, mappingContext, queryMapper));
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.MongoOperations#aggregateStream(org.springframework.data.mongodb.core.aggregation.Aggregation, java.lang.String, java.lang.Class)
+	 */
+	@Override
+	public <O> CloseableIterator<O> aggregateStream(Aggregation aggregation, String collectionName, Class<O> outputType) {
+		return aggregateStream(aggregation, collectionName, outputType, null);
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.MongoOperations#findAllAndRemove(org.springframework.data.mongodb.core.query.Query, java.lang.String)
@@ -1646,6 +1675,62 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		return mappedResults;
 	}
 
+	protected <O> CloseableIterator<O> aggregateStream(Aggregation aggregation, String collectionName,
+			Class<O> outputType, AggregationOperationContext context) {
+
+		Assert.hasText(collectionName, "Collection name must not be null or empty!");
+		Assert.notNull(aggregation, "Aggregation pipeline must not be null!");
+		Assert.notNull(outputType, "Output type must not be null!");
+
+		AggregationOperationContext rootContext = context == null ? Aggregation.DEFAULT_CONTEXT : context;
+
+		Document command = aggregation.toDocument(collectionName, rootContext);
+
+		assertNotExplain(command);
+
+		if (LOGGER.isDebugEnabled()) {
+			LOGGER.debug("Streaming aggregation: {}", serializeToJsonSafely(command));
+		}
+
+		ReadDocumentCallback<O> readCallback = new ReadDocumentCallback<O>(mongoConverter, outputType, collectionName);
+
+		return execute(collectionName, new CollectionCallback<CloseableIterator<O>>() {
+
+			@Override
+			public CloseableIterator<O> doInCollection(MongoCollection<Document> collection)
+					throws MongoException, DataAccessException {
+
+				List<Document> pipeline = (List<Document>) command.get("pipeline");
+
+				AggregationOptions options = AggregationOptions.fromDocument(command);
+
+				AggregateIterable<Document> cursor = collection.aggregate(pipeline).allowDiskUse(options.isAllowDiskUse())
+						.useCursor(true);
+
+				Integer cursorBatchSize = options.getCursorBatchSize();
+				if (cursorBatchSize != null) {
+					cursor.batchSize(cursorBatchSize);
+				}
+
+				return new CloseableIterableCursorAdapter<O>(cursor.iterator(), exceptionTranslator, readCallback);
+			}
+		});
+	}
+
+	/**
+	 * Assert that the {@link Document} does not enable Aggregation explain mode.
+	 *
+	 * @param command the command {@link Document}.
+	 */
+	private void assertNotExplain(Document command) {
+
+		Boolean explain = command.get("explain", Boolean.class);
+
+		if (explain != null && explain) {
+			throw new IllegalArgumentException("Can't use explain option with streaming!");
+		}
+	}
+
 	protected String replaceWithResourceIfNecessary(String function) {
 
 		String func = function;
@@ -1745,7 +1830,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	 */
 	protected <T> T doFindOne(String collectionName, Document query, Document fields, Class<T> entityClass) {
 
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
+		Optional<? extends MongoPersistentEntity<?>> entity = mappingContext.getPersistentEntity(entityClass);
 		Document mappedQuery = queryMapper.getMappedObject(query, entity);
 		Document mappedFields = fields == null ? null : queryMapper.getMappedObject(fields, entity);
 
@@ -1795,7 +1880,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	protected <S, T> List<T> doFind(String collectionName, Document query, Document fields, Class<S> entityClass,
 			CursorPreparer preparer, DocumentCallback<T> objectCallback) {
 
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
+		Optional<? extends MongoPersistentEntity<?>> entity = mappingContext.getPersistentEntity(entityClass);
 
 		Document mappedFields = queryMapper.getMappedFields(fields, entity);
 		Document mappedQuery = queryMapper.getMappedObject(query, entity);
@@ -1846,7 +1931,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 					serializeToJsonSafely(query), fields, sort, entityClass, collectionName);
 		}
 
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
+		Optional<? extends MongoPersistentEntity<?>> entity = mappingContext.getPersistentEntity(entityClass);
 
 		return executeFindOneInternal(new FindAndRemoveCallback(queryMapper.getMappedObject(query, entity), fields, sort),
 				new ReadDocumentCallback<T>(readerToUse, entityClass, collectionName), collectionName);
@@ -1861,7 +1946,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 			options = new FindAndModifyOptions();
 		}
 
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
+		Optional<? extends MongoPersistentEntity<?>> entity = mappingContext.getPersistentEntity(entityClass);
 
 		increaseVersionForUpdateIfNecessary(entity, update);
 
@@ -1897,21 +1982,17 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 			return;
 		}
 
-		MongoPersistentProperty idProp = getIdPropertyFor(savedObject.getClass());
+		getIdPropertyFor(savedObject.getClass()).ifPresent(idProp -> {
 
-		if (idProp == null) {
-			return;
-		}
+			ConversionService conversionService = mongoConverter.getConversionService();
+			MongoPersistentEntity<?> entity = mappingContext.getRequiredPersistentEntity(savedObject.getClass());
+			PersistentPropertyAccessor accessor = entity.getPropertyAccessor(savedObject);
 
-		ConversionService conversionService = mongoConverter.getConversionService();
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(savedObject.getClass());
-		PersistentPropertyAccessor accessor = entity.getPropertyAccessor(savedObject);
-
-		if (accessor.getProperty(idProp) != null) {
-			return;
-		}
-
-		new ConvertingPropertyAccessor(accessor, conversionService).setProperty(idProp, id);
+			Optional<Object> value = accessor.getProperty(idProp);
+			if (!value.isPresent()) {
+				new ConvertingPropertyAccessor(accessor, conversionService).setProperty(idProp, Optional.of(id));
+			}
+		});
 	}
 
 	private MongoCollection<Document> getAndPrepareCollection(MongoDatabase db, String collectionName) {
@@ -1939,7 +2020,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	 * @return
 	 */
 	private <T> T executeFindOneInternal(CollectionCallback<Document> collectionCallback,
-										 DocumentCallback<T> objectCallback, String collectionName) {
+			DocumentCallback<T> objectCallback, String collectionName) {
 
 		try {
 			T result = objectCallback
@@ -1969,7 +2050,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	 * @return
 	 */
 	private <T> List<T> executeFindMultiInternal(CollectionCallback<FindIterable<Document>> collectionCallback,
-												 CursorPreparer preparer, DocumentCallback<T> objectCallback, String collectionName) {
+			CursorPreparer preparer, DocumentCallback<T> objectCallback, String collectionName) {
 
 		try {
 
@@ -2042,13 +2123,12 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		return exceptionTranslator;
 	}
 
-	private MongoPersistentEntity<?> getPersistentEntity(Class<?> type) {
-		return type == null ? null : mappingContext.getPersistentEntity(type);
+	private Optional<? extends MongoPersistentEntity<?>> getPersistentEntity(Class<?> type) {
+		return Optional.ofNullable(type).flatMap(it -> mappingContext.getPersistentEntity(it));
 	}
 
-	private MongoPersistentProperty getIdPropertyFor(Class<?> type) {
-		MongoPersistentEntity<?> persistentEntity = mappingContext.getPersistentEntity(type);
-		return persistentEntity == null ? null : persistentEntity.getIdProperty();
+	private Optional<MongoPersistentProperty> getIdPropertyFor(Class<?> type) {
+		return mappingContext.getPersistentEntity(type).flatMap(it -> it.getIdProperty());
 	}
 
 	private <T> String determineEntityCollectionName(T obj) {
@@ -2066,76 +2146,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 					"No class parameter provided, entity collection can't be determined!");
 		}
 
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
-		if (entity == null) {
-			throw new InvalidDataAccessApiUsageException(
-					"No Persistent Entity information found for the class " + entityClass.getName());
-		}
-		return entity.getCollection();
-	}
-
-	/**
-	 * Handles {@link WriteResult} errors based on the configured {@link WriteResultChecking}.
-	 *
-	 * @param writeResult
-	 * @param query
-	 * @param operation
-	 */
-	protected void handleAnyWriteResultErrors(WriteResult writeResult, Document query, MongoActionOperation operation) {
-
-		if (writeResultChecking == WriteResultChecking.NONE) {
-			return;
-		}
-
-		String error = ReflectiveWriteResultInvoker.getError(writeResult);
-
-		if (error == null) {
-			return;
-		}
-
-		String message;
-
-		switch (operation) {
-
-			case INSERT:
-			case SAVE:
-				message = String.format("Insert/Save for %s failed: %s", query, error);
-				break;
-			case INSERT_LIST:
-				message = String.format("Insert list failed: %s", error);
-				break;
-			default:
-				message = String.format("Execution of %s%s failed: %s", operation,
-						query == null ? "" : " using query " + query.toString(), error);
-		}
-
-		if (writeResultChecking == WriteResultChecking.EXCEPTION) {
-			throw new MongoDataIntegrityViolationException(message, writeResult, operation);
-		} else {
-			LOGGER.error(message);
-			return;
-		}
-	}
-
-	/**
-	 * Inspects the given {@link CommandResult} for erros and potentially throws an
-	 * {@link InvalidDataAccessApiUsageException} for that error.
-	 *
-	 * @param result must not be {@literal null}.
-	 * @param source must not be {@literal null}.
-	 */
-	private void handleCommandError(CommandResult result, Document source) {
-
-		try {
-			result.throwOnError();
-		} catch (MongoException ex) {
-
-			String error = result.getErrorMessage();
-			error = error == null ? "NO MESSAGE" : error;
-
-			throw new InvalidDataAccessApiUsageException(
-					"Command execution failed:  Error [" + error + "], Command = " + source, ex);
-		}
+		return mappingContext.getRequiredPersistentEntity(entityClass).getCollection();
 	}
 
 	private static final MongoConverter getDefaultMongoConverter(MongoDbFactory factory) {
@@ -2173,11 +2184,10 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	 * Returns all identifiers for the given documents. Will augment the given identifiers and fill in only the ones that
 	 * are {@literal null} currently. This would've been better solved in {@link #insertDBObjectList(String, List)}
 	 * directly but would require a signature change of that method.
-	 * 
+	 *
 	 * @param ids
 	 * @param documents
-	 * @return 
-	 * TODO: Remove for 2.0 and change method signature of {@link #insertDBObjectList(String, List)}.
+	 * @return TODO: Remove for 2.0 and change method signature of {@link #insertDBObjectList(String, List)}.
 	 */
 	private static List<Object> consolidateIdentifiers(List<ObjectId> ids, List<Document> documents) {
 
@@ -2348,8 +2358,9 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 
 		public ReadDocumentCallback(EntityReader<? super T, Bson> reader, Class<T> type, String collectionName) {
 
-			Assert.notNull(reader);
-			Assert.notNull(type);
+			Assert.notNull(reader, "EntityReader must not be null!");
+			Assert.notNull(type, "Entity type must not be null!");
+
 			this.reader = reader;
 			this.type = type;
 			this.collectionName = collectionName;
@@ -2426,7 +2437,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 
 			try {
 				if (query.getSkip() > 0) {
-					cursorToUse = cursorToUse.skip(query.getSkip());
+					cursorToUse = cursorToUse.skip((int) query.getSkip());
 				}
 				if (query.getLimit() > 0) {
 					cursorToUse = cursorToUse.limit(query.getLimit());
@@ -2491,7 +2502,9 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		 * @param delegate must not be {@literal null}.
 		 */
 		public GeoNearResultDocumentCallback(DocumentCallback<T> delegate, Metric metric) {
-			Assert.notNull(delegate);
+
+			Assert.notNull(delegate, "DocumentCallback must not be null!");
+
 			this.delegate = delegate;
 			this.metric = metric;
 		}
@@ -2587,10 +2600,6 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		}
 	}
 
-	public Mongo getMongo() {
-		return mongo;
-	}
-
 	public MongoDbFactory getMongoDbFactory() {
 		return mongoDbFactory;
 	}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReactiveMongoOperations.java

@@ -46,10 +46,10 @@ import reactor.core.publisher.Mono;
  *
  * @author Mark Paluch
  * @author Christoph Strobl
+ * @since 2.0
  * @see Flux
  * @see Mono
- * @see http://projectreactor.io/docs/
- * @since 2.0
+ * @see <a href="http://projectreactor.io/docs/">Project Reactor</a>
  */
 public interface ReactiveMongoOperations {
 
@@ -393,7 +393,7 @@ public interface ReactiveMongoOperations {
 	<T> Flux<GeoResult<T>> geoNear(NearQuery near, Class<T> entityClass, String collectionName);
 
 	/**
-	 * Triggers <a href="http://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
+	 * Triggers <a href="https://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
 	 * to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query}.
 	 *
 	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
@@ -405,7 +405,7 @@ public interface ReactiveMongoOperations {
 	<T> Mono<T> findAndModify(Query query, Update update, Class<T> entityClass);
 
 	/**
-	 * Triggers <a href="http://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
+	 * Triggers <a href="https://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
 	 * to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query}.
 	 *
 	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
@@ -418,7 +418,7 @@ public interface ReactiveMongoOperations {
 	<T> Mono<T> findAndModify(Query query, Update update, Class<T> entityClass, String collectionName);
 
 	/**
-	 * Triggers <a href="http://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
+	 * Triggers <a href="https://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
 	 * to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query} taking
 	 * {@link FindAndModifyOptions} into account.
 	 *
@@ -432,7 +432,7 @@ public interface ReactiveMongoOperations {
 	<T> Mono<T> findAndModify(Query query, Update update, FindAndModifyOptions options, Class<T> entityClass);
 
 	/**
-	 * Triggers <a href="http://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
+	 * Triggers <a href="https://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
 	 * to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query} taking
 	 * {@link FindAndModifyOptions} into account.
 	 *

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReactiveMongoTemplate.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,6 +27,7 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.Optional;
 import java.util.Set;
 import java.util.function.Function;
 import java.util.stream.Collectors;
@@ -373,7 +374,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#execute(java.lang.String, org.springframework.data.mongodb.core.ReactiveCollectionCallback)
 	 */
 	public <T> Flux<T> execute(String collectionName, ReactiveCollectionCallback<T> callback) {
-		Assert.notNull(callback);
+
+		Assert.notNull(callback, "ReactiveCollectionCallback must not be null!");
 		return createFlux(collectionName, callback);
 	}
 
@@ -386,7 +388,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	public <T> Flux<T> createFlux(ReactiveDatabaseCallback<T> callback) {
 
-		Assert.notNull(callback);
+		Assert.notNull(callback, "ReactiveDatabaseCallback must not be null!");
 
 		return Flux.defer(() -> callback.doInDB(getMongoDatabase())).onErrorResumeWith(translateFluxException());
 	}
@@ -400,7 +402,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	public <T> Mono<T> createMono(final ReactiveDatabaseCallback<T> callback) {
 
-		Assert.notNull(callback);
+		Assert.notNull(callback, "ReactiveDatabaseCallback must not be null!");
 
 		return Mono.defer(() -> Mono.from(callback.doInDB(getMongoDatabase()))).otherwise(translateMonoException());
 	}
@@ -414,8 +416,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	public <T> Flux<T> createFlux(String collectionName, ReactiveCollectionCallback<T> callback) {
 
-		Assert.hasText(collectionName);
-		Assert.notNull(callback);
+		Assert.hasText(collectionName, "Collection name must not be null or empty!");
+		Assert.notNull(callback, "ReactiveDatabaseCallback must not be null!");
 
 		Mono<MongoCollection<Document>> collectionPublisher = Mono
 				.fromCallable(() -> getAndPrepareCollection(getMongoDatabase(), collectionName));
@@ -433,8 +435,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	public <T> Mono<T> createMono(String collectionName, ReactiveCollectionCallback<T> callback) {
 
-		Assert.hasText(collectionName);
-		Assert.notNull(callback);
+		Assert.hasText(collectionName, "Collection name must not be null or empty!");
+		Assert.notNull(callback, "ReactiveCollectionCallback must not be null!");
 
 		Mono<MongoCollection<Document>> collectionPublisher = Mono
 				.fromCallable(() -> getAndPrepareCollection(getMongoDatabase(), collectionName));
@@ -609,8 +611,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	public <T> Mono<T> findById(Object id, Class<T> entityClass, String collectionName) {
 
-		MongoPersistentEntity<?> persistentEntity = mappingContext.getPersistentEntity(entityClass);
-		MongoPersistentProperty idProperty = persistentEntity == null ? null : persistentEntity.getIdProperty();
+		Optional<? extends MongoPersistentEntity<?>> persistentEntity = mappingContext.getPersistentEntity(entityClass);
+		MongoPersistentProperty idProperty = persistentEntity.isPresent() ? persistentEntity.get().getIdProperty().orElse(null) : null;
 
 		String idKey = idProperty == null ? ID_FIELD : idProperty.getName();
 
@@ -729,7 +731,9 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#count(org.springframework.data.mongodb.core.query.Query, java.lang.Class)
 	 */
 	public Mono<Long> count(Query query, Class<?> entityClass) {
-		Assert.notNull(entityClass);
+
+		Assert.notNull(entityClass, "Entity class must not be null!");
+
 		return count(query, entityClass, determineCollectionName(entityClass));
 	}
 
@@ -745,13 +749,13 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	public Mono<Long> count(final Query query, final Class<?> entityClass, String collectionName) {
 
-		Assert.hasText(collectionName);
+		Assert.hasText(collectionName, "Collection name must not be null or empty!");
 
 		return createMono(collectionName, collection -> {
 
 			final Document Document = query == null ? null
 					: queryMapper.getMappedObject(query.getQueryObject(),
-							entityClass == null ? null : mappingContext.getPersistentEntity(entityClass));
+							entityClass == null ? Optional.empty() : mappingContext.getPersistentEntity(entityClass));
 
 			return collection.count(Document);
 		});
@@ -856,11 +860,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		final Map<String, List<T>> elementsByCollection = new HashMap<String, List<T>>();
 
 		listToSave.forEach(element -> {
-			MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(element.getClass());
-
-			if (entity == null) {
-				throw new InvalidDataAccessApiUsageException("No PersistentEntity information found for " + element.getClass());
-			}
+			MongoPersistentEntity<?> entity = mappingContext.getRequiredPersistentEntity(element.getClass());
 
 			String collection = entity.getCollection();
 			List<T> collectionElements = elementsByCollection.get(collection);
@@ -880,7 +880,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	protected <T> Flux<T> doInsertBatch(final String collectionName, final Collection<? extends T> batchToSave,
 			final MongoWriter<Object> writer) {
 
-		Assert.notNull(writer);
+		Assert.notNull(writer, "MongoWriter must not be null!");
 
 		Mono<List<Tuple2<T, Document>>> prepareDocuments = Flux.fromIterable(batchToSave)
 				.flatMap(new Function<T, Flux<Tuple2<T, Document>>>() {
@@ -933,7 +933,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	public <T> Mono<T> save(T objectToSave) {
 
-		Assert.notNull(objectToSave);
+		Assert.notNull(objectToSave, "Object to save must not be null!");
 		return save(objectToSave, determineEntityCollectionName(objectToSave));
 	}
 
@@ -942,8 +942,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	public <T> Mono<T> save(T objectToSave, String collectionName) {
 
-		Assert.notNull(objectToSave);
-		Assert.hasText(collectionName);
+		Assert.notNull(objectToSave, "Object to save must not be null!");
+		Assert.hasText(collectionName, "Collection name must not be null or empty!");
 
 		MongoPersistentEntity<?> mongoPersistentEntity = getPersistentEntity(objectToSave.getClass());
 
@@ -962,25 +962,25 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 			ConvertingPropertyAccessor convertingAccessor = new ConvertingPropertyAccessor(
 					entity.getPropertyAccessor(objectToSave), mongoConverter.getConversionService());
 
-			MongoPersistentProperty idProperty = entity.getIdProperty();
-			MongoPersistentProperty versionProperty = entity.getVersionProperty();
+			MongoPersistentProperty idProperty = entity.getIdProperty().orElseThrow(() -> new IllegalArgumentException("No id property present!"));
+			MongoPersistentProperty versionProperty = entity.getVersionProperty().orElseThrow(() -> new IllegalArgumentException("No version property present!"));;
 
-			Object version = convertingAccessor.getProperty(versionProperty);
-			Number versionNumber = convertingAccessor.getProperty(versionProperty, Number.class);
+			Optional<Object> version = convertingAccessor.getProperty(versionProperty);
+			Optional<Number> versionNumber = convertingAccessor.getProperty(versionProperty, Number.class);
 
 			// Fresh instance -> initialize version property
-			if (version == null) {
+			if (!version.isPresent()) {
 				return doInsert(collectionName, objectToSave, mongoConverter);
 			}
 
 			ReactiveMongoTemplate.this.assertUpdateableIdIfNotSet(objectToSave);
 
 			// Create query for entity with the id and old version
-			Object id = convertingAccessor.getProperty(idProperty);
-			Query query = new Query(Criteria.where(idProperty.getName()).is(id).and(versionProperty.getName()).is(version));
+			Optional<Object> id = convertingAccessor.getProperty(idProperty);
+			Query query = new Query(Criteria.where(idProperty.getName()).is(id.get()).and(versionProperty.getName()).is(version.get()));
 
 			// Bump version number
-			convertingAccessor.setProperty(versionProperty, versionNumber.longValue() + 1);
+			convertingAccessor.setProperty(versionProperty, Optional.of(versionNumber.orElse(0).longValue() + 1));
 
 			ReactiveMongoTemplate.this.maybeEmitEvent(new BeforeConvertEvent<T>(objectToSave, collectionName));
 
@@ -1226,7 +1226,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	private void increaseVersionForUpdateIfNecessary(MongoPersistentEntity<?> persistentEntity, Update update) {
 
 		if (persistentEntity != null && persistentEntity.hasVersionProperty()) {
-			String versionFieldName = persistentEntity.getVersionProperty().getFieldName();
+			String versionFieldName = persistentEntity.getVersionProperty().get().getFieldName();
 			if (!update.modifies(versionFieldName)) {
 				update.inc(versionFieldName, 1L);
 			}
@@ -1239,7 +1239,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 			return false;
 		}
 
-		return document.containsKey(persistentEntity.getVersionProperty().getFieldName());
+		return document.containsKey(persistentEntity.getVersionProperty().get().getFieldName());
 	}
 
 	/* (non-Javadoc)
@@ -1275,7 +1275,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	public Mono<DeleteResult> remove(Object object, String collection) {
 
-		Assert.hasText(collection);
+		Assert.hasText(collection, "Collection name must not be null or empty!");
 
 		if (object == null) {
 			return null;
@@ -1301,15 +1301,15 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 			return Collections.singletonMap(ID_FIELD, ((Document) object).get(ID_FIELD)).entrySet().iterator().next();
 		}
 
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(objectType);
-		MongoPersistentProperty idProp = entity == null ? null : entity.getIdProperty();
+		Optional<? extends MongoPersistentEntity<?>> entity = mappingContext.getPersistentEntity(objectType);
+		MongoPersistentProperty idProp = entity.isPresent() ? entity.get().getIdProperty().orElse(null) : null;
 
 		if (idProp == null) {
 			throw new MappingException("No id property found for object of type " + objectType);
 		}
 
-		Object idValue = entity.getPropertyAccessor(object).getProperty(idProp);
-		return Collections.singletonMap(idProp.getFieldName(), idValue).entrySet().iterator().next();
+		Optional<Object> idValue = entity.get().getPropertyAccessor(object).getProperty(idProp);
+		return Collections.singletonMap(idProp.getFieldName(), idValue.get()).entrySet().iterator().next();
 	}
 
 	/**
@@ -1349,18 +1349,18 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 
 	private void assertUpdateableIdIfNotSet(Object entity) {
 
-		MongoPersistentEntity<?> persistentEntity = mappingContext.getPersistentEntity(entity.getClass());
-		MongoPersistentProperty idProperty = persistentEntity == null ? null : persistentEntity.getIdProperty();
+		Optional<? extends MongoPersistentEntity<?>> persistentEntity = mappingContext.getPersistentEntity(entity.getClass());
+		Optional<MongoPersistentProperty> idProperty = persistentEntity.isPresent() ? persistentEntity.get().getIdProperty() : Optional.empty();
 
-		if (idProperty == null) {
+		if (!idProperty.isPresent()) {
 			return;
 		}
 
-		Object idValue = persistentEntity.getPropertyAccessor(entity).getProperty(idProperty);
+		Optional<Object> idValue = persistentEntity.get().getPropertyAccessor(entity).getProperty(idProperty.get());
 
-		if (idValue == null && !MongoSimpleTypes.AUTOGENERATED_ID_TYPES.contains(idProperty.getType())) {
+		if (!idValue.isPresent() && !MongoSimpleTypes.AUTOGENERATED_ID_TYPES.contains(idProperty.get().getType())) {
 			throw new InvalidDataAccessApiUsageException(
-					String.format("Cannot autogenerate id of type %s for entity of type %s!", idProperty.getType().getName(),
+					String.format("Cannot autogenerate id of type %s for entity of type %s!", idProperty.get().getType().getName(),
 							entity.getClass().getName()));
 		}
 	}
@@ -1532,7 +1532,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	protected <T> Mono<T> doFindOne(String collectionName, Document query, Document fields, Class<T> entityClass) {
 
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
+		Optional<? extends MongoPersistentEntity<?>> entity = mappingContext.getPersistentEntity(entityClass);
 		Document mappedQuery = queryMapper.getMappedObject(query, entity);
 		Document mappedFields = fields == null ? null : queryMapper.getMappedObject(fields, entity);
 
@@ -1582,7 +1582,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	protected <S, T> Flux<T> doFind(String collectionName, Document query, Document fields, Class<S> entityClass,
 			FindPublisherPreparer preparer, DocumentCallback<T> objectCallback) {
 
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
+		Optional<? extends MongoPersistentEntity<?>> entity = mappingContext.getPersistentEntity(entityClass);
 
 		Document mappedFields = queryMapper.getMappedFields(fields, entity);
 		Document mappedQuery = queryMapper.getMappedObject(query, entity);
@@ -1635,7 +1635,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 					serializeToJsonSafely(query), fields, sort, entityClass, collectionName));
 		}
 
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
+		Optional<? extends MongoPersistentEntity<?>> entity = mappingContext.getPersistentEntity(entityClass);
 
 		return executeFindOneInternal(new FindAndRemoveCallback(queryMapper.getMappedObject(query, entity), fields, sort),
 				new ReadDocumentCallback<T>(this.mongoConverter, entityClass, collectionName), collectionName);
@@ -1651,11 +1651,11 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 			optionsToUse = options;
 		}
 
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
+		Optional<? extends MongoPersistentEntity<?>> entity = mappingContext.getPersistentEntity(entityClass);
 
 		return Mono.defer(() -> {
 
-			increaseVersionForUpdateIfNecessary(entity, update);
+			increaseVersionForUpdateIfNecessary(entity.get(), update);
 
 			Document mappedQuery = queryMapper.getMappedObject(query, entity);
 			Document mappedUpdate = updateMapper.getMappedObject(update.getUpdateObject(), entity);
@@ -1703,14 +1703,14 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		}
 
 		ConversionService conversionService = mongoConverter.getConversionService();
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(savedObject.getClass());
+		MongoPersistentEntity<?> entity = mappingContext.getRequiredPersistentEntity(savedObject.getClass());
 		PersistentPropertyAccessor accessor = entity.getPropertyAccessor(savedObject);
 
-		if (accessor.getProperty(idProp) != null) {
+		if (accessor.getProperty(idProp).isPresent()) {
 			return;
 		}
 
-		new ConvertingPropertyAccessor(accessor, conversionService).setProperty(idProp, id);
+		new ConvertingPropertyAccessor(accessor, conversionService).setProperty(idProp, Optional.ofNullable(id));
 	}
 
 	private MongoCollection<Document> getAndPrepareCollection(MongoDatabase db, String collectionName) {
@@ -1839,7 +1839,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 
 	private <T> T execute(MongoDatabaseCallback<T> action) {
 
-		Assert.notNull(action);
+		Assert.notNull(action, "MongoDatabaseCallback must not be null!");
 
 		try {
 			MongoDatabase db = this.getMongoDatabase();
@@ -1898,12 +1898,12 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	}
 
 	private MongoPersistentEntity<?> getPersistentEntity(Class<?> type) {
-		return type == null ? null : mappingContext.getPersistentEntity(type);
+		return type == null ? null : mappingContext.getPersistentEntity(type).orElse(null);
 	}
 
 	private MongoPersistentProperty getIdPropertyFor(Class<?> type) {
-		MongoPersistentEntity<?> persistentEntity = mappingContext.getPersistentEntity(type);
-		return persistentEntity == null ? null : persistentEntity.getIdProperty();
+		Optional<? extends MongoPersistentEntity<?>> persistentEntity = mappingContext.getPersistentEntity(type);
+		return persistentEntity.isPresent() ? persistentEntity.get().getIdProperty().orElse(null) : null;
 	}
 
 	private <T> String determineEntityCollectionName(T obj) {
@@ -1922,13 +1922,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 					"No class parameter provided, entity collection can't be determined!");
 		}
 
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
-
-		if (entity == null) {
-			throw new InvalidDataAccessApiUsageException(
-					"No Persistent Entity information found for the class " + entityClass.getName());
-		}
-
+		MongoPersistentEntity<?> entity = mappingContext.getRequiredPersistentEntity(entityClass);
 		return entity.getCollection();
 	}
 
@@ -1983,7 +1977,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		if (mongoPersistentEntity != null && mongoPersistentEntity.hasVersionProperty()) {
 			ConvertingPropertyAccessor accessor = new ConvertingPropertyAccessor(
 					mongoPersistentEntity.getPropertyAccessor(entity), mongoConverter.getConversionService());
-			accessor.setProperty(mongoPersistentEntity.getVersionProperty(), 0);
+			accessor.setProperty(mongoPersistentEntity.getVersionProperty().get(), Optional.of(0));
 		}
 	}
 
@@ -2202,8 +2196,9 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 
 		ReadDocumentCallback(EntityReader<? super T, Bson> reader, Class<T> type, String collectionName) {
 
-			Assert.notNull(reader);
-			Assert.notNull(type);
+			Assert.notNull(reader, "EntityReader must not be null!");
+			Assert.notNull(type, "Entity type must not be null!");
+
 			this.reader = reader;
 			this.type = type;
 			this.collectionName = collectionName;
@@ -2240,7 +2235,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		 */
 		GeoNearResultDbObjectCallback(DocumentCallback<T> delegate, Metric metric) {
 
-			Assert.notNull(delegate);
+			Assert.notNull(delegate, "DocumentCallback must not be null!");
+
 			this.delegate = delegate;
 			this.metric = metric;
 		}
@@ -2285,7 +2281,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 
 			try {
 				if (query.getSkip() > 0) {
-					findPublisherToUse = findPublisherToUse.skip(query.getSkip());
+					findPublisherToUse = findPublisherToUse.skip((int)query.getSkip());
 				}
 				if (query.getLimit() > 0) {
 					findPublisherToUse = findPublisherToUse.limit(query.getLimit());
@@ -2341,9 +2337,9 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	static class NoOpDbRefResolver implements DbRefResolver {
 
 		@Override
-		public Object resolveDbRef(MongoPersistentProperty property, DBRef dbref, DbRefResolverCallback callback,
+		public Optional<Object> resolveDbRef(MongoPersistentProperty property, DBRef dbref, DbRefResolverCallback callback,
 				DbRefProxyHandler proxyHandler) {
-			return null;
+			return Optional.empty();
 		}
 
 		@Override

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReflectiveDBCollectionInvoker.java

@@ -1,109 +0,0 @@
-/*
- * Copyright 2015 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import static org.springframework.data.mongodb.util.MongoClientVersion.*;
-import static org.springframework.util.ReflectionUtils.*;
-
-import java.lang.reflect.Method;
-
-import org.bson.Document;
-import org.springframework.data.mongodb.util.MongoClientVersion;
-
-import com.mongodb.DBCollection;
-
-/**
- * {@link ReflectiveDBCollectionInvoker} provides reflective access to {@link DBCollection} API that is not consistently
- * available for various driver versions.
- * 
- * @author Christoph Strobl
- * @author Oliver Gierke
- * @since 1.7
- */
-class ReflectiveDBCollectionInvoker {
-
-	private static final Method GEN_INDEX_NAME_METHOD;
-	private static final Method RESET_INDEX_CHACHE_METHOD;
-
-	static {
-
-		GEN_INDEX_NAME_METHOD = findMethod(DBCollection.class, "genIndexName", Document.class);
-		RESET_INDEX_CHACHE_METHOD = findMethod(DBCollection.class, "resetIndexCache");
-	}
-
-	private ReflectiveDBCollectionInvoker() {}
-
-	/**
-	 * Convenience method to generate an index name from the set of fields it is over. Will fall back to a MongoDB Java
-	 * driver version 2 compatible way of generating index name in case of {@link MongoClientVersion#isMongo3Driver()}.
-	 * 
-	 * @param keys the names of the fields used in this index
-	 * @return
-	 */
-	public static String generateIndexName(Document keys) {
-
-		if (isMongo3Driver()) {
-			return genIndexName(keys);
-		}
-		return (String) invokeMethod(GEN_INDEX_NAME_METHOD, null, keys);
-	}
-
-	/**
-	 * In case of MongoDB Java driver version 2 all indices that have not yet been applied to this collection will be
-	 * cleared. Since this method is not available for the MongoDB Java driver version 3 the operation will throw
-	 * {@link UnsupportedOperationException}.
-	 * 
-	 * @param dbCollection
-	 * @throws UnsupportedOperationException
-	 */
-	public static void resetIndexCache(DBCollection dbCollection) {
-
-		if (isMongo3Driver()) {
-			throw new UnsupportedOperationException("The mongo java driver 3 does no loger support resetIndexCache!");
-		}
-
-		invokeMethod(RESET_INDEX_CHACHE_METHOD, dbCollection);
-	}
-
-	/**
-	 * Borrowed from MongoDB Java driver version 2. See
-	 * <a href="http://github.com/mongodb/mongo-java-driver/blob/r2.13.0/src/main/com/mongodb/DBCollection.java#L754" >
-	 * http://github.com/mongodb/mongo-java-driver/blob/r2.13.0/src/main/com/mongodb/DBCollection.java#L754</a>
-	 * 
-	 * @param keys
-	 * @return
-	 */
-	private static String genIndexName(Document keys) {
-
-		StringBuilder name = new StringBuilder();
-
-		for (String s : keys.keySet()) {
-
-			if (name.length() > 0) {
-				name.append('_');
-			}
-
-			name.append(s).append('_');
-			Object val = keys.get(s);
-
-			if (val instanceof Number || val instanceof String) {
-				name.append(val.toString().replace(' ', '_'));
-			}
-		}
-
-		return name.toString();
-	}
-}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReflectiveDbInvoker.java

@@ -1,134 +0,0 @@
-/*
- * Copyright 2015-2016 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import static org.springframework.data.mongodb.util.MongoClientVersion.*;
-import static org.springframework.util.ReflectionUtils.*;
-
-import java.lang.reflect.Method;
-
-import org.springframework.data.authentication.UserCredentials;
-import org.springframework.data.mongodb.CannotGetMongoDbConnectionException;
-import org.springframework.data.mongodb.util.MongoClientVersion;
-
-import com.mongodb.DB;
-import com.mongodb.Mongo;
-
-/**
- * {@link ReflectiveDbInvoker} provides reflective access to {@link DB} API that is not consistently available for
- * various driver versions.
- *
- * @author Christoph Strobl
- * @author Oliver Gierke
- * @since 1.7
- */
-final class ReflectiveDbInvoker {
-
-	private static final Method DB_IS_AUTHENTICATED_METHOD;
-	private static final Method DB_AUTHENTICATE_METHOD;
-	private static final Method DB_REQUEST_DONE_METHOD;
-	private static final Method DB_ADD_USER_METHOD;
-	private static final Method DB_REQUEST_START_METHOD;
-
-	static {
-
-		DB_IS_AUTHENTICATED_METHOD = findMethod(DB.class, "isAuthenticated");
-		DB_AUTHENTICATE_METHOD = findMethod(DB.class, "authenticate", String.class, char[].class);
-		DB_REQUEST_DONE_METHOD = findMethod(DB.class, "requestDone");
-		DB_ADD_USER_METHOD = findMethod(DB.class, "addUser", String.class, char[].class);
-		DB_REQUEST_START_METHOD = findMethod(DB.class, "requestStart");
-	}
-
-	private ReflectiveDbInvoker() {}
-
-	/**
-	 * Authenticate against database using provided credentials in case of a MongoDB Java driver version 2.
-	 *
-	 * @param mongo must not be {@literal null}.
-	 * @param db must not be {@literal null}.
-	 * @param credentials must not be {@literal null}.
-	 * @param authenticationDatabaseName
-	 */
-	public static void authenticate(Mongo mongo, DB db, UserCredentials credentials, String authenticationDatabaseName) {
-
-		String databaseName = db.getName();
-
-		DB authDb = databaseName.equals(authenticationDatabaseName) ? db : mongo.getDB(authenticationDatabaseName);
-
-		synchronized (authDb) {
-
-			Boolean isAuthenticated = (Boolean) invokeMethod(DB_IS_AUTHENTICATED_METHOD, authDb);
-			if (!isAuthenticated) {
-
-				String username = credentials.getUsername();
-				String password = credentials.hasPassword() ? credentials.getPassword() : null;
-
-				Boolean authenticated = (Boolean) invokeMethod(DB_AUTHENTICATE_METHOD, authDb, username,
-						password == null ? null : password.toCharArray());
-				if (!authenticated) {
-					throw new CannotGetMongoDbConnectionException("Failed to authenticate to database [" + databaseName + "], "
-							+ credentials.toString(), databaseName, credentials);
-				}
-			}
-		}
-	}
-
-	/**
-	 * Starts a new 'consistent request' in case of MongoDB Java driver version 2. Will do nothing for MongoDB Java driver
-	 * version 3 since the operation is no longer available.
-	 *
-	 * @param db
-	 */
-	public static void requestStart(DB db) {
-
-		if (isMongo3Driver()) {
-			return;
-		}
-
-		invokeMethod(DB_REQUEST_START_METHOD, db);
-	}
-
-	/**
-	 * Ends the current 'consistent request'. a new 'consistent request' in case of MongoDB Java driver version 2. Will do
-	 * nothing for MongoDB Java driver version 3 since the operation is no longer available
-	 *
-	 * @param db
-	 */
-	public static void requestDone(DB db) {
-
-		if (MongoClientVersion.isMongo3Driver()) {
-			return;
-		}
-
-		invokeMethod(DB_REQUEST_DONE_METHOD, db);
-	}
-
-	/**
-	 * @param db
-	 * @param username
-	 * @param password
-	 * @throws UnsupportedOperationException
-	 */
-	public static void addUser(DB db, String username, char[] password) {
-
-		if (isMongo3Driver()) {
-			throw new UnsupportedOperationException(
-					"Please use DB.command(…) to call either the createUser or updateUser command!");
-		}
-
-		invokeMethod(DB_ADD_USER_METHOD, db, username, password);
-	}
-}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReflectiveMapReduceInvoker.java

@@ -1,62 +0,0 @@
-/*
- * Copyright 2015 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import static org.springframework.data.mongodb.util.MongoClientVersion.*;
-import static org.springframework.util.ReflectionUtils.*;
-
-import java.lang.reflect.Method;
-
-import org.springframework.util.Assert;
-
-import com.mongodb.MapReduceCommand;
-
-/**
- * {@link ReflectiveMapReduceInvoker} provides reflective access to {@link MapReduceCommand} API that is not
- * consistently available for various driver versions.
- * 
- * @author Christoph Strobl
- * @author Oliver Gierke
- * @since 1.7
- */
-final class ReflectiveMapReduceInvoker {
-
-	private static final Method ADD_EXTRA_OPTION_METHOD;
-
-	static {
-
-		ADD_EXTRA_OPTION_METHOD = findMethod(MapReduceCommand.class, "addExtraOption", String.class, Object.class);
-	}
-
-	private ReflectiveMapReduceInvoker() {}
-
-	/**
-	 * Sets the extra option for MongoDB Java driver version 2. Will do nothing for MongoDB Java driver version 2.
-	 * 
-	 * @param cmd can be {@literal null} for MongoDB Java driver version 2.
-	 * @param key
-	 * @param value
-	 */
-	public static void addExtraOption(MapReduceCommand cmd, String key, Object value) {
-
-		if (isMongo3Driver()) {
-			return;
-		}
-
-		Assert.notNull(cmd, "MapReduceCommand must not be null!");
-		invokeMethod(ADD_EXTRA_OPTION_METHOD, cmd, key, value);
-	}
-}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReflectiveMongoOptionsInvoker.java

@@ -1,158 +0,0 @@
-/*
- * Copyright 2015 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import static org.springframework.data.mongodb.util.MongoClientVersion.*;
-import static org.springframework.util.ReflectionUtils.*;
-
-import java.lang.reflect.Method;
-
-import org.springframework.beans.DirectFieldAccessor;
-import org.springframework.util.ReflectionUtils;
-
-import com.mongodb.MongoOptions;
-
-/**
- * {@link ReflectiveMongoOptionsInvoker} provides reflective access to {@link MongoOptions} API that is not consistently
- * available for various driver versions.
- * 
- * @author Christoph Strobl
- * @author Oliver Gierke
- * @since 1.7
- */
-@SuppressWarnings("deprecation")
-class ReflectiveMongoOptionsInvoker {
-
-	private static final Method GET_AUTO_CONNECT_RETRY_METHOD;
-	private static final Method SET_AUTO_CONNECT_RETRY_METHOD;
-	private static final Method GET_MAX_AUTO_CONNECT_RETRY_TIME_METHOD;
-	private static final Method SET_MAX_AUTO_CONNECT_RETRY_TIME_METHOD;
-
-	static {
-
-		SET_AUTO_CONNECT_RETRY_METHOD = ReflectionUtils
-				.findMethod(MongoOptions.class, "setAutoConnectRetry", boolean.class);
-		GET_AUTO_CONNECT_RETRY_METHOD = ReflectionUtils.findMethod(MongoOptions.class, "isAutoConnectRetry");
-		SET_MAX_AUTO_CONNECT_RETRY_TIME_METHOD = ReflectionUtils.findMethod(MongoOptions.class,
-				"setMaxAutoConnectRetryTime", long.class);
-		GET_MAX_AUTO_CONNECT_RETRY_TIME_METHOD = ReflectionUtils.findMethod(MongoOptions.class,
-				"getMaxAutoConnectRetryTime");
-	}
-
-	private ReflectiveMongoOptionsInvoker() {}
-
-	/**
-	 * Sets the retry connection flag for MongoDB Java driver version 2. Will do nothing for MongoDB Java driver version 3
-	 * since the method has been removed.
-	 * 
-	 * @param options can be {@literal null} for MongoDB Java driver version 3.
-	 * @param autoConnectRetry
-	 */
-	public static void setAutoConnectRetry(MongoOptions options, boolean autoConnectRetry) {
-
-		if (isMongo3Driver()) {
-			return;
-		}
-
-		invokeMethod(SET_AUTO_CONNECT_RETRY_METHOD, options, autoConnectRetry);
-	}
-
-	/**
-	 * Sets the maxAutoConnectRetryTime attribute for MongoDB Java driver version 2. Will do nothing for MongoDB Java
-	 * driver version 3 since the method has been removed.
-	 * 
-	 * @param options can be {@literal null} for MongoDB Java driver version 3.
-	 * @param maxAutoConnectRetryTime
-	 */
-	public static void setMaxAutoConnectRetryTime(MongoOptions options, long maxAutoConnectRetryTime) {
-
-		if (isMongo3Driver()) {
-			return;
-		}
-
-		invokeMethod(SET_MAX_AUTO_CONNECT_RETRY_TIME_METHOD, options, maxAutoConnectRetryTime);
-	}
-
-	/**
-	 * Sets the slaveOk attribute for MongoDB Java driver version 2. Will do nothing for MongoDB Java driver version 3
-	 * since the method has been removed.
-	 * 
-	 * @param options can be {@literal null} for MongoDB Java driver version 3.
-	 * @param slaveOk
-	 */
-	public static void setSlaveOk(MongoOptions options, boolean slaveOk) {
-
-		if (isMongo3Driver()) {
-			return;
-		}
-
-		new DirectFieldAccessor(options).setPropertyValue("slaveOk", slaveOk);
-	}
-
-	/**
-	 * Gets the slaveOk attribute for MongoDB Java driver version 2. Throws {@link UnsupportedOperationException} for
-	 * MongoDB Java driver version 3 since the method has been removed.
-	 * 
-	 * @param options can be {@literal null} for MongoDB Java driver version 3.
-	 * @return
-	 * @throws UnsupportedOperationException
-	 */
-	public static boolean getSlaveOk(MongoOptions options) {
-
-		if (isMongo3Driver()) {
-			throw new UnsupportedOperationException(
-					"Cannot get value for autoConnectRetry which has been removed in MongoDB Java driver version 3.");
-		}
-
-		return ((Boolean) new DirectFieldAccessor(options).getPropertyValue("slaveOk")).booleanValue();
-	}
-
-	/**
-	 * Gets the autoConnectRetry attribute for MongoDB Java driver version 2. Throws {@link UnsupportedOperationException}
-	 * for MongoDB Java driver version 3 since the method has been removed.
-	 * 
-	 * @param options can be {@literal null} for MongoDB Java driver version 3.
-	 * @return
-	 * @throws UnsupportedOperationException
-	 */
-	public static boolean getAutoConnectRetry(MongoOptions options) {
-
-		if (isMongo3Driver()) {
-			throw new UnsupportedOperationException(
-					"Cannot get value for autoConnectRetry which has been removed in MongoDB Java driver version 3.");
-		}
-
-		return ((Boolean) invokeMethod(GET_AUTO_CONNECT_RETRY_METHOD, options)).booleanValue();
-	}
-
-	/**
-	 * Gets the maxAutoConnectRetryTime attribute for MongoDB Java driver version 2. Throws
-	 * {@link UnsupportedOperationException} for MongoDB Java driver version 3 since the method has been removed.
-	 * 
-	 * @param options can be {@literal null} for MongoDB Java driver version 3.
-	 * @return
-	 * @throws UnsupportedOperationException
-	 */
-	public static long getMaxAutoConnectRetryTime(MongoOptions options) {
-
-		if (isMongo3Driver()) {
-			throw new UnsupportedOperationException(
-					"Cannot get value for maxAutoConnectRetryTime which has been removed in MongoDB Java driver version 3.");
-		}
-
-		return ((Long) invokeMethod(GET_MAX_AUTO_CONNECT_RETRY_TIME_METHOD, options)).longValue();
-	}
-}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReflectiveWriteConcernInvoker.java

@@ -1,48 +0,0 @@
-/*
- * Copyright 2015 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import static org.springframework.data.mongodb.util.MongoClientVersion.*;
-
-import org.springframework.beans.DirectFieldAccessor;
-
-import com.mongodb.WriteConcern;
-
-/**
- * {@link ReflectiveWriteConcernInvoker} provides reflective access to {@link WriteConcern} API that is not consistently
- * available for various driver versions.
- * 
- * @author Christoph Strobl
- * @author Oliver Gierke
- * @since 1.7
- */
-class ReflectiveWriteConcernInvoker {
-
-	private static final WriteConcern NONE_OR_UNACKNOWLEDGED;
-
-	static {
-
-		NONE_OR_UNACKNOWLEDGED = isMongo3Driver() ? WriteConcern.UNACKNOWLEDGED : (WriteConcern) new DirectFieldAccessor(
-				new WriteConcern()).getPropertyValue("NONE");
-	}
-
-	/**
-	 * @return {@link WriteConcern#NONE} for MongoDB Java driver version 2, otherwise {@link WriteConcern#UNACKNOWLEDGED}.
-	 */
-	public static WriteConcern noneOrUnacknowledged() {
-		return NONE_OR_UNACKNOWLEDGED;
-	}
-}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/ReflectiveWriteResultInvoker.java

@@ -1,78 +0,0 @@
-/*
- * Copyright 2015 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import static org.springframework.data.mongodb.util.MongoClientVersion.*;
-import static org.springframework.util.ReflectionUtils.*;
-
-import java.lang.reflect.Method;
-
-import com.mongodb.MongoException;
-import com.mongodb.WriteResult;
-import com.mongodb.client.result.UpdateResult;
-
-/**
- * {@link ReflectiveWriteResultInvoker} provides reflective access to {@link WriteResult} API that is not consistently
- * available for various driver versions.
- * 
- * @author Christoph Strobl
- * @author Oliver Gierke
- * @since 1.7
- */
-final class ReflectiveWriteResultInvoker {
-
-	private static final Method GET_ERROR_METHOD;
-	private static final Method WAS_ACKNOWLEDGED_METHOD;
-	private static final Method WAS_ACKNOWLEDGED_METHOD_UR;
-
-	private ReflectiveWriteResultInvoker() {}
-
-	static {
-
-		GET_ERROR_METHOD = findMethod(WriteResult.class, "getError");
-		WAS_ACKNOWLEDGED_METHOD = findMethod(WriteResult.class, "wasAcknowledged");
-		WAS_ACKNOWLEDGED_METHOD_UR = findMethod(UpdateResult.class, "wasAcknowledged");
-	}
-
-	/**
-	 * @param writeResult can be {@literal null} for MongoDB Java driver version 3.
-	 * @return null in case of MongoDB Java driver version 3 since errors are thrown as {@link MongoException}.
-	 */
-	public static String getError(WriteResult writeResult) {
-
-		if (isMongo3Driver()) {
-			return null;
-		}
-
-		return (String) invokeMethod(GET_ERROR_METHOD, writeResult);
-	}
-
-	/**
-	 * @param writeResult
-	 * @return return in case of MongoDB Java driver version 2.
-	 */
-	public static boolean wasAcknowledged(WriteResult writeResult) {
-		return isMongo3Driver() ? ((Boolean) invokeMethod(WAS_ACKNOWLEDGED_METHOD, writeResult)).booleanValue() : true;
-	}
-
-	/**
-	 * @param writeResult
-	 * @return return in case of MongoDB Java driver version 2.
-	 */
-	public static boolean wasAcknowledged(UpdateResult writeResult) {
-		return isMongo3Driver() ? ((Boolean) invokeMethod(WAS_ACKNOWLEDGED_METHOD_UR, writeResult)).booleanValue() : true;
-	}
-}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/SimpleMongoDbFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2016 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,24 +19,18 @@ import java.net.UnknownHostException;
 
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.dao.DataAccessException;
-import org.springframework.dao.InvalidDataAccessApiUsageException;
 import org.springframework.dao.support.PersistenceExceptionTranslator;
-import org.springframework.data.authentication.UserCredentials;
 import org.springframework.data.mongodb.MongoDbFactory;
 import org.springframework.util.Assert;
-import org.springframework.util.StringUtils;
 
 import com.mongodb.DB;
-import com.mongodb.Mongo;
 import com.mongodb.MongoClient;
 import com.mongodb.MongoClientURI;
-import com.mongodb.MongoException;
-import com.mongodb.MongoURI;
 import com.mongodb.WriteConcern;
 import com.mongodb.client.MongoDatabase;
 
 /**
- * Factory to create {@link DB} instances from a {@link Mongo} instance.
+ * Factory to create {@link DB} instances from a {@link MongoClient} instance.
  * 
  * @author Mark Pollack
  * @author Oliver Gierke
@@ -45,70 +39,13 @@ import com.mongodb.client.MongoDatabase;
  */
 public class SimpleMongoDbFactory implements DisposableBean, MongoDbFactory {
 
-	private final Mongo mongo;
+	private final MongoClient mongoClient;
 	private final String databaseName;
 	private final boolean mongoInstanceCreated;
-	private final UserCredentials credentials;
 	private final PersistenceExceptionTranslator exceptionTranslator;
-	private final String authenticationDatabaseName;
 
 	private WriteConcern writeConcern;
 
-	/**
-	 * Create an instance of {@link SimpleMongoDbFactory} given the {@link Mongo} instance and database name.
-	 * 
-	 * @param mongo Mongo instance, must not be {@literal null}.
-	 * @param databaseName database name, not be {@literal null} or empty.
-	 * @deprecated since 1.7. Please use {@link #SimpleMongoDbFactory(MongoClient, String)}.
-	 */
-	@Deprecated
-	public SimpleMongoDbFactory(Mongo mongo, String databaseName) {
-		this(mongo, databaseName, null);
-	}
-
-	/**
-	 * Create an instance of SimpleMongoDbFactory given the Mongo instance, database name, and username/password
-	 * 
-	 * @param mongo Mongo instance, must not be {@literal null}.
-	 * @param databaseName Database name, must not be {@literal null} or empty.
-	 * @param credentials username and password.
-	 * @deprecated since 1.7. The credentials used should be provided by {@link MongoClient#getCredentialsList()}.
-	 */
-	@Deprecated
-	public SimpleMongoDbFactory(Mongo mongo, String databaseName, UserCredentials credentials) {
-		this(mongo, databaseName, credentials, false, null);
-	}
-
-	/**
-	 * Create an instance of SimpleMongoDbFactory given the Mongo instance, database name, and username/password
-	 * 
-	 * @param mongo Mongo instance, must not be {@literal null}.
-	 * @param databaseName Database name, must not be {@literal null} or empty.
-	 * @param credentials username and password.
-	 * @param authenticationDatabaseName the database name to use for authentication
-	 * @deprecated since 1.7. The credentials used should be provided by {@link MongoClient#getCredentialsList()}.
-	 */
-	@Deprecated
-	public SimpleMongoDbFactory(Mongo mongo, String databaseName, UserCredentials credentials,
-			String authenticationDatabaseName) {
-		this(mongo, databaseName, credentials, false, authenticationDatabaseName);
-	}
-
-	/**
-	 * Creates a new {@link SimpleMongoDbFactory} instance from the given {@link MongoURI}.
-	 * 
-	 * @param uri must not be {@literal null}.
-	 * @throws MongoException
-	 * @throws UnknownHostException
-	 * @see MongoURI
-	 * @deprecated since 1.7. Please use {@link #SimpleMongoDbFactory(MongoClientURI)} instead.
-	 */
-	@Deprecated
-	public SimpleMongoDbFactory(MongoURI uri) throws MongoException, UnknownHostException {
-		this(new Mongo(uri), uri.getDatabase(), new UserCredentials(uri.getUsername(), parseChars(uri.getPassword())), true,
-				uri.getDatabase());
-	}
-
 	/**
 	 * Creates a new {@link SimpleMongoDbFactory} instance from the given {@link MongoClientURI}.
 	 * 
@@ -116,7 +53,7 @@ public class SimpleMongoDbFactory implements DisposableBean, MongoDbFactory {
 	 * @throws UnknownHostException
 	 * @since 1.7
 	 */
-	public SimpleMongoDbFactory(MongoClientURI uri) throws UnknownHostException {
+	public SimpleMongoDbFactory(MongoClientURI uri) {
 		this(new MongoClient(uri), uri.getDatabase(), true);
 	}
 
@@ -131,48 +68,23 @@ public class SimpleMongoDbFactory implements DisposableBean, MongoDbFactory {
 		this(mongoClient, databaseName, false);
 	}
 
-	private SimpleMongoDbFactory(Mongo mongo, String databaseName, UserCredentials credentials,
-			boolean mongoInstanceCreated, String authenticationDatabaseName) {
-
-		if (mongo instanceof MongoClient && (credentials != null && !UserCredentials.NO_CREDENTIALS.equals(credentials))) {
-			throw new InvalidDataAccessApiUsageException(
-					"Usage of 'UserCredentials' with 'MongoClient' is no longer supported. Please use 'MongoCredential' for 'MongoClient' or just 'Mongo'.");
-		}
-
-		Assert.notNull(mongo, "Mongo must not be null");
-		Assert.hasText(databaseName, "Database name must not be empty");
-		Assert.isTrue(databaseName.matches("[\\w-]+"),
-				"Database name must only contain letters, numbers, underscores and dashes!");
-
-		this.mongo = mongo;
-		this.databaseName = databaseName;
-		this.mongoInstanceCreated = mongoInstanceCreated;
-		this.credentials = credentials == null ? UserCredentials.NO_CREDENTIALS : credentials;
-		this.exceptionTranslator = new MongoExceptionTranslator();
-		this.authenticationDatabaseName = StringUtils.hasText(authenticationDatabaseName) ? authenticationDatabaseName
-				: databaseName;
-
-		Assert.isTrue(this.authenticationDatabaseName.matches("[\\w-]+"),
-				"Authentication database name must only contain letters, numbers, underscores and dashes!");
-	}
-
 	/**
 	 * @param client
 	 * @param databaseName
 	 * @param mongoInstanceCreated
 	 * @since 1.7
 	 */
-	private SimpleMongoDbFactory(MongoClient client, String databaseName, boolean mongoInstanceCreated) {
+	private SimpleMongoDbFactory(MongoClient mongoClient, String databaseName, boolean mongoInstanceCreated) {
 
-		Assert.notNull(client, "MongoClient must not be null!");
+		Assert.notNull(mongoClient, "MongoClient must not be null!");
 		Assert.hasText(databaseName, "Database name must not be empty!");
+		Assert.isTrue(databaseName.matches("[\\w-]+"),
+				"Database name must only contain letters, numbers, underscores and dashes!");
 
-		this.mongo = client;
+		this.mongoClient = mongoClient;
 		this.databaseName = databaseName;
 		this.mongoInstanceCreated = mongoInstanceCreated;
 		this.exceptionTranslator = new MongoExceptionTranslator();
-		this.credentials = UserCredentials.NO_CREDENTIALS;
-		this.authenticationDatabaseName = databaseName;
 	}
 
 	/**
@@ -200,7 +112,7 @@ public class SimpleMongoDbFactory implements DisposableBean, MongoDbFactory {
 
 		Assert.hasText(dbName, "Database name must not be empty.");
 
-		MongoDatabase db = ((MongoClient) mongo).getDatabase(dbName);
+		MongoDatabase db = mongoClient.getDatabase(dbName);
 
 		if (writeConcern == null) {
 			return db;
@@ -216,14 +128,10 @@ public class SimpleMongoDbFactory implements DisposableBean, MongoDbFactory {
 	 */
 	public void destroy() throws Exception {
 		if (mongoInstanceCreated) {
-			mongo.close();
+			mongoClient.close();
 		}
 	}
 
-	private static String parseChars(char[] chars) {
-		return chars == null ? null : String.valueOf(chars);
-	}
-
 	/* 
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.MongoDbFactory#getExceptionTranslator()
@@ -236,6 +144,6 @@ public class SimpleMongoDbFactory implements DisposableBean, MongoDbFactory {
 	@SuppressWarnings("deprecation")
 	@Override
 	public DB getLegacyDb() {
-		return mongo.getDB(databaseName);
+		return mongoClient.getDB(databaseName);
 	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/WriteResultChecking.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012 the original author or authors.
+ * Copyright 2012-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,12 +17,12 @@ package org.springframework.data.mongodb.core;
 
 /**
  * Enum to represent how strict the check of {@link com.mongodb.WriteResult} shall be. It can either be skipped entirely
- * (use {@link #NONE}), or errors can be logged ({@link #LOG}) or cause an exception to be thrown {@link #EXCEPTION}.
- * 
+ * (use {@link #NONE}) or cause an exception to be thrown {@link #EXCEPTION}.
+ *
  * @author Thomas Risberg
  * @author Oliver Gierke
  */
 public enum WriteResultChecking {
 
-	NONE, LOG, EXCEPTION
+	NONE, EXCEPTION
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AbstractAggregationExpression.java

@@ -0,0 +1,151 @@
+/*
+ * Copyright 2016. the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+
+import org.bson.Document;
+import org.springframework.util.ObjectUtils;
+
+/**
+ * @author Christoph Strobl
+ * @since 1.10
+ */
+abstract class AbstractAggregationExpression implements AggregationExpression {
+
+	private final Object value;
+
+	protected AbstractAggregationExpression(Object value) {
+		this.value = value;
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationExpression#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public Document toDocument(AggregationOperationContext context) {
+		return toDocument(this.value, context);
+	}
+
+	@SuppressWarnings("unchecked")
+	public Document toDocument(Object value, AggregationOperationContext context) {
+
+		Object valueToUse;
+		if (value instanceof List) {
+
+			List<Object> arguments = (List<Object>) value;
+			List<Object> args = new ArrayList<Object>(arguments.size());
+
+			for (Object val : arguments) {
+				args.add(unpack(val, context));
+			}
+			valueToUse = args;
+		} else if (value instanceof java.util.Map) {
+
+			Document dbo = new Document();
+			for (java.util.Map.Entry<String, Object> entry : ((java.util.Map<String, Object>) value).entrySet()) {
+				dbo.put(entry.getKey(), unpack(entry.getValue(), context));
+			}
+			valueToUse = dbo;
+		} else {
+			valueToUse = unpack(value, context);
+		}
+
+		return new Document(getMongoMethod(), valueToUse);
+	}
+
+	protected static List<Field> asFields(String... fieldRefs) {
+
+		if (ObjectUtils.isEmpty(fieldRefs)) {
+			return Collections.emptyList();
+		}
+
+		return Fields.fields(fieldRefs).asList();
+	}
+
+	@SuppressWarnings("unchecked")
+	private Object unpack(Object value, AggregationOperationContext context) {
+
+		if (value instanceof AggregationExpression) {
+			return ((AggregationExpression) value).toDocument(context);
+		}
+
+		if (value instanceof Field) {
+			return context.getReference((Field) value).toString();
+		}
+
+		if (value instanceof List) {
+
+			List<Object> sourceList = (List<Object>) value;
+			List<Object> mappedList = new ArrayList<Object>(sourceList.size());
+
+			for (Object item : sourceList) {
+				mappedList.add(unpack(item, context));
+			}
+			return mappedList;
+		}
+
+		return value;
+	}
+
+	protected List<Object> append(Object value) {
+
+		if (this.value instanceof List) {
+
+			List<Object> clone = new ArrayList<Object>((List) this.value);
+
+			if (value instanceof List) {
+				for (Object val : (List) value) {
+					clone.add(val);
+				}
+			} else {
+				clone.add(value);
+			}
+			return clone;
+		}
+
+		return Arrays.asList(this.value, value);
+	}
+
+	@SuppressWarnings("unchecked")
+	protected java.util.Map<String, Object> append(String key, Object value) {
+
+		if (!(this.value instanceof java.util.Map)) {
+			throw new IllegalArgumentException("o_O");
+		}
+		java.util.Map<String, Object> clone = new LinkedHashMap<String, Object>((java.util.Map<String, Object>) this.value);
+		clone.put(key, value);
+		return clone;
+
+	}
+
+	protected List<Object> values() {
+
+		if (value instanceof List) {
+			return new ArrayList<Object>((List) value);
+		}
+		if (value instanceof java.util.Map) {
+			return new ArrayList<Object>(((java.util.Map) value).values());
+		}
+		return new ArrayList<Object>(Collections.singletonList(value));
+	}
+
+	protected abstract String getMongoMethod();
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AccumulatorOperators.java

@@ -0,0 +1,647 @@
+/*
+ * Copyright 2016. the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.Collections;
+import java.util.List;
+
+import org.bson.Document;
+import org.springframework.util.Assert;
+
+/**
+ * Gateway to {@literal accumulator} aggregation operations.
+ *
+ * @author Christoph Strobl
+ * @since 1.10
+ * @soundtrack Rage Against The Machine - Killing In The Name
+ */
+public class AccumulatorOperators {
+
+	/**
+	 * Take the numeric value referenced by given {@literal fieldReference}.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return
+	 */
+	public static AccumulatorOperatorFactory valueOf(String fieldReference) {
+		return new AccumulatorOperatorFactory(fieldReference);
+	}
+
+	/**
+	 * Take the numeric value referenced resulting from given {@link AggregationExpression}.
+	 *
+	 * @param expression must not be {@literal null}.
+	 * @return
+	 */
+	public static AccumulatorOperatorFactory valueOf(AggregationExpression expression) {
+		return new AccumulatorOperatorFactory(expression);
+	}
+
+	/**
+	 * @author Christoph Strobl
+	 */
+	public static class AccumulatorOperatorFactory {
+
+		private final String fieldReference;
+		private final AggregationExpression expression;
+
+		/**
+		 * Creates new {@link AccumulatorOperatorFactory} for given {@literal fieldReference}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 */
+		public AccumulatorOperatorFactory(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			this.fieldReference = fieldReference;
+			this.expression = null;
+		}
+
+		/**
+		 * Creates new {@link AccumulatorOperatorFactory} for given {@link AggregationExpression}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 */
+		public AccumulatorOperatorFactory(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			this.fieldReference = null;
+			this.expression = expression;
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated numeric value expression and calculates and
+		 * returns the sum.
+		 *
+		 * @return
+		 */
+		public Sum sum() {
+			return usesFieldRef() ? Sum.sumOf(fieldReference) : Sum.sumOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated numeric value expression and returns the
+		 * average value.
+		 *
+		 * @return
+		 */
+		public Avg avg() {
+			return usesFieldRef() ? Avg.avgOf(fieldReference) : Avg.avgOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated numeric value expression and returns the
+		 * maximum value.
+		 *
+		 * @return
+		 */
+		public Max max() {
+			return usesFieldRef() ? Max.maxOf(fieldReference) : Max.maxOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated numeric value expression and returns the
+		 * minimum value.
+		 *
+		 * @return
+		 */
+		public Min min() {
+			return usesFieldRef() ? Min.minOf(fieldReference) : Min.minOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated numeric value expression and calculates the
+		 * population standard deviation of the input values.
+		 *
+		 * @return
+		 */
+		public StdDevPop stdDevPop() {
+			return usesFieldRef() ? StdDevPop.stdDevPopOf(fieldReference) : StdDevPop.stdDevPopOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated numeric value expression and calculates the
+		 * sample standard deviation of the input values.
+		 *
+		 * @return
+		 */
+		public StdDevSamp stdDevSamp() {
+			return usesFieldRef() ? StdDevSamp.stdDevSampOf(fieldReference) : StdDevSamp.stdDevSampOf(expression);
+		}
+
+		private boolean usesFieldRef() {
+			return fieldReference != null;
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $sum}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Sum extends AbstractAggregationExpression {
+
+		private Sum(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$sum";
+		}
+
+		/**
+		 * Creates new {@link Sum}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Sum sumOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Sum(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Sum}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Sum sumOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Sum(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link Sum} with all previously added arguments appending the given one. <br />
+		 * <strong>NOTE:</strong> Only possible in {@code $project} stage.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Sum and(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Sum(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link Sum} with all previously added arguments appending the given one. <br />
+		 * <strong>NOTE:</strong> Only possible in {@code $project} stage.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Sum and(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Sum(append(expression));
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AccumulatorOperators.AbstractAggregationExpression#toDocument(java.lang.Object, org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		@SuppressWarnings("unchecked")
+		public Document toDocument(Object value, AggregationOperationContext context) {
+
+			if (value instanceof List) {
+				if (((List) value).size() == 1) {
+					return super.toDocument(((List<Object>) value).iterator().next(), context);
+				}
+			}
+
+			return super.toDocument(value, context);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $avg}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Avg extends AbstractAggregationExpression {
+
+		private Avg(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$avg";
+		}
+
+		/**
+		 * Creates new {@link Avg}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Avg avgOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Avg(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Avg}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Avg avgOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Avg(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link Avg} with all previously added arguments appending the given one. <br />
+		 * <strong>NOTE:</strong> Only possible in {@code $project} stage.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Avg and(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Avg(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link Avg} with all previously added arguments appending the given one. <br />
+		 * <strong>NOTE:</strong> Only possible in {@code $project} stage.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Avg and(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Avg(append(expression));
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AccumulatorOperators.AbstractAggregationExpression#toDocument(java.lang.Object, org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		@SuppressWarnings("unchecked")
+		public Document toDocument(Object value, AggregationOperationContext context) {
+
+			if (value instanceof List) {
+				if (((List) value).size() == 1) {
+					return super.toDocument(((List<Object>) value).iterator().next(), context);
+				}
+			}
+
+			return super.toDocument(value, context);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $max}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Max extends AbstractAggregationExpression {
+
+		private Max(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$max";
+		}
+
+		/**
+		 * Creates new {@link Max}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Max maxOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Max(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Max}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Max maxOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Max(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link Max} with all previously added arguments appending the given one. <br />
+		 * <strong>NOTE:</strong> Only possible in {@code $project} stage.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Max and(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Max(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link Max} with all previously added arguments appending the given one. <br />
+		 * <strong>NOTE:</strong> Only possible in {@code $project} stage.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Max and(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Max(append(expression));
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AccumulatorOperators.AbstractAggregationExpression#toDocument(java.lang.Object, org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		@SuppressWarnings("unchecked")
+		public Document toDocument(Object value, AggregationOperationContext context) {
+
+			if (value instanceof List) {
+				if (((List) value).size() == 1) {
+					return super.toDocument(((List<Object>) value).iterator().next(), context);
+				}
+			}
+
+			return super.toDocument(value, context);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $min}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Min extends AbstractAggregationExpression {
+
+		private Min(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$min";
+		}
+
+		/**
+		 * Creates new {@link Min}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Min minOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Min(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Min}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Min minOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Min(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link Min} with all previously added arguments appending the given one. <br />
+		 * <strong>NOTE:</strong> Only possible in {@code $project} stage.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Min and(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Min(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link Min} with all previously added arguments appending the given one. <br />
+		 * <strong>NOTE:</strong> Only possible in {@code $project} stage.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Min and(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Min(append(expression));
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AccumulatorOperators.AbstractAggregationExpression#toDocument(java.lang.Object, org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		@SuppressWarnings("unchecked")
+		public Document toDocument(Object value, AggregationOperationContext context) {
+
+			if (value instanceof List) {
+				if (((List) value).size() == 1) {
+					return super.toDocument(((List<Object>) value).iterator().next(), context);
+				}
+			}
+
+			return super.toDocument(value, context);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $stdDevPop}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class StdDevPop extends AbstractAggregationExpression {
+
+		private StdDevPop(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$stdDevPop";
+		}
+
+		/**
+		 * Creates new {@link StdDevPop}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static StdDevPop stdDevPopOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new StdDevPop(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link StdDevPop} with all previously added arguments appending the given one.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static StdDevPop stdDevPopOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new StdDevPop(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link StdDevPop} with all previously added arguments appending the given one. <br/>
+		 * <strong>NOTE:</strong> Only possible in {@code $project} stage.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public StdDevPop and(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new StdDevPop(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link StdDevSamp} with all previously added arguments appending the given one. <br />
+		 * <strong>NOTE:</strong> Only possible in {@code $project} stage.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public StdDevPop and(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new StdDevPop(append(expression));
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AccumulatorOperators.AbstractAggregationExpression#toDocument(java.lang.Object, org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		@SuppressWarnings("unchecked")
+		public Document toDocument(Object value, AggregationOperationContext context) {
+
+			if (value instanceof List) {
+				if (((List) value).size() == 1) {
+					return super.toDocument(((List<Object>) value).iterator().next(), context);
+				}
+			}
+
+			return super.toDocument(value, context);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $stdDevSamp}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class StdDevSamp extends AbstractAggregationExpression {
+
+		private StdDevSamp(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$stdDevSamp";
+		}
+
+		/**
+		 * Creates new {@link StdDevSamp}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static StdDevSamp stdDevSampOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new StdDevSamp(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link StdDevSamp}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static StdDevSamp stdDevSampOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new StdDevSamp(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link StdDevSamp} with all previously added arguments appending the given one. <br />
+		 * <strong>NOTE:</strong> Only possible in {@code $project} stage.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public StdDevSamp and(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new StdDevSamp(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link StdDevSamp} with all previously added arguments appending the given one. <br />
+		 * <strong>NOTE:</strong> Only possible in {@code $project} stage.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public StdDevSamp and(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new StdDevSamp(append(expression));
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AccumulatorOperators.AbstractAggregationExpression#toDocument(java.lang.Object, org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		@SuppressWarnings("unchecked")
+		public Document toDocument(Object value, AggregationOperationContext context) {
+
+			if (value instanceof List) {
+				if (((List) value).size() == 1) {
+					return super.toDocument(((List<Object>) value).iterator().next(), context);
+				}
+			}
+
+			return super.toDocument(value, context);
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/Aggregation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,11 +24,18 @@ import java.util.List;
 import org.bson.Document;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.domain.Sort.Direction;
+import org.springframework.data.mongodb.core.aggregation.CountOperation.CountOperationBuilder;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.DirectFieldReference;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference;
-import org.springframework.data.mongodb.core.aggregation.Fields.AggregationField;
+import org.springframework.data.mongodb.core.aggregation.FacetOperation.FacetOperationBuilder;
 import org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation.InheritsFieldsAggregationOperation;
+import org.springframework.data.mongodb.core.aggregation.GraphLookupOperation.StartWithBuilder;
+import org.springframework.data.mongodb.core.aggregation.ReplaceRootOperation.ReplaceRootDocumentOperationBuilder;
+import org.springframework.data.mongodb.core.aggregation.ReplaceRootOperation.ReplaceRootOperationBuilder;
+import org.springframework.data.mongodb.core.aggregation.Fields.*;
 import org.springframework.data.mongodb.core.query.Criteria;
+import org.springframework.data.mongodb.core.query.CriteriaDefinition;
 import org.springframework.data.mongodb.core.query.NearQuery;
 import org.springframework.data.mongodb.core.query.SerializationUtils;
 import org.springframework.util.Assert;
@@ -60,7 +67,7 @@ public class Aggregation {
 	 */
 	public static final String CURRENT = SystemVariable.CURRENT.toString();
 
-	public static final AggregationOperationContext DEFAULT_CONTEXT = new NoOpAggregationOperationContext();
+	public static final AggregationOperationContext DEFAULT_CONTEXT = AggregationOperationRenderer.DEFAULT_CONTEXT;
 	public static final AggregationOptions DEFAULT_OPTIONS = newAggregationOptions().build();
 
 	protected final List<AggregationOperation> operations;
@@ -194,7 +201,7 @@ public class Aggregation {
 	}
 
 	/**
-	 * Creates a new {@link ProjectionOperation} includeing the given {@link Fields}.
+	 * Creates a new {@link ProjectionOperation} including the given {@link Fields}.
 	 *
 	 * @param fields must not be {@literal null}.
 	 * @return
@@ -213,6 +220,40 @@ public class Aggregation {
 		return new UnwindOperation(field(field));
 	}
 
+	/**
+	 * Factory method to create a new {@link ReplaceRootOperation} for the field with the given name.
+	 *
+	 * @param fieldName must not be {@literal null} or empty.
+	 * @return
+	 * @since 1.10
+	 */
+	public static ReplaceRootOperation replaceRoot(String fieldName) {
+		return ReplaceRootOperation.builder().withValueOf(fieldName);
+	}
+
+	/**
+	 * Factory method to create a new {@link ReplaceRootOperation} for the field with the given
+	 * {@link AggregationExpression}.
+	 *
+	 * @param aggregationExpression must not be {@literal null}.
+	 * @return
+	 * @since 1.10
+	 */
+	public static ReplaceRootOperation replaceRoot(AggregationExpression aggregationExpression) {
+		return ReplaceRootOperation.builder().withValueOf(aggregationExpression);
+	}
+
+	/**
+	 * Factory method to create a new {@link ReplaceRootDocumentOperationBuilder} to configure a
+	 * {@link ReplaceRootOperation}.
+	 *
+	 * @return the {@literal ReplaceRootDocumentOperationBuilder}.
+	 * @since 1.10
+	 */
+	public static ReplaceRootOperationBuilder replaceRoot() {
+		return ReplaceRootOperation.builder();
+	}
+
 	/**
 	 * Factory method to create a new {@link UnwindOperation} for the field with the given name and
 	 * {@code preserveNullAndEmptyArrays}. Note that extended unwind is supported in MongoDB version 3.2+.
@@ -277,6 +318,18 @@ public class Aggregation {
 		return new GroupOperation(fields);
 	}
 
+	/**
+	 * Creates a new {@link GraphLookupOperation.GraphLookupOperationFromBuilder} to construct a
+	 * {@link GraphLookupOperation} given {@literal fromCollection}.
+	 *
+	 * @param fromCollection must not be {@literal null} or empty.
+	 * @return
+	 * @since 1.10
+	 */
+	public static StartWithBuilder graphLookup(String fromCollection) {
+		return GraphLookupOperation.builder().from(fromCollection);
+	}
+
 	/**
 	 * Factory method to create a new {@link SortOperation} for the given {@link Sort}.
 	 *
@@ -339,6 +392,17 @@ public class Aggregation {
 		return new MatchOperation(criteria);
 	}
 
+	/**
+	 * Creates a new {@link MatchOperation} using the given {@link CriteriaDefinition}.
+	 *
+	 * @param criteria must not be {@literal null}.
+	 * @return
+	 * @since 1.10
+	 */
+	public static MatchOperation match(CriteriaDefinition criteria) {
+		return new MatchOperation(criteria);
+	}
+
 	/**
 	 * Creates a new {@link OutOperation} using the given collection name. This operation must be the last operation in
 	 * the pipeline.
@@ -353,6 +417,73 @@ public class Aggregation {
 		return new OutOperation(outCollectionName);
 	}
 
+	/**
+	 * Creates a new {@link BucketOperation} given {@literal groupByField}.
+	 *
+	 * @param groupByField must not be {@literal null} or empty.
+	 * @return
+	 * @since 1.10
+	 */
+	public static BucketOperation bucket(String groupByField) {
+		return new BucketOperation(field(groupByField));
+	}
+
+	/**
+	 * Creates a new {@link BucketOperation} given {@link AggregationExpression group-by expression}.
+	 *
+	 * @param groupByExpression must not be {@literal null}.
+	 * @return
+	 * @since 1.10
+	 */
+	public static BucketOperation bucket(AggregationExpression groupByExpression) {
+		return new BucketOperation(groupByExpression);
+	}
+
+	/**
+	 * Creates a new {@link BucketAutoOperation} given {@literal groupByField}.
+	 *
+	 * @param groupByField must not be {@literal null} or empty.
+	 * @param buckets number of buckets, must be a positive integer.
+	 * @return
+	 * @since 1.10
+	 */
+	public static BucketAutoOperation bucketAuto(String groupByField, int buckets) {
+		return new BucketAutoOperation(field(groupByField), buckets);
+	}
+
+	/**
+	 * Creates a new {@link BucketAutoOperation} given {@link AggregationExpression group-by expression}.
+	 *
+	 * @param groupByExpression must not be {@literal null}.
+	 * @param buckets number of buckets, must be a positive integer.
+	 * @return
+	 * @since 1.10
+	 */
+	public static BucketAutoOperation bucketAuto(AggregationExpression groupByExpression, int buckets) {
+		return new BucketAutoOperation(groupByExpression, buckets);
+	}
+
+	/**
+	 * Creates a new {@link FacetOperation}.
+	 *
+	 * @return
+	 * @since 1.10
+	 */
+	public static FacetOperation facet() {
+		return FacetOperation.EMPTY;
+	}
+
+	/**
+	 * Creates a new {@link FacetOperationBuilder} given {@link Aggregation}.
+	 *
+	 * @param aggregationOperations the sub-pipeline, must not be {@literal null}.
+	 * @return
+	 * @since 1.10
+	 */
+	public static FacetOperationBuilder facet(AggregationOperation... aggregationOperations) {
+		return facet().and(aggregationOperations);
+	}
+
 	/**
 	 * Creates a new {@link LookupOperation}.
 	 *
@@ -382,65 +513,13 @@ public class Aggregation {
 	}
 
 	/**
-	 * Creates a new {@link IfNullOperator} for the given {@code field} and {@code replacement} value.
+	 * Creates a new {@link CountOperationBuilder}.
 	 *
-	 * @param field must not be {@literal null}.
-	 * @param replacement must not be {@literal null}.
 	 * @return never {@literal null}.
 	 * @since 1.10
 	 */
-	public static IfNullOperator ifNull(String field, Object replacement) {
-		return IfNullOperator.newBuilder().ifNull(field).thenReplaceWith(replacement);
-	}
-
-	/**
-	 * Creates a new {@link IfNullOperator} for the given {@link Field} and {@link Field} to obtain a value from.
-	 *
-	 * @param field must not be {@literal null}.
-	 * @param replacement must not be {@literal null}.
-	 * @return never {@literal null}.
-	 * @since 1.10
-	 */
-	public static IfNullOperator ifNull(Field field, Field replacement) {
-		return IfNullOperator.newBuilder().ifNull(field).thenReplaceWith(replacement);
-	}
-
-	/**
-	 * Creates a new {@link IfNullOperator} for the given {@link Field} and {@code replacement} value.
-	 *
-	 * @param field must not be {@literal null}.
-	 * @param replacement must not be {@literal null}.
-	 * @return never {@literal null}.
-	 * @since 1.10
-	 */
-	public static IfNullOperator ifNull(Field field, Object replacement) {
-		return IfNullOperator.newBuilder().ifNull(field).thenReplaceWith(replacement);
-	}
-
-	/**
-	 * Creates a new {@link ConditionalOperator} for the given {@link Field} that holds a {@literal boolean} value.
-	 *
-	 * @param booleanField must not be {@literal null}.
-	 * @param then must not be {@literal null}.
-	 * @param otherwise must not be {@literal null}.
-	 * @return never {@literal null}.
-	 * @since 1.10
-	 */
-	public static ConditionalOperator conditional(Field booleanField, Object then, Object otherwise) {
-		return ConditionalOperator.newBuilder().when(booleanField).then(then).otherwise(otherwise);
-	}
-
-	/**
-	 * Creates a new {@link ConditionalOperator} for the given {@link Criteria}.
-	 *
-	 * @param criteria must not be {@literal null}.
-	 * @param then must not be {@literal null}.
-	 * @param otherwise must not be {@literal null}.
-	 * @return never {@literal null}.
-	 * @since 1.10
-	 */
-	public static ConditionalOperator conditional(Criteria criteria, Object then, Object otherwise) {
-		return ConditionalOperator.newBuilder().when(criteria).then(then).otherwise(otherwise);
+	public static CountOperationBuilder count() {
+		return new CountOperationBuilder();
 	}
 
 	/**
@@ -496,24 +575,7 @@ public class Aggregation {
 	 */
 	public Document toDocument(String inputCollectionName, AggregationOperationContext rootContext) {
 
-		AggregationOperationContext context = rootContext;
-		List<Document> operationDocuments = new ArrayList<Document>(operations.size());
-
-		for (AggregationOperation operation : operations) {
-
-			operationDocuments.add(operation.toDocument(context));
-
-			if (operation instanceof FieldsExposingAggregationOperation) {
-
-				FieldsExposingAggregationOperation exposedFieldsOperation = (FieldsExposingAggregationOperation) operation;
-
-				if (operation instanceof InheritsFieldsAggregationOperation) {
-					context = new InheritingExposedFieldsAggregationOperationContext(exposedFieldsOperation.getFields(), context);
-				} else {
-					context = new ExposedFieldsAggregationOperationContext(exposedFieldsOperation.getFields(), context);
-				}
-			}
-		}
+		List<Document> operationDocuments = AggregationOperationRenderer.toDocument(operations, rootContext);
 
 		Document command = new Document("aggregate", inputCollectionName);
 		command.put("pipeline", operationDocuments);
@@ -529,50 +591,14 @@ public class Aggregation {
 	 */
 	@Override
 	public String toString() {
-		return SerializationUtils
-				.serializeToJsonSafely(toDocument("__collection__", new NoOpAggregationOperationContext()));
-	}
-
-	/**
-	 * Simple {@link AggregationOperationContext} that just returns {@link FieldReference}s as is.
-	 *
-	 * @author Oliver Gierke
-	 */
-	private static class NoOpAggregationOperationContext implements AggregationOperationContext {
-
-		/* 
-		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getMappedObject(com.mongodb.Document)
-		 */
-		@Override
-		public Document getMappedObject(Document document) {
-			return document;
-		}
-
-		/* 
-		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getReference(org.springframework.data.mongodb.core.aggregation.ExposedFields.AvailableField)
-		 */
-		@Override
-		public FieldReference getReference(Field field) {
-			return new FieldReference(new ExposedField(field, true));
-		}
-
-		/* 
-		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getReference(java.lang.String)
-		 */
-		@Override
-		public FieldReference getReference(String name) {
-			return new FieldReference(new ExposedField(new AggregationField(name), true));
-		}
+		return SerializationUtils.serializeToJsonSafely(toDocument("__collection__", DEFAULT_CONTEXT));
 	}
 
 	/**
 	 * Describes the system variables available in MongoDB aggregation framework pipeline expressions.
 	 *
 	 * @author Thomas Darimont
-	 * @see http://docs.mongodb.org/manual/reference/aggregation-variables
+	 * @see <a href="https://docs.mongodb.org/manual/reference/aggregation-variables">Aggregation Variables</a>
 	 */
 	enum SystemVariable {
 
@@ -605,7 +631,7 @@ public class Aggregation {
 			return false;
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see java.lang.Enum#toString()
 		 */

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AggregationFunctionExpressions.java

@@ -30,10 +30,12 @@ import org.springframework.util.Assert;
  * @author Christoph Strobl
  * @author Mark Paluch
  * @since 1.7
+ * @deprecated since 1.10. Please use {@link ArithmeticOperators} and {@link ComparisonOperators} instead.
  */
+@Deprecated
 public enum AggregationFunctionExpressions {
 
-	SIZE;
+	SIZE, CMP, EQ, GT, GTE, LT, LTE, NE, SUBTRACT, ADD, MULTIPLY;
 
 	/**
 	 * Returns an {@link AggregationExpression} build from the current {@link Enum} name and the given parameters.
@@ -52,7 +54,7 @@ public enum AggregationFunctionExpressions {
 	 * 
 	 * @author Thomas Darimont
 	 * @author Oliver Gierke
-	 * @since 1.10
+	 * @since 1.7
 	 */
 	static class FunctionExpression implements AggregationExpression {
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AggregationOperationRenderer.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright 2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.bson.Document;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.DirectFieldReference;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference;
+import org.springframework.data.mongodb.core.aggregation.Fields.AggregationField;
+import org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation.InheritsFieldsAggregationOperation;
+
+/**
+ * Rendering support for {@link AggregationOperation} into a {@link List} of {@link org.bson.Document}.
+ *
+ * @author Mark Paluch
+ * @author Christoph Strobl
+ * @since 1.10
+ */
+class AggregationOperationRenderer {
+
+	static final AggregationOperationContext DEFAULT_CONTEXT = new NoOpAggregationOperationContext();
+
+	/**
+	 * Render a {@link List} of {@link AggregationOperation} given {@link AggregationOperationContext} into their
+	 * {@link Document} representation.
+	 *
+	 * @param operations must not be {@literal null}.
+	 * @param context must not be {@literal null}.
+	 * @return the {@link List} of {@link Document}.
+	 */
+	static List<Document> toDocument(List<AggregationOperation> operations, AggregationOperationContext rootContext) {
+
+		List<Document> operationDocuments = new ArrayList<Document>(operations.size());
+
+		AggregationOperationContext contextToUse = rootContext;
+
+		for (AggregationOperation operation : operations) {
+
+			operationDocuments.add(operation.toDocument(contextToUse));
+
+			if (operation instanceof FieldsExposingAggregationOperation) {
+
+				FieldsExposingAggregationOperation exposedFieldsOperation = (FieldsExposingAggregationOperation) operation;
+				ExposedFields fields = exposedFieldsOperation.getFields();
+
+				if (operation instanceof InheritsFieldsAggregationOperation) {
+					contextToUse = new InheritingExposedFieldsAggregationOperationContext(fields, contextToUse);
+				} else {
+					contextToUse = fields.exposesNoFields() ? DEFAULT_CONTEXT
+							: new ExposedFieldsAggregationOperationContext(exposedFieldsOperation.getFields(), contextToUse);
+				}
+			}
+		}
+
+		return operationDocuments;
+	}
+
+	/**
+	 * Simple {@link AggregationOperationContext} that just returns {@link FieldReference}s as is.
+	 *
+	 * @author Oliver Gierke
+	 */
+	private static class NoOpAggregationOperationContext implements AggregationOperationContext {
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getMappedObject(org.bson.Document)
+		 */
+		@Override
+		public Document getMappedObject(Document document) {
+			return document;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getReference(org.springframework.data.mongodb.core.aggregation.ExposedFields.AvailableField)
+		 */
+		@Override
+		public FieldReference getReference(Field field) {
+			return new DirectFieldReference(new ExposedField(field, true));
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getReference(java.lang.String)
+		 */
+		@Override
+		public FieldReference getReference(String name) {
+			return new DirectFieldReference(new ExposedField(new AggregationField(name), true));
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AggregationOptions.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2016 the original author or authors.
+ * Copyright 2014-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,21 +16,26 @@
 package org.springframework.data.mongodb.core.aggregation;
 
 import org.bson.Document;
+import org.springframework.util.Assert;
+
+import com.mongodb.DBObject;
 
 /**
  * Holds a set of configurable aggregation options that can be used within an aggregation pipeline. A list of support
  * aggregation options can be found in the MongoDB reference documentation
- * http://docs.mongodb.org/manual/reference/command/aggregate/#aggregate
- * 
+ * https://docs.mongodb.org/manual/reference/command/aggregate/#aggregate
+ *
  * @author Thomas Darimont
  * @author Oliver Gierke
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @see Aggregation#withOptions(AggregationOptions)
  * @see TypedAggregation#withOptions(AggregationOptions)
  * @since 1.6
  */
 public class AggregationOptions {
 
+	private static final String BATCH_SIZE = "batchSize";
 	private static final String CURSOR = "cursor";
 	private static final String EXPLAIN = "explain";
 	private static final String ALLOW_DISK_USE = "allowDiskUse";
@@ -41,7 +46,7 @@ public class AggregationOptions {
 
 	/**
 	 * Creates a new {@link AggregationOptions}.
-	 * 
+	 *
 	 * @param allowDiskUse whether to off-load intensive sort-operations to disk.
 	 * @param explain whether to get the execution plan for the aggregation instead of the actual results.
 	 * @param cursor can be {@literal null}, used to pass additional options to the aggregation.
@@ -53,10 +58,52 @@ public class AggregationOptions {
 		this.cursor = cursor;
 	}
 
+	/**
+	 * Creates a new {@link AggregationOptions}.
+	 *
+	 * @param allowDiskUse whether to off-load intensive sort-operations to disk.
+	 * @param explain whether to get the execution plan for the aggregation instead of the actual results.
+	 * @param cursorBatchSize initial cursor batch size.
+	 * @since 2.0
+	 */
+	public AggregationOptions(boolean allowDiskUse, boolean explain, int cursorBatchSize) {
+		this(allowDiskUse, explain, createCursor(cursorBatchSize));
+	}
+
+	/**
+	 * Creates new {@link AggregationOptions} given {@link DBObject} containing aggregation options.
+	 *
+	 * @param document must not be {@literal null}.
+	 * @return the {@link AggregationOptions}.
+	 * @since 2.0
+	 */
+	public static AggregationOptions fromDocument(Document document) {
+
+		Assert.notNull(document, "Document must not be null!");
+
+		boolean allowDiskUse = false;
+		boolean explain = false;
+		Document cursor = null;
+
+		if (document.containsKey(ALLOW_DISK_USE)) {
+			allowDiskUse = document.get(ALLOW_DISK_USE, Boolean.class);
+		}
+
+		if (document.containsKey(EXPLAIN)) {
+			explain = (Boolean) document.get(EXPLAIN);
+		}
+
+		if (document.containsKey(CURSOR)) {
+			cursor = document.get(CURSOR, Document.class);
+		}
+
+		return new AggregationOptions(allowDiskUse, explain, cursor);
+	}
+
 	/**
 	 * Enables writing to temporary files. When set to true, aggregation stages can write data to the _tmp subdirectory in
 	 * the dbPath directory.
-	 * 
+	 *
 	 * @return
 	 */
 	public boolean isAllowDiskUse() {
@@ -65,16 +112,31 @@ public class AggregationOptions {
 
 	/**
 	 * Specifies to return the information on the processing of the pipeline.
-	 * 
+	 *
 	 * @return
 	 */
 	public boolean isExplain() {
 		return explain;
 	}
 
+	/**
+	 * The initial cursor batch size, if available, otherwise {@literal null}.
+	 *
+	 * @return the batch size or {@literal null}.
+	 * @since 2.0
+	 */
+	public Integer getCursorBatchSize() {
+
+		if (cursor != null && cursor.containsKey("batchSize")) {
+			return cursor.get("batchSize", Integer.class);
+		}
+
+		return null;
+	}
+
 	/**
 	 * Specify a document that contains options that control the creation of the cursor object.
-	 * 
+	 *
 	 * @return
 	 */
 	public Document getCursor() {
@@ -84,7 +146,7 @@ public class AggregationOptions {
 	/**
 	 * Returns a new potentially adjusted copy for the given {@code aggregationCommandObject} with the configuration
 	 * applied.
-	 * 
+	 *
 	 * @param command the aggregation command.
 	 * @return
 	 */
@@ -101,7 +163,7 @@ public class AggregationOptions {
 		}
 
 		if (cursor != null && !result.containsKey(CURSOR)) {
-			result.put("cursor", cursor);
+			result.put(CURSOR, cursor);
 		}
 
 		return result;
@@ -109,7 +171,7 @@ public class AggregationOptions {
 
 	/**
 	 * Returns a {@link Document} representation of this {@link AggregationOptions}.
-	 * 
+	 *
 	 * @return
 	 */
 	public Document toDocument() {
@@ -130,10 +192,15 @@ public class AggregationOptions {
 		return toDocument().toJson();
 	}
 
+	static Document createCursor(int cursorBatchSize) {
+		return new Document("batchSize", cursorBatchSize);
+	}
+
 	/**
 	 * A Builder for {@link AggregationOptions}.
-	 * 
+	 *
 	 * @author Thomas Darimont
+	 * @author Mark Paluch
 	 */
 	public static class Builder {
 
@@ -143,7 +210,7 @@ public class AggregationOptions {
 
 		/**
 		 * Defines whether to off-load intensive sort-operations to disk.
-		 * 
+		 *
 		 * @param allowDiskUse
 		 * @return
 		 */
@@ -155,7 +222,7 @@ public class AggregationOptions {
 
 		/**
 		 * Defines whether to get the execution plan for the aggregation instead of the actual results.
-		 * 
+		 *
 		 * @param explain
 		 * @return
 		 */
@@ -167,7 +234,7 @@ public class AggregationOptions {
 
 		/**
 		 * Additional options to the aggregation.
-		 * 
+		 *
 		 * @param cursor
 		 * @return
 		 */
@@ -177,9 +244,22 @@ public class AggregationOptions {
 			return this;
 		}
 
+		/**
+		 * Define the initial cursor batch size.
+		 *
+		 * @param batchSize
+		 * @return
+		 * @since 2.0
+		 */
+		public Builder cursorBatchSize(int batchSize) {
+
+			this.cursor = createCursor(batchSize);
+			return this;
+		}
+
 		/**
 		 * Returns a new {@link AggregationOptions} instance with the given configuration.
-		 * 
+		 *
 		 * @return
 		 */
 		public AggregationOptions build() {

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AggregationResults.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,6 +29,7 @@ import org.springframework.util.Assert;
  * @author Oliver Gierke
  * @author Thomas Darimont
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @param <T> The class in which the results are mapped onto.
  * @since 1.3
  */
@@ -46,8 +47,8 @@ public class AggregationResults<T> implements Iterable<T> {
 	 */
 	public AggregationResults(List<T> mappedResults, Document rawResults) {
 
-		Assert.notNull(mappedResults);
-		Assert.notNull(rawResults);
+		Assert.notNull(mappedResults, "List of mapped results must not be null!");
+		Assert.notNull(rawResults, "Raw results must not be null!");
 
 		this.mappedResults = Collections.unmodifiableList(mappedResults);
 		this.rawResults = rawResults;

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/AggregationSpELExpression.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2016. the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import org.bson.Document;
+import org.springframework.util.Assert;
+
+/**
+ * An {@link AggregationExpression} that renders a MongoDB Aggregation Framework expression from the AST of a
+ * <a href="http://docs.spring.io/spring/docs/current/spring-framework-reference/html/expressions.html">SpEL
+ * expression</a>. <br />
+ * <br />
+ * <strong>Samples:</strong> <br />
+ * <code>
+ * <pre>
+ * // { $and: [ { $gt: [ "$qty", 100 ] }, { $lt: [ "$qty", 250 ] } ] }
+ * expressionOf("qty > 100 && qty < 250);
+ *
+ * // { $cond : { if : { $gte : [ "$a", 42 ]}, then : "answer", else : "no-answer" } }
+ * expressionOf("cond(a >= 42, 'answer', 'no-answer')");
+ * </pre>
+ * </code>
+ * 
+ * @author Christoph Strobl
+ * @see SpelExpressionTransformer
+ * @since 1.10
+ */
+public class AggregationSpELExpression implements AggregationExpression {
+
+	private static final SpelExpressionTransformer TRANSFORMER = new SpelExpressionTransformer();
+	private final String rawExpression;
+	private final Object[] parameters;
+
+	private AggregationSpELExpression(String rawExpression, Object[] parameters) {
+
+		this.rawExpression = rawExpression;
+		this.parameters = parameters;
+	}
+
+	/**
+	 * Creates new {@link AggregationSpELExpression} for the given {@literal expressionString} and {@literal parameters}.
+	 *
+	 * @param expressionString must not be {@literal null}.
+	 * @param parameters can be empty.
+	 * @return
+	 */
+	public static AggregationSpELExpression expressionOf(String expressionString, Object... parameters) {
+
+		Assert.notNull(expressionString, "ExpressionString must not be null!");
+		return new AggregationSpELExpression(expressionString, parameters);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationExpression#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public Document toDocument(AggregationOperationContext context) {
+		return (Document) TRANSFORMER.transform(rawExpression, context, parameters);
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BooleanOperators.java

@@ -0,0 +1,353 @@
+/*
+ * Copyright 2016. the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.springframework.util.Assert;
+
+/**
+ * Gateway to {@literal boolean expressions} that evaluate their argument expressions as booleans and return a boolean
+ * as the result.
+ *
+ * @author Christoph Strobl
+ * @since 1.10
+ */
+public class BooleanOperators {
+
+	/**
+	 * Take the array referenced by given {@literal fieldReference}.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return
+	 */
+	public static BooleanOperatorFactory valueOf(String fieldReference) {
+		return new BooleanOperatorFactory(fieldReference);
+	}
+
+	/**
+	 * Take the value resulting of the given {@link AggregationExpression}.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return
+	 */
+	public static BooleanOperatorFactory valueOf(AggregationExpression fieldReference) {
+		return new BooleanOperatorFactory(fieldReference);
+	}
+
+	/**
+	 * Creates new {@link AggregationExpression} that evaluates the boolean value of the referenced field and returns the
+	 * opposite boolean value.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return
+	 */
+	public static Not not(String fieldReference) {
+		return Not.not(fieldReference);
+	}
+
+	/**
+	 * Creates new {@link AggregationExpression} that evaluates the boolean value of {@link AggregationExpression} result
+	 * and returns the opposite boolean value.
+	 *
+	 * @param expression must not be {@literal null}.
+	 * @return
+	 */
+	public static Not not(AggregationExpression expression) {
+		return Not.not(expression);
+	}
+
+	/**
+	 * @author Christoph Strobl
+	 */
+	public static class BooleanOperatorFactory {
+
+		private final String fieldReference;
+		private final AggregationExpression expression;
+
+		/**
+		 * Creates new {@link BooleanOperatorFactory} for given {@literal fieldReference}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 */
+		public BooleanOperatorFactory(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			this.fieldReference = fieldReference;
+			this.expression = null;
+		}
+
+		/**
+		 * Creates new {@link BooleanOperatorFactory} for given {@link AggregationExpression}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 */
+		public BooleanOperatorFactory(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			this.fieldReference = null;
+			this.expression = expression;
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that evaluates one or more expressions and returns {@literal true} if
+		 * all of the expressions are {@literal true}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public And and(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return createAnd().andExpression(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that evaluates one or more expressions and returns {@literal true} if
+		 * all of the expressions are {@literal true}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public And and(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return createAnd().andField(fieldReference);
+		}
+
+		private And createAnd() {
+			return usesFieldRef() ? And.and(Fields.field(fieldReference)) : And.and(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that evaluates one or more expressions and returns {@literal true} if
+		 * any of the expressions are {@literal true}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Or or(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return createOr().orExpression(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that evaluates one or more expressions and returns {@literal true} if
+		 * any of the expressions are {@literal true}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Or or(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return createOr().orField(fieldReference);
+		}
+
+		private Or createOr() {
+			return usesFieldRef() ? Or.or(Fields.field(fieldReference)) : Or.or(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that evaluates a boolean and returns the opposite boolean value.
+		 *
+		 * @return
+		 */
+		public Not not() {
+			return usesFieldRef() ? Not.not(fieldReference) : Not.not(expression);
+		}
+
+		private boolean usesFieldRef() {
+			return this.fieldReference != null;
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $and}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class And extends AbstractAggregationExpression {
+
+		private And(List<?> values) {
+			super(values);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$and";
+		}
+
+		/**
+		 * Creates new {@link And} that evaluates one or more expressions and returns {@literal true} if all of the
+		 * expressions are {@literal true}.
+		 *
+		 * @param expressions
+		 * @return
+		 */
+		public static And and(Object... expressions) {
+			return new And(Arrays.asList(expressions));
+		}
+
+		/**
+		 * Creates new {@link And} with all previously added arguments appending the given one.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public And andExpression(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new And(append(expression));
+		}
+
+		/**
+		 * Creates new {@link And} with all previously added arguments appending the given one.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public And andField(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new And(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link And} with all previously added arguments appending the given one.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public And andValue(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+			return new And(append(value));
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $or}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Or extends AbstractAggregationExpression {
+
+		private Or(List<?> values) {
+			super(values);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$or";
+		}
+
+		/**
+		 * Creates new {@link Or} that evaluates one or more expressions and returns {@literal true} if any of the
+		 * expressions are {@literal true}.
+		 *
+		 * @param expressions must not be {@literal null}.
+		 * @return
+		 */
+		public static Or or(Object... expressions) {
+
+			Assert.notNull(expressions, "Expressions must not be null!");
+			return new Or(Arrays.asList(expressions));
+		}
+
+		/**
+		 * Creates new {@link Or} with all previously added arguments appending the given one.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Or orExpression(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Or(append(expression));
+		}
+
+		/**
+		 * Creates new {@link Or} with all previously added arguments appending the given one.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Or orField(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Or(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link Or} with all previously added arguments appending the given one.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Or orValue(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+			return new Or(append(value));
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $not}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Not extends AbstractAggregationExpression {
+
+		private Not(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$not";
+		}
+
+		/**
+		 * Creates new {@link Not} that evaluates the boolean value of the referenced field and returns the opposite boolean
+		 * value.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Not not(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Not(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Not} that evaluates the resulting boolean value of the given {@link AggregationExpression} and
+		 * returns the opposite boolean value.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Not not(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Not(Collections.singletonList(expression));
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketAutoOperation.java

@@ -0,0 +1,275 @@
+/*
+ * Copyright 2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import org.springframework.data.mongodb.core.aggregation.BucketAutoOperation.BucketAutoOperationOutputBuilder;
+import org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OutputBuilder;
+import org.springframework.util.Assert;
+
+import org.bson.Document;
+
+/**
+ * Encapsulates the aggregation framework {@code $bucketAuto}-operation. <br />
+ * Bucket stage is typically used with {@link Aggregation} and {@code $facet}. Categorizes incoming documents into a
+ * specific number of groups, called buckets, based on a specified expression. Bucket boundaries are automatically
+ * determined in an attempt to evenly distribute the documents into the specified number of buckets. <br />
+ * We recommend to use the static factory method {@link Aggregation#bucketAuto(String, int)} instead of creating
+ * instances of this class directly.
+ *
+ * @see <a href=
+ *      "https://docs.mongodb.org/manual/reference/aggregation/bucketAuto/">https://docs.mongodb.org/manual/reference/aggregation/bucketAuto/</a>
+ * @see BucketOperationSupport
+ * @author Mark Paluch
+ * @author Christoph Strobl
+ * @since 1.10
+ */
+public class BucketAutoOperation extends BucketOperationSupport<BucketAutoOperation, BucketAutoOperationOutputBuilder>
+		implements FieldsExposingAggregationOperation {
+
+	private final int buckets;
+	private final String granularity;
+
+	/**
+	 * Creates a new {@link BucketAutoOperation} given a {@link Field group-by field}.
+	 *
+	 * @param groupByField must not be {@literal null}.
+	 * @param buckets number of buckets, must be a positive integer.
+	 */
+	public BucketAutoOperation(Field groupByField, int buckets) {
+
+		super(groupByField);
+
+		Assert.isTrue(buckets > 0, "Number of buckets must be greater 0!");
+
+		this.buckets = buckets;
+		this.granularity = null;
+	}
+
+	/**
+	 * Creates a new {@link BucketAutoOperation} given a {@link AggregationExpression group-by expression}.
+	 *
+	 * @param groupByExpression must not be {@literal null}.
+	 * @param buckets number of buckets, must be a positive integer.
+	 */
+	public BucketAutoOperation(AggregationExpression groupByExpression, int buckets) {
+
+		super(groupByExpression);
+
+		Assert.isTrue(buckets > 0, "Number of buckets must be greater 0!");
+
+		this.buckets = buckets;
+		this.granularity = null;
+	}
+
+	private BucketAutoOperation(BucketAutoOperation bucketOperation, Outputs outputs) {
+
+		super(bucketOperation, outputs);
+
+		this.buckets = bucketOperation.buckets;
+		this.granularity = bucketOperation.granularity;
+	}
+
+	private BucketAutoOperation(BucketAutoOperation bucketOperation, int buckets, String granularity) {
+
+		super(bucketOperation);
+
+		this.buckets = buckets;
+		this.granularity = granularity;
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public Document toDocument(AggregationOperationContext context) {
+
+		Document options = new Document();
+
+		options.put("buckets", buckets);
+
+		if (granularity != null) {
+			options.put("granularity", granularity);
+		}
+
+		options.putAll(super.toDocument(context));
+
+		return new Document("$bucketAuto", options);
+	}
+
+	/**
+	 * Configures a number of bucket {@literal buckets} and return a new {@link BucketAutoOperation}.
+	 *
+	 * @param buckets must be a positive number.
+	 * @return
+	 */
+	public BucketAutoOperation withBuckets(int buckets) {
+
+		Assert.isTrue(buckets > 0, "Number of buckets must be greater 0!");
+		return new BucketAutoOperation(this, buckets, granularity);
+	}
+
+	/**
+	 * Configures {@link Granularity granularity} that specifies the preferred number series to use to ensure that the
+	 * calculated boundary edges end on preferred round numbers or their powers of 10 and return a new
+	 * {@link BucketAutoOperation}. <br />
+	 * Use either predefined {@link Granularities} or provide a own one.
+	 *
+	 * @param granularity must not be {@literal null}.
+	 * @return
+	 */
+	public BucketAutoOperation withGranularity(Granularity granularity) {
+
+		Assert.notNull(granularity, "Granularity must not be null!");
+
+		return new BucketAutoOperation(this, buckets, granularity.getMongoRepresentation());
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#newBucketOperation(org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.Outputs)
+	 */
+	@Override
+	protected BucketAutoOperation newBucketOperation(Outputs outputs) {
+		return new BucketAutoOperation(this, outputs);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#andOutputExpression(java.lang.String, java.lang.Object[])
+	 */
+	@Override
+	public ExpressionBucketAutoOperationBuilder andOutputExpression(String expression, Object... params) {
+		return new ExpressionBucketAutoOperationBuilder(expression, this, params);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#andOutput(org.springframework.data.mongodb.core.aggregation.AggregationExpression)
+	 */
+	@Override
+	public BucketAutoOperationOutputBuilder andOutput(AggregationExpression expression) {
+		return new BucketAutoOperationOutputBuilder(expression, this);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#andOutput(java.lang.String)
+	 */
+	@Override
+	public BucketAutoOperationOutputBuilder andOutput(String fieldName) {
+		return new BucketAutoOperationOutputBuilder(Fields.field(fieldName), this);
+	}
+
+	/**
+	 * {@link OutputBuilder} implementation for {@link BucketAutoOperation}.
+	 */
+	public static class BucketAutoOperationOutputBuilder
+			extends OutputBuilder<BucketAutoOperationOutputBuilder, BucketAutoOperation> {
+
+		/**
+		 * Creates a new {@link BucketAutoOperationOutputBuilder} fot the given value and {@link BucketAutoOperation}.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @param operation must not be {@literal null}.
+		 */
+		protected BucketAutoOperationOutputBuilder(Object value, BucketAutoOperation operation) {
+			super(value, operation);
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OutputBuilder#apply(org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OperationOutput)
+		 */
+		@Override
+		protected BucketAutoOperationOutputBuilder apply(OperationOutput operationOutput) {
+			return new BucketAutoOperationOutputBuilder(operationOutput, this.operation);
+		}
+	}
+
+	/**
+	 * {@link ExpressionBucketOperationBuilderSupport} implementation for {@link BucketAutoOperation} using SpEL
+	 * expression based {@link Output}.
+	 *
+	 * @author Mark Paluch
+	 */
+	public static class ExpressionBucketAutoOperationBuilder
+			extends ExpressionBucketOperationBuilderSupport<BucketAutoOperationOutputBuilder, BucketAutoOperation> {
+
+		/**
+		 * Creates a new {@link ExpressionBucketAutoOperationBuilder} for the given value, {@link BucketAutoOperation} and
+		 * parameters.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @param operation must not be {@literal null}.
+		 * @param parameters
+		 */
+		protected ExpressionBucketAutoOperationBuilder(String expression, BucketAutoOperation operation,
+				Object[] parameters) {
+			super(expression, operation, parameters);
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OutputBuilder#apply(org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OperationOutput)
+		 */
+		@Override
+		protected BucketAutoOperationOutputBuilder apply(OperationOutput operationOutput) {
+			return new BucketAutoOperationOutputBuilder(operationOutput, this.operation);
+		}
+	}
+
+	/**
+	 * @author Mark Paluch
+	 */
+	public interface Granularity {
+
+		/**
+		 * @return a String that represents a MongoDB granularity to be used with {@link BucketAutoOperation}. Never
+		 *         {@literal null}.
+		 */
+		String getMongoRepresentation();
+	}
+
+	/**
+	 * Supported MongoDB granularities.
+	 *
+	 * @see <a
+	 *      href="https://docs.mongodb.com/manual/reference/operator/aggregation/bucketAuto/#granularity>https://docs.mongodb.com/manual/reference/operator/aggregation/bucketAuto/#granularity</a>
+	 * @author Mark Paluch
+	 */
+	public enum Granularities implements Granularity {
+
+		R5, R10, R20, R40, R80, //
+
+		SERIES_1_2_5("1-2-5"), //
+
+		E6, E12, E24, E48, E96, E192, //
+
+		POWERSOF2;
+
+		private final String granularity;
+
+		Granularities() {
+			this.granularity = name();
+		}
+
+		Granularities(String granularity) {
+			this.granularity = granularity;
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.GranularitytoMongoGranularity()
+		 */
+		@Override
+		public String getMongoRepresentation() {
+			return granularity;
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketOperation.java

@@ -0,0 +1,226 @@
+/*
+ * Copyright 2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.springframework.data.mongodb.core.aggregation.BucketOperation.BucketOperationOutputBuilder;
+import org.springframework.util.Assert;
+
+import org.bson.Document;
+
+/**
+ * Encapsulates the aggregation framework {@code $bucket}-operation. <br />
+ *
+ * Bucket stage is typically used with {@link Aggregation} and {@code $facet}. Categorizes incoming documents into
+ * groups, called buckets, based on a specified expression and bucket boundaries. <br />
+ *
+ * We recommend to use the static factory method {@link Aggregation#bucket(String)} instead of creating instances of
+ * this class directly.
+ *
+ * @see <a href="https://docs.mongodb.org/manual/reference/aggregation/bucket/">https://docs.mongodb.org/manual/reference/aggregation/bucket/</a>
+ * @see BucketOperationSupport
+ * @author Mark Paluch
+ * @since 1.10
+ */
+public class BucketOperation extends BucketOperationSupport<BucketOperation, BucketOperationOutputBuilder>
+		implements FieldsExposingAggregationOperation {
+
+	private final List<Object> boundaries;
+	private final Object defaultBucket;
+
+	/**
+	 * Creates a new {@link BucketOperation} given a {@link Field group-by field}.
+	 *
+	 * @param groupByField must not be {@literal null}.
+	 */
+	public BucketOperation(Field groupByField) {
+
+		super(groupByField);
+
+		this.boundaries = Collections.emptyList();
+		this.defaultBucket = null;
+	}
+
+	/**
+	 * Creates a new {@link BucketOperation} given a {@link AggregationExpression group-by expression}.
+	 *
+	 * @param groupByExpression must not be {@literal null}.
+	 */
+	public BucketOperation(AggregationExpression groupByExpression) {
+
+		super(groupByExpression);
+
+		this.boundaries = Collections.emptyList();
+		this.defaultBucket = null;
+	}
+
+	private BucketOperation(BucketOperation bucketOperation, Outputs outputs) {
+
+		super(bucketOperation, outputs);
+
+		this.boundaries = bucketOperation.boundaries;
+		this.defaultBucket = bucketOperation.defaultBucket;
+	}
+
+	private BucketOperation(BucketOperation bucketOperation, List<Object> boundaries, Object defaultBucket) {
+
+		super(bucketOperation);
+
+		this.boundaries = new ArrayList<Object>(boundaries);
+		this.defaultBucket = defaultBucket;
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public Document toDocument(AggregationOperationContext context) {
+
+		Document options = new Document();
+
+		options.put("boundaries", context.getMappedObject(new Document("$set", boundaries)).get("$set"));
+
+		if (defaultBucket != null) {
+			options.put("default", context.getMappedObject(new Document("$set", defaultBucket)).get("$set"));
+		}
+
+		options.putAll(super.toDocument(context));
+
+		return new Document("$bucket", options);
+	}
+
+	/**
+	 * Configures a default bucket {@literal literal} and return a new {@link BucketOperation}.
+	 *
+	 * @param literal must not be {@literal null}.
+	 * @return
+	 */
+	public BucketOperation withDefaultBucket(Object literal) {
+
+		Assert.notNull(literal, "Default bucket literal must not be null!");
+		return new BucketOperation(this, boundaries, literal);
+	}
+
+	/**
+	 * Configures {@literal boundaries} and return a new {@link BucketOperation}. Existing {@literal boundaries} are
+	 * preserved and the new {@literal boundaries} are appended.
+	 *
+	 * @param boundaries must not be {@literal null}.
+	 * @return
+	 */
+	public BucketOperation withBoundaries(Object... boundaries) {
+
+		Assert.notNull(boundaries, "Boundaries must not be null!");
+		Assert.noNullElements(boundaries, "Boundaries must not contain null values!");
+
+		List<Object> newBoundaries = new ArrayList<Object>(this.boundaries.size() + boundaries.length);
+		newBoundaries.addAll(this.boundaries);
+		newBoundaries.addAll(Arrays.asList(boundaries));
+
+		return new BucketOperation(this, newBoundaries, defaultBucket);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#newBucketOperation(org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.Outputs)
+	 */
+	@Override
+	protected BucketOperation newBucketOperation(Outputs outputs) {
+		return new BucketOperation(this, outputs);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#andOutputExpression(java.lang.String, java.lang.Object[])
+	 */
+	@Override
+	public ExpressionBucketOperationBuilder andOutputExpression(String expression, Object... params) {
+		return new ExpressionBucketOperationBuilder(expression, this, params);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#andOutput(org.springframework.data.mongodb.core.aggregation.AggregationExpression)
+	 */
+	@Override
+	public BucketOperationOutputBuilder andOutput(AggregationExpression expression) {
+		return new BucketOperationOutputBuilder(expression, this);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#andOutput(java.lang.String)
+	 */
+	@Override
+	public BucketOperationOutputBuilder andOutput(String fieldName) {
+		return new BucketOperationOutputBuilder(Fields.field(fieldName), this);
+	}
+
+	/**
+	 * {@link OutputBuilder} implementation for {@link BucketOperation}.
+	 */
+	public static class BucketOperationOutputBuilder
+			extends BucketOperationSupport.OutputBuilder<BucketOperationOutputBuilder, BucketOperation> {
+
+		/**
+		 * Creates a new {@link BucketOperationOutputBuilder} fot the given value and {@link BucketOperation}.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @param operation must not be {@literal null}.
+		 */
+		protected BucketOperationOutputBuilder(Object value, BucketOperation operation) {
+			super(value, operation);
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OutputBuilder#apply(org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OperationOutput)
+		 */
+		@Override
+		protected BucketOperationOutputBuilder apply(OperationOutput operationOutput) {
+			return new BucketOperationOutputBuilder(operationOutput, this.operation);
+		}
+	}
+
+	/**
+	 * {@link ExpressionBucketOperationBuilderSupport} implementation for {@link BucketOperation} using SpEL expression
+	 * based {@link Output}.
+	 *
+	 * @author Mark Paluch
+	 */
+	public static class ExpressionBucketOperationBuilder
+			extends ExpressionBucketOperationBuilderSupport<BucketOperationOutputBuilder, BucketOperation> {
+
+		/**
+		 * Creates a new {@link ExpressionBucketOperationBuilderSupport} for the given value, {@link BucketOperation}
+		 * and parameters.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @param operation must not be {@literal null}.
+		 * @param parameters
+		 */
+		protected ExpressionBucketOperationBuilder(String expression, BucketOperation operation, Object[] parameters) {
+			super(expression, operation, parameters);
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OutputBuilder#apply(org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OperationOutput)
+		 */
+		@Override
+		protected BucketOperationOutputBuilder apply(OperationOutput operationOutput) {
+			return new BucketOperationOutputBuilder(operationOutput, this.operation);
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/BucketOperationSupport.java

@@ -0,0 +1,679 @@
+/*
+ * Copyright 2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+
+import org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.OutputBuilder;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
+import org.springframework.data.mongodb.core.aggregation.ProjectionOperation.ProjectionOperationBuilder;
+import org.springframework.expression.spel.ast.Projection;
+import org.springframework.util.Assert;
+
+import org.bson.Document;
+
+/**
+ * Base class for bucket operations that support output expressions the aggregation framework. <br />
+ * Bucket stages collect documents into buckets and can contribute output fields. <br />
+ * Implementing classes are required to provide an {@link OutputBuilder}.
+ *
+ * @author Mark Paluch
+ * @author Christoph Strobl
+ * @since 1.10
+ */
+public abstract class BucketOperationSupport<T extends BucketOperationSupport<T, B>, B extends OutputBuilder<B, T>>
+		implements FieldsExposingAggregationOperation {
+
+	private final Field groupByField;
+	private final AggregationExpression groupByExpression;
+	private final Outputs outputs;
+
+	/**
+	 * Creates a new {@link BucketOperationSupport} given a {@link Field group-by field}.
+	 *
+	 * @param groupByField must not be {@literal null}.
+	 */
+	protected BucketOperationSupport(Field groupByField) {
+
+		Assert.notNull(groupByField, "Group by field must not be null!");
+
+		this.groupByField = groupByField;
+		this.groupByExpression = null;
+		this.outputs = Outputs.EMPTY;
+	}
+
+	/**
+	 * Creates a new {@link BucketOperationSupport} given a {@link AggregationExpression group-by expression}.
+	 *
+	 * @param groupByExpression must not be {@literal null}.
+	 */
+	protected BucketOperationSupport(AggregationExpression groupByExpression) {
+
+		Assert.notNull(groupByExpression, "Group by AggregationExpression must not be null!");
+
+		this.groupByExpression = groupByExpression;
+		this.groupByField = null;
+		this.outputs = Outputs.EMPTY;
+	}
+
+	/**
+	 * Creates a copy of {@link BucketOperationSupport}.
+	 *
+	 * @param operationSupport must not be {@literal null}.
+	 */
+	protected BucketOperationSupport(BucketOperationSupport<?, ?> operationSupport) {
+		this(operationSupport, operationSupport.outputs);
+	}
+
+	/**
+	 * Creates a copy of {@link BucketOperationSupport} and applies the new {@link Outputs}.
+	 *
+	 * @param operationSupport must not be {@literal null}.
+	 * @param outputs must not be {@literal null}.
+	 */
+	protected BucketOperationSupport(BucketOperationSupport<?, ?> operationSupport, Outputs outputs) {
+
+		Assert.notNull(operationSupport, "BucketOperationSupport must not be null!");
+		Assert.notNull(outputs, "Outputs must not be null!");
+
+		this.groupByField = operationSupport.groupByField;
+		this.groupByExpression = operationSupport.groupByExpression;
+		this.outputs = outputs;
+	}
+
+	/**
+	 * Creates a new {@link ExpressionBucketOperationBuilderSupport} given a SpEL {@literal expression} and optional
+	 * {@literal params} to add an output field to the resulting bucket documents.
+	 *
+	 * @param expression the SpEL expression, must not be {@literal null} or empty.
+	 * @param params must not be {@literal null}
+	 * @return
+	 */
+	public abstract ExpressionBucketOperationBuilderSupport<B, T> andOutputExpression(String expression,
+			Object... params);
+
+	/**
+	 * Creates a new {@link BucketOperationSupport} given an {@link AggregationExpression} to add an output field to the
+	 * resulting bucket documents.
+	 *
+	 * @param expression the SpEL expression, must not be {@literal null} or empty.
+	 * @return
+	 */
+	public abstract B andOutput(AggregationExpression expression);
+
+	/**
+	 * Creates a new {@link BucketOperationSupport} given {@literal fieldName} to add an output field to the resulting
+	 * bucket documents. {@link BucketOperationSupport} exposes accumulation operations that can be applied to
+	 * {@literal fieldName}.
+	 *
+	 * @param fieldName must not be {@literal null} or empty.
+	 * @return
+	 */
+	public abstract B andOutput(String fieldName);
+
+	/**
+	 * Creates a new {@link BucketOperationSupport} given to add a count field to the resulting bucket documents.
+	 *
+	 * @return
+	 */
+	public B andOutputCount() {
+		return andOutput(new AggregationExpression() {
+			@Override
+			public Document toDocument(AggregationOperationContext context) {
+				return new Document("$sum", 1);
+			}
+		});
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public Document toDocument(AggregationOperationContext context) {
+
+		Document document = new Document();
+
+		document.put("groupBy", groupByExpression == null ? context.getReference(groupByField).toString()
+				: groupByExpression.toDocument(context));
+
+		if (!outputs.isEmpty()) {
+			document.put("output", outputs.toDocument(context));
+		}
+
+		return document;
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation#getFields()
+	 */
+	@Override
+	public ExposedFields getFields() {
+		return outputs.asExposedFields();
+	}
+
+	/**
+	 * Implementation hook to create a new bucket operation.
+	 *
+	 * @param outputs the outputs
+	 * @return the new bucket operation.
+	 */
+	protected abstract T newBucketOperation(Outputs outputs);
+
+	protected T andOutput(Output output) {
+		return newBucketOperation(outputs.and(output));
+	}
+
+	/**
+	 * Builder for SpEL expression-based {@link Output}.
+	 *
+	 * @author Mark Paluch
+	 */
+	public abstract static class ExpressionBucketOperationBuilderSupport<B extends OutputBuilder<B, T>, T extends BucketOperationSupport<T, B>>
+			extends OutputBuilder<B, T> {
+
+		/**
+		 * Creates a new {@link ExpressionBucketOperationBuilderSupport} for the given value, {@link BucketOperationSupport}
+		 * and parameters.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @param operation must not be {@literal null}.
+		 * @param parameters
+		 */
+		protected ExpressionBucketOperationBuilderSupport(String expression, T operation, Object[] parameters) {
+			super(new SpelExpressionOutput(expression, parameters), operation);
+		}
+	}
+
+	/**
+	 * Base class for {@link Output} builders that result in a {@link BucketOperationSupport} providing the built
+	 * {@link Output}.
+	 *
+	 * @author Mark Paluch
+	 */
+	public abstract static class OutputBuilder<B extends OutputBuilder<B, T>, T extends BucketOperationSupport<T, B>> {
+
+		protected final Object value;
+		protected final T operation;
+
+		/**
+		 * Creates a new {@link OutputBuilder} for the given value and {@link BucketOperationSupport}.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @param operation must not be {@literal null}.
+		 */
+		protected OutputBuilder(Object value, T operation) {
+
+			Assert.notNull(value, "Value must not be null or empty!");
+			Assert.notNull(operation, "ProjectionOperation must not be null!");
+
+			this.value = value;
+			this.operation = operation;
+		}
+
+		/**
+		 * Generates a builder for a {@code $sum}-expression. <br />
+		 * Count expressions are emulated via {@code $sum: 1}.
+		 *
+		 * @return
+		 */
+		public B count() {
+			return sum(1);
+		}
+
+		/**
+		 * Generates a builder for a {@code $sum}-expression for the current value.
+		 *
+		 * @return
+		 */
+		public B sum() {
+			return apply(Accumulators.SUM);
+		}
+
+		/**
+		 * Generates a builder for a {@code $sum}-expression for the given {@literal value}.
+		 *
+		 * @param value
+		 * @return
+		 */
+		public B sum(Number value) {
+			return apply(new OperationOutput(Accumulators.SUM.getMongoOperator(), Collections.singleton(value)));
+		}
+
+		/**
+		 * Generates a builder for an {@code $last}-expression for the current value..
+		 *
+		 * @return
+		 */
+		public B last() {
+			return apply(Accumulators.LAST);
+		}
+
+		/**
+		 * Generates a builder for a {@code $first}-expression the current value.
+		 *
+		 * @return
+		 */
+		public B first() {
+			return apply(Accumulators.FIRST);
+		}
+
+		/**
+		 * Generates a builder for an {@code $avg}-expression for the current value.
+		 *
+		 * @param reference
+		 * @return
+		 */
+		public B avg() {
+			return apply(Accumulators.AVG);
+		}
+
+		/**
+		 * Generates a builder for an {@code $min}-expression for the current value.
+		 *
+		 * @return
+		 */
+		public B min() {
+			return apply(Accumulators.MIN);
+		}
+
+		/**
+		 * Generates a builder for an {@code $max}-expression for the current value.
+		 *
+		 * @return
+		 */
+		public B max() {
+			return apply(Accumulators.MAX);
+		}
+
+		/**
+		 * Generates a builder for an {@code $push}-expression for the current value.
+		 *
+		 * @return
+		 */
+		public B push() {
+			return apply(Accumulators.PUSH);
+		}
+
+		/**
+		 * Generates a builder for an {@code $addToSet}-expression for the current value.
+		 *
+		 * @return
+		 */
+		public B addToSet() {
+			return apply(Accumulators.ADDTOSET);
+		}
+
+		/**
+		 * Apply an operator to the current value.
+		 *
+		 * @param operation the operation name, must not be {@literal null} or empty.
+		 * @param values must not be {@literal null}.
+		 * @return
+		 */
+		public B apply(String operation, Object... values) {
+
+			Assert.hasText(operation, "Operation must not be empty or null!");
+			Assert.notNull(value, "Values must not be null!");
+
+			List<Object> objects = new ArrayList<Object>(values.length + 1);
+			objects.add(value);
+			objects.addAll(Arrays.asList(values));
+			return apply(new OperationOutput(operation, objects));
+		}
+
+		/**
+		 * Apply an {@link OperationOutput} to this output.
+		 *
+		 * @param operationOutput must not be {@literal null}.
+		 * @return
+		 */
+		protected abstract B apply(OperationOutput operationOutput);
+
+		private B apply(Accumulators operation) {
+			return this.apply(operation.getMongoOperator());
+		}
+
+		/**
+		 * Returns the finally to be applied {@link BucketOperation} with the given alias.
+		 *
+		 * @param alias will never be {@literal null} or empty.
+		 * @return
+		 */
+		public T as(String alias) {
+
+			if (value instanceof OperationOutput) {
+				return this.operation.andOutput(((OperationOutput) this.value).withAlias(alias));
+			}
+
+			if (value instanceof Field) {
+				throw new IllegalStateException("Cannot add a field as top-level output. Use accumulator expressions.");
+			}
+
+			return this.operation
+					.andOutput(new AggregationExpressionOutput(Fields.field(alias), (AggregationExpression) value));
+		}
+	}
+
+	private enum Accumulators {
+
+		SUM("$sum"), AVG("$avg"), FIRST("$first"), LAST("$last"), MAX("$max"), MIN("$min"), PUSH("$push"), ADDTOSET(
+				"$addToSet");
+
+		private String mongoOperator;
+
+		Accumulators(String mongoOperator) {
+			this.mongoOperator = mongoOperator;
+		}
+
+		public String getMongoOperator() {
+			return mongoOperator;
+		}
+	}
+
+	/**
+	 * Encapsulates {@link Output}s.
+	 *
+	 * @author Mark Paluch
+	 */
+	protected static class Outputs implements AggregationExpression {
+
+		protected static final Outputs EMPTY = new Outputs();
+
+		private List<Output> outputs;
+
+		/**
+		 * Creates a new, empty {@link Outputs}.
+		 */
+		private Outputs() {
+			this.outputs = new ArrayList<Output>();
+		}
+
+		/**
+		 * Creates new {@link Outputs} containing all given {@link Output}s.
+		 *
+		 * @param current
+		 * @param output
+		 */
+		private Outputs(Collection<Output> current, Output output) {
+
+			this.outputs = new ArrayList<Output>(current.size() + 1);
+			this.outputs.addAll(current);
+			this.outputs.add(output);
+		}
+
+		/**
+		 * @return the {@link ExposedFields} derived from {@link Output}.
+		 */
+		protected ExposedFields asExposedFields() {
+
+			// The count field is included by default when the output is not specified.
+			if (isEmpty()) {
+				return ExposedFields.from(new ExposedField("count", true));
+			}
+
+			ExposedFields fields = ExposedFields.from();
+
+			for (Output output : outputs) {
+				fields = fields.and(output.getExposedField());
+			}
+
+			return fields;
+		}
+
+		/**
+		 * Create a new {@link Outputs} that contains the new {@link Output}.
+		 *
+		 * @param output must not be {@literal null}.
+		 * @return the new {@link Outputs} that contains the new {@link Output}
+		 */
+		protected Outputs and(Output output) {
+
+			Assert.notNull(output, "BucketOutput must not be null!");
+			return new Outputs(this.outputs, output);
+		}
+
+		/**
+		 * @return {@literal true} if {@link Outputs} contains no {@link Output}.
+		 */
+		protected boolean isEmpty() {
+			return outputs.isEmpty();
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AggregationExpression#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocument(AggregationOperationContext context) {
+
+			Document document = new Document();
+
+			for (Output output : outputs) {
+				document.put(output.getExposedField().getName(), output.toDocument(context));
+			}
+
+			return document;
+		}
+
+	}
+
+	/**
+	 * Encapsulates an output field in a bucket aggregation stage. <br />
+	 * Output fields can be either top-level fields that define a valid field name or nested output fields using
+	 * operators.
+	 *
+	 * @author Mark Paluch
+	 */
+	protected abstract static class Output implements AggregationExpression {
+
+		private final ExposedField field;
+
+		/**
+		 * Creates new {@link Projection} for the given {@link Field}.
+		 *
+		 * @param field must not be {@literal null}.
+		 */
+		protected Output(Field field) {
+
+			Assert.notNull(field, "Field must not be null!");
+			this.field = new ExposedField(field, true);
+		}
+
+		/**
+		 * Returns the field exposed by the {@link Output}.
+		 *
+		 * @return will never be {@literal null}.
+		 */
+		protected ExposedField getExposedField() {
+			return field;
+		}
+	}
+
+	/**
+	 * Output field that uses a Mongo operation (expression object) to generate an output field value. <br />
+	 * {@link OperationOutput} is used either with a regular field name or an operation keyword (e.g.
+	 * {@literal $sum, $count}).
+	 *
+	 * @author Mark Paluch
+	 */
+	protected static class OperationOutput extends Output {
+
+		private final String operation;
+		private final List<Object> values;
+
+		/**
+		 * Creates a new {@link Output} for the given field.
+		 *
+		 * @param operation the actual operation key, must not be {@literal null} or empty.
+		 * @param values the values to pass into the operation, must not be {@literal null}.
+		 */
+		public OperationOutput(String operation, Collection<? extends Object> values) {
+
+			super(Fields.field(operation));
+
+			Assert.hasText(operation, "Operation must not be null or empty!");
+			Assert.notNull(values, "Values must not be null!");
+
+			this.operation = operation;
+			this.values = new ArrayList<Object>(values);
+		}
+
+		private OperationOutput(Field field, OperationOutput operationOutput) {
+
+			super(field);
+
+			this.operation = operationOutput.operation;
+			this.values = operationOutput.values;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.ProjectionOperation.Projection#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocument(AggregationOperationContext context) {
+
+			List<Object> operationArguments = getOperationArguments(context);
+			return new Document(operation,
+					operationArguments.size() == 1 ? operationArguments.get(0) : operationArguments);
+		}
+
+		protected List<Object> getOperationArguments(AggregationOperationContext context) {
+
+			List<Object> result = new ArrayList<Object>(values != null ? values.size() : 1);
+
+			for (Object element : values) {
+
+				if (element instanceof Field) {
+					result.add(context.getReference((Field) element).toString());
+				} else if (element instanceof Fields) {
+					for (Field field : (Fields) element) {
+						result.add(context.getReference(field).toString());
+					}
+				} else if (element instanceof AggregationExpression) {
+					result.add(((AggregationExpression) element).toDocument(context));
+				} else {
+					result.add(element);
+				}
+			}
+
+			return result;
+		}
+
+		/**
+		 * Returns the field that holds the {@link ProjectionOperationBuilder.OperationProjection}.
+		 *
+		 * @return
+		 */
+		protected Field getField() {
+			return getExposedField();
+		}
+
+		/**
+		 * Creates a new instance of this {@link OperationOutput} with the given alias.
+		 *
+		 * @param alias the alias to set
+		 * @return
+		 */
+		public OperationOutput withAlias(String alias) {
+
+			final Field aliasedField = Fields.field(alias);
+			return new OperationOutput(aliasedField, this) {
+
+				@Override
+				protected Field getField() {
+					return aliasedField;
+				}
+
+				@Override
+				protected List<Object> getOperationArguments(AggregationOperationContext context) {
+
+					// We have to make sure that we use the arguments from the "previous" OperationOutput that we replace
+					// with this new instance.
+					return OperationOutput.this.getOperationArguments(context);
+				}
+			};
+		}
+	}
+
+	/**
+	 * A {@link Output} based on a SpEL expression.
+	 */
+	private static class SpelExpressionOutput extends Output {
+
+		private static final SpelExpressionTransformer TRANSFORMER = new SpelExpressionTransformer();
+
+		private final String expression;
+		private final Object[] params;
+
+		/**
+		 * Creates a new {@link SpelExpressionOutput} for the given field, SpEL expression and parameters.
+		 *
+		 * @param expression must not be {@literal null} or empty.
+		 * @param parameters must not be {@literal null}.
+		 */
+		public SpelExpressionOutput(String expression, Object[] parameters) {
+
+			super(Fields.field(expression));
+
+			Assert.hasText(expression, "Expression must not be null!");
+			Assert.notNull(parameters, "Parameters must not be null!");
+
+			this.expression = expression;
+			this.params = parameters.clone();
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.Output#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocument(AggregationOperationContext context) {
+			return (Document) TRANSFORMER.transform(expression, context, params);
+		}
+	}
+
+	/**
+	 * @author Mark Paluch
+	 */
+	private static class AggregationExpressionOutput extends Output {
+
+		private final AggregationExpression expression;
+
+		/**
+		 * Creates a new {@link AggregationExpressionOutput}.
+		 *
+		 * @param field
+		 * @param expression
+		 */
+		protected AggregationExpressionOutput(Field field, AggregationExpression expression) {
+
+			super(field);
+
+			this.expression = expression;
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.Output#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocument(AggregationOperationContext context) {
+			return expression.toDocument(context);
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ComparisonOperators.java

@@ -0,0 +1,879 @@
+/*
+ * Copyright 2016. the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.Collections;
+import java.util.List;
+
+import org.springframework.util.Assert;
+
+/**
+ * Gateway to {@literal comparison expressions}.
+ *
+ * @author Christoph Strobl
+ * @since 1.10
+ */
+public class ComparisonOperators {
+
+	/**
+	 * Take the field referenced by given {@literal fieldReference}.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return
+	 */
+	public static ComparisonOperatorFactory valueOf(String fieldReference) {
+		return new ComparisonOperatorFactory(fieldReference);
+	}
+
+	/**
+	 * Take the value resulting from the given {@link AggregationExpression}.
+	 *
+	 * @param expression must not be {@literal null}.
+	 * @return
+	 */
+	public static ComparisonOperatorFactory valueOf(AggregationExpression expression) {
+		return new ComparisonOperatorFactory(expression);
+	}
+
+	public static class ComparisonOperatorFactory {
+
+		private final String fieldReference;
+		private final AggregationExpression expression;
+
+		/**
+		 * Creates new {@link ComparisonOperatorFactory} for given {@literal fieldReference}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 */
+		public ComparisonOperatorFactory(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			this.fieldReference = fieldReference;
+			this.expression = null;
+		}
+
+		/**
+		 * Creates new {@link ComparisonOperatorFactory} for given {@link AggregationExpression}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 */
+		public ComparisonOperatorFactory(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			this.fieldReference = null;
+			this.expression = expression;
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Cmp compareTo(String fieldReference) {
+			return createCmp().compareTo(fieldReference);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Cmp compareTo(AggregationExpression expression) {
+			return createCmp().compareTo(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Cmp compareToValue(Object value) {
+			return createCmp().compareToValue(value);
+		}
+
+		private Cmp createCmp() {
+			return usesFieldRef() ? Cmp.valueOf(fieldReference) : Cmp.valueOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is equal to the value of the referenced field.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Eq equalTo(String fieldReference) {
+			return createEq().equalTo(fieldReference);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is equal to the expression result.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Eq equalTo(AggregationExpression expression) {
+			return createEq().equalTo(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is equal to the given value.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Eq equalToValue(Object value) {
+			return createEq().equalToValue(value);
+		}
+
+		private Eq createEq() {
+			return usesFieldRef() ? Eq.valueOf(fieldReference) : Eq.valueOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is greater than the value of the referenced field.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Gt greaterThan(String fieldReference) {
+			return createGt().greaterThan(fieldReference);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is greater than the expression result.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Gt greaterThan(AggregationExpression expression) {
+			return createGt().greaterThan(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is greater than the given value.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Gt greaterThanValue(Object value) {
+			return createGt().greaterThanValue(value);
+		}
+
+		private Gt createGt() {
+			return usesFieldRef() ? Gt.valueOf(fieldReference) : Gt.valueOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is greater than or equivalent to the value of the referenced field.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Gte greaterThanEqualTo(String fieldReference) {
+			return createGte().greaterThanEqualTo(fieldReference);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is greater than or equivalent to the expression result.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Gte greaterThanEqualTo(AggregationExpression expression) {
+			return createGte().greaterThanEqualTo(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is greater than or equivalent to the given value.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Gte greaterThanEqualToValue(Object value) {
+			return createGte().greaterThanEqualToValue(value);
+		}
+
+		private Gte createGte() {
+			return usesFieldRef() ? Gte.valueOf(fieldReference) : Gte.valueOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is less than the value of the referenced field.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Lt lessThan(String fieldReference) {
+			return createLt().lessThan(fieldReference);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is less than the expression result.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Lt lessThan(AggregationExpression expression) {
+			return createLt().lessThan(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is less than to the given value.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Lt lessThanValue(Object value) {
+			return createLt().lessThanValue(value);
+		}
+
+		private Lt createLt() {
+			return usesFieldRef() ? Lt.valueOf(fieldReference) : Lt.valueOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is less than or equivalent to the value of the referenced field.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Lte lessThanEqualTo(String fieldReference) {
+			return createLte().lessThanEqualTo(fieldReference);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is less than or equivalent to the expression result.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Lte lessThanEqualTo(AggregationExpression expression) {
+			return createLte().lessThanEqualTo(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the first
+		 * value is less than or equivalent to the given value.
+		 *
+		 * @param value
+		 * @return
+		 */
+		public Lte lessThanEqualToValue(Object value) {
+			return createLte().lessThanEqualToValue(value);
+		}
+
+		private Lte createLte() {
+			return usesFieldRef() ? Lte.valueOf(fieldReference) : Lte.valueOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the values
+		 * are not equivalent.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Ne notEqualTo(String fieldReference) {
+			return createNe().notEqualTo(fieldReference);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the values
+		 * are not equivalent.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Ne notEqualTo(AggregationExpression expression) {
+			return createNe().notEqualTo(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares two values and returns {@literal true} when the values
+		 * are not equivalent.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Ne notEqualToValue(Object value) {
+			return createNe().notEqualToValue(value);
+		}
+
+		private Ne createNe() {
+			return usesFieldRef() ? Ne.valueOf(fieldReference) : Ne.valueOf(expression);
+		}
+
+		private boolean usesFieldRef() {
+			return fieldReference != null;
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $cmp}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Cmp extends AbstractAggregationExpression {
+
+		private Cmp(List<?> value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$cmp";
+		}
+
+		/**
+		 * Creates new {@link Cmp}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Cmp valueOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Cmp(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Cmp}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Cmp valueOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Cmp(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link Cmp} with all previously added arguments appending the given one.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Cmp compareTo(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Cmp(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link Cmp} with all previously added arguments appending the given one.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Cmp compareTo(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Cmp(append(expression));
+		}
+
+		/**
+		 * Creates new {@link Cmp} with all previously added arguments appending the given one.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Cmp compareToValue(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+			return new Cmp(append(value));
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $eq}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Eq extends AbstractAggregationExpression {
+
+		private Eq(List<?> value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$eq";
+		}
+
+		/**
+		 * Creates new {@link Eq}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Eq valueOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Eq(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Eq}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Eq valueOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Eq(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link Eq} with all previously added arguments appending the given one.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Eq equalTo(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Eq(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link Eq} with all previously added arguments appending the given one.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Eq equalTo(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Eq(append(expression));
+		}
+
+		/**
+		 * Creates new {@link Eq} with all previously added arguments appending the given one.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Eq equalToValue(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+			return new Eq(append(value));
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $gt}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Gt extends AbstractAggregationExpression {
+
+		private Gt(List<?> value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$gt";
+		}
+
+		/**
+		 * Creates new {@link Gt}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Gt valueOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Gt(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Gt}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Gt valueOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Gt(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link Gt} with all previously added arguments appending the given one.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Gt greaterThan(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Gt(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link Gt} with all previously added arguments appending the given one.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Gt greaterThan(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Gt(append(expression));
+		}
+
+		/**
+		 * Creates new {@link Gt} with all previously added arguments appending the given one.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Gt greaterThanValue(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+			return new Gt(append(value));
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $lt}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Lt extends AbstractAggregationExpression {
+
+		private Lt(List<?> value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$lt";
+		}
+
+		/**
+		 * Creates new {@link Lt}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Lt valueOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Lt(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Lt}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Lt valueOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Lt(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link Lt} with all previously added arguments appending the given one.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Lt lessThan(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Lt(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link Lt} with all previously added arguments appending the given one.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Lt lessThan(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Lt(append(expression));
+		}
+
+		/**
+		 * Creates new {@link Lt} with all previously added arguments appending the given one.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Lt lessThanValue(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+			return new Lt(append(value));
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $gte}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Gte extends AbstractAggregationExpression {
+
+		private Gte(List<?> value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$gte";
+		}
+
+		/**
+		 * Creates new {@link Gte}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Gte valueOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Gte(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Gte}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Gte valueOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Gte(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link Gte} with all previously added arguments appending the given one.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Gte greaterThanEqualTo(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Gte(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link Gte} with all previously added arguments appending the given one.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Gte greaterThanEqualTo(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Gte(append(expression));
+		}
+
+		/**
+		 * Creates new {@link Gte} with all previously added arguments appending the given one.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Gte greaterThanEqualToValue(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+			return new Gte(append(value));
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $lte}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Lte extends AbstractAggregationExpression {
+
+		private Lte(List<?> value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$lte";
+		}
+
+		/**
+		 * Creates new {@link Lte}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Lte valueOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Lte(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Lte}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Lte valueOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Lte(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link Lte} with all previously added arguments appending the given one.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Lte lessThanEqualTo(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Lte(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link Lte} with all previously added arguments appending the given one.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Lte lessThanEqualTo(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Lte(append(expression));
+		}
+
+		/**
+		 * Creates new {@link Lte} with all previously added arguments appending the given one.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Lte lessThanEqualToValue(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+			return new Lte(append(value));
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $ne}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Ne extends AbstractAggregationExpression {
+
+		private Ne(List<?> value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$ne";
+		}
+
+		/**
+		 * Creates new {@link Ne}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Ne valueOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Ne(asFields(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Ne}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Ne valueOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Ne(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link Ne} with all previously added arguments appending the given one.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public Ne notEqualTo(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Ne(append(Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link Ne} with all previously added arguments appending the given one.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public Ne notEqualTo(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Ne(append(expression));
+		}
+
+		/**
+		 * Creates new {@link Eq} with all previously added arguments appending the given one.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public Ne notEqualToValue(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+			return new Ne(append(value));
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ConditionalOperator.java

@@ -1,392 +0,0 @@
-/*
- * Copyright 2016 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core.aggregation;
-
-import java.util.ArrayList;
-import java.util.List;
-
-import org.bson.Document;
-import org.springframework.dao.InvalidDataAccessApiUsageException;
-import org.springframework.data.mongodb.core.query.CriteriaDefinition;
-import org.springframework.util.Assert;
-import org.springframework.util.ClassUtils;
-
-/**
- * Encapsulates the aggregation framework {@code $cond} operator. A {@link ConditionalOperator} allows nested conditions
- * {@code if-then[if-then-else]-else} using {@link Field}, {@link CriteriaDefinition} or a {@link Document custom}
- * condition. Replacement values can be either {@link Field field references}, values of simple MongoDB types or values
- * that can be converted to a simple MongoDB type.
- * 
- * @see http://docs.mongodb.com/manual/reference/operator/aggregation/cond/
- * @author Mark Paluch
- * @author Christoph Strobl
- * @since 1.10
- */
-public class ConditionalOperator implements AggregationExpression {
-
-	private final Object condition;
-	private final Object thenValue;
-	private final Object otherwiseValue;
-
-	/**
-	 * Creates a new {@link ConditionalOperator} for a given {@link Field} and {@code then}/{@code otherwise} values.
-	 *
-	 * @param condition must not be {@literal null}.
-	 * @param thenValue must not be {@literal null}.
-	 * @param otherwiseValue must not be {@literal null}.
-	 */
-	public ConditionalOperator(Field condition, Object thenValue, Object otherwiseValue) {
-		this((Object) condition, thenValue, otherwiseValue);
-	}
-
-	/**
-	 * Creates a new {@link ConditionalOperator} for a given {@link CriteriaDefinition} and {@code then}/{@code otherwise}
-	 * values.
-	 *
-	 * @param condition must not be {@literal null}.
-	 * @param thenValue must not be {@literal null}.
-	 * @param otherwiseValue must not be {@literal null}.
-	 */
-	public ConditionalOperator(CriteriaDefinition condition, Object thenValue, Object otherwiseValue) {
-		this((Object) condition, thenValue, otherwiseValue);
-	}
-
-	/**
-	 * Creates a new {@link ConditionalOperator} for a given {@link Document criteria} and {@code then}/{@code otherwise}
-	 * values.
-	 *
-	 * @param condition must not be {@literal null}.
-	 * @param thenValue must not be {@literal null}.
-	 * @param otherwiseValue must not be {@literal null}.
-	 */
-	public ConditionalOperator(Document condition, Object thenValue, Object otherwiseValue) {
-		this((Object) condition, thenValue, otherwiseValue);
-	}
-
-	private ConditionalOperator(Object condition, Object thenValue, Object otherwiseValue) {
-
-		Assert.notNull(condition, "Condition must not be null!");
-		Assert.notNull(thenValue, "'Then value' must not be null!");
-		Assert.notNull(otherwiseValue, "'Otherwise value' must not be null!");
-
-		assertNotBuilder(condition, "Condition");
-		assertNotBuilder(thenValue, "'Then value'");
-		assertNotBuilder(otherwiseValue, "'Otherwise value'");
-
-		this.condition = condition;
-		this.thenValue = thenValue;
-		this.otherwiseValue = otherwiseValue;
-	}
-
-	/* 
-	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.core.aggregation.AggregationExpression#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
-	 */
-	@Override
-	public Document toDocument(AggregationOperationContext context) {
-
-		Document condObject = new Document();
-
-		condObject.append("if", resolveCriteria(context, condition));
-		condObject.append("then", resolveValue(context, thenValue));
-		condObject.append("else", resolveValue(context, otherwiseValue));
-
-		return new Document("$cond", condObject);
-	}
-
-	private Object resolveValue(AggregationOperationContext context, Object value) {
-
-		if (value instanceof Document || value instanceof Field) {
-			return resolve(context, value);
-		}
-
-		if (value instanceof ConditionalOperator) {
-			return ((ConditionalOperator) value).toDocument(context);
-		}
-
-		return context.getMappedObject(new Document("$set", value)).get("$set");
-	}
-
-	private Object resolveCriteria(AggregationOperationContext context, Object value) {
-
-		if (value instanceof Document || value instanceof Field) {
-			return resolve(context, value);
-		}
-
-		if (value instanceof CriteriaDefinition) {
-
-			Document mappedObject = context.getMappedObject(((CriteriaDefinition) value).getCriteriaObject());
-			List<Object> clauses = new ArrayList<Object>();
-
-			clauses.addAll(getClauses(context, mappedObject));
-
-			if (clauses.size() == 1) {
-				return clauses.get(0);
-			}
-
-			return clauses;
-		}
-
-		throw new InvalidDataAccessApiUsageException(
-				String.format("Invalid value in condition. Supported: Document, Field references, Criteria, got: %s", value));
-	}
-
-	private List<Object> getClauses(AggregationOperationContext context, Document mappedObject) {
-
-		List<Object> clauses = new ArrayList<Object>();
-
-		for (String key : mappedObject.keySet()) {
-
-			Object predicate = mappedObject.get(key);
-			clauses.addAll(getClauses(context, key, predicate));
-		}
-
-		return clauses;
-	}
-
-	private List<Object> getClauses(AggregationOperationContext context, String key, Object predicate) {
-
-		List<Object> clauses = new ArrayList<Object>();
-
-		if (predicate instanceof List) {
-
-			List<Object> args = new ArrayList<Object>();
-			for (Object clause : (List<?>) predicate) {
-				if (clause instanceof Document) {
-					args.addAll(getClauses(context, (Document) clause));
-				}
-			}
-
-			clauses.add(new Document(key, args));
-
-		} else if (predicate instanceof Document) {
-
-			Document nested = (Document) predicate;
-
-			for (String s : nested.keySet()) {
-
-				if (!isKeyword(s)) {
-					continue;
-				}
-
-				List<Object> args = new ArrayList<Object>();
-				args.add("$" + key);
-				args.add(nested.get(s));
-				clauses.add(new Document(s, args));
-			}
-
-		} else if (!isKeyword(key)) {
-
-			List<Object> args = new ArrayList<Object>();
-			args.add("$" + key);
-			args.add(predicate);
-			clauses.add(new Document("$eq", args));
-		}
-
-		return clauses;
-	}
-
-	/**
-	 * Returns whether the given {@link String} is a MongoDB keyword.
-	 *
-	 * @param candidate
-	 * @return
-	 */
-	private boolean isKeyword(String candidate) {
-		return candidate.startsWith("$");
-	}
-
-	private Object resolve(AggregationOperationContext context, Object value) {
-
-		if (value instanceof Document) {
-			return context.getMappedObject((Document) value);
-		}
-
-		return context.getReference((Field) value).toString();
-	}
-
-	private void assertNotBuilder(Object toCheck, String name) {
-		Assert.isTrue(!ClassUtils.isAssignableValue(ConditionalExpressionBuilder.class, toCheck),
-				String.format("%s must not be of type %s", name, ConditionalExpressionBuilder.class.getSimpleName()));
-	}
-
-	/**
-	 * Get a builder that allows fluent creation of {@link ConditionalOperator}.
-	 *
-	 * @return a new {@link ConditionalExpressionBuilder}.
-	 */
-	public static ConditionalExpressionBuilder newBuilder() {
-		return ConditionalExpressionBuilder.newBuilder();
-	}
-
-	/**
-	 * @since 1.10
-	 */
-	public static interface WhenBuilder {
-
-		/**
-		 * @param booleanExpression expression that yields in a boolean result, must not be {@literal null}.
-		 * @return the {@link ThenBuilder}
-		 */
-		ThenBuilder when(Document booleanExpression);
-
-		/**
-		 * @param booleanField reference to a field holding a boolean value, must not be {@literal null}.
-		 * @return the {@link ThenBuilder}
-		 */
-		ThenBuilder when(Field booleanField);
-
-		/**
-		 * @param booleanField name of a field holding a boolean value, must not be {@literal null}.
-		 * @return the {@link ThenBuilder}
-		 */
-		ThenBuilder when(String booleanField);
-
-		/**
-		 * @param criteria criteria to evaluate, must not be {@literal null}.
-		 * @return the {@link ThenBuilder}
-		 */
-		ThenBuilder when(CriteriaDefinition criteria);
-	}
-
-	/**
-	 * @since 1.10
-	 */
-	public static interface ThenBuilder {
-
-		/**
-		 * @param value the value to be used if the condition evaluates {@literal true}. Can be a {@link Document}, a value
-		 *          that is supported by MongoDB or a value that can be converted to a MongoDB representation but must not
-		 *          be {@literal null}.
-		 * @return the {@link OtherwiseBuilder}
-		 */
-		OtherwiseBuilder then(Object value);
-	}
-
-	/**
-	 * @since 1.10
-	 */
-	public static interface OtherwiseBuilder {
-
-		/**
-		 * @param value the value to be used if the condition evaluates {@literal false}. Can be a {@link Document}, a value
-		 *          that is supported by MongoDB or a value that can be converted to a MongoDB representation but must not
-		 *          be {@literal null}.
-		 * @return the {@link ConditionalOperator}
-		 */
-		ConditionalOperator otherwise(Object value);
-	}
-
-	/**
-	 * Builder for fluent {@link ConditionalOperator} creation.
-	 *
-	 * @author Mark Paluch
-	 * @since 1.10
-	 */
-	public static final class ConditionalExpressionBuilder implements WhenBuilder, ThenBuilder, OtherwiseBuilder {
-
-		private Object condition;
-		private Object thenValue;
-
-		private ConditionalExpressionBuilder() {}
-
-		/**
-		 * Creates a new builder for {@link ConditionalOperator}.
-		 *
-		 * @return never {@literal null}.
-		 */
-		public static ConditionalExpressionBuilder newBuilder() {
-			return new ConditionalExpressionBuilder();
-		}
-
-		/* 
-		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperator.WhenBuilder#when(org.bson.Document)
-		 */
-		@Override
-		public ConditionalExpressionBuilder when(Document booleanExpression) {
-
-			Assert.notNull(booleanExpression, "'Boolean expression' must not be null!");
-
-			this.condition = booleanExpression;
-			return this;
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperator.WhenBuilder#when(org.springframework.data.mongodb.core.query.CriteriaDefinition)
-		 */
-		@Override
-		public ThenBuilder when(CriteriaDefinition criteria) {
-
-			Assert.notNull(criteria, "Criteria must not be null!");
-
-			this.condition = criteria;
-			return this;
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperator.WhenBuilder#when(org.springframework.data.mongodb.core.aggregation.Field)
-		 */
-		@Override
-		public ThenBuilder when(Field booleanField) {
-
-			Assert.notNull(booleanField, "Boolean field must not be null!");
-
-			this.condition = booleanField;
-			return this;
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperator.WhenBuilder#when(java.lang.String)
-		 */
-		@Override
-		public ThenBuilder when(String booleanField) {
-
-			Assert.hasText(booleanField, "Boolean field name must not be null or empty!");
-
-			this.condition = Fields.field(booleanField);
-			return this;
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperator.ThenBuilder#then(java.lang.Object)
-		 */
-		@Override
-		public OtherwiseBuilder then(Object thenValue) {
-
-			Assert.notNull(thenValue, "'Then-value' must not be null!");
-
-			this.thenValue = thenValue;
-			return this;
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperator.OtherwiseBuilder#otherwise(java.lang.Object)
-		 */
-		@Override
-		public ConditionalOperator otherwise(Object otherwiseValue) {
-
-			Assert.notNull(otherwiseValue, "'Otherwise-value' must not be null!");
-
-			return new ConditionalOperator(condition, thenValue, otherwiseValue);
-		}
-	}
-}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ConditionalOperators.java

@@ -0,0 +1,976 @@
+/*
+ * Copyright 2016. the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.bson.Document;
+import org.springframework.dao.InvalidDataAccessApiUsageException;
+import org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.OtherwiseBuilder;
+import org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.ThenBuilder;
+import org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Switch.CaseOperator;
+import org.springframework.data.mongodb.core.query.CriteriaDefinition;
+import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
+
+/**
+ * Gateway to {@literal conditional expressions} that evaluate their argument expressions as booleans to a value.
+ *
+ * @author Mark Paluch
+ * @since 1.10
+ */
+public class ConditionalOperators {
+
+	/**
+	 * Take the field referenced by given {@literal fieldReference}.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return
+	 */
+	public static ConditionalOperatorFactory when(String fieldReference) {
+		return new ConditionalOperatorFactory(fieldReference);
+	}
+
+	/**
+	 * Take the value resulting from the given {@literal expression}.
+	 *
+	 * @param expression must not be {@literal null}.
+	 * @return
+	 */
+	public static ConditionalOperatorFactory when(AggregationExpression expression) {
+		return new ConditionalOperatorFactory(expression);
+	}
+
+	/**
+	 * Take the value resulting from the given {@literal criteriaDefinition}.
+	 *
+	 * @param criteriaDefinition must not be {@literal null}.
+	 * @return
+	 */
+	public static ConditionalOperatorFactory when(CriteriaDefinition criteriaDefinition) {
+		return new ConditionalOperatorFactory(criteriaDefinition);
+	}
+
+	/**
+	 * Creates new {@link AggregationExpression} that evaluates an expression and returns the value of the expression if
+	 * the expression evaluates to a non-null value. If the expression evaluates to a {@literal null} value, including
+	 * instances of undefined values or missing fields, returns the value of the replacement expression.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return
+	 */
+	public static IfNull.ThenBuilder ifNull(String fieldReference) {
+
+		Assert.notNull(fieldReference, "FieldReference must not be null!");
+		return IfNull.ifNull(fieldReference);
+	}
+
+	/**
+	 * Creates new {@link AggregationExpression} that evaluates an expression and returns the value of the expression if
+	 * the expression evaluates to a non-null value. If the expression evaluates to a {@literal null} value, including
+	 * instances of undefined values or missing fields, returns the value of the replacement expression.
+	 *
+	 * @param expression must not be {@literal null}.
+	 * @return
+	 */
+	public static IfNull.ThenBuilder ifNull(AggregationExpression expression) {
+
+		Assert.notNull(expression, "Expression must not be null!");
+		return IfNull.ifNull(expression);
+	}
+
+	/**
+	 * Creates new {@link AggregationExpression} that evaluates a series of {@link CaseOperator} expressions. When it
+	 * finds an expression which evaluates to {@literal true}, {@code $switch} executes a specified expression and breaks
+	 * out of the control flow.
+	 *
+	 * @param conditions must not be {@literal null}.
+	 * @return
+	 */
+	public static Switch switchCases(CaseOperator... conditions) {
+		return Switch.switchCases(conditions);
+	}
+
+	/**
+	 * Creates new {@link AggregationExpression} that evaluates a series of {@link CaseOperator} expressions. When it
+	 * finds an expression which evaluates to {@literal true}, {@code $switch} executes a specified expression and breaks
+	 * out of the control flow.
+	 *
+	 * @param conditions must not be {@literal null}.
+	 * @return
+	 */
+	public static Switch switchCases(List<CaseOperator> conditions) {
+		return Switch.switchCases(conditions);
+	}
+
+	public static class ConditionalOperatorFactory {
+
+		private final String fieldReference;
+		private final AggregationExpression expression;
+		private final CriteriaDefinition criteriaDefinition;
+
+		/**
+		 * Creates new {@link ConditionalOperatorFactory} for given {@literal fieldReference}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 */
+		public ConditionalOperatorFactory(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+
+			this.fieldReference = fieldReference;
+			this.expression = null;
+			this.criteriaDefinition = null;
+		}
+
+		/**
+		 * Creates new {@link ConditionalOperatorFactory} for given {@link AggregationExpression}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 */
+		public ConditionalOperatorFactory(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+
+			this.fieldReference = null;
+			this.expression = expression;
+			this.criteriaDefinition = null;
+		}
+
+		/**
+		 * Creates new {@link ConditionalOperatorFactory} for given {@link CriteriaDefinition}.
+		 *
+		 * @param criteriaDefinition must not be {@literal null}.
+		 */
+		public ConditionalOperatorFactory(CriteriaDefinition criteriaDefinition) {
+
+			Assert.notNull(criteriaDefinition, "CriteriaDefinition must not be null!");
+
+			this.fieldReference = null;
+			this.expression = null;
+			this.criteriaDefinition = criteriaDefinition;
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that evaluates a boolean expression to return one of the two specified
+		 * return expressions.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public OtherwiseBuilder then(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+			return createThenBuilder().then(value);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that evaluates a boolean expression to return one of the two specified
+		 * return expressions.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public OtherwiseBuilder thenValueOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return createThenBuilder().then(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that evaluates a boolean expression to return one of the two specified
+		 * return expressions.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public OtherwiseBuilder thenValueOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return createThenBuilder().then(fieldReference);
+		}
+
+		private ThenBuilder createThenBuilder() {
+
+			if (usesFieldRef()) {
+				return Cond.newBuilder().when(fieldReference);
+			}
+
+			return usesCriteriaDefinition() ? Cond.newBuilder().when(criteriaDefinition) : Cond.newBuilder().when(expression);
+		}
+
+		private boolean usesFieldRef() {
+			return this.fieldReference != null;
+		}
+
+		private boolean usesCriteriaDefinition() {
+			return this.criteriaDefinition != null;
+		}
+	}
+
+	/**
+	 * Encapsulates the aggregation framework {@code $ifNull} operator. Replacement values can be either {@link Field
+	 * field references}, {@link AggregationExpression expressions}, values of simple MongoDB types or values that can be
+	 * converted to a simple MongoDB type.
+	 *
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/ifNull/">https://docs.mongodb.com/manual/reference/operator/aggregation/ifNull/</a>
+	 * @author Mark Paluch
+	 */
+	public static class IfNull implements AggregationExpression {
+
+		private final Object condition;
+		private final Object value;
+
+		private IfNull(Object condition, Object value) {
+
+			this.condition = condition;
+			this.value = value;
+		}
+
+		/**
+		 * Creates new {@link IfNull}.
+		 *
+		 * @param fieldReference the field to check for a {@literal null} value, field reference must not be {@literal null}
+		 *          .
+		 * @return
+		 */
+		public static ThenBuilder ifNull(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new IfNullOperatorBuilder().ifNull(fieldReference);
+		}
+
+		/**
+		 * Creates new {@link IfNull}.
+		 *
+		 * @param expression the expression to check for a {@literal null} value, field reference must not be
+		 *          {@literal null}.
+		 * @return
+		 */
+		public static ThenBuilder ifNull(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new IfNullOperatorBuilder().ifNull(expression);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AggregationExpression#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocument(AggregationOperationContext context) {
+
+			List<Object> list = new ArrayList<Object>();
+
+			if (condition instanceof Field) {
+				list.add(context.getReference((Field) condition).toString());
+			} else if (condition instanceof AggregationExpression) {
+				list.add(((AggregationExpression) condition).toDocument(context));
+			} else {
+				list.add(condition);
+			}
+
+			list.add(resolve(value, context));
+
+			return new Document("$ifNull", list);
+		}
+
+		private Object resolve(Object value, AggregationOperationContext context) {
+
+			if (value instanceof Field) {
+				return context.getReference((Field) value).toString();
+			} else if (value instanceof AggregationExpression) {
+				return ((AggregationExpression) value).toDocument(context);
+			} else if (value instanceof Document) {
+				return value;
+			}
+
+			return context.getMappedObject(new Document("$set", value)).get("$set");
+		}
+
+		/**
+		 * @author Mark Paluch
+		 */
+		public interface IfNullBuilder {
+
+			/**
+			 * @param fieldReference the field to check for a {@literal null} value, field reference must not be
+			 *          {@literal null}.
+			 * @return the {@link ThenBuilder}
+			 */
+			ThenBuilder ifNull(String fieldReference);
+
+			/**
+			 * @param expression the expression to check for a {@literal null} value, field name must not be {@literal null}
+			 *          or empty.
+			 * @return the {@link ThenBuilder}
+			 */
+			ThenBuilder ifNull(AggregationExpression expression);
+		}
+
+		/**
+		 * @author Mark Paluch
+		 */
+		public interface ThenBuilder {
+
+			/**
+			 * @param value the value to be used if the {@code $ifNull} condition evaluates {@literal true}. Can be a
+			 *          {@link Document}, a value that is supported by MongoDB or a value that can be converted to a MongoDB
+			 *          representation but must not be {@literal null}.
+			 * @return
+			 */
+			IfNull then(Object value);
+
+			/**
+			 * @param fieldReference the field holding the replacement value, must not be {@literal null}.
+			 * @return
+			 */
+			IfNull thenValueOf(String fieldReference);
+
+			/**
+			 * @param expression the expression yielding to the replacement value, must not be {@literal null}.
+			 * @return
+			 */
+			IfNull thenValueOf(AggregationExpression expression);
+		}
+
+		/**
+		 * Builder for fluent {@link IfNull} creation.
+		 *
+		 * @author Mark Paluch
+		 */
+		static final class IfNullOperatorBuilder implements IfNullBuilder, ThenBuilder {
+
+			private Object condition;
+
+			private IfNullOperatorBuilder() {}
+
+			/**
+			 * Creates a new builder for {@link IfNull}.
+			 *
+			 * @return never {@literal null}.
+			 */
+			public static IfNullOperatorBuilder newBuilder() {
+				return new IfNullOperatorBuilder();
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.IfNull.IfNullBuilder#ifNull(java.lang.String)
+			 */
+			public ThenBuilder ifNull(String fieldReference) {
+
+				Assert.hasText(fieldReference, "FieldReference name must not be null or empty!");
+				this.condition = Fields.field(fieldReference);
+				return this;
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.IfNull.IfNullBuilder#ifNull(org.springframework.data.mongodb.core.aggregation.AggregationExpression)
+			 */
+			@Override
+			public ThenBuilder ifNull(AggregationExpression expression) {
+
+				Assert.notNull(expression, "AggregationExpression name must not be null or empty!");
+				this.condition = expression;
+				return this;
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.IfNull.ThenBuilder#then(java.lang.Object)
+			 */
+			public IfNull then(Object value) {
+				return new IfNull(condition, value);
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.IfNull.ThenBuilder#thenValueOf(java.lang.String)
+			 */
+			public IfNull thenValueOf(String fieldReference) {
+
+				Assert.notNull(fieldReference, "FieldReference must not be null!");
+				return new IfNull(condition, Fields.field(fieldReference));
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.IfNull.ThenBuilder#thenValueOf(org.springframework.data.mongodb.core.aggregation.AggregationExpression)
+			 */
+			public IfNull thenValueOf(AggregationExpression expression) {
+
+				Assert.notNull(expression, "Expression must not be null!");
+				return new IfNull(condition, expression);
+			}
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $switch}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Switch extends AbstractAggregationExpression {
+
+		private Switch(java.util.Map<String, Object> values) {
+			super(values);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$switch";
+		}
+
+		/**
+		 * Creates new {@link Switch}.
+		 *
+		 * @param conditions must not be {@literal null}.
+		 */
+		public static Switch switchCases(CaseOperator... conditions) {
+
+			Assert.notNull(conditions, "Conditions must not be null!");
+			return switchCases(Arrays.asList(conditions));
+		}
+
+		/**
+		 * Creates new {@link Switch}.
+		 *
+		 * @param conditions must not be {@literal null}.
+		 */
+		public static Switch switchCases(List<CaseOperator> conditions) {
+
+			Assert.notNull(conditions, "Conditions must not be null!");
+			return new Switch(Collections.<String, Object> singletonMap("branches", new ArrayList<CaseOperator>(conditions)));
+		}
+
+		public Switch defaultTo(Object value) {
+			return new Switch(append("default", value));
+		}
+
+		/**
+		 * Encapsulates the aggregation framework case document inside a {@code $switch}-operation.
+		 */
+		public static class CaseOperator implements AggregationExpression {
+
+			private final AggregationExpression when;
+			private final Object then;
+
+			private CaseOperator(AggregationExpression when, Object then) {
+
+				this.when = when;
+				this.then = then;
+			}
+
+			public static ThenBuilder when(final AggregationExpression condition) {
+
+				Assert.notNull(condition, "Condition must not be null!");
+
+				return new ThenBuilder() {
+
+					@Override
+					public CaseOperator then(Object value) {
+
+						Assert.notNull(value, "Value must not be null!");
+						return new CaseOperator(condition, value);
+					}
+				};
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.AggregationExpression#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+			 */
+			@Override
+			public Document toDocument(AggregationOperationContext context) {
+
+				Document dbo = new Document("case", when.toDocument(context));
+
+				if (then instanceof AggregationExpression) {
+					dbo.put("then", ((AggregationExpression) then).toDocument(context));
+				} else if (then instanceof Field) {
+					dbo.put("then", context.getReference((Field) then).toString());
+				} else {
+					dbo.put("then", then);
+				}
+
+				return dbo;
+			}
+
+			/**
+			 * @author Christoph Strobl
+			 */
+			public interface ThenBuilder {
+
+				/**
+				 * Set the then {@literal value}.
+				 *
+				 * @param value must not be {@literal null}.
+				 * @return
+				 */
+				CaseOperator then(Object value);
+			}
+		}
+	}
+
+	/**
+	 * Encapsulates the aggregation framework {@code $cond} operator. A {@link Cond} allows nested conditions
+	 * {@code if-then[if-then-else]-else} using {@link Field}, {@link CriteriaDefinition}, {@link AggregationExpression}
+	 * or a {@link Document custom} condition. Replacement values can be either {@link Field field references},
+	 * {@link AggregationExpression expressions}, values of simple MongoDB types or values that can be converted to a
+	 * simple MongoDB type.
+	 *
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/cond/">https://docs.mongodb.com/manual/reference/operator/aggregation/cond/</a>
+	 * @author Mark Paluch
+	 * @author Christoph Strobl
+	 */
+	public static class Cond implements AggregationExpression {
+
+		private final Object condition;
+		private final Object thenValue;
+		private final Object otherwiseValue;
+
+		/**
+		 * Creates a new {@link Cond} for a given {@link Field} and {@code then}/{@code otherwise} values.
+		 *
+		 * @param condition must not be {@literal null}.
+		 * @param thenValue must not be {@literal null}.
+		 * @param otherwiseValue must not be {@literal null}.
+		 */
+		private Cond(Field condition, Object thenValue, Object otherwiseValue) {
+			this((Object) condition, thenValue, otherwiseValue);
+		}
+
+		/**
+		 * Creates a new {@link Cond} for a given {@link CriteriaDefinition} and {@code then}/{@code otherwise} values.
+		 *
+		 * @param condition must not be {@literal null}.
+		 * @param thenValue must not be {@literal null}.
+		 * @param otherwiseValue must not be {@literal null}.
+		 */
+		private Cond(CriteriaDefinition condition, Object thenValue, Object otherwiseValue) {
+			this((Object) condition, thenValue, otherwiseValue);
+		}
+
+		private Cond(Object condition, Object thenValue, Object otherwiseValue) {
+
+			Assert.notNull(condition, "Condition must not be null!");
+			Assert.notNull(thenValue, "Then value must not be null!");
+			Assert.notNull(otherwiseValue, "Otherwise value must not be null!");
+
+			assertNotBuilder(condition, "Condition");
+			assertNotBuilder(thenValue, "Then value");
+			assertNotBuilder(otherwiseValue, "Otherwise value");
+
+			this.condition = condition;
+			this.thenValue = thenValue;
+			this.otherwiseValue = otherwiseValue;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AggregationExpression#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocument(AggregationOperationContext context) {
+
+			Document condObject = new Document();
+
+			condObject.append("if", resolveCriteria(context, condition));
+			condObject.append("then", resolveValue(context, thenValue));
+			condObject.append("else", resolveValue(context, otherwiseValue));
+
+			return new Document("$cond", condObject);
+		}
+
+		private Object resolveValue(AggregationOperationContext context, Object value) {
+
+			if (value instanceof Document || value instanceof Field) {
+				return resolve(context, value);
+			}
+
+			if (value instanceof AggregationExpression) {
+				return ((AggregationExpression) value).toDocument(context);
+			}
+
+			return context.getMappedObject(new Document("$set", value)).get("$set");
+		}
+
+		private Object resolveCriteria(AggregationOperationContext context, Object value) {
+
+			if (value instanceof Document || value instanceof Field) {
+				return resolve(context, value);
+			}
+
+			if (value instanceof AggregationExpression) {
+				return ((AggregationExpression) value).toDocument(context);
+			}
+
+			if (value instanceof CriteriaDefinition) {
+
+				Document mappedObject = context.getMappedObject(((CriteriaDefinition) value).getCriteriaObject());
+				List<Object> clauses = new ArrayList<Object>();
+
+				clauses.addAll(getClauses(context, mappedObject));
+
+				return clauses.size() == 1 ? clauses.get(0) : clauses;
+			}
+
+			throw new InvalidDataAccessApiUsageException(
+					String.format("Invalid value in condition. Supported: Document, Field references, Criteria, got: %s", value));
+		}
+
+		private List<Object> getClauses(AggregationOperationContext context, Document mappedObject) {
+
+			List<Object> clauses = new ArrayList<Object>();
+
+			for (String key : mappedObject.keySet()) {
+
+				Object predicate = mappedObject.get(key);
+				clauses.addAll(getClauses(context, key, predicate));
+			}
+
+			return clauses;
+		}
+
+		private List<Object> getClauses(AggregationOperationContext context, String key, Object predicate) {
+
+			List<Object> clauses = new ArrayList<Object>();
+
+			if (predicate instanceof List) {
+
+				List<Object> args = new ArrayList<Object>();
+				for (Object clause : (List<?>) predicate) {
+					if (clause instanceof Document) {
+						args.addAll(getClauses(context, (Document) clause));
+					}
+				}
+
+				clauses.add(new Document(key, args));
+
+			} else if (predicate instanceof Document) {
+
+				Document nested = (Document) predicate;
+
+				for (String s : nested.keySet()) {
+
+					if (!isKeyword(s)) {
+						continue;
+					}
+
+					List<Object> args = new ArrayList<Object>();
+					args.add("$" + key);
+					args.add(nested.get(s));
+					clauses.add(new Document(s, args));
+				}
+
+			} else if (!isKeyword(key)) {
+
+				List<Object> args = new ArrayList<Object>();
+				args.add("$" + key);
+				args.add(predicate);
+				clauses.add(new Document("$eq", args));
+			}
+
+			return clauses;
+		}
+
+		/**
+		 * Returns whether the given {@link String} is a MongoDB keyword.
+		 *
+		 * @param candidate
+		 * @return
+		 */
+		private boolean isKeyword(String candidate) {
+			return candidate.startsWith("$");
+		}
+
+		private Object resolve(AggregationOperationContext context, Object value) {
+
+			if (value instanceof Document) {
+				return context.getMappedObject((Document) value);
+			}
+
+			return context.getReference((Field) value).toString();
+		}
+
+		private void assertNotBuilder(Object toCheck, String name) {
+			Assert.isTrue(!ClassUtils.isAssignableValue(ConditionalExpressionBuilder.class, toCheck),
+					String.format("%s must not be of type %s", name, ConditionalExpressionBuilder.class.getSimpleName()));
+		}
+
+		/**
+		 * Get a builder that allows fluent creation of {@link Cond}.
+		 *
+		 * @return never {@literal null}.
+		 */
+		public static WhenBuilder newBuilder() {
+			return ConditionalExpressionBuilder.newBuilder();
+		}
+
+		/**
+		 * Start creating new {@link Cond} by providing the boolean expression used in {@code if}.
+		 *
+		 * @param booleanExpression must not be {@literal null}.
+		 * @return never {@literal null}.
+		 */
+		public static ThenBuilder when(Document booleanExpression) {
+			return ConditionalExpressionBuilder.newBuilder().when(booleanExpression);
+		}
+
+		/**
+		 * Start creating new {@link Cond} by providing the {@link AggregationExpression} used in {@code if}.
+		 *
+		 * @param expression expression that yields in a boolean result, must not be {@literal null}.
+		 * @return never {@literal null}.
+		 */
+		public static ThenBuilder when(AggregationExpression expression) {
+			return ConditionalExpressionBuilder.newBuilder().when(expression);
+		}
+
+		/**
+		 * Start creating new {@link Cond} by providing the field reference used in {@code if}.
+		 *
+		 * @param booleanField name of a field holding a boolean value, must not be {@literal null}.
+		 * @return never {@literal null}.
+		 */
+		public static ThenBuilder when(String booleanField) {
+			return ConditionalExpressionBuilder.newBuilder().when(booleanField);
+		}
+
+		/**
+		 * Start creating new {@link Cond} by providing the {@link CriteriaDefinition} used in {@code if}.
+		 *
+		 * @param criteria criteria to evaluate, must not be {@literal null}.
+		 * @return the {@link ThenBuilder}
+		 */
+		public static ThenBuilder when(CriteriaDefinition criteria) {
+			return ConditionalExpressionBuilder.newBuilder().when(criteria);
+		}
+
+		/**
+		 * @author Mark Paluch
+		 */
+		public interface WhenBuilder {
+
+			/**
+			 * @param booleanExpression expression that yields in a boolean result, must not be {@literal null}.
+			 * @return the {@link ThenBuilder}
+			 */
+			ThenBuilder when(Document booleanExpression);
+
+			/**
+			 * @param expression expression that yields in a boolean result, must not be {@literal null}.
+			 * @return the {@link ThenBuilder}
+			 */
+			ThenBuilder when(AggregationExpression expression);
+
+			/**
+			 * @param booleanField name of a field holding a boolean value, must not be {@literal null}.
+			 * @return the {@link ThenBuilder}
+			 */
+			ThenBuilder when(String booleanField);
+
+			/**
+			 * @param criteria criteria to evaluate, must not be {@literal null}.
+			 * @return the {@link ThenBuilder}
+			 */
+			ThenBuilder when(CriteriaDefinition criteria);
+		}
+
+		/**
+		 * @author Mark Paluch
+		 */
+		public interface ThenBuilder {
+
+			/**
+			 * @param value the value to be used if the condition evaluates {@literal true}. Can be a {@link Document}, a
+			 *          value that is supported by MongoDB or a value that can be converted to a MongoDB representation but
+			 *          must not be {@literal null}.
+			 * @return the {@link OtherwiseBuilder}
+			 */
+			OtherwiseBuilder then(Object value);
+
+			/**
+			 * @param fieldReference must not be {@literal null}.
+			 * @return the {@link OtherwiseBuilder}
+			 */
+			OtherwiseBuilder thenValueOf(String fieldReference);
+
+			/**
+			 * @param expression must not be {@literal null}.
+			 * @return the {@link OtherwiseBuilder}
+			 */
+			OtherwiseBuilder thenValueOf(AggregationExpression expression);
+		}
+
+		/**
+		 * @author Mark Paluch
+		 */
+		public interface OtherwiseBuilder {
+
+			/**
+			 * @param value the value to be used if the condition evaluates {@literal false}. Can be a {@link Document}, a
+			 *          value that is supported by MongoDB or a value that can be converted to a MongoDB representation but
+			 *          must not be {@literal null}.
+			 * @return the {@link Cond}
+			 */
+			Cond otherwise(Object value);
+
+			/**
+			 * @param fieldReference must not be {@literal null}.
+			 * @return the {@link Cond}
+			 */
+			Cond otherwiseValueOf(String fieldReference);
+
+			/**
+			 * @param expression must not be {@literal null}.
+			 * @return the {@link Cond}
+			 */
+			Cond otherwiseValueOf(AggregationExpression expression);
+		}
+
+		/**
+		 * Builder for fluent {@link Cond} creation.
+		 *
+		 * @author Mark Paluch
+		 */
+		static class ConditionalExpressionBuilder implements WhenBuilder, ThenBuilder, OtherwiseBuilder {
+
+			private Object condition;
+			private Object thenValue;
+
+			private ConditionalExpressionBuilder() {}
+
+			/**
+			 * Creates a new builder for {@link Cond}.
+			 *
+			 * @return never {@literal null}.
+			 */
+			public static ConditionalExpressionBuilder newBuilder() {
+				return new ConditionalExpressionBuilder();
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.WhenBuilder#when(org.bson.Document)
+			 */
+			@Override
+			public ConditionalExpressionBuilder when(Document booleanExpression) {
+
+				Assert.notNull(booleanExpression, "'Boolean expression' must not be null!");
+
+				this.condition = booleanExpression;
+				return this;
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.WhenBuilder#when(org.springframework.data.mongodb.core.query.CriteriaDefinition)
+			 */
+			@Override
+			public ThenBuilder when(CriteriaDefinition criteria) {
+
+				Assert.notNull(criteria, "Criteria must not be null!");
+				this.condition = criteria;
+				return this;
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.WhenBuilder#when(org.springframework.data.mongodb.core.aggregation.AggregationExpression)
+			 */
+			@Override
+			public ThenBuilder when(AggregationExpression expression) {
+
+				Assert.notNull(expression, "AggregationExpression field must not be null!");
+				this.condition = expression;
+				return this;
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.WhenBuilder#when(java.lang.String)
+			 */
+			@Override
+			public ThenBuilder when(String booleanField) {
+
+				Assert.hasText(booleanField, "Boolean field name must not be null or empty!");
+				this.condition = Fields.field(booleanField);
+				return this;
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.ThenBuilder#then(java.lang.Object)
+			 */
+			@Override
+			public OtherwiseBuilder then(Object thenValue) {
+
+				Assert.notNull(thenValue, "Then-value must not be null!");
+				this.thenValue = thenValue;
+				return this;
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.ThenBuilder#thenValueOf(java.lang.String)
+			 */
+			@Override
+			public OtherwiseBuilder thenValueOf(String fieldReference) {
+
+				Assert.notNull(fieldReference, "FieldReference must not be null!");
+				this.thenValue = Fields.field(fieldReference);
+				return this;
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.ThenBuilder#thenValueOf(org.springframework.data.mongodb.core.aggregation.AggregationExpression)
+			 */
+			@Override
+			public OtherwiseBuilder thenValueOf(AggregationExpression expression) {
+
+				Assert.notNull(expression, "AggregationExpression must not be null!");
+				this.thenValue = expression;
+				return this;
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.OtherwiseBuilder#otherwise(java.lang.Object)
+			 */
+			@Override
+			public Cond otherwise(Object otherwiseValue) {
+
+				Assert.notNull(otherwiseValue, "Value must not be null!");
+				return new Cond(condition, thenValue, otherwiseValue);
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.OtherwiseBuilder#otherwiseValueOf(java.lang.String)
+			 */
+			@Override
+			public Cond otherwiseValueOf(String fieldReference) {
+
+				Assert.notNull(fieldReference, "FieldReference must not be null!");
+				return new Cond(condition, thenValue, Fields.field(fieldReference));
+			}
+
+			/* (non-Javadoc)
+			 * @see org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.OtherwiseBuilder#otherwiseValueOf(org.springframework.data.mongodb.core.aggregation.AggregationExpression)
+			 */
+			@Override
+			public Cond otherwiseValueOf(AggregationExpression expression) {
+
+				Assert.notNull(expression, "AggregationExpression must not be null!");
+				return new Cond(condition, thenValue, expression);
+			}
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/CountOperation.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright 2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import org.bson.Document;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
+import org.springframework.util.Assert;
+
+/**
+ * Encapsulates the aggregation framework {@code $count}-operation. <br />
+ * We recommend to use the static factory method {@link Aggregation#count()} instead of creating instances of this class
+ * directly.
+ *
+ * @see <a href=
+ *      "https://docs.mongodb.com/manual/reference/operator/aggregation/count/#pipe._S_count">https://docs.mongodb.com/manual/reference/operator/aggregation/count/</a>
+ * @author Mark Paluch
+ * @since 1.10
+ */
+public class CountOperation implements FieldsExposingAggregationOperation {
+
+	private final String fieldName;
+
+	/**
+	 * Creates a new {@link CountOperation} given the {@link fieldName} field name.
+	 *
+	 * @param asFieldName must not be {@literal null} or empty.
+	 */
+	public CountOperation(String fieldName) {
+
+		Assert.hasText(fieldName, "Field name must not be null or empty!");
+		this.fieldName = fieldName;
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public Document toDocument(AggregationOperationContext context) {
+		return new Document("$count", fieldName);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation#getFields()
+	 */
+	@Override
+	public ExposedFields getFields() {
+		return ExposedFields.from(new ExposedField(fieldName, true));
+	}
+
+	/**
+	 * Builder for {@link CountOperation}.
+	 *
+	 * @author Mark Paluch
+	 */
+	public static class CountOperationBuilder {
+
+		/**
+		 * Returns the finally to be applied {@link CountOperation} with the given alias.
+		 *
+		 * @param fieldName must not be {@literal null} or empty.
+		 * @return
+		 */
+		public CountOperation as(String fieldName) {
+			return new CountOperation(fieldName);
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/DataTypeOperators.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2016. the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import org.springframework.util.Assert;
+
+/**
+ * Gateway to {@literal data type} expressions.
+ *
+ * @author Christoph Strobl
+ * @since 1.10
+ * @soundtrack Clawfinger - Catch Me
+ */
+public class DataTypeOperators {
+
+	/**
+	 * Return the BSON data type of the given {@literal field}.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return
+	 */
+	public static Type typeOf(String fieldReference) {
+		return Type.typeOf(fieldReference);
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $type}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Type extends AbstractAggregationExpression {
+
+		private Type(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$type";
+		}
+
+		/**
+		 * Creates new {@link Type}.
+		 *
+		 * @param field must not be {@literal null}.
+		 * @return
+		 */
+		public static Type typeOf(String field) {
+
+			Assert.notNull(field, "Field must not be null!");
+			return new Type(Fields.field(field));
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/DateOperators.java

@@ -0,0 +1,837 @@
+/*
+ * Copyright 2016. the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.LinkedHashMap;
+
+import org.springframework.data.mongodb.core.aggregation.ArithmeticOperators.ArithmeticOperatorFactory;
+import org.springframework.util.Assert;
+
+/**
+ * Gateway to {@literal Date} aggregation operations.
+ *
+ * @author Christoph Strobl
+ * @since 1.10
+ */
+public class DateOperators {
+
+	/**
+	 * Take the date referenced by given {@literal fieldReference}.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return
+	 */
+	public static DateOperatorFactory dateOf(String fieldReference) {
+
+		Assert.notNull(fieldReference, "FieldReference must not be null!");
+		return new DateOperatorFactory(fieldReference);
+	}
+
+	/**
+	 * Take the date resulting from the given {@link AggregationExpression}.
+	 *
+	 * @param expression must not be {@literal null}.
+	 * @return
+	 */
+	public static DateOperatorFactory dateOf(AggregationExpression expression) {
+
+		Assert.notNull(expression, "Expression must not be null!");
+		return new DateOperatorFactory(expression);
+	}
+
+	/**
+	 * @author Christoph Strobl
+	 */
+	public static class DateOperatorFactory {
+
+		private final String fieldReference;
+		private final AggregationExpression expression;
+
+		/**
+		 * Creates new {@link ArithmeticOperatorFactory} for given {@literal fieldReference}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 */
+		public DateOperatorFactory(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			this.fieldReference = fieldReference;
+			this.expression = null;
+		}
+
+		/**
+		 * Creates new {@link ArithmeticOperatorFactory} for given {@link AggregationExpression}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 */
+		public DateOperatorFactory(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			this.fieldReference = null;
+			this.expression = expression;
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that returns the day of the year for a date as a number between 1 and
+		 * 366.
+		 *
+		 * @return
+		 */
+		public DayOfYear dayOfYear() {
+			return usesFieldRef() ? DayOfYear.dayOfYear(fieldReference) : DayOfYear.dayOfYear(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that returns the day of the month for a date as a number between 1 and
+		 * 31.
+		 *
+		 * @return
+		 */
+		public DayOfMonth dayOfMonth() {
+			return usesFieldRef() ? DayOfMonth.dayOfMonth(fieldReference) : DayOfMonth.dayOfMonth(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that returns the day of the week for a date as a number between 1
+		 * (Sunday) and 7 (Saturday).
+		 *
+		 * @return
+		 */
+		public DayOfWeek dayOfWeek() {
+			return usesFieldRef() ? DayOfWeek.dayOfWeek(fieldReference) : DayOfWeek.dayOfWeek(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that returns the year portion of a date.
+		 *
+		 * @return
+		 */
+		public Year year() {
+			return usesFieldRef() ? Year.yearOf(fieldReference) : Year.yearOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that returns the month of a date as a number between 1 and 12.
+		 *
+		 * @return
+		 */
+		public Month month() {
+			return usesFieldRef() ? Month.monthOf(fieldReference) : Month.monthOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that returns the week of the year for a date as a number between 0 and
+		 * 53.
+		 *
+		 * @return
+		 */
+		public Week week() {
+			return usesFieldRef() ? Week.weekOf(fieldReference) : Week.weekOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that returns the hour portion of a date as a number between 0 and 23.
+		 *
+		 * @return
+		 */
+		public Hour hour() {
+			return usesFieldRef() ? Hour.hourOf(fieldReference) : Hour.hourOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that returns the minute portion of a date as a number between 0 and 59.
+		 *
+		 * @return
+		 */
+		public Minute minute() {
+			return usesFieldRef() ? Minute.minuteOf(fieldReference) : Minute.minuteOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that returns the second portion of a date as a number between 0 and 59,
+		 * but can be 60 to account for leap seconds.
+		 *
+		 * @return
+		 */
+		public Second second() {
+			return usesFieldRef() ? Second.secondOf(fieldReference) : Second.secondOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that returns the millisecond portion of a date as an integer between 0
+		 * and 999.
+		 *
+		 * @return
+		 */
+		public Millisecond millisecond() {
+			return usesFieldRef() ? Millisecond.millisecondOf(fieldReference) : Millisecond.millisecondOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that converts a date object to a string according to a user-specified
+		 * {@literal format}.
+		 *
+		 * @param format must not be {@literal null}.
+		 * @return
+		 */
+		public DateToString toString(String format) {
+			return (usesFieldRef() ? DateToString.dateOf(fieldReference) : DateToString.dateOf(expression)).toString(format);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that returns the weekday number in ISO 8601 format, ranging from 1 (for
+		 * Monday) to 7 (for Sunday).
+		 *
+		 * @return
+		 */
+		public IsoDayOfWeek isoDayOfWeek() {
+			return usesFieldRef() ? IsoDayOfWeek.isoDayOfWeek(fieldReference) : IsoDayOfWeek.isoDayOfWeek(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that returns the week number in ISO 8601 format, ranging from 1 to 53.
+		 *
+		 * @return
+		 */
+		public IsoWeek isoWeek() {
+			return usesFieldRef() ? IsoWeek.isoWeekOf(fieldReference) : IsoWeek.isoWeekOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that returns the year number in ISO 8601 format.
+		 *
+		 * @return
+		 */
+		public IsoWeekYear isoWeekYear() {
+			return usesFieldRef() ? IsoWeekYear.isoWeekYearOf(fieldReference) : IsoWeekYear.isoWeekYearOf(expression);
+		}
+
+		private boolean usesFieldRef() {
+			return fieldReference != null;
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $dayOfYear}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class DayOfYear extends AbstractAggregationExpression {
+
+		private DayOfYear(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$dayOfYear";
+		}
+
+		/**
+		 * Creates new {@link DayOfYear}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static DayOfYear dayOfYear(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new DayOfYear(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link DayOfYear}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static DayOfYear dayOfYear(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new DayOfYear(expression);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $dayOfMonth}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class DayOfMonth extends AbstractAggregationExpression {
+
+		private DayOfMonth(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$dayOfMonth";
+		}
+
+		/**
+		 * Creates new {@link DayOfMonth}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static DayOfMonth dayOfMonth(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new DayOfMonth(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link DayOfMonth}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static DayOfMonth dayOfMonth(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new DayOfMonth(expression);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $dayOfWeek}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class DayOfWeek extends AbstractAggregationExpression {
+
+		private DayOfWeek(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$dayOfWeek";
+		}
+
+		/**
+		 * Creates new {@link DayOfWeek}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static DayOfWeek dayOfWeek(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new DayOfWeek(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link DayOfWeek}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static DayOfWeek dayOfWeek(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new DayOfWeek(expression);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $year}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Year extends AbstractAggregationExpression {
+
+		private Year(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$year";
+		}
+
+		/**
+		 * Creates new {@link Year}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Year yearOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Year(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Year}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Year yearOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Year(expression);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $month}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Month extends AbstractAggregationExpression {
+
+		private Month(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$month";
+		}
+
+		/**
+		 * Creates new {@link Month}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Month monthOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Month(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Month}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Month monthOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Month(expression);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $week}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Week extends AbstractAggregationExpression {
+
+		private Week(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$week";
+		}
+
+		/**
+		 * Creates new {@link Week}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Week weekOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Week(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Week}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Week weekOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Week(expression);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $hour}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Hour extends AbstractAggregationExpression {
+
+		private Hour(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$hour";
+		}
+
+		/**
+		 * Creates new {@link Hour}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Hour hourOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Hour(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Hour}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Hour hourOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Hour(expression);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $minute}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Minute extends AbstractAggregationExpression {
+
+		private Minute(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$minute";
+		}
+
+		/**
+		 * Creates new {@link Minute}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Minute minuteOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Minute(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Minute}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Minute minuteOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Minute(expression);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $second}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Second extends AbstractAggregationExpression {
+
+		private Second(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$second";
+		}
+
+		/**
+		 * Creates new {@link Second}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Second secondOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Second(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Second}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Second secondOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Second(expression);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $millisecond}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Millisecond extends AbstractAggregationExpression {
+
+		private Millisecond(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$millisecond";
+		}
+
+		/**
+		 * Creates new {@link Millisecond}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static Millisecond millisecondOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Millisecond(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Millisecond}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static Millisecond millisecondOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Millisecond(expression);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $dateToString}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class DateToString extends AbstractAggregationExpression {
+
+		private DateToString(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$dateToString";
+		}
+
+		/**
+		 * Creates new {@link FormatBuilder} allowing to define the date format to apply.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static FormatBuilder dateOf(final String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+
+			return new FormatBuilder() {
+
+				@Override
+				public DateToString toString(String format) {
+
+					Assert.notNull(format, "Format must not be null!");
+					return new DateToString(argumentMap(Fields.field(fieldReference), format));
+				}
+			};
+		}
+
+		/**
+		 * Creates new {@link FormatBuilder} allowing to define the date format to apply.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static FormatBuilder dateOf(final AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+
+			return new FormatBuilder() {
+
+				@Override
+				public DateToString toString(String format) {
+
+					Assert.notNull(format, "Format must not be null!");
+					return new DateToString(argumentMap(expression, format));
+				}
+			};
+		}
+
+		private static java.util.Map<String, Object> argumentMap(Object date, String format) {
+
+			java.util.Map<String, Object> args = new LinkedHashMap<String, Object>(2);
+			args.put("format", format);
+			args.put("date", date);
+			return args;
+		}
+
+		public interface FormatBuilder {
+
+			/**
+			 * Creates new {@link DateToString} with all previously added arguments appending the given one.
+			 *
+			 * @param format must not be {@literal null}.
+			 * @return
+			 */
+			DateToString toString(String format);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $isoDayOfWeek}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class IsoDayOfWeek extends AbstractAggregationExpression {
+
+		private IsoDayOfWeek(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$isoDayOfWeek";
+		}
+
+		/**
+		 * Creates new {@link IsoDayOfWeek}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static IsoDayOfWeek isoDayOfWeek(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new IsoDayOfWeek(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link IsoDayOfWeek}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static IsoDayOfWeek isoDayOfWeek(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new IsoDayOfWeek(expression);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $isoWeek}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class IsoWeek extends AbstractAggregationExpression {
+
+		private IsoWeek(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$isoWeek";
+		}
+
+		/**
+		 * Creates new {@link IsoWeek}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static IsoWeek isoWeekOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new IsoWeek(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link IsoWeek}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static IsoWeek isoWeekOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new IsoWeek(expression);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $isoWeekYear}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class IsoWeekYear extends AbstractAggregationExpression {
+
+		private IsoWeekYear(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$isoWeekYear";
+		}
+
+		/**
+		 * Creates new {@link IsoWeekYear}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static IsoWeekYear isoWeekYearOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new IsoWeekYear(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Millisecond}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static IsoWeekYear isoWeekYearOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new IsoWeekYear(expression);
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ExposedFields.java

@@ -22,8 +22,10 @@ import java.util.Iterator;
 import java.util.List;
 
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
+import org.springframework.data.mongodb.core.aggregation.Fields.AggregationField;
 import org.springframework.util.Assert;
 import org.springframework.util.CompositeIterator;
+import org.springframework.util.ObjectUtils;
 
 /**
  * Value object to capture the fields exposed by an {@link AggregationOperation}.
@@ -104,7 +106,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 			result.add(new ExposedField(field, synthetic));
 		}
 
-		return ExposedFields.from(result);
+		return from(result);
 	}
 
 	/**
@@ -336,12 +338,36 @@ public final class ExposedFields implements Iterable<ExposedField> {
 		}
 	}
 
+	/**
+	 * A reference to an {@link ExposedField}.
+	 *
+	 * @author Christoph Strobl
+	 * @since 1.10
+	 */
+	interface FieldReference {
+
+		/**
+		 * Returns the raw, unqualified reference, i.e. the field reference without a {@literal $} prefix.
+		 *
+		 * @return
+		 */
+		String getRaw();
+
+		/**
+		 * Returns the reference value for the given field reference. Will return 1 for a synthetic, unaliased field or the
+		 * raw rendering of the reference otherwise.
+		 *
+		 * @return
+		 */
+		Object getReferenceValue();
+	}
+
 	/**
 	 * A reference to an {@link ExposedField}.
 	 * 
 	 * @author Oliver Gierke
 	 */
-	static class FieldReference {
+	static class DirectFieldReference implements FieldReference {
 
 		private final ExposedField field;
 
@@ -350,17 +376,16 @@ public final class ExposedFields implements Iterable<ExposedField> {
 		 * 
 		 * @param field must not be {@literal null}.
 		 */
-		public FieldReference(ExposedField field) {
+		public DirectFieldReference(ExposedField field) {
 
 			Assert.notNull(field, "ExposedField must not be null!");
 
 			this.field = field;
 		}
 
-		/**
-		 * Returns the raw, unqualified reference, i.e. the field reference without a {@literal $} prefix.
-		 * 
-		 * @return
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference#getRaw()
 		 */
 		public String getRaw() {
 
@@ -368,11 +393,9 @@ public final class ExposedFields implements Iterable<ExposedField> {
 			return field.synthetic ? target : String.format("%s.%s", Fields.UNDERSCORE_ID, target);
 		}
 
-		/**
-		 * Returns the reference value for the given field reference. Will return 1 for a synthetic, unaliased field or the
-		 * raw rendering of the reference otherwise.
-		 * 
-		 * @return
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference#getReferenceValue()
 		 */
 		public Object getReferenceValue() {
 			return field.synthetic && !field.isAliased() ? 1 : toString();
@@ -384,6 +407,11 @@ public final class ExposedFields implements Iterable<ExposedField> {
 		 */
 		@Override
 		public String toString() {
+
+			if(getRaw().startsWith("$")) {
+				return getRaw();
+			}
+
 			return String.format("$%s", getRaw());
 		}
 
@@ -398,11 +426,11 @@ public final class ExposedFields implements Iterable<ExposedField> {
 				return true;
 			}
 
-			if (!(obj instanceof FieldReference)) {
+			if (!(obj instanceof DirectFieldReference)) {
 				return false;
 			}
 
-			FieldReference that = (FieldReference) obj;
+			DirectFieldReference that = (DirectFieldReference) obj;
 
 			return this.field.equals(that.field);
 		}
@@ -416,4 +444,78 @@ public final class ExposedFields implements Iterable<ExposedField> {
 			return field.hashCode();
 		}
 	}
+
+	/**
+	 * A {@link FieldReference} to a {@link Field} used within a nested {@link AggregationExpression}.
+	 *
+	 * @author Christoph Strobl
+	 * @since 1.10
+	 */
+	static class ExpressionFieldReference implements FieldReference {
+
+		private FieldReference delegate;
+
+		/**
+		 * Creates a new {@link FieldReference} for the given {@link ExposedField}.
+		 *
+		 * @param field must not be {@literal null}.
+		 */
+		public ExpressionFieldReference(FieldReference field) {
+			delegate = field;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference#getRaw()
+		 */
+		@Override
+		public String getRaw() {
+			return delegate.getRaw();
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference#getReferenceValue()
+		 */
+		@Override
+		public Object getReferenceValue() {
+			return delegate.getReferenceValue();
+		}
+
+		@Override
+		public String toString() {
+
+			String fieldRef = delegate.toString();
+
+			if (fieldRef.startsWith("$$")) {
+				return fieldRef;
+			}
+
+			if (fieldRef.startsWith("$")) {
+				return "$" + fieldRef;
+			}
+
+			return fieldRef;
+		}
+
+		@Override
+		public boolean equals(Object obj) {
+
+			if (this == obj) {
+				return true;
+			}
+
+			if (!(obj instanceof ExpressionFieldReference)) {
+				return false;
+			}
+
+			ExpressionFieldReference that = (ExpressionFieldReference) obj;
+			return ObjectUtils.nullSafeEquals(this.delegate, that.delegate);
+		}
+
+		@Override
+		public int hashCode() {
+			return delegate.hashCode();
+		}
+	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ExposedFieldsAggregationOperationContext.java

@@ -17,6 +17,7 @@ package org.springframework.data.mongodb.core.aggregation;
 
 import org.bson.Document;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.DirectFieldReference;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference;
 import org.springframework.util.Assert;
 
@@ -54,7 +55,7 @@ class ExposedFieldsAggregationOperationContext implements AggregationOperationCo
 
 	/* 
 	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getMappedObject(com.mongodb.Document)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getMappedObject(org.bson.Document)
 	 */
 	@Override
 	public Document getMappedObject(Document document) {
@@ -112,10 +113,10 @@ class ExposedFieldsAggregationOperationContext implements AggregationOperationCo
 
 			if (field != null) {
 				// we return a FieldReference to the given field directly to make sure that we reference the proper alias here.
-				return new FieldReference(new ExposedField(field, exposedField.isSynthetic()));
+				return new DirectFieldReference(new ExposedField(field, exposedField.isSynthetic()));
 			}
 
-			return new FieldReference(exposedField);
+			return new DirectFieldReference(exposedField);
 		}
 
 		if (name.contains(".")) {
@@ -126,7 +127,7 @@ class ExposedFieldsAggregationOperationContext implements AggregationOperationCo
 			if (rootField != null) {
 
 				// We have to synthetic to true, in order to render the field-name as is.
-				return new FieldReference(new ExposedField(name, true));
+				return new DirectFieldReference(new ExposedField(name, true));
 			}
 		}
 		return null;

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/FacetOperation.java

@@ -0,0 +1,227 @@
+/*
+ * Copyright 2016-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.springframework.data.mongodb.core.aggregation.BucketOperationSupport.Output;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
+import org.springframework.util.Assert;
+
+import org.bson.Document;
+
+/**
+ * Encapsulates the aggregation framework {@code $facet}-operation. <br />
+ * Facet of {@link AggregationOperation}s to be used in an {@link Aggregation}. Processes multiple
+ * {@link AggregationOperation} pipelines within a single stage on the same set of input documents. Each sub-pipeline
+ * has its own field in the output document where its results are stored as an array of documents.
+ * {@link FacetOperation} enables various aggregations on the same set of input documents, without needing to retrieve
+ * the input documents multiple times. <br />
+ * As of MongoDB 3.4, {@link FacetOperation} cannot be used with nested pipelines containing {@link GeoNearOperation},
+ * {@link OutOperation} and {@link FacetOperation}. <br />
+ * We recommend to use the static factory method {@link Aggregation#facet()} instead of creating instances of this class
+ * directly.
+ *
+ * @author Mark Paluch
+ * @author Christoph Strobl
+ * @since 1.10
+ * @see <a href="https://docs.mongodb.org/manual/reference/aggregation/facet/">MongoDB Aggregation Framework: $facet</a>
+ */
+public class FacetOperation implements FieldsExposingAggregationOperation {
+
+	/**
+	 * Empty (initial) {@link FacetOperation}.
+	 */
+	public static final FacetOperation EMPTY = new FacetOperation();
+
+	private final Facets facets;
+
+	/**
+	 * Creates a new {@link FacetOperation}.
+	 */
+	public FacetOperation() {
+		this(Facets.EMPTY);
+	}
+
+	private FacetOperation(Facets facets) {
+		this.facets = facets;
+	}
+
+	/**
+	 * Creates a new {@link FacetOperationBuilder} to append a new facet using {@literal operations}. <br />
+	 * {@link FacetOperationBuilder} takes a pipeline of {@link AggregationOperation} to categorize documents into a
+	 * single facet.
+	 *
+	 * @param operations must not be {@literal null} or empty.
+	 * @return
+	 */
+	public FacetOperationBuilder and(AggregationOperation... operations) {
+
+		Assert.notNull(operations, "AggregationOperations must not be null!");
+		Assert.notEmpty(operations, "AggregationOperations must not be empty!");
+
+		return new FacetOperationBuilder(facets, Arrays.asList(operations));
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public Document toDocument(AggregationOperationContext context) {
+		return new Document("$facet", facets.toDocument(context));
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation#getFields()
+	 */
+	@Override
+	public ExposedFields getFields() {
+		return facets.asExposedFields();
+	}
+
+	/**
+	 * Builder for {@link FacetOperation} by adding existing and the new pipeline of {@link AggregationOperation} to the
+	 * new {@link FacetOperation}.
+	 *
+	 * @author Mark Paluch
+	 */
+	public static class FacetOperationBuilder {
+
+		private final Facets current;
+		private final List<AggregationOperation> operations;
+
+		private FacetOperationBuilder(Facets current, List<AggregationOperation> operations) {
+			this.current = current;
+			this.operations = operations;
+		}
+
+		/**
+		 * Creates a new {@link FacetOperation} that contains the configured pipeline of {@link AggregationOperation}
+		 * exposed as {@literal fieldName} in the resulting facet document.
+		 *
+		 * @param fieldName must not be {@literal null} or empty.
+		 * @return
+		 */
+		public FacetOperation as(String fieldName) {
+
+			Assert.hasText(fieldName, "FieldName must not be null or empty!");
+
+			return new FacetOperation(current.and(fieldName, operations));
+		}
+	}
+
+	/**
+	 * Encapsulates multiple {@link Facet}s
+	 *
+	 * @author Mark Paluch
+	 */
+	private static class Facets {
+
+		private static final Facets EMPTY = new Facets(Collections.<Facet> emptyList());
+
+		private List<Facet> facets;
+
+		/**
+		 * Creates a new {@link Facets} given {@link List} of {@link Facet}.
+		 *
+		 * @param facets
+		 */
+		private Facets(List<Facet> facets) {
+			this.facets = facets;
+		}
+
+		/**
+		 * @return the {@link ExposedFields} derived from {@link Output}.
+		 */
+		ExposedFields asExposedFields() {
+
+			ExposedFields fields = ExposedFields.from();
+
+			for (Facet facet : facets) {
+				fields = fields.and(facet.getExposedField());
+			}
+
+			return fields;
+		}
+
+		protected Document toDocument(AggregationOperationContext context) {
+
+			Document document = new Document();
+
+			for (Facet facet : facets) {
+				document.put(facet.getExposedField().getName(), facet.toDocuments(context));
+			}
+
+			return document;
+		}
+
+		/**
+		 * Adds a facet to this {@link Facets}.
+		 *
+		 * @param fieldName must not be {@literal null}.
+		 * @param operations must not be {@literal null}.
+		 * @return the new {@link Facets}.
+		 */
+		Facets and(String fieldName, List<AggregationOperation> operations) {
+
+			Assert.hasText(fieldName, "FieldName must not be null or empty!");
+			Assert.notNull(operations, "AggregationOperations must not be null!");
+
+			List<Facet> facets = new ArrayList<Facet>(this.facets.size() + 1);
+			facets.addAll(this.facets);
+			facets.add(new Facet(new ExposedField(fieldName, true), operations));
+
+			return new Facets(facets);
+		}
+	}
+
+	/**
+	 * A single facet with a {@link ExposedField} and its {@link AggregationOperation} pipeline.
+	 *
+	 * @author Mark Paluch
+	 */
+	private static class Facet {
+
+		private final ExposedField exposedField;
+		private final List<AggregationOperation> operations;
+
+		/**
+		 * Creates a new {@link Facet} given {@link ExposedField} and {@link AggregationOperation} pipeline.
+		 *
+		 * @param exposedField must not be {@literal null}.
+		 * @param operations must not be {@literal null}.
+		 */
+		Facet(ExposedField exposedField, List<AggregationOperation> operations) {
+
+			Assert.notNull(exposedField, "ExposedField must not be null!");
+			Assert.notNull(operations, "AggregationOperations must not be null!");
+
+			this.exposedField = exposedField;
+			this.operations = operations;
+		}
+
+		ExposedField getExposedField() {
+			return exposedField;
+		}
+
+		protected List<Document> toDocuments(AggregationOperationContext context) {
+			return AggregationOperationRenderer.toDocument(operations, context);
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/Fields.java

@@ -17,6 +17,7 @@ package org.springframework.data.mongodb.core.aggregation;
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
@@ -185,6 +186,14 @@ public final class Fields implements Iterable<Field> {
 		return fields.iterator();
 	}
 
+	/**
+	 * @return
+	 * @since 1.10
+	 */
+	public List<Field> asList() {
+		return Collections.unmodifiableList(fields);
+	}
+
 	/**
 	 * Value object to encapsulate a field in an aggregation operation.
 	 * 
@@ -192,6 +201,7 @@ public final class Fields implements Iterable<Field> {
 	 */
 	static class AggregationField implements Field {
 
+		private final String raw;
 		private final String name;
 		private final String target;
 
@@ -216,6 +226,7 @@ public final class Fields implements Iterable<Field> {
 		 */
 		public AggregationField(String name, String target) {
 
+			raw = name;
 			String nameToSet = cleanUp(name);
 			String targetToSet = cleanUp(target);
 
@@ -257,6 +268,11 @@ public final class Fields implements Iterable<Field> {
 		 * @see org.springframework.data.mongodb.core.aggregation.Field#getAlias()
 		 */
 		public String getTarget() {
+
+			if (isLocalVar()) {
+				return this.getRaw();
+			}
+
 			return StringUtils.hasText(this.target) ? this.target : this.name;
 		}
 
@@ -269,6 +285,22 @@ public final class Fields implements Iterable<Field> {
 			return !getName().equals(getTarget());
 		}
 
+		/**
+		 * @return {@literal true} in case the field name starts with {@code $$}.
+		 * @since 1.10
+		 */
+		public boolean isLocalVar() {
+			return raw.startsWith("$$") && !raw.startsWith("$$$");
+		}
+
+		/**
+		 * @return
+		 * @since 1.10
+		 */
+		public String getRaw() {
+			return raw;
+		}
+
 		/* 
 		 * (non-Javadoc)
 		 * @see java.lang.Object#toString()

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/GraphLookupOperation.java

@@ -0,0 +1,409 @@
+/*
+ * Copyright 2016-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import org.bson.Document;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
+import org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation.InheritsFieldsAggregationOperation;
+import org.springframework.data.mongodb.core.query.CriteriaDefinition;
+import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
+
+/**
+ * Encapsulates the aggregation framework {@code $graphLookup}-operation. <br />
+ * Performs a recursive search on a collection, with options for restricting the search by recursion depth and query
+ * filter. <br />
+ * We recommend to use the static factory method {@link Aggregation#graphLookup(String)} instead of creating instances
+ * of this class directly.
+ *
+ * @see <a href=
+ *      "https://docs.mongodb.org/manual/reference/aggregation/graphLookup/">https://docs.mongodb.org/manual/reference/aggregation/graphLookup/</a>
+ * @author Mark Paluch
+ * @author Christoph Strobl
+ * @since 1.10
+ */
+public class GraphLookupOperation implements InheritsFieldsAggregationOperation {
+
+	private static final Set<Class<?>> ALLOWED_START_TYPES = new HashSet<Class<?>>(
+			Arrays.<Class<?>> asList(AggregationExpression.class, String.class, Field.class, Document.class));
+
+	private final String from;
+	private final List<Object> startWith;
+	private final Field connectFrom;
+	private final Field connectTo;
+	private final Field as;
+	private final Long maxDepth;
+	private final Field depthField;
+	private final CriteriaDefinition restrictSearchWithMatch;
+
+	private GraphLookupOperation(String from, List<Object> startWith, Field connectFrom, Field connectTo, Field as,
+			Long maxDepth, Field depthField, CriteriaDefinition restrictSearchWithMatch) {
+
+		this.from = from;
+		this.startWith = startWith;
+		this.connectFrom = connectFrom;
+		this.connectTo = connectTo;
+		this.as = as;
+		this.maxDepth = maxDepth;
+		this.depthField = depthField;
+		this.restrictSearchWithMatch = restrictSearchWithMatch;
+	}
+
+	/**
+	 * Creates a new {@link FromBuilder} to build {@link GraphLookupOperation}.
+	 *
+	 * @return a new {@link FromBuilder}.
+	 */
+	public static FromBuilder builder() {
+		return new GraphLookupOperationFromBuilder();
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public Document toDocument(AggregationOperationContext context) {
+
+		Document graphLookup = new Document();
+
+		graphLookup.put("from", from);
+
+		List<Object> mappedStartWith = new ArrayList<Object>(startWith.size());
+
+		for (Object startWithElement : startWith) {
+
+			if (startWithElement instanceof AggregationExpression) {
+				mappedStartWith.add(((AggregationExpression) startWithElement).toDocument(context));
+			} else if (startWithElement instanceof Field) {
+				mappedStartWith.add(context.getReference((Field) startWithElement).toString());
+			} else {
+				mappedStartWith.add(startWithElement);
+			}
+		}
+
+		graphLookup.put("startWith", mappedStartWith.size() == 1 ? mappedStartWith.iterator().next() : mappedStartWith);
+
+		graphLookup.put("connectFromField", connectFrom.getName());
+		graphLookup.put("connectToField", connectTo.getName());
+		graphLookup.put("as", as.getName());
+
+		if (maxDepth != null) {
+			graphLookup.put("maxDepth", maxDepth);
+		}
+
+		if (depthField != null) {
+			graphLookup.put("depthField", depthField.getName());
+		}
+
+		if (restrictSearchWithMatch != null) {
+			graphLookup.put("restrictSearchWithMatch", context.getMappedObject(restrictSearchWithMatch.getCriteriaObject()));
+		}
+
+		return new Document("$graphLookup", graphLookup);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation#getFields()
+	 */
+	@Override
+	public ExposedFields getFields() {
+		return ExposedFields.from(new ExposedField(as, true));
+	}
+
+	/**
+	 * @author Mark Paluch
+	 */
+	public interface FromBuilder {
+
+		/**
+		 * Set the {@literal collectionName} to apply the {@code $graphLookup} to.
+		 *
+		 * @param collectionName must not be {@literal null} or empty.
+		 * @return
+		 */
+		StartWithBuilder from(String collectionName);
+	}
+
+	/**
+	 * @author Mark Paluch
+	 * @author Christoph Strobl
+	 */
+	public interface StartWithBuilder {
+
+		/**
+		 * Set the startWith {@literal fieldReferences} to apply the {@code $graphLookup} to.
+		 *
+		 * @param fieldReferences must not be {@literal null}.
+		 * @return
+		 */
+		ConnectFromBuilder startWith(String... fieldReferences);
+
+		/**
+		 * Set the startWith {@literal expressions} to apply the {@code $graphLookup} to.
+		 *
+		 * @param expressions must not be {@literal null}.
+		 * @return
+		 */
+		ConnectFromBuilder startWith(AggregationExpression... expressions);
+
+		/**
+		 * Set the startWith as either {@literal fieldReferences}, {@link Fields}, {@link Document} or
+		 * {@link AggregationExpression} to apply the {@code $graphLookup} to.
+		 *
+		 * @param expressions must not be {@literal null}.
+		 * @return
+		 * @throws IllegalArgumentException
+		 */
+		ConnectFromBuilder startWith(Object... expressions);
+	}
+
+	/**
+	 * @author Mark Paluch
+	 */
+	public interface ConnectFromBuilder {
+
+		/**
+		 * Set the connectFrom {@literal fieldName} to apply the {@code $graphLookup} to.
+		 *
+		 * @param fieldName must not be {@literal null} or empty.
+		 * @return
+		 */
+		ConnectToBuilder connectFrom(String fieldName);
+	}
+
+	/**
+	 * @author Mark Paluch
+	 */
+	public interface ConnectToBuilder {
+
+		/**
+		 * Set the connectTo {@literal fieldName} to apply the {@code $graphLookup} to.
+		 *
+		 * @param fieldName must not be {@literal null} or empty.
+		 * @return
+		 */
+		GraphLookupOperationBuilder connectTo(String fieldName);
+	}
+
+	/**
+	 * Builder to build the initial {@link GraphLookupOperationBuilder} that configures the initial mandatory set of
+	 * {@link GraphLookupOperation} properties.
+	 *
+	 * @author Mark Paluch
+	 */
+	static final class GraphLookupOperationFromBuilder
+			implements FromBuilder, StartWithBuilder, ConnectFromBuilder, ConnectToBuilder {
+
+		private String from;
+		private List<? extends Object> startWith;
+		private String connectFrom;
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.GraphLookupOperation.FromBuilder#from(java.lang.String)
+		 */
+		@Override
+		public StartWithBuilder from(String collectionName) {
+
+			Assert.hasText(collectionName, "CollectionName must not be null or empty!");
+
+			this.from = collectionName;
+			return this;
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.GraphLookupOperation.StartWithBuilder#startWith(java.lang.String[])
+		 */
+		@Override
+		public ConnectFromBuilder startWith(String... fieldReferences) {
+
+			Assert.notNull(fieldReferences, "FieldReferences must not be null!");
+			Assert.noNullElements(fieldReferences, "FieldReferences must not contain null elements!");
+
+			List<Object> fields = new ArrayList<Object>(fieldReferences.length);
+
+			for (String fieldReference : fieldReferences) {
+				fields.add(Fields.field(fieldReference));
+			}
+
+			this.startWith = fields;
+			return this;
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.GraphLookupOperation.StartWithBuilder#startWith(org.springframework.data.mongodb.core.aggregation.AggregationExpression[])
+		 */
+		@Override
+		public ConnectFromBuilder startWith(AggregationExpression... expressions) {
+
+			Assert.notNull(expressions, "AggregationExpressions must not be null!");
+			Assert.noNullElements(expressions, "AggregationExpressions must not contain null elements!");
+
+			this.startWith = Arrays.asList(expressions);
+			return this;
+		}
+
+		@Override
+		public ConnectFromBuilder startWith(Object... expressions) {
+
+			Assert.notNull(expressions, "Expressions must not be null!");
+			Assert.noNullElements(expressions, "Expressions must not contain null elements!");
+
+			this.startWith = verifyAndPotentiallyTransformStartsWithTypes(expressions);
+			return this;
+		}
+
+		private List<Object> verifyAndPotentiallyTransformStartsWithTypes(Object... expressions) {
+
+			List<Object> expressionsToUse = new ArrayList<Object>(expressions.length);
+
+			for (Object expression : expressions) {
+
+				assertStartWithType(expression);
+
+				if (expression instanceof String) {
+					expressionsToUse.add(Fields.field((String) expression));
+				} else {
+					expressionsToUse.add(expression);
+				}
+
+			}
+			return expressionsToUse;
+		}
+
+		private void assertStartWithType(Object expression) {
+
+			for (Class<?> type : ALLOWED_START_TYPES) {
+
+				if (ClassUtils.isAssignable(type, expression.getClass())) {
+					return;
+				}
+			}
+
+			throw new IllegalArgumentException(
+					String.format("Expression must be any of %s but was %s", ALLOWED_START_TYPES, expression.getClass()));
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.GraphLookupOperation.ConnectFromBuilder#connectFrom(java.lang.String)
+		 */
+		@Override
+		public ConnectToBuilder connectFrom(String fieldName) {
+
+			Assert.hasText(fieldName, "ConnectFrom must not be null or empty!");
+
+			this.connectFrom = fieldName;
+			return this;
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.GraphLookupOperation.ConnectToBuilder#connectTo(java.lang.String)
+		 */
+		@Override
+		public GraphLookupOperationBuilder connectTo(String fieldName) {
+
+			Assert.hasText(fieldName, "ConnectTo must not be null or empty!");
+
+			return new GraphLookupOperationBuilder(from, startWith, connectFrom, fieldName);
+		}
+	}
+
+	/**
+	 * @author Mark Paluch
+	 */
+	public static final class GraphLookupOperationBuilder {
+
+		private final String from;
+		private final List<Object> startWith;
+		private final Field connectFrom;
+		private final Field connectTo;
+		private Long maxDepth;
+		private Field depthField;
+		private CriteriaDefinition restrictSearchWithMatch;
+
+		protected GraphLookupOperationBuilder(String from, List<? extends Object> startWith, String connectFrom,
+				String connectTo) {
+
+			this.from = from;
+			this.startWith = new ArrayList<Object>(startWith);
+			this.connectFrom = Fields.field(connectFrom);
+			this.connectTo = Fields.field(connectTo);
+		}
+
+		/**
+		 * Optionally limit the number of recursions.
+		 *
+		 * @param numberOfRecursions must be greater or equal to zero.
+		 * @return
+		 */
+		public GraphLookupOperationBuilder maxDepth(long numberOfRecursions) {
+
+			Assert.isTrue(numberOfRecursions >= 0, "Max depth must be >= 0!");
+
+			this.maxDepth = numberOfRecursions;
+			return this;
+		}
+
+		/**
+		 * Optionally add a depth field {@literal fieldName} to each traversed document in the search path.
+		 *
+		 * @param fieldName must not be {@literal null} or empty.
+		 * @return
+		 */
+		public GraphLookupOperationBuilder depthField(String fieldName) {
+
+			Assert.hasText(fieldName, "Depth field name must not be null or empty!");
+
+			this.depthField = Fields.field(fieldName);
+			return this;
+		}
+
+		/**
+		 * Optionally add a query specifying conditions to the recursive search.
+		 *
+		 * @param criteriaDefinition must not be {@literal null}.
+		 * @return
+		 */
+		public GraphLookupOperationBuilder restrict(CriteriaDefinition criteriaDefinition) {
+
+			Assert.notNull(criteriaDefinition, "CriteriaDefinition must not be null!");
+
+			this.restrictSearchWithMatch = criteriaDefinition;
+			return this;
+		}
+
+		/**
+		 * Set the name of the array field added to each output document and return the final {@link GraphLookupOperation}.
+		 * Contains the documents traversed in the {@literal $graphLookup} stage to reach the document.
+		 *
+		 * @param fieldName must not be {@literal null} or empty.
+		 * @return the final {@link GraphLookupOperation}.
+		 */
+		public GraphLookupOperation as(String fieldName) {
+
+			Assert.hasText(fieldName, "As field name must not be null or empty!");
+
+			return new GraphLookupOperation(from, startWith, connectFrom, connectTo, Fields.field(fieldName), maxDepth,
+					depthField, restrictSearchWithMatch);
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/GroupOperation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -33,12 +33,13 @@ import org.springframework.util.StringUtils;
  * We recommend to use the static factory method {@link Aggregation#group(Fields)} instead of creating instances of this
  * class directly.
  * 
- * @see http://docs.mongodb.org/manual/reference/aggregation/group/#stage._S_group
  * @author Sebastian Herold
  * @author Thomas Darimont
  * @author Oliver Gierke
+ * @author Gustavo de Geus
  * @author Christoph Strobl
  * @since 1.3
+ * @see <a href="https://docs.mongodb.org/manual/reference/aggregation/group/">MongoDB Aggregation Framework: $group</a>
  */
 public class GroupOperation implements FieldsExposingAggregationOperation {
 
@@ -311,6 +312,51 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 		return newBuilder(GroupOps.MAX, null, expr);
 	}
 
+	/**
+	 * Generates an {@link GroupOperationBuilder} for an {@code $stdDevSamp}-expression that for the given
+	 * field-reference.
+	 *
+	 * @param reference must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @since 1.10
+	 */
+	public GroupOperationBuilder stdDevSamp(String reference) {
+		return newBuilder(GroupOps.STD_DEV_SAMP, reference, null);
+	}
+
+	/**
+	 * Generates an {@link GroupOperationBuilder} for an {@code $stdDevSamp}-expression that for the given {@link AggregationExpression}.
+	 *
+	 * @param expr must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @since 1.10
+	 */
+	public GroupOperationBuilder stdDevSamp(AggregationExpression expr) {
+		return newBuilder(GroupOps.STD_DEV_SAMP, null, expr);
+	}
+
+	/**
+	 * Generates an {@link GroupOperationBuilder} for an {@code $stdDevPop}-expression that for the given field-reference.
+	 *
+	 * @param reference must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @since 1.10
+	 */
+	public GroupOperationBuilder stdDevPop(String reference) {
+		return newBuilder(GroupOps.STD_DEV_POP, reference, null);
+	}
+
+	/**
+	 * Generates an {@link GroupOperationBuilder} for an {@code $stdDevPop}-expression that for the given {@link AggregationExpression}.
+	 *
+	 * @param expr must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @since 1.10
+	 */
+	public GroupOperationBuilder stdDevPop(AggregationExpression expr) {
+		return newBuilder(GroupOps.STD_DEV_POP, null, expr);
+	}
+
 	private GroupOperationBuilder newBuilder(Keyword keyword, String reference, Object value) {
 		return new GroupOperationBuilder(this, new Operation(keyword, null, reference, value));
 	}
@@ -375,21 +421,18 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	private static enum GroupOps implements Keyword {
 
-		SUM, LAST, FIRST, PUSH, AVG, MIN, MAX, ADD_TO_SET, COUNT;
+		SUM("$sum"), LAST("$last"), FIRST("$first"), PUSH("$push"), AVG("$avg"), MIN("$min"), MAX("$max"), ADD_TO_SET("$addToSet"), STD_DEV_POP("$stdDevPop"), STD_DEV_SAMP("$stdDevSamp");
+
+		private String mongoOperator;
+
+		GroupOps(String mongoOperator) {
+			this.mongoOperator = mongoOperator;
+		}
+
 
 		@Override
 		public String toString() {
-
-			String[] parts = name().split("_");
-
-			StringBuilder builder = new StringBuilder();
-
-			for (String part : parts) {
-				String lowerCase = part.toLowerCase(Locale.US);
-				builder.append(builder.length() == 0 ? lowerCase : StringUtils.capitalize(lowerCase));
-			}
-
-			return "$" + builder.toString();
+			return mongoOperator;
 		}
 	}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/IfNullOperator.java

@@ -1,195 +0,0 @@
-/*
- * Copyright 2016 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core.aggregation;
-
-import java.util.ArrayList;
-import java.util.List;
-
-import org.bson.Document;
-import org.springframework.util.Assert;
-
-/**
- * Encapsulates the aggregation framework {@code $ifNull} operator. Replacement values can be either {@link Field field
- * references}, values of simple MongoDB types or values that can be converted to a simple MongoDB type.
- *
- * @see http://docs.mongodb.com/manual/reference/operator/aggregation/ifNull/
- * @author Mark Paluch
- * @author Christoph Strobl
- * @since 1.10
- */
-public class IfNullOperator implements AggregationExpression {
-
-	private final Field field;
-	private final Object value;
-
-	/**
-	 * Creates a new {@link IfNullOperator} for the given {@link Field} and replacement {@code value}.
-	 *
-	 * @param field must not be {@literal null}.
-	 * @param value must not be {@literal null}.
-	 */
-	public IfNullOperator(Field field, Object value) {
-
-		Assert.notNull(field, "Field must not be null!");
-		Assert.notNull(value, "'Replacement-value' must not be null!");
-
-		this.field = field;
-		this.value = value;
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.core.aggregation.AggregationExpression#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
-	 */
-	@Override
-	public Document toDocument(AggregationOperationContext context) {
-
-		List<Object> list = new ArrayList<Object>();
-
-		list.add(context.getReference(field).toString());
-		list.add(resolve(value, context));
-
-		return new Document("$ifNull", list);
-	}
-
-	private Object resolve(Object value, AggregationOperationContext context) {
-
-		if (value instanceof Field) {
-			return context.getReference((Field) value).toString();
-		} else if (value instanceof Document) {
-			return value;
-		}
-
-		return context.getMappedObject(new Document("$set", value)).get("$set");
-	}
-
-	/**
-	 * Get a builder that allows fluent creation of {@link IfNullOperator}.
-	 *
-	 * @return a new {@link IfNullBuilder}.
-	 */
-	public static IfNullBuilder newBuilder() {
-		return IfNullOperatorBuilder.newBuilder();
-	}
-
-	/**
-	 * @since 1.10
-	 */
-	public static interface IfNullBuilder {
-
-		/**
-		 * @param field the field to check for a {@literal null} value, field reference must not be {@literal null}.
-		 * @return the {@link ThenBuilder}
-		 */
-		ThenBuilder ifNull(Field field);
-
-		/**
-		 * @param field the field to check for a {@literal null} value, field name must not be {@literal null} or empty.
-		 * @return the {@link ThenBuilder}
-		 */
-		ThenBuilder ifNull(String field);
-	}
-
-	/**
-	 * @since 1.10
-	 */
-	public static interface ThenBuilder {
-
-		/**
-		 * @param field the field holding the replacement value, must not be {@literal null}.
-		 * @return the {@link IfNullOperator}
-		 */
-		IfNullOperator thenReplaceWith(Field field);
-
-		/**
-		 * @param value the value to be used if the {@code $ifNull }condition evaluates {@literal true}. Can be a
-		 *          {@link Document}, a value that is supported by MongoDB or a value that can be converted to a MongoDB
-		 *          representation but must not be {@literal null}.
-		 * @return the {@link IfNullOperator}
-		 */
-		IfNullOperator thenReplaceWith(Object value);
-	}
-
-	/**
-	 * Builder for fluent {@link IfNullOperator} creation.
-	 *
-	 * @author Mark Paluch
-	 * @since 1.10
-	 */
-	public static final class IfNullOperatorBuilder implements IfNullBuilder, ThenBuilder {
-
-		private Field field;
-
-		private IfNullOperatorBuilder() {}
-
-		/**
-		 * Creates a new builder for {@link IfNullOperator}.
-		 *
-		 * @return never {@literal null}.
-		 */
-		public static IfNullOperatorBuilder newBuilder() {
-			return new IfNullOperatorBuilder();
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.IfNullOperator.IfNullBuilder#ifNull(org.springframework.data.mongodb.core.aggregation.Field)
-		 */
-		public ThenBuilder ifNull(Field field) {
-
-			Assert.notNull(field, "Field must not be null!");
-
-			this.field = field;
-			return this;
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.IfNullOperator.IfNullBuilder#ifNull(java.lang.String)
-		 */
-		public ThenBuilder ifNull(String name) {
-
-			Assert.hasText(name, "Field name must not be null or empty!");
-
-			this.field = Fields.field(name);
-			return this;
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.IfNullOperator.ThenReplaceBuilder#thenReplaceWith(org.springframework.data.mongodb.core.aggregation.Field)
-		 */
-		@Override
-		public IfNullOperator thenReplaceWith(Field replacementField) {
-
-			Assert.notNull(replacementField, "Replacement field must not be null!");
-
-			return new IfNullOperator(this.field, replacementField);
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.aggregation.IfNullOperator.ThenReplaceBuilder#thenReplaceWith(java.lang.Object)
-		 */
-		@Override
-		public IfNullOperator thenReplaceWith(Object value) {
-
-			Assert.notNull(value, "'Replacement-value' must not be null!");
-
-			return new IfNullOperator(this.field, value);
-		}
-	}
-}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/InheritingExposedFieldsAggregationOperationContext.java

@@ -13,17 +13,16 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
 package org.springframework.data.mongodb.core.aggregation;
 
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference;
-import org.springframework.util.Assert;
 
 /**
  * {@link ExposedFieldsAggregationOperationContext} that inherits fields from its parent
  * {@link AggregationOperationContext}.
  *
  * @author Mark Paluch
+ * @since 1.9
  */
 class InheritingExposedFieldsAggregationOperationContext extends ExposedFieldsAggregationOperationContext {
 
@@ -40,7 +39,7 @@ class InheritingExposedFieldsAggregationOperationContext extends ExposedFieldsAg
 			AggregationOperationContext previousContext) {
 
 		super(exposedFields, previousContext);
-		Assert.notNull(previousContext, "PreviousContext must not be null!");
+
 		this.previousContext = previousContext;
 	}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/LimitOperation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,12 +23,12 @@ import org.springframework.util.Assert;
  * <p>
  * We recommend to use the static factory method {@link Aggregation#limit(long)} instead of creating instances of this
  * class directly.
- * 
- * @see http://docs.mongodb.org/manual/reference/aggregation/limit/
+ *
  * @author Thomas Darimont
  * @author Oliver Gierke
  * @author Christoph Strobl
  * @since 1.3
+ * @see <a href="https://docs.mongodb.org/manual/reference/aggregation/limit/">MongoDB Aggregation Framework: $limit</a>
  */
 public class LimitOperation implements AggregationOperation {
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/LiteralOperators.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2016. the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import org.springframework.util.Assert;
+
+/**
+ * Gateway to {@literal literal} aggregation operations.
+ *
+ * @author Christoph Strobl
+ * @since 1.10
+ */
+public class LiteralOperators {
+
+	/**
+	 * Take the value referenced by given {@literal value}.
+	 *
+	 * @param value must not be {@literal null}.
+	 * @return
+	 */
+	public static LiteralOperatorFactory valueOf(Object value) {
+
+		Assert.notNull(value, "Value must not be null!");
+		return new LiteralOperatorFactory(value);
+	}
+
+	/**
+	 * @author Christoph Strobl
+	 */
+	public static class LiteralOperatorFactory {
+
+		private final Object value;
+
+		/**
+		 * Creates new {@link LiteralOperatorFactory} for given {@literal value}.
+		 *
+		 * @param value must not be {@literal null}.
+		 */
+		public LiteralOperatorFactory(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+			this.value = value;
+		}
+
+		/**
+		 * Creates new {@link Literal} that returns the associated value without parsing.
+		 *
+		 * @return
+		 */
+		public Literal asLiteral() {
+			return Literal.asLiteral(value);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $literal}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class Literal extends AbstractAggregationExpression {
+
+		private Literal(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$literal";
+		}
+
+		/**
+		 * Creates new {@link Literal}.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public static Literal asLiteral(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+			return new Literal(value);
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/LookupOperation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,8 +27,8 @@ import org.springframework.util.Assert;
  * @author Alessio Fachechi
  * @author Christoph Strobl
  * @author Mark Paluch
- * @see http://docs.mongodb.org/manual/reference/aggregation/lookup/#stage._S_lookup
  * @since 1.9
+ * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/">MongoDB Aggregation Framework: $lookup</a>
  */
 public class LookupOperation implements FieldsExposingAggregationOperation, InheritsFieldsAggregationOperation {
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/MatchOperation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2015 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,11 +26,11 @@ import org.springframework.util.Assert;
  * {@link Aggregation#match(org.springframework.data.mongodb.core.query.Criteria)} instead of creating instances of this
  * class directly.
  * 
- * @see http://docs.mongodb.org/manual/reference/aggregation/match/
  * @author Sebastian Herold
  * @author Thomas Darimont
  * @author Oliver Gierke
  * @since 1.3
+ * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/match/">MongoDB Aggregation Framework: $match</a>
  */
 public class MatchOperation implements AggregationOperation {
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/NestedDelegatingExpressionAggregationOperationContext.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2016. the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import org.bson.Document;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExpressionFieldReference;
+import org.springframework.util.Assert;
+
+/**
+ * {@link AggregationOperationContext} that delegates {@link FieldReference} resolution and mapping to a parent one, but
+ * assures {@link FieldReference} get converted into {@link ExpressionFieldReference} using {@code $$} to ref an inner
+ * variable.
+ *
+ * @author Christoph Strobl
+ * @since 1.10
+ */
+class NestedDelegatingExpressionAggregationOperationContext implements AggregationOperationContext {
+
+	private final AggregationOperationContext delegate;
+
+	/**
+	 * Creates new {@link NestedDelegatingExpressionAggregationOperationContext}.
+	 *
+	 * @param referenceContext must not be {@literal null}.
+	 */
+	public NestedDelegatingExpressionAggregationOperationContext(AggregationOperationContext referenceContext) {
+
+		Assert.notNull(referenceContext, "Reference context must not be null!");
+		this.delegate = referenceContext;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getMappedObject(org.bson.Document)
+	 */
+	@Override
+	public Document getMappedObject(Document document) {
+		return delegate.getMappedObject(document);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getReference(org.springframework.data.mongodb.core.aggregation.Field)
+	 */
+	@Override
+	public FieldReference getReference(Field field) {
+		return new ExpressionFieldReference(delegate.getReference(field));
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getReference(java.lang.String)
+	 */
+	@Override
+	public FieldReference getReference(String name) {
+		return new ExpressionFieldReference(delegate.getReference(name));
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/OutOperation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,9 +24,9 @@ import org.springframework.util.Assert;
  * We recommend to use the static factory method {@link Aggregation#out(String)} instead of creating instances of this
  * class directly.
  *
- * @see http://docs.mongodb.org/manual/reference/aggregation/out/
  * @author Nikolay Bogdanov
  * @author Christoph Strobl
+ * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/out/">MongoDB Aggregation Framework: $out</a>
  */
 public class OutOperation implements AggregationOperation {
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ProjectionOperation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,13 +17,18 @@ package org.springframework.data.mongodb.core.aggregation;
 
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 
 import org.bson.Document;
+import org.springframework.data.mongodb.core.aggregation.VariableOperators.Let.ExpressionVariable;
+import org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond;
+import org.springframework.data.mongodb.core.aggregation.ConditionalOperators.IfNull;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
 import org.springframework.data.mongodb.core.aggregation.Fields.AggregationField;
 import org.springframework.data.mongodb.core.aggregation.ProjectionOperation.ProjectionOperationBuilder.FieldProjection;
+import org.springframework.data.mongodb.core.aggregation.VariableOperators.Let.ExpressionVariable;
 import org.springframework.util.Assert;
 
 /**
@@ -35,13 +40,13 @@ import org.springframework.util.Assert;
  * We recommend to use the static factory method {@link Aggregation#project(Fields)} instead of creating instances of
  * this class directly.
  * 
- * @see http://docs.mongodb.org/manual/reference/aggregation/project/
  * @author Tobias Trelle
  * @author Thomas Darimont
  * @author Oliver Gierke
  * @author Christoph Strobl
  * @author Mark Paluch
  * @since 1.3
+ * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/project/">MongoDB Aggregation Framework: $project</a>
  */
 public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
@@ -241,22 +246,22 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		public abstract ProjectionOperation as(String alias);
 
 		/**
-		 * Apply a conditional projection using {@link ConditionalOperator}.
+		 * Apply a conditional projection using {@link Cond}.
 		 *
-		 * @param conditionalOperator must not be {@literal null}.
+		 * @param cond must not be {@literal null}.
 		 * @return never {@literal null}.
 		 * @since 1.10
 		 */
-		public abstract ProjectionOperation applyCondition(ConditionalOperator conditionalOperator);
+		public abstract ProjectionOperation applyCondition(Cond cond);
 
 		/**
-		 * Apply a conditional value replacement for {@literal null} values using {@link IfNullOperator}.
+		 * Apply a conditional value replacement for {@literal null} values using {@link IfNull}.
 		 *
-		 * @param ifNullOperator must not be {@literal null}.
+		 * @param ifNull must not be {@literal null}.
 		 * @return never {@literal null}.
 		 * @since 1.10
 		 */
-		public abstract ProjectionOperation applyCondition(IfNullOperator ifNullOperator);
+		public abstract ProjectionOperation applyCondition(IfNull ifNull);
 	}
 
 	/**
@@ -460,10 +465,10 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @see org.springframework.data.mongodb.core.aggregation.ProjectionOperation.AbstractProjectionOperationBuilder#transform(org.springframework.data.mongodb.core.aggregation.ConditionalOperator)
 		 */
 		@Override
-		public ProjectionOperation applyCondition(ConditionalOperator conditionalOperator) {
+		public ProjectionOperation applyCondition(Cond cond) {
 
-			Assert.notNull(conditionalOperator, "ConditionalOperator must not be null!");
-			return this.operation.and(new ExpressionProjection(Fields.field(name), conditionalOperator));
+			Assert.notNull(cond, "ConditionalOperator must not be null!");
+			return this.operation.and(new ExpressionProjection(Fields.field(name), cond));
 		}
 
 		/*
@@ -471,10 +476,10 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @see org.springframework.data.mongodb.core.aggregation.ProjectionOperation.AbstractProjectionOperationBuilder#transform(org.springframework.data.mongodb.core.aggregation.IfNullOperator)
 		 */
 		@Override
-		public ProjectionOperation applyCondition(IfNullOperator ifNullOperator) {
+		public ProjectionOperation applyCondition(IfNull ifNull) {
 
-			Assert.notNull(ifNullOperator, "IfNullOperator must not be null!");
-			return this.operation.and(new ExpressionProjection(Fields.field(name), ifNullOperator));
+			Assert.notNull(ifNull, "IfNullOperator must not be null!");
+			return this.operation.and(new ExpressionProjection(Fields.field(name), ifNull));
 		}
 
 		/**
@@ -526,6 +531,20 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			return project("subtract", Fields.field(fieldReference));
 		}
 
+		/**
+		 * Generates an {@code $subtract} expression that subtracts the result of the given {@link AggregationExpression}
+		 * from the previously mentioned field.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder minus(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return project("subtract", expression);
+		}
+
 		/**
 		 * Generates an {@code $multiply} expression that multiplies the given number with the previously mentioned field.
 		 * 
@@ -551,6 +570,20 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			return project("multiply", Fields.field(fieldReference));
 		}
 
+		/**
+		 * Generates an {@code $multiply} expression that multiplies the previously with the result of the
+		 * {@link AggregationExpression}. mentioned field.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder multiply(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return project("multiply", expression);
+		}
+
 		/**
 		 * Generates an {@code $divide} expression that divides the previously mentioned field by the given number.
 		 * 
@@ -577,6 +610,20 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			return project("divide", Fields.field(fieldReference));
 		}
 
+		/**
+		 * Generates an {@code $divide} expression that divides the value of the previously mentioned by the result of the
+		 * {@link AggregationExpression}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder divide(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return project("divide", expression);
+		}
+
 		/**
 		 * Generates an {@code $mod} expression that divides the previously mentioned field by the given number and returns
 		 * the remainder.
@@ -594,7 +641,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		/**
 		 * Generates an {@code $mod} expression that divides the value of the given field by the previously mentioned field
 		 * and returns the remainder.
-		 * 
+		 *
 		 * @param fieldReference
 		 * @return
 		 */
@@ -604,6 +651,20 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			return project("mod", Fields.field(fieldReference));
 		}
 
+		/**
+		 * Generates an {@code $mod} expression that divides the value of the previously mentioned field by the result of
+		 * the {@link AggregationExpression}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder mod(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return project("mod", expression);
+		}
+
 		/**
 		 * Generates a {@code $size} expression that returns the size of the array held by the given field. <br />
 		 *
@@ -614,6 +675,85 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			return project("size");
 		}
 
+		/**
+		 * Generates a {@code $cmp} expression (compare to) that compares the value of the field to a given value or field.
+		 *
+		 * @param compareValue compare value or a {@link Field} object.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder cmp(Object compareValue) {
+			return project("cmp", compareValue);
+		}
+
+		/**
+		 * Generates a {@code $eq} expression (equal) that compares the value of the field to a given value or field.
+		 *
+		 * @param compareValue compare value or a {@link Field} object.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder eq(Object compareValue) {
+			return project("eq", compareValue);
+		}
+
+		/**
+		 * Generates a {@code $gt} expression (greater than) that compares the value of the field to a given value or field.
+		 *
+		 * @param compareValue compare value or a {@link Field} object.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder gt(Object compareValue) {
+			return project("gt", compareValue);
+		}
+
+		/**
+		 * Generates a {@code $gte} expression (greater than equal) that compares the value of the field to a given value or
+		 * field.
+		 *
+		 * @param compareValue compare value or a {@link Field} object.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder gte(Object compareValue) {
+			return project("gte", compareValue);
+		}
+
+		/**
+		 * Generates a {@code $lt} expression (less than) that compares the value of the field to a given value or field.
+		 *
+		 * @param compareValue compare value or a {@link Field} object.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder lt(Object compareValue) {
+			return project("lt", compareValue);
+		}
+
+		/**
+		 * Generates a {@code $lte} expression (less than equal) that compares the value of the field to a given value or
+		 * field.
+		 *
+		 * @param compareValue the compare value or a {@link Field} object.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder lte(Object compareValue) {
+			return project("lte", compareValue);
+		}
+
+		/**
+		 * Generates a {@code $ne} expression (not equal) that compares the value of the field to a given value or field.
+		 *
+		 * @param compareValue compare value or a {@link Field} object.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder ne(Object compareValue) {
+			return project("ne", compareValue);
+		}
+
 		/**
 		 * Generates a {@code $slice} expression that returns a subset of the array held by the given field. <br />
 		 * If {@literal n} is positive, $slice returns up to the first n elements in the array. <br />
@@ -639,7 +779,453 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			return project("slice", offset, count);
 		}
 
-		/* 
+		/**
+		 * Generates a {@code $filter} expression that returns a subset of the array held by the given field.
+		 *
+		 * @param as The variable name for the element in the input array. Must not be {@literal null}.
+		 * @param condition The {@link AggregationExpression} that determines whether to include the element in the
+		 *          resulting array. Must not be {@literal null}.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder filter(String as, AggregationExpression condition) {
+			return this.operation.and(ArrayOperators.Filter.filter(name).as(as).by(condition));
+		}
+
+		// SET OPERATORS
+
+		/**
+		 * Generates a {@code $setEquals} expression that compares the previously mentioned field to one or more arrays and
+		 * returns {@literal true} if they have the same distinct elements and {@literal false} otherwise.
+		 *
+		 * @param arrays must not be {@literal null}.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder equalsArrays(String... arrays) {
+
+			Assert.notEmpty(arrays, "Arrays must not be null or empty!");
+			return project("setEquals", Fields.fields(arrays));
+		}
+
+		/**
+		 * Generates a {@code $setIntersection} expression that takes array of the previously mentioned field and one or
+		 * more arrays and returns an array that contains the elements that appear in every of those.
+		 *
+		 * @param arrays must not be {@literal null}.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder intersectsArrays(String... arrays) {
+
+			Assert.notEmpty(arrays, "Arrays must not be null or empty!");
+			return project("setIntersection", Fields.fields(arrays));
+		}
+
+		/**
+		 * Generates a {@code $setUnion} expression that takes array of the previously mentioned field and one or more
+		 * arrays and returns an array that contains the elements that appear in any of those.
+		 *
+		 * @param arrays must not be {@literal null}.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder unionArrays(String... arrays) {
+
+			Assert.notEmpty(arrays, "Arrays must not be null or empty!");
+			return project("setUnion", Fields.fields(arrays));
+		}
+
+		/**
+		 * Generates a {@code $setDifference} expression that takes array of the previously mentioned field and returns an
+		 * array containing the elements that do not exist in the given {@literal array}.
+		 *
+		 * @param array must not be {@literal null}.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder differenceToArray(String array) {
+
+			Assert.hasText(array, "Array must not be null or empty!");
+			return project("setDifference", Fields.fields(array));
+		}
+
+		/**
+		 * Generates a {@code $setIsSubset} expression that takes array of the previously mentioned field and returns
+		 * {@literal true} if it is a subset of the given {@literal array}.
+		 *
+		 * @param array must not be {@literal null}.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder subsetOfArray(String array) {
+
+			Assert.hasText(array, "Array must not be null or empty!");
+			return project("setIsSubset", Fields.fields(array));
+		}
+
+		/**
+		 * Generates an {@code $anyElementTrue} expression that Takes array of the previously mentioned field and returns
+		 * {@literal true} if any of the elements are {@literal true} and {@literal false} otherwise.
+		 *
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder anyElementInArrayTrue() {
+			return project("anyElementTrue");
+		}
+
+		/**
+		 * Generates an {@code $allElementsTrue} expression that takes array of the previously mentioned field and returns
+		 * {@literal true} if no elements is {@literal false}.
+		 *
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder allElementsInArrayTrue() {
+			return project("allElementsTrue");
+		}
+
+		/**
+		 * Generates a {@code $abs} expression that takes the number of the previously mentioned field and returns the
+		 * absolute value of it.
+		 *
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder absoluteValue() {
+			return this.operation.and(ArithmeticOperators.Abs.absoluteValueOf(name));
+		}
+
+		/**
+		 * Generates a {@code $ceil} expression that takes the number of the previously mentioned field and returns the
+		 * smallest integer greater than or equal to the specified number.
+		 *
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder ceil() {
+			return this.operation.and(ArithmeticOperators.Ceil.ceilValueOf(name));
+		}
+
+		/**
+		 * Generates a {@code $exp} expression that takes the number of the previously mentioned field and raises Euler’s
+		 * number (i.e. e ) on it.
+		 *
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder exp() {
+			return this.operation.and(ArithmeticOperators.Exp.expValueOf(name));
+		}
+
+		/**
+		 * Generates a {@code $floor} expression that takes the number of the previously mentioned field and returns the
+		 * largest integer less than or equal to it.
+		 *
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder floor() {
+			return this.operation.and(ArithmeticOperators.Floor.floorValueOf(name));
+		}
+
+		/**
+		 * Generates a {@code $ln} expression that takes the number of the previously mentioned field and calculates the
+		 * natural logarithm ln (i.e loge) of it.
+		 *
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder ln() {
+			return this.operation.and(ArithmeticOperators.Ln.lnValueOf(name));
+		}
+
+		/**
+		 * Generates a {@code $log} expression that takes the number of the previously mentioned field and calculates the
+		 * log of the associated number in the specified base.
+		 *
+		 * @param baseFieldRef must not be {@literal null}.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder log(String baseFieldRef) {
+			return this.operation.and(ArithmeticOperators.Log.valueOf(name).log(baseFieldRef));
+		}
+
+		/**
+		 * Generates a {@code $log} expression that takes the number of the previously mentioned field and calculates the
+		 * log of the associated number in the specified base.
+		 *
+		 * @param base must not be {@literal null}.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder log(Number base) {
+			return this.operation.and(ArithmeticOperators.Log.valueOf(name).log(base));
+		}
+
+		/**
+		 * Generates a {@code $log} expression that takes the number of the previously mentioned field and calculates the
+		 * log of the associated number in the specified base.
+		 *
+		 * @param base must not be {@literal null}.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder log(AggregationExpression base) {
+			return this.operation.and(ArithmeticOperators.Log.valueOf(name).log(base));
+		}
+
+		/**
+		 * Generates a {@code $log10} expression that takes the number of the previously mentioned field and calculates the
+		 * log base 10.
+		 *
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder log10() {
+			return this.operation.and(ArithmeticOperators.Log10.log10ValueOf(name));
+		}
+
+		/**
+		 * Generates a {@code $pow} expression that takes the number of the previously mentioned field and raises it by the
+		 * specified exponent.
+		 *
+		 * @param exponentFieldRef must not be {@literal null}.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder pow(String exponentFieldRef) {
+			return this.operation.and(ArithmeticOperators.Pow.valueOf(name).pow(exponentFieldRef));
+		}
+
+		/**
+		 * Generates a {@code $pow} expression that takes the number of the previously mentioned field and raises it by the
+		 * specified exponent.
+		 *
+		 * @param exponent must not be {@literal null}.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder pow(Number exponent) {
+			return this.operation.and(ArithmeticOperators.Pow.valueOf(name).pow(exponent));
+		}
+
+		/**
+		 * Generates a {@code $pow} expression that Takes the number of the previously mentioned field and raises it by the
+		 * specified exponent.
+		 *
+		 * @param exponentExpression must not be {@literal null}.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder pow(AggregationExpression exponentExpression) {
+			return this.operation.and(ArithmeticOperators.Pow.valueOf(name).pow(exponentExpression));
+		}
+
+		/**
+		 * Generates a {@code $sqrt} expression that takes the number of the previously mentioned field and calculates the
+		 * square root.
+		 *
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder sqrt() {
+			return this.operation.and(ArithmeticOperators.Sqrt.sqrtOf(name));
+		}
+
+		/**
+		 * Takes the number of the previously mentioned field and truncates it to its integer value.
+		 *
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder trunc() {
+			return this.operation.and(ArithmeticOperators.Trunc.truncValueOf(name));
+		}
+
+		/**
+		 * Generates a {@code $concat} expression that takes the string representation of the previously mentioned field and
+		 * concats given values to it.
+		 *
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder concat(Object... values) {
+			return project("concat", values);
+		}
+
+		/**
+		 * Generates a {@code $substr} expression that Takes the string representation of the previously mentioned field and
+		 * returns a substring starting at a specified index position.
+		 *
+		 * @param start
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder substring(int start) {
+			return substring(start, -1);
+		}
+
+		/**
+		 * Generates a {@code $substr} expression that takes the string representation of the previously mentioned field and
+		 * returns a substring starting at a specified index position including the specified number of characters.
+		 *
+		 * @param start
+		 * @param nrOfChars
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder substring(int start, int nrOfChars) {
+			return project("substr", start, nrOfChars);
+		}
+
+		/**
+		 * Generates a {@code $toLower} expression that takes the string representation of the previously mentioned field
+		 * and lowers it.
+		 *
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder toLower() {
+			return this.operation.and(StringOperators.ToLower.lowerValueOf(name));
+		}
+
+		/**
+		 * Generates a {@code $toUpper} expression that takes the string representation of the previously mentioned field
+		 * and uppers it.
+		 *
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder toUpper() {
+			return this.operation.and(StringOperators.ToUpper.upperValueOf(name));
+		}
+
+		/**
+		 * Generates a {@code $strcasecmp} expression that takes the string representation of the previously mentioned field
+		 * and performs case-insensitive comparison to the given {@literal value}.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder strCaseCmp(String value) {
+			return project("strcasecmp", value);
+		}
+
+		/**
+		 * Generates a {@code $strcasecmp} expression that takes the string representation of the previously mentioned field
+		 * and performs case-insensitive comparison to the referenced {@literal fieldRef}.
+		 *
+		 * @param fieldRef must not be {@literal null}.
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder strCaseCmpValueOf(String fieldRef) {
+			return project("strcasecmp", fieldRef);
+		}
+
+		/**
+		 * Generates a {@code $strcasecmp} expression that takes the string representation of the previously mentioned field
+		 * and performs case-insensitive comparison to the result of the given {@link AggregationExpression}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder strCaseCmp(AggregationExpression expression) {
+			return project("strcasecmp", expression);
+		}
+
+		/**
+		 * Generates a {@code $arrayElemAt} expression that takes the string representation of the previously mentioned
+		 * field and returns the element at the specified array {@literal position}.
+		 *
+		 * @param position
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder arrayElementAt(int position) {
+			return project("arrayElemAt", position);
+		}
+
+		/**
+		 * Generates a {@code $concatArrays} expression that takes the string representation of the previously mentioned
+		 * field and concats it with the arrays from the referenced {@literal fields}.
+		 *
+		 * @param fields must not be {@literal null}.
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder concatArrays(String... fields) {
+			return project("concatArrays", Fields.fields(fields));
+		}
+
+		/**
+		 * Generates a {@code $isArray} expression that takes the string representation of the previously mentioned field
+		 * and checks if its an array.
+		 *
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder isArray() {
+			return this.operation.and(ArrayOperators.IsArray.isArray(name));
+		}
+
+		/**
+		 * Generates a {@code $literal} expression that Takes the value previously and uses it as literal.
+		 *
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder asLiteral() {
+			return this.operation.and(LiteralOperators.Literal.asLiteral(name));
+		}
+
+		/**
+		 * Generates a {@code $dateToString} expression that takes the date representation of the previously mentioned field
+		 * and applies given {@literal format} to it.
+		 *
+		 * @param format must not be {@literal null}.
+		 * @return
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder dateAsFormattedString(String format) {
+			return this.operation.and(DateOperators.DateToString.dateOf(name).toString(format));
+		}
+
+		/**
+		 * Generates a {@code $let} expression that binds variables for use in the specified expression, and returns the
+		 * result of the expression.
+		 *
+		 * @param valueExpression The {@link AggregationExpression} bound to {@literal variableName}.
+		 * @param variableName The variable name to be used in the {@literal in} {@link AggregationExpression}.
+		 * @param in The {@link AggregationExpression} to evaluate.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder let(AggregationExpression valueExpression, String variableName,
+				AggregationExpression in) {
+			return this.operation.and(VariableOperators.Let
+					.define(ExpressionVariable.newVariable(variableName).forExpression(valueExpression)).andApply(in));
+		}
+
+		/**
+		 * Generates a {@code $let} expression that binds variables for use in the specified expression, and returns the
+		 * result of the expression.
+		 *
+		 * @param variables The bound {@link ExpressionVariable}s.
+		 * @param in The {@link AggregationExpression} to evaluate.
+		 * @return never {@literal null}.
+		 * @since 1.10
+		 */
+		public ProjectionOperationBuilder let(Collection<ExpressionVariable> variables, AggregationExpression in) {
+			return this.operation.and(VariableOperators.Let.define(variables).andApply(in));
+		}
+
+		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
 		 */
@@ -695,6 +1281,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * 
 		 * @author Oliver Gierke
 		 * @author Thomas Darimont
+		 * @author Mark Paluch
 		 */
 		static class FieldProjection extends Projection {
 
@@ -713,7 +1300,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 			private FieldProjection(Field field, Object value) {
 
-				super(field);
+				super(new ExposedField(field.getName(), true));
 
 				this.field = field;
 				this.value = value;
@@ -823,7 +1410,18 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 				result.add(context.getReference(getField().getName()).toString());
 
 				for (Object element : values) {
-					result.add(element instanceof Field ? context.getReference((Field) element).toString() : element);
+
+					if (element instanceof Field) {
+						result.add(context.getReference((Field) element).toString());
+					} else if (element instanceof Fields) {
+						for (Field field : (Fields) element) {
+							result.add(context.getReference(field).toString());
+						}
+					} else if (element instanceof AggregationExpression) {
+						result.add(((AggregationExpression) element).toDocument(context));
+					} else {
+						result.add(element);
+					}
 				}
 
 				return result;

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ReplaceRootOperation.java

@@ -0,0 +1,567 @@
+/*
+ * Copyright 2016-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+
+import org.bson.Document;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
+import org.springframework.expression.spel.ast.Projection;
+import org.springframework.util.Assert;
+
+/**
+ * Encapsulates the aggregation framework {@code $replaceRoot}-operation. <br />
+ * We recommend to use the static factory method {@link Aggregation#replaceRoot(String)} instead of creating instances
+ * of this class directly.
+ *
+ * @author Mark Paluch
+ * @author Christoph Strobl
+ * @since 1.10
+ * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/replaceRoot/">MongoDB Aggregation Framework: $replaceRoot</a>
+ */
+public class ReplaceRootOperation implements FieldsExposingAggregationOperation {
+
+	private final Replacement replacement;
+
+	/**
+	 * Creates a new {@link ReplaceRootOperation} given the {@link Field} field name.
+	 *
+	 * @param field must not be {@literal null} or empty.
+	 */
+	public ReplaceRootOperation(Field field) {
+		this(new FieldReplacement(field));
+	}
+
+	/**
+	 * Creates a new {@link ReplaceRootOperation} given the {@link AggregationExpression} pointing to a document.
+	 *
+	 * @param aggregationExpression must not be {@literal null}.
+	 */
+	public ReplaceRootOperation(AggregationExpression aggregationExpression) {
+		this(new AggregationExpressionReplacement(aggregationExpression));
+	}
+
+	/**
+	 * Creates a new {@link ReplaceRootOperation} given the {@link Replacement}.
+	 *
+	 * @param replacement must not be {@literal null}.
+	 */
+	public ReplaceRootOperation(Replacement replacement) {
+
+		Assert.notNull(replacement, "Replacement must not be null!");
+		this.replacement = replacement;
+	}
+
+	/**
+	 * Creates a new {@link ReplaceRootDocumentOperationBuilder}.
+	 *
+	 * @return a new {@link ReplaceRootDocumentOperationBuilder}.
+	 */
+	public static ReplaceRootOperationBuilder builder() {
+		return new ReplaceRootOperationBuilder();
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public Document toDocument(AggregationOperationContext context) {
+		return new Document("$replaceRoot", new Document("newRoot", replacement.toDocumentExpression(context)));
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation#getFields()
+	 */
+	@Override
+	public ExposedFields getFields() {
+		return ExposedFields.from();
+	}
+
+	/**
+	 * Builder for {@link ReplaceRootOperation}.
+	 *
+	 * @author Mark Paluch
+	 */
+	public static class ReplaceRootOperationBuilder {
+
+		/**
+		 * Defines a root document replacement based on a {@literal fieldName} that resolves to a document.
+		 *
+		 * @param fieldName must not be {@literal null} or empty.
+		 * @return the final {@link ReplaceRootOperation}.
+		 */
+		public ReplaceRootOperation withValueOf(String fieldName) {
+			return new ReplaceRootOperation(Fields.field(fieldName));
+		}
+
+		/**
+		 * Defines a root document replacement based on a {@link AggregationExpression} that resolves to a document.
+		 *
+		 * @param aggregationExpression must not be {@literal null}.
+		 * @return the final {@link ReplaceRootOperation}.
+		 */
+		public ReplaceRootOperation withValueOf(AggregationExpression aggregationExpression) {
+			return new ReplaceRootOperation(aggregationExpression);
+		}
+
+		/**
+		 * Defines a root document replacement based on a composable document that is empty initially. <br />
+		 * {@link ReplaceRootOperation} can be populated with individual entries and derive its values from other, existing
+		 * documents.
+		 *
+		 * @return the {@link ReplaceRootDocumentOperation}.
+		 */
+		public ReplaceRootDocumentOperation withDocument() {
+			return new ReplaceRootDocumentOperation();
+		}
+
+		/**
+		 * Defines a root document replacement based on a composable document given {@literal document}. <br />
+		 * {@link ReplaceRootOperation} can be populated with individual entries and derive its values from other, existing
+		 * documents.
+		 *
+		 * @param document must not be {@literal null}.
+		 * @return the final {@link ReplaceRootOperation}.
+		 */
+		public ReplaceRootOperation withDocument(Document document) {
+
+			Assert.notNull(document, "Document must not be null!");
+
+			return new ReplaceRootDocumentOperation().andValuesOf(document);
+		}
+	}
+
+	/**
+	 * Encapsulates the aggregation framework {@code $replaceRoot}-operation to result in a composable replacement
+	 * document. <br />
+	 * Instances of {@link ReplaceRootDocumentOperation} yield empty upon construction and can be populated with single
+	 * values and documents.
+	 *
+	 * @author Mark Paluch
+	 */
+	static class ReplaceRootDocumentOperation extends ReplaceRootOperation {
+
+		private final static ReplacementDocument EMPTY = new ReplacementDocument();
+		private final ReplacementDocument current;
+
+		/**
+		 * Creates an empty {@link ReplaceRootDocumentOperation}.
+		 */
+		public ReplaceRootDocumentOperation() {
+			this(EMPTY);
+		}
+
+		private ReplaceRootDocumentOperation(ReplacementDocument replacementDocument) {
+			super(replacementDocument);
+			current = replacementDocument;
+		}
+
+		/**
+		 * Creates an extended {@link ReplaceRootDocumentOperation} that combines {@link ReplacementDocument}s from the
+		 * {@literal currentOperation} and {@literal extension} operation.
+		 *
+		 * @param currentOperation must not be {@literal null}.
+		 * @param extension must not be {@literal null}.
+		 */
+		protected ReplaceRootDocumentOperation(ReplaceRootDocumentOperation currentOperation,
+				ReplacementDocument extension) {
+			this(currentOperation.current.extendWith(extension));
+		}
+
+		/**
+		 * Creates a new {@link ReplaceRootDocumentOperationBuilder} to define a field for the
+		 * {@link AggregationExpression}.
+		 *
+		 * @param aggregationExpression must not be {@literal null}.
+		 * @return the {@link ReplaceRootDocumentOperationBuilder}.
+		 */
+		public ReplaceRootDocumentOperationBuilder and(AggregationExpression aggregationExpression) {
+			return new ReplaceRootDocumentOperationBuilder(this, aggregationExpression);
+		}
+
+		/**
+		 * Creates a new {@link ReplaceRootDocumentOperationBuilder} to define a field for the {@literal value}.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return the {@link ReplaceRootDocumentOperationBuilder}.
+		 */
+		public ReplaceRootDocumentOperationBuilder andValue(Object value) {
+			return new ReplaceRootDocumentOperationBuilder(this, value);
+		}
+
+		/**
+		 * Creates a new {@link ReplaceRootDocumentOperation} that merges all existing replacement values with values from
+		 * {@literal value}. Existing replacement values are overwritten.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return the {@link ReplaceRootDocumentOperation}.
+		 */
+		public ReplaceRootDocumentOperation andValuesOf(Object value) {
+			return new ReplaceRootDocumentOperation(this, ReplacementDocument.valueOf(value));
+		}
+	}
+
+	/**
+	 * Builder for {@link ReplaceRootDocumentOperation} to populate {@link ReplacementDocument}
+	 *
+	 * @author Mark Paluch
+	 */
+	public static class ReplaceRootDocumentOperationBuilder {
+
+		private final ReplaceRootDocumentOperation currentOperation;
+		private final Object value;
+
+		protected ReplaceRootDocumentOperationBuilder(ReplaceRootDocumentOperation currentOperation, Object value) {
+
+			Assert.notNull(currentOperation, "Current ReplaceRootDocumentOperation must not be null!");
+			Assert.notNull(value, "Value must not be null!");
+
+			this.currentOperation = currentOperation;
+			this.value = value;
+		}
+
+		public ReplaceRootDocumentOperation as(String fieldName) {
+
+			if (value instanceof AggregationExpression) {
+				return new ReplaceRootDocumentOperation(currentOperation,
+						ReplacementDocument.forExpression(fieldName, (AggregationExpression) value));
+			}
+
+			return new ReplaceRootDocumentOperation(currentOperation, ReplacementDocument.forSingleValue(fieldName, value));
+		}
+	}
+
+	/**
+	 * Replacement object that results in a replacement document or an expression that results in a document.
+	 *
+	 * @author Mark Paluch
+	 * @author Christoph Strobl
+	 */
+	public interface Replacement {
+
+		/**
+		 * Renders the current {@link Replacement} into a its MongoDB representation based on the given
+		 * {@link AggregationOperationContext}.
+		 *
+		 * @param context will never be {@literal null}.
+		 * @return a replacement document or an expression that results in a document.
+		 */
+		Object toDocumentExpression(AggregationOperationContext context);
+	}
+
+	/**
+	 * {@link Replacement} that uses a {@link AggregationExpression} that results in a replacement document.
+	 *
+	 * @author Mark Paluch
+	 */
+	private static class AggregationExpressionReplacement implements Replacement {
+
+		private final AggregationExpression aggregationExpression;
+
+		protected AggregationExpressionReplacement(AggregationExpression aggregationExpression) {
+
+			Assert.notNull(aggregationExpression, "AggregationExpression must not be null!");
+			this.aggregationExpression = aggregationExpression;
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.ReplaceRootOperation.Replacement#toObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocumentExpression(AggregationOperationContext context) {
+			return aggregationExpression.toDocument(context);
+		}
+	}
+
+	/**
+	 * {@link Replacement that references a {@link Field} inside the current aggregation pipeline.
+	 *
+	 * @author Mark Paluch
+	 */
+	private static class FieldReplacement implements Replacement {
+
+		private final Field field;
+
+		/**
+		 * Creates {@link FieldReplacement} given {@link Field}.
+		 */
+		protected FieldReplacement(Field field) {
+
+			Assert.notNull(field, "Field must not be null!");
+			this.field = field;
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.ReplaceRootOperation.Replacement#toObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Object toDocumentExpression(AggregationOperationContext context) {
+			return context.getReference(field).toString();
+		}
+	}
+
+	/**
+	 * Replacement document consisting of multiple {@link ReplacementContributor}s.
+	 *
+	 * @author Mark Paluch
+	 */
+	private static class ReplacementDocument implements Replacement {
+
+		private final Collection<ReplacementContributor> replacements;
+
+		/**
+		 * Creates an empty {@link ReplacementDocument}.
+		 */
+		protected ReplacementDocument() {
+			replacements = new ArrayList<ReplacementContributor>();
+		}
+
+		/**
+		 * Creates a {@link ReplacementDocument} given {@link ReplacementContributor}.
+		 *
+		 * @param contributor
+		 */
+		protected ReplacementDocument(ReplacementContributor contributor) {
+
+			Assert.notNull(contributor, "ReplacementContributor must not be null!");
+			replacements = Collections.singleton(contributor);
+		}
+
+		private ReplacementDocument(Collection<ReplacementContributor> replacements) {
+			this.replacements = replacements;
+		}
+
+		/**
+		 * Creates a {@link ReplacementDocument} given a {@literal value}.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public static ReplacementDocument valueOf(Object value) {
+			return new ReplacementDocument(new DocumentContributor(value));
+		}
+
+		/**
+		 * Creates a {@link ReplacementDocument} given a single {@literal field} and {@link AggregationExpression}.
+		 *
+		 * @param aggregationExpression must not be {@literal null}.
+		 * @return
+		 */
+		public static ReplacementDocument forExpression(String field, AggregationExpression aggregationExpression) {
+			return new ReplacementDocument(new ExpressionFieldContributor(Fields.field(field), aggregationExpression));
+		}
+
+		/**
+		 * Creates a {@link ReplacementDocument} given a single {@literal field} and {@literal value}.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return
+		 */
+		public static ReplacementDocument forSingleValue(String field, Object value) {
+			return new ReplacementDocument(new ValueFieldContributor(Fields.field(field), value));
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.ReplaceRootOperation.Replacement#toObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocumentExpression(AggregationOperationContext context) {
+
+			Document document = new Document();
+
+			for (ReplacementContributor replacement : replacements) {
+				document.putAll(replacement.toDocument(context));
+			}
+
+			return document;
+		}
+
+		/**
+		 * Extend a replacement document that merges {@code this} and {@literal replacement} {@link ReplacementContributor}s
+		 * in a new {@link ReplacementDocument}.
+		 *
+		 * @param extension must not be {@literal null}.
+		 * @return the new, extended {@link ReplacementDocument}
+		 */
+		public ReplacementDocument extendWith(ReplacementDocument extension) {
+
+			Assert.notNull(extension, "ReplacementDocument must not be null");
+
+			ReplacementDocument replacementDocument = new ReplacementDocument();
+
+			List<ReplacementContributor> replacements = new ArrayList<ReplacementContributor>(
+					this.replacements.size() + extension.replacements.size());
+
+			replacements.addAll(this.replacements);
+			replacements.addAll(extension.replacements);
+
+			return new ReplacementDocument(replacements);
+		}
+	}
+
+	/**
+	 * Partial {@link Document} contributor for document replacement.
+	 *
+	 * @author Mark Paluch
+	 */
+	private interface ReplacementContributor extends AggregationExpression {
+
+		/**
+		 * Renders the current {@link ReplacementContributor} into a {@link Document} based on the given
+		 * {@link AggregationOperationContext}.
+		 *
+		 * @param context will never be {@literal null}.
+		 * @return
+		 */
+		Document toDocument(AggregationOperationContext context);
+	}
+
+	/**
+	 * {@link ReplacementContributor} to contribute multiple fields based on the input {@literal value}. <br />
+	 * The value object is mapped into a MongoDB {@link Document}.
+	 *
+	 * @author Mark Paluch
+	 * @author Christoph Strobl
+	 */
+	private static class DocumentContributor implements ReplacementContributor {
+
+		private final Object value;
+
+		/**
+		 * Creates new {@link Projection} for the given {@link Field}.
+		 *
+		 * @param value must not be {@literal null}.
+		 */
+		public DocumentContributor(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+			this.value = value;
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.ReplaceRootOperation.ReplacementContributor#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocument(AggregationOperationContext context) {
+
+			Document document = new Document("$set", value);
+
+			return (Document) context.getMappedObject(document).get("$set");
+		}
+	}
+
+	/**
+	 * Base class for {@link ReplacementContributor} implementations to contribute a single {@literal field} Typically
+	 * used to construct a composite document that should contain the resulting key-value pair.
+	 *
+	 * @author Mark Paluch
+	 */
+	private abstract static class FieldContributorSupport implements ReplacementContributor {
+
+		private final ExposedField field;
+
+		/**
+		 * Creates new {@link FieldContributorSupport} for the given {@link Field}.
+		 *
+		 * @param field must not be {@literal null}.
+		 */
+		public FieldContributorSupport(Field field) {
+
+			Assert.notNull(field, "Field must not be null!");
+			this.field = new ExposedField(field, true);
+		}
+
+		/**
+		 * @return the {@link ExposedField}.
+		 */
+		public ExposedField getField() {
+			return field;
+		}
+	}
+
+	/**
+	 * {@link ReplacementContributor} to contribute a single {@literal field} and {@literal value}. The {@literal value}
+	 * is mapped to a MongoDB {@link Document} and can be a singular value, a list or subdocument.
+	 *
+	 * @author Mark Paluch
+	 */
+	private static class ValueFieldContributor extends FieldContributorSupport {
+
+		private final Object value;
+
+		/**
+		 * Creates new {@link Projection} for the given {@link Field}.
+		 *
+		 * @param field must not be {@literal null}.
+		 * @param value must not be {@literal null}.
+		 */
+		public ValueFieldContributor(Field field, Object value) {
+
+			super(field);
+
+			Assert.notNull(value, "Value must not be null!");
+
+			this.value = value;
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.ReplaceRootOperation.ReplacementContributor#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocument(AggregationOperationContext context) {
+
+			Document document = new Document("$set", value);
+			return new Document(getField().getTarget(), context.getMappedObject(document).get("$set"));
+		}
+	}
+
+	/**
+	 * {@link ReplacementContributor} to contribute a single {@literal field} and value based on a
+	 * {@link AggregationExpression}.
+	 *
+	 * @author Mark Paluch
+	 */
+	private static class ExpressionFieldContributor extends FieldContributorSupport {
+
+		private final AggregationExpression aggregationExpression;
+
+		/**
+		 * Creates new {@link Projection} for the given {@link Field}.
+		 *
+		 * @param field must not be {@literal null}.
+		 * @param aggregationExpression must not be {@literal null}.
+		 */
+		public ExpressionFieldContributor(Field field, AggregationExpression aggregationExpression) {
+
+			super(field);
+
+			Assert.notNull(aggregationExpression, "AggregationExpression must not be null!");
+
+			this.aggregationExpression = aggregationExpression;
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.ReplaceRootOperation.ReplacementContributor#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocument(AggregationOperationContext context) {
+			return new Document(getField().getTarget(), aggregationExpression.toDocument(context));
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/SetOperators.java

@@ -0,0 +1,666 @@
+/*
+ * Copyright 2016. the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.springframework.data.mongodb.core.aggregation.AccumulatorOperators.Sum;
+import org.springframework.util.Assert;
+
+/**
+ * Gateway to {@literal Set expressions} which perform {@literal set} operation on arrays, treating arrays as sets.
+ *
+ * @author Christoph Strobl
+ * @since 1.10
+ */
+public class SetOperators {
+
+	/**
+	 * Take the array referenced by given {@literal fieldReference}.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return
+	 */
+	public static SetOperatorFactory arrayAsSet(String fieldReference) {
+		return new SetOperatorFactory(fieldReference);
+	}
+
+	/**
+	 * Take the array resulting from the given {@link AggregationExpression}.
+	 *
+	 * @param expression must not be {@literal null}.
+	 * @return
+	 */
+	public static SetOperatorFactory arrayAsSet(AggregationExpression expression) {
+		return new SetOperatorFactory(expression);
+	}
+
+	/**
+	 * @author Christoph Strobl
+	 */
+	public static class SetOperatorFactory {
+
+		private final String fieldReference;
+		private final AggregationExpression expression;
+
+		/**
+		 * Creates new {@link SetOperatorFactory} for given {@literal fieldReference}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 */
+		public SetOperatorFactory(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			this.fieldReference = fieldReference;
+			this.expression = null;
+		}
+
+		/**
+		 * Creates new {@link SetOperatorFactory} for given {@link AggregationExpression}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 */
+		public SetOperatorFactory(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			this.fieldReference = null;
+			this.expression = expression;
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares the previously mentioned field to one or more arrays and
+		 * returns {@literal true} if they have the same distinct elements and {@literal false} otherwise.
+		 *
+		 * @param arrayReferences must not be {@literal null}.
+		 * @return
+		 */
+		public SetEquals isEqualTo(String... arrayReferences) {
+			return createSetEquals().isEqualTo(arrayReferences);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that compares the previously mentioned field to one or more arrays and
+		 * returns {@literal true} if they have the same distinct elements and {@literal false} otherwise.
+		 *
+		 * @param expressions must not be {@literal null}.
+		 * @return
+		 */
+		public SetEquals isEqualTo(AggregationExpression... expressions) {
+			return createSetEquals().isEqualTo(expressions);
+		}
+
+		private SetEquals createSetEquals() {
+			return usesFieldRef() ? SetEquals.arrayAsSet(fieldReference) : SetEquals.arrayAsSet(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes array of the previously mentioned field and one or more
+		 * arrays and returns an array that contains the elements that appear in every of those.
+		 *
+		 * @param arrayReferences must not be {@literal null}.
+		 * @return
+		 */
+		public SetIntersection intersects(String... arrayReferences) {
+			return createSetIntersection().intersects(arrayReferences);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes array of the previously mentioned field and one or more
+		 * arrays and returns an array that contains the elements that appear in every of those.
+		 *
+		 * @param expressions must not be {@literal null}.
+		 * @return
+		 */
+		public SetIntersection intersects(AggregationExpression... expressions) {
+			return createSetIntersection().intersects(expressions);
+		}
+
+		private SetIntersection createSetIntersection() {
+			return usesFieldRef() ? SetIntersection.arrayAsSet(fieldReference) : SetIntersection.arrayAsSet(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes array of the previously mentioned field and one or more
+		 * arrays and returns an array that contains the elements that appear in any of those.
+		 *
+		 * @param arrayReferences must not be {@literal null}.
+		 * @return
+		 */
+		public SetUnion union(String... arrayReferences) {
+			return createSetUnion().union(arrayReferences);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes array of the previously mentioned field and one or more
+		 * arrays and returns an array that contains the elements that appear in any of those.
+		 *
+		 * @param expressions must not be {@literal null}.
+		 * @return
+		 */
+		public SetUnion union(AggregationExpression... expressions) {
+			return createSetUnion().union(expressions);
+		}
+
+		private SetUnion createSetUnion() {
+			return usesFieldRef() ? SetUnion.arrayAsSet(fieldReference) : SetUnion.arrayAsSet(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes array of the previously mentioned field and returns an array
+		 * containing the elements that do not exist in the given {@literal arrayReference}.
+		 *
+		 * @param arrayReference must not be {@literal null}.
+		 * @return
+		 */
+		public SetDifference differenceTo(String arrayReference) {
+			return createSetDifference().differenceTo(arrayReference);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes array of the previously mentioned field and returns an array
+		 * containing the elements that do not exist in the given {@link AggregationExpression}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public SetDifference differenceTo(AggregationExpression expression) {
+			return createSetDifference().differenceTo(expression);
+		}
+
+		private SetDifference createSetDifference() {
+			return usesFieldRef() ? SetDifference.arrayAsSet(fieldReference) : SetDifference.arrayAsSet(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes array of the previously mentioned field and returns
+		 * {@literal true} if it is a subset of the given {@literal arrayReference}.
+		 *
+		 * @param arrayReference must not be {@literal null}.
+		 * @return
+		 */
+		public SetIsSubset isSubsetOf(String arrayReference) {
+			return createSetIsSubset().isSubsetOf(arrayReference);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes array of the previously mentioned field and returns
+		 * {@literal true} if it is a subset of the given {@link AggregationExpression}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public SetIsSubset isSubsetOf(AggregationExpression expression) {
+			return createSetIsSubset().isSubsetOf(expression);
+		}
+
+		private SetIsSubset createSetIsSubset() {
+			return usesFieldRef() ? SetIsSubset.arrayAsSet(fieldReference) : SetIsSubset.arrayAsSet(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes array of the previously mentioned field and returns
+		 * {@literal true} if any of the elements are {@literal true} and {@literal false} otherwise.
+		 *
+		 * @return
+		 */
+		public AnyElementTrue anyElementTrue() {
+			return usesFieldRef() ? AnyElementTrue.arrayAsSet(fieldReference) : AnyElementTrue.arrayAsSet(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that tkes array of the previously mentioned field and returns
+		 * {@literal true} if no elements is {@literal false}.
+		 *
+		 * @return
+		 */
+		public AllElementsTrue allElementsTrue() {
+			return usesFieldRef() ? AllElementsTrue.arrayAsSet(fieldReference) : AllElementsTrue.arrayAsSet(expression);
+		}
+
+		private boolean usesFieldRef() {
+			return this.fieldReference != null;
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $setEquals}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class SetEquals extends AbstractAggregationExpression {
+
+		private SetEquals(List<?> arrays) {
+			super(arrays);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$setEquals";
+		}
+
+		/**
+		 * Create new {@link SetEquals}.
+		 *
+		 * @param arrayReference must not be {@literal null}.
+		 * @return
+		 */
+		public static SetEquals arrayAsSet(String arrayReference) {
+
+			Assert.notNull(arrayReference, "ArrayReference must not be null!");
+			return new SetEquals(asFields(arrayReference));
+		}
+
+		/**
+		 * Create new {@link SetEquals}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static SetEquals arrayAsSet(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new SetEquals(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link java.util.Set} with all previously added arguments appending the given one.
+		 *
+		 * @param arrayReferences must not be {@literal null}.
+		 * @return
+		 */
+		public SetEquals isEqualTo(String... arrayReferences) {
+
+			Assert.notNull(arrayReferences, "ArrayReferences must not be null!");
+			return new SetEquals(append(Fields.fields(arrayReferences).asList()));
+		}
+
+		/**
+		 * Creates new {@link Sum} with all previously added arguments appending the given one.
+		 *
+		 * @param expressions must not be {@literal null}.
+		 * @return
+		 */
+		public SetEquals isEqualTo(AggregationExpression... expressions) {
+
+			Assert.notNull(expressions, "Expressions must not be null!");
+			return new SetEquals(append(Arrays.asList(expressions)));
+		}
+
+		/**
+		 * Creates new {@link Sum} with all previously added arguments appending the given one.
+		 *
+		 * @param array must not be {@literal null}.
+		 * @return
+		 */
+		public SetEquals isEqualTo(Object[] array) {
+
+			Assert.notNull(array, "Array must not be null!");
+			return new SetEquals(append(array));
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $setIntersection}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class SetIntersection extends AbstractAggregationExpression {
+
+		private SetIntersection(List<?> arrays) {
+			super(arrays);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$setIntersection";
+		}
+
+		/**
+		 * Creates new {@link SetIntersection}
+		 *
+		 * @param arrayReference must not be {@literal null}.
+		 * @return
+		 */
+		public static SetIntersection arrayAsSet(String arrayReference) {
+
+			Assert.notNull(arrayReference, "ArrayReference must not be null!");
+			return new SetIntersection(asFields(arrayReference));
+		}
+
+		/**
+		 * Creates new {@link SetIntersection}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static SetIntersection arrayAsSet(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new SetIntersection(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link SetIntersection} with all previously added arguments appending the given one.
+		 *
+		 * @param arrayReferences must not be {@literal null}.
+		 * @return
+		 */
+		public SetIntersection intersects(String... arrayReferences) {
+
+			Assert.notNull(arrayReferences, "ArrayReferences must not be null!");
+			return new SetIntersection(append(asFields(arrayReferences)));
+		}
+
+		/**
+		 * Creates new {@link SetIntersection} with all previously added arguments appending the given one.
+		 *
+		 * @param expressions must not be {@literal null}.
+		 * @return
+		 */
+		public SetIntersection intersects(AggregationExpression... expressions) {
+
+			Assert.notNull(expressions, "Expressions must not be null!");
+			return new SetIntersection(append(Arrays.asList(expressions)));
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $setUnion}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class SetUnion extends AbstractAggregationExpression {
+
+		private SetUnion(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$setUnion";
+		}
+
+		/**
+		 * Creates new {@link SetUnion}.
+		 *
+		 * @param arrayReference must not be {@literal null}.
+		 * @return
+		 */
+		public static SetUnion arrayAsSet(String arrayReference) {
+
+			Assert.notNull(arrayReference, "ArrayReference must not be null!");
+			return new SetUnion(asFields(arrayReference));
+		}
+
+		/**
+		 * Creates new {@link SetUnion}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static SetUnion arrayAsSet(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new SetUnion(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link SetUnion} with all previously added arguments appending the given one.
+		 *
+		 * @param arrayReferences must not be {@literal null}.
+		 * @return
+		 */
+		public SetUnion union(String... arrayReferences) {
+
+			Assert.notNull(arrayReferences, "ArrayReferences must not be null!");
+			return new SetUnion(append(asFields(arrayReferences)));
+		}
+
+		/**
+		 * Creates new {@link SetUnion} with all previously added arguments appending the given one.
+		 *
+		 * @param expressions must not be {@literal null}.
+		 * @return
+		 */
+		public SetUnion union(AggregationExpression... expressions) {
+
+			Assert.notNull(expressions, "Expressions must not be null!");
+			return new SetUnion(append(Arrays.asList(expressions)));
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $setDifference}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class SetDifference extends AbstractAggregationExpression {
+
+		private SetDifference(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$setDifference";
+		}
+
+		/**
+		 * Creates new {@link SetDifference}.
+		 *
+		 * @param arrayReference must not be {@literal null}.
+		 * @return
+		 */
+		public static SetDifference arrayAsSet(String arrayReference) {
+
+			Assert.notNull(arrayReference, "ArrayReference must not be null!");
+			return new SetDifference(asFields(arrayReference));
+		}
+
+		/**
+		 * Creates new {@link SetDifference}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static SetDifference arrayAsSet(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new SetDifference(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link SetDifference} with all previously added arguments appending the given one.
+		 *
+		 * @param arrayReference must not be {@literal null}.
+		 * @return
+		 */
+		public SetDifference differenceTo(String arrayReference) {
+
+			Assert.notNull(arrayReference, "ArrayReference must not be null!");
+			return new SetDifference(append(Fields.field(arrayReference)));
+		}
+
+		/**
+		 * Creates new {@link SetDifference} with all previously added arguments appending the given one.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public SetDifference differenceTo(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new SetDifference(append(expression));
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $setIsSubset}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class SetIsSubset extends AbstractAggregationExpression {
+
+		private SetIsSubset(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$setIsSubset";
+		}
+
+		/**
+		 * Creates new {@link SetIsSubset}.
+		 *
+		 * @param arrayReference must not be {@literal null}.
+		 * @return
+		 */
+		public static SetIsSubset arrayAsSet(String arrayReference) {
+
+			Assert.notNull(arrayReference, "ArrayReference must not be null!");
+			return new SetIsSubset(asFields(arrayReference));
+		}
+
+		/**
+		 * Creates new {@link SetIsSubset}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static SetIsSubset arrayAsSet(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new SetIsSubset(Collections.singletonList(expression));
+		}
+
+		/**
+		 * Creates new {@link SetIsSubset} with all previously added arguments appending the given one.
+		 *
+		 * @param arrayReference must not be {@literal null}.
+		 * @return
+		 */
+		public SetIsSubset isSubsetOf(String arrayReference) {
+
+			Assert.notNull(arrayReference, "ArrayReference must not be null!");
+			return new SetIsSubset(append(Fields.field(arrayReference)));
+		}
+
+		/**
+		 * Creates new {@link SetIsSubset} with all previously added arguments appending the given one.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public SetIsSubset isSubsetOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new SetIsSubset(append(expression));
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $anyElementTrue}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class AnyElementTrue extends AbstractAggregationExpression {
+
+		private AnyElementTrue(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$anyElementTrue";
+		}
+
+		/**
+		 * Creates new {@link AnyElementTrue}.
+		 *
+		 * @param arrayReference must not be {@literal null}.
+		 * @return
+		 */
+		public static AnyElementTrue arrayAsSet(String arrayReference) {
+
+			Assert.notNull(arrayReference, "ArrayReference must not be null!");
+			return new AnyElementTrue(asFields(arrayReference));
+		}
+
+		/**
+		 * Creates new {@link AnyElementTrue}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static AnyElementTrue arrayAsSet(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new AnyElementTrue(Collections.singletonList(expression));
+		}
+
+		public AnyElementTrue anyElementTrue() {
+			return this;
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $allElementsTrue}.
+	 *
+	 * @author Christoph Strobl
+	 */
+	public static class AllElementsTrue extends AbstractAggregationExpression {
+
+		private AllElementsTrue(Object value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$allElementsTrue";
+		}
+
+		/**
+		 * Creates new {@link AllElementsTrue}.
+		 *
+		 * @param arrayReference must not be {@literal null}.
+		 * @return
+		 */
+		public static AllElementsTrue arrayAsSet(String arrayReference) {
+
+			Assert.notNull(arrayReference, "ArrayReference must not be null!");
+			return new AllElementsTrue(asFields(arrayReference));
+		}
+
+		/**
+		 * Creates new {@link AllElementsTrue}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return
+		 */
+		public static AllElementsTrue arrayAsSet(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new AllElementsTrue(Collections.singletonList(expression));
+		}
+
+		public AllElementsTrue allElementsTrue() {
+			return this;
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/SkipOperation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,11 +24,11 @@ import org.springframework.util.Assert;
  * We recommend to use the static factory method {@link Aggregation#skip(int)} instead of creating instances of this
  * class directly.
  * 
- * @see http://docs.mongodb.org/manual/reference/aggregation/skip/
  * @author Thomas Darimont
  * @author Oliver Gierke
  * @author Christoph Strobl
  * @since 1.3
+ * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/skip/">MongoDB Aggregation Framework: $skip</a>
  */
 public class SkipOperation implements AggregationOperation {
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/SortOperation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -27,12 +27,12 @@ import org.springframework.util.Assert;
  * <p>
  * We recommend to use the static factory method {@link Aggregation#sort(Direction, String...)} instead of creating
  * instances of this class directly.
- * 
- * @see http://docs.mongodb.org/manual/reference/aggregation/sort/#pipe._S_sort
+ *
  * @author Thomas Darimont
  * @author Oliver Gierke
  * @author Christoph Strobl
  * @since 1.3
+ * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/sort/">MongoDB Aggregation Framework: $sort</a>
  */
 public class SortOperation implements AggregationOperation {
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/SpelExpressionTransformer.java

@@ -26,24 +26,32 @@ import org.springframework.data.mongodb.core.spel.ExpressionNode;
 import org.springframework.data.mongodb.core.spel.ExpressionTransformationContextSupport;
 import org.springframework.data.mongodb.core.spel.LiteralNode;
 import org.springframework.data.mongodb.core.spel.MethodReferenceNode;
+import org.springframework.data.mongodb.core.spel.MethodReferenceNode.AggregationMethodReference;
+import org.springframework.data.mongodb.core.spel.MethodReferenceNode.AggregationMethodReference.ArgumentType;
+import org.springframework.data.mongodb.core.spel.NotOperatorNode;
 import org.springframework.data.mongodb.core.spel.OperatorNode;
 import org.springframework.expression.spel.ExpressionState;
 import org.springframework.expression.spel.SpelNode;
 import org.springframework.expression.spel.SpelParserConfiguration;
 import org.springframework.expression.spel.ast.CompoundExpression;
+import org.springframework.expression.spel.ast.ConstructorReference;
 import org.springframework.expression.spel.ast.Indexer;
 import org.springframework.expression.spel.ast.InlineList;
+import org.springframework.expression.spel.ast.InlineMap;
+import org.springframework.expression.spel.ast.OperatorNot;
 import org.springframework.expression.spel.ast.PropertyOrFieldReference;
 import org.springframework.expression.spel.standard.SpelExpression;
 import org.springframework.expression.spel.standard.SpelExpressionParser;
 import org.springframework.expression.spel.support.StandardEvaluationContext;
 import org.springframework.util.Assert;
 import org.springframework.util.NumberUtils;
+import org.springframework.util.ObjectUtils;
 
 /**
  * Renders the AST of a SpEL expression as a MongoDB Aggregation Framework projection expression.
  * 
  * @author Thomas Darimont
+ * @author Christoph Strobl
  */
 class SpelExpressionTransformer implements AggregationExpressionTransformer {
 
@@ -65,6 +73,8 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 		conversions.add(new PropertyOrFieldReferenceNodeConversion(this));
 		conversions.add(new CompoundExpressionNodeConversion(this));
 		conversions.add(new MethodReferenceNodeConversion(this));
+		conversions.add(new NotOperatorNodeConversion(this));
+		conversions.add(new ValueRetrievingNodeConversion(this));
 
 		this.conversions = Collections.unmodifiableList(conversions);
 	}
@@ -231,8 +241,17 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 		protected Object convert(AggregationExpressionTransformationContext<OperatorNode> context) {
 
 			OperatorNode currentNode = context.getCurrentNode();
-
 			Document operationObject = createOperationObjectAndAddToPreviousArgumentsIfNecessary(context, currentNode);
+
+			if (currentNode.isLogicalOperator()) {
+
+				for (ExpressionNode expressionNode : currentNode) {
+					transform(expressionNode, currentNode, operationObject, context);
+				}
+
+				return operationObject;
+			}
+
 			Object leftResult = transform(currentNode.getLeft(), currentNode, operationObject, context);
 
 			if (currentNode.isUnaryMinus()) {
@@ -286,7 +305,7 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 		 */
 		@Override
 		protected boolean supports(ExpressionNode node) {
-			return node.isMathematicalOperation();
+			return node.isMathematicalOperation() || node.isLogicalOperator();
 		}
 	}
 
@@ -459,13 +478,33 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 		protected Object convert(AggregationExpressionTransformationContext<MethodReferenceNode> context) {
 
 			MethodReferenceNode node = context.getCurrentNode();
-			List<Object> args = new ArrayList<Object>();
+			AggregationMethodReference methodReference = node.getMethodReference();
 
-			for (ExpressionNode childNode : node) {
-				args.add(transform(childNode, context));
+			Object args = null;
+
+			if (ObjectUtils.nullSafeEquals(methodReference.getArgumentType(), ArgumentType.SINGLE)) {
+				args = transform(node.getChild(0), context);
+			} else if (ObjectUtils.nullSafeEquals(methodReference.getArgumentType(), ArgumentType.MAP)) {
+
+				Document dbo = new Document();
+
+				int i = 0;
+				for(ExpressionNode child : node) {
+					dbo.put(methodReference.getArgumentMap()[i++], transform(child, context));
+				}
+				args = dbo;
+			} else {
+
+				List<Object> argList = new ArrayList<Object>();
+
+				for (ExpressionNode childNode : node) {
+					argList.add(transform(childNode, context));
+				}
+
+				args = argList;
 			}
 
-			return context.addToPreviousOrReturn(new Document(node.getMethodName(), args));
+			return context.addToPreviousOrReturn(new Document(methodReference.getMongoOperator(), args));
 		}
 	}
 
@@ -507,4 +546,83 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 			return node.isOfType(CompoundExpression.class);
 		}
 	}
+
+	/**
+	 * @author Christoph Strobl
+	 * @since 1.10
+	 */
+	static class NotOperatorNodeConversion extends ExpressionNodeConversion<NotOperatorNode> {
+
+		/**
+		 * Creates a new {@link ExpressionNodeConversion}.
+		 *
+		 * @param transformer must not be {@literal null}.
+		 */
+		public NotOperatorNodeConversion(AggregationExpressionTransformer transformer) {
+			super(transformer);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.SpelExpressionTransformer.SpelNodeWrapper#convertSpelNodeToMongoObjectExpression(org.springframework.data.mongodb.core.aggregation.SpelExpressionTransformer.ExpressionConversionContext)
+		 */
+		@Override
+		protected Object convert(AggregationExpressionTransformationContext<NotOperatorNode> context) {
+
+			NotOperatorNode node = context.getCurrentNode();
+			List<Object> args = new ArrayList<Object>();
+
+			for (ExpressionNode childNode : node) {
+				args.add(transform(childNode, context));
+			}
+
+			return context.addToPreviousOrReturn(new Document(node.getMongoOperator(), args));
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.SpelExpressionTransformer.NodeConversion#supports(org.springframework.data.mongodb.core.spel.ExpressionNode)
+		 */
+		@Override
+		protected boolean supports(ExpressionNode node) {
+			return node.isOfType(OperatorNot.class);
+		}
+	}
+
+	/**
+	 * @author Christoph Strobl
+	 * @since 1.10
+	 */
+	static class ValueRetrievingNodeConversion extends ExpressionNodeConversion<ExpressionNode> {
+
+		/**
+		 * Creates a new {@link ExpressionNodeConversion}.
+		 *
+		 * @param transformer must not be {@literal null}.
+		 */
+		public ValueRetrievingNodeConversion(AggregationExpressionTransformer transformer) {
+			super(transformer);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.SpelExpressionTransformer.SpelNodeWrapper#convertSpelNodeToMongoObjectExpression(org.springframework.data.mongodb.core.aggregation.SpelExpressionTransformer.ExpressionConversionContext)
+		 */
+		@Override
+		protected Object convert(AggregationExpressionTransformationContext<ExpressionNode> context) {
+
+			Object value = context.getCurrentNode().getValue();
+			return ObjectUtils.isArray(value) ? Arrays.asList(ObjectUtils.toObjectArray(value)) : value;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.SpelExpressionTransformer.NodeConversion#supports(org.springframework.data.mongodb.core.spel.ExpressionNode)
+		 */
+		@Override
+		protected boolean supports(ExpressionNode node) {
+			return node.isOfType(InlineMap.class) || node.isOfType(InlineList.class)
+					|| node.isOfType(ConstructorReference.class);
+		}
+	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/TypeBasedAggregationOperationContext.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,6 +23,7 @@ import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.mapping.context.PersistentPropertyPath;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.DirectFieldReference;
 import org.springframework.data.mongodb.core.convert.QueryMapper;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
@@ -34,6 +35,7 @@ import org.springframework.util.Assert;
  * 
  * @author Oliver Gierke
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @since 1.3
  */
 public class TypeBasedAggregationOperationContext implements AggregationOperationContext {
@@ -64,7 +66,7 @@ public class TypeBasedAggregationOperationContext implements AggregationOperatio
 
 	/* 
 	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getMappedObject(com.mongodb.Document)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getMappedObject(org.bson.Document)
 	 */
 	@Override
 	public Document getMappedObject(Document document) {
@@ -93,11 +95,11 @@ public class TypeBasedAggregationOperationContext implements AggregationOperatio
 
 	private FieldReference getReferenceFor(Field field) {
 
-		PersistentPropertyPath<MongoPersistentProperty> propertyPath = mappingContext
-				.getPersistentPropertyPath(field.getTarget(), type);
-		Field mappedField = field(propertyPath.getLeafProperty().getName(),
+		PersistentPropertyPath<MongoPersistentProperty> propertyPath = mappingContext.getPersistentPropertyPath(
+				field.getTarget(), type);
+		Field mappedField = field(field.getName(),
 				propertyPath.toDotPath(MongoPersistentProperty.PropertyToFieldNameConverter.INSTANCE));
 
-		return new FieldReference(new ExposedField(mappedField, true));
+		return new DirectFieldReference(new ExposedField(mappedField, true));
 	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/UnwindOperation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,12 +25,12 @@ import org.springframework.util.Assert;
  * We recommend to use the static factory method {@link Aggregation#unwind(String)} instead of creating instances of
  * this class directly.
  * 
- * @see http://docs.mongodb.org/manual/reference/aggregation/unwind/#pipe._S_unwind
  * @author Thomas Darimont
  * @author Oliver Gierke
  * @author Mark Paluch
  * @author Christoph Strobl
  * @since 1.3
+ * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/unwind/">MongoDB Aggregation Framework: $unwind</a>
  */
 public class UnwindOperation
 		implements AggregationOperation, FieldsExposingAggregationOperation.InheritsFieldsAggregationOperation {

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/VariableOperators.java

@@ -0,0 +1,389 @@
+/*
+ * Copyright 2016. the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+
+import org.bson.Document;
+import org.springframework.data.mongodb.core.aggregation.VariableOperators.Let.ExpressionVariable;
+import org.springframework.util.Assert;
+
+/**
+ * Gateway to {@literal variable} aggregation operations.
+ *
+ * @author Christoph Strobl
+ * @author Mark Paluch
+ * @since 1.10
+ */
+public class VariableOperators {
+
+	/**
+	 * Starts building new {@link Map} that applies an {@link AggregationExpression} to each item of a referenced array
+	 * and returns an array with the applied results.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return
+	 */
+	public static Map.AsBuilder mapItemsOf(String fieldReference) {
+		return Map.itemsOf(fieldReference);
+	}
+
+	/**
+	 * Starts building new {@link Map} that applies an {@link AggregationExpression} to each item of a referenced array
+	 * and returns an array with the applied results.
+	 *
+	 * @param expression must not be {@literal null}.
+	 * @return
+	 */
+	public static Map.AsBuilder mapItemsOf(AggregationExpression expression) {
+		return Map.itemsOf(expression);
+	}
+
+	/**
+	 * Start creating new {@link Let} that allows definition of {@link ExpressionVariable} that can be used within a
+	 * nested {@link AggregationExpression}.
+	 *
+	 * @param variables must not be {@literal null}.
+	 * @return
+	 */
+	public static Let.LetBuilder define(ExpressionVariable... variables) {
+		return Let.define(variables);
+	}
+
+	/**
+	 * Start creating new {@link Let} that allows definition of {@link ExpressionVariable} that can be used within a
+	 * nested {@link AggregationExpression}.
+	 *
+	 * @param variables must not be {@literal null}.
+	 * @return
+	 */
+	public static Let.LetBuilder define(Collection<ExpressionVariable> variables) {
+		return Let.define(variables);
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $map}.
+	 */
+	public static class Map implements AggregationExpression {
+
+		private Object sourceArray;
+		private String itemVariableName;
+		private AggregationExpression functionToApply;
+
+		private Map(Object sourceArray, String itemVariableName, AggregationExpression functionToApply) {
+
+			Assert.notNull(sourceArray, "SourceArray must not be null!");
+			Assert.notNull(itemVariableName, "ItemVariableName must not be null!");
+			Assert.notNull(functionToApply, "FunctionToApply must not be null!");
+
+			this.sourceArray = sourceArray;
+			this.itemVariableName = itemVariableName;
+			this.functionToApply = functionToApply;
+		}
+
+		/**
+		 * Starts building new {@link Map} that applies an {@link AggregationExpression} to each item of a referenced array
+		 * and returns an array with the applied results.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return
+		 */
+		public static AsBuilder itemsOf(final String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+
+			return new AsBuilder() {
+
+				@Override
+				public FunctionBuilder as(final String variableName) {
+
+					Assert.notNull(variableName, "VariableName must not be null!");
+
+					return new FunctionBuilder() {
+
+						@Override
+						public Map andApply(final AggregationExpression expression) {
+
+							Assert.notNull(expression, "AggregationExpression must not be null!");
+							return new Map(Fields.field(fieldReference), variableName, expression);
+						}
+					};
+				}
+
+			};
+		}
+
+		/**
+		 * Starts building new {@link Map} that applies an {@link AggregationExpression} to each item of a referenced array
+		 * and returns an array with the applied results.
+		 *
+		 * @param source must not be {@literal null}.
+		 * @return
+		 */
+		public static AsBuilder itemsOf(final AggregationExpression source) {
+
+			Assert.notNull(source, "AggregationExpression must not be null!");
+
+			return new AsBuilder() {
+
+				@Override
+				public FunctionBuilder as(final String variableName) {
+
+					Assert.notNull(variableName, "VariableName must not be null!");
+
+					return new FunctionBuilder() {
+
+						@Override
+						public Map andApply(final AggregationExpression expression) {
+
+							Assert.notNull(expression, "AggregationExpression must not be null!");
+							return new Map(source, variableName, expression);
+						}
+					};
+				}
+			};
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AggregationExpression#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocument(final AggregationOperationContext context) {
+			return toMap(ExposedFields.synthetic(Fields.fields(itemVariableName)), context);
+		}
+
+		private Document toMap(ExposedFields exposedFields, AggregationOperationContext context) {
+
+			Document map = new Document();
+			InheritingExposedFieldsAggregationOperationContext operationContext = new InheritingExposedFieldsAggregationOperationContext(
+					exposedFields, context);
+
+			Document input;
+			if (sourceArray instanceof Field) {
+				input = new Document("input", context.getReference((Field) sourceArray).toString());
+			} else {
+				input = new Document("input", ((AggregationExpression) sourceArray).toDocument(context));
+			}
+
+			map.putAll(context.getMappedObject(input));
+			map.put("as", itemVariableName);
+			map.put("in",
+					functionToApply.toDocument(new NestedDelegatingExpressionAggregationOperationContext(operationContext)));
+
+			return new Document("$map", map);
+		}
+
+		public interface AsBuilder {
+
+			/**
+			 * Define the {@literal variableName} for addressing items within the array.
+			 *
+			 * @param variableName must not be {@literal null}.
+			 * @return
+			 */
+			FunctionBuilder as(String variableName);
+		}
+
+		public interface FunctionBuilder {
+
+			/**
+			 * Creates new {@link Map} that applies the given {@link AggregationExpression} to each item of the referenced
+			 * array and returns an array with the applied results.
+			 *
+			 * @param expression must not be {@literal null}.
+			 * @return
+			 */
+			Map andApply(AggregationExpression expression);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $let} that binds {@link AggregationExpression} to variables for use in the
+	 * specified {@code in} expression, and returns the result of the expression.
+	 *
+	 * @author Christoph Strobl
+	 * @since 1.10
+	 */
+	public static class Let implements AggregationExpression {
+
+		private final List<ExpressionVariable> vars;
+		private final AggregationExpression expression;
+
+		private Let(List<ExpressionVariable> vars, AggregationExpression expression) {
+
+			this.vars = vars;
+			this.expression = expression;
+		}
+
+		/**
+		 * Start creating new {@link Let} by defining the variables for {@code $vars}.
+		 *
+		 * @param variables must not be {@literal null}.
+		 * @return
+		 */
+		public static LetBuilder define(final Collection<ExpressionVariable> variables) {
+
+			Assert.notNull(variables, "Variables must not be null!");
+
+			return new LetBuilder() {
+
+				@Override
+				public Let andApply(final AggregationExpression expression) {
+
+					Assert.notNull(expression, "Expression must not be null!");
+					return new Let(new ArrayList<ExpressionVariable>(variables), expression);
+				}
+			};
+		}
+
+		/**
+		 * Start creating new {@link Let} by defining the variables for {@code $vars}.
+		 *
+		 * @param variables must not be {@literal null}.
+		 * @return
+		 */
+		public static LetBuilder define(final ExpressionVariable... variables) {
+
+			Assert.notNull(variables, "Variables must not be null!");
+
+			return new LetBuilder() {
+
+				@Override
+				public Let andApply(final AggregationExpression expression) {
+
+					Assert.notNull(expression, "Expression must not be null!");
+					return new Let(Arrays.asList(variables), expression);
+				}
+			};
+		}
+
+		public interface LetBuilder {
+
+			/**
+			 * Define the {@link AggregationExpression} to evaluate.
+			 *
+			 * @param expression must not be {@literal null}.
+			 * @return
+			 */
+			Let andApply(AggregationExpression expression);
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AggregationExpression#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocument(final AggregationOperationContext context) {
+			return toLet(ExposedFields.synthetic(Fields.fields(getVariableNames())), context);
+		}
+
+		private String[] getVariableNames() {
+
+			String[] varNames = new String[this.vars.size()];
+			for (int i = 0; i < this.vars.size(); i++) {
+				varNames[i] = this.vars.get(i).variableName;
+			}
+
+			return varNames;
+		}
+
+		private Document toLet(ExposedFields exposedFields, AggregationOperationContext context) {
+
+			Document letExpression = new Document();
+			Document mappedVars = new Document();
+			InheritingExposedFieldsAggregationOperationContext operationContext = new InheritingExposedFieldsAggregationOperationContext(
+					exposedFields, context);
+
+			for (ExpressionVariable var : this.vars) {
+				mappedVars.putAll(getMappedVariable(var, context));
+			}
+
+			letExpression.put("vars", mappedVars);
+			letExpression.put("in", getMappedIn(operationContext));
+
+			return new Document("$let", letExpression);
+		}
+
+		private Document getMappedVariable(ExpressionVariable var, AggregationOperationContext context) {
+
+			return new Document(var.variableName, var.expression instanceof AggregationExpression
+					? ((AggregationExpression) var.expression).toDocument(context) : var.expression);
+		}
+
+		private Object getMappedIn(AggregationOperationContext context) {
+			return expression.toDocument(new NestedDelegatingExpressionAggregationOperationContext(context));
+		}
+
+		/**
+		 * @author Christoph Strobl
+		 */
+		public static class ExpressionVariable {
+
+			private final String variableName;
+			private final Object expression;
+
+			/**
+			 * Creates new {@link ExpressionVariable}.
+			 *
+			 * @param variableName can be {@literal null}.
+			 * @param expression can be {@literal null}.
+			 */
+			private ExpressionVariable(String variableName, Object expression) {
+
+				this.variableName = variableName;
+				this.expression = expression;
+			}
+
+			/**
+			 * Create a new {@link ExpressionVariable} with given name.
+			 *
+			 * @param variableName must not be {@literal null}.
+			 * @return never {@literal null}.
+			 */
+			public static ExpressionVariable newVariable(String variableName) {
+
+				Assert.notNull(variableName, "VariableName must not be null!");
+				return new ExpressionVariable(variableName, null);
+			}
+
+			/**
+			 * Create a new {@link ExpressionVariable} with current name and given {@literal expression}.
+			 *
+			 * @param expression must not be {@literal null}.
+			 * @return never {@literal null}.
+			 */
+			public ExpressionVariable forExpression(AggregationExpression expression) {
+
+				Assert.notNull(expression, "Expression must not be null!");
+				return new ExpressionVariable(variableName, expression);
+			}
+
+			/**
+			 * Create a new {@link ExpressionVariable} with current name and given {@literal expressionObject}.
+			 *
+			 * @param expressionObject must not be {@literal null}.
+			 * @return never {@literal null}.
+			 */
+			public ExpressionVariable forExpression(Document expressionObject) {
+
+				Assert.notNull(expressionObject, "Expression must not be null!");
+				return new ExpressionVariable(variableName, expressionObject);
+			}
+		}
+	}
+}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/ConverterRegistration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,6 +23,7 @@ import org.springframework.util.Assert;
  * Conversion registration information.
  * 
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 class ConverterRegistration {
 
@@ -39,7 +40,7 @@ class ConverterRegistration {
 	 */
 	public ConverterRegistration(ConvertiblePair convertiblePair, boolean isReading, boolean isWriting) {
 
-		Assert.notNull(convertiblePair);
+		Assert.notNull(convertiblePair, "ConvertiblePair must not be null!");
 
 		this.convertiblePair = convertiblePair;
 		this.reading = isReading;

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/CustomConversions.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2016 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,6 +24,7 @@ import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 
@@ -43,7 +44,6 @@ import org.springframework.data.convert.ThreeTenBackPortConverters;
 import org.springframework.data.convert.WritingConverter;
 import org.springframework.data.mapping.model.SimpleTypeHolder;
 import org.springframework.data.mongodb.core.mapping.MongoSimpleTypes;
-import org.springframework.data.util.CacheValue;
 import org.springframework.util.Assert;
 
 /**
@@ -56,6 +56,7 @@ import org.springframework.util.Assert;
  * @author Oliver Gierke
  * @author Thomas Darimont
  * @author Christoph Strobl
+ * @author Mark Paluch
  */
 public class CustomConversions {
 
@@ -70,9 +71,9 @@ public class CustomConversions {
 
 	private final List<Object> converters;
 
-	private final Map<ConvertiblePair, CacheValue<Class<?>>> customReadTargetTypes;
-	private final Map<ConvertiblePair, CacheValue<Class<?>>> customWriteTargetTypes;
-	private final Map<Class<?>, CacheValue<Class<?>>> rawWriteTargetTypes;
+	private final Map<ConvertiblePair, Optional<Class<?>>> customReadTargetTypes;
+	private final Map<ConvertiblePair, Optional<Class<?>>> customWriteTargetTypes;
+	private final Map<Class<?>, Optional<Class<?>>> rawWriteTargetTypes;
 
 	/**
 	 * Creates an empty {@link CustomConversions} object.
@@ -88,14 +89,14 @@ public class CustomConversions {
 	 */
 	public CustomConversions(List<?> converters) {
 
-		Assert.notNull(converters);
+		Assert.notNull(converters, "List of converters must not be null!");
 
-		this.readingPairs = new LinkedHashSet<ConvertiblePair>();
-		this.writingPairs = new LinkedHashSet<ConvertiblePair>();
-		this.customSimpleTypes = new HashSet<Class<?>>();
-		this.customReadTargetTypes = new ConcurrentHashMap<ConvertiblePair, CacheValue<Class<?>>>();
-		this.customWriteTargetTypes = new ConcurrentHashMap<ConvertiblePair, CacheValue<Class<?>>>();
-		this.rawWriteTargetTypes = new ConcurrentHashMap<Class<?>, CacheValue<Class<?>>>();
+		this.readingPairs = new LinkedHashSet<>();
+		this.writingPairs = new LinkedHashSet<>();
+		this.customSimpleTypes = new HashSet<>();
+		this.customReadTargetTypes = new ConcurrentHashMap<>();
+		this.customWriteTargetTypes = new ConcurrentHashMap<>();
+		this.rawWriteTargetTypes = new ConcurrentHashMap<>();
 
 		List<Object> toRegister = new ArrayList<Object>();
 
@@ -240,13 +241,8 @@ public class CustomConversions {
 	 */
 	public Class<?> getCustomWriteTarget(final Class<?> sourceType) {
 
-		return getOrCreateAndCache(sourceType, rawWriteTargetTypes, new Producer() {
-
-			@Override
-			public Class<?> get() {
-				return getCustomTarget(sourceType, null, writingPairs);
-			}
-		});
+		return rawWriteTargetTypes.computeIfAbsent(sourceType, it -> getCustomTarget(sourceType, null, writingPairs))
+				.orElse(null);
 	}
 
 	/**
@@ -264,14 +260,8 @@ public class CustomConversions {
 			return getCustomWriteTarget(sourceType);
 		}
 
-		return getOrCreateAndCache(new ConvertiblePair(sourceType, requestedTargetType), customWriteTargetTypes,
-				new Producer() {
-
-					@Override
-					public Class<?> get() {
-						return getCustomTarget(sourceType, requestedTargetType, writingPairs);
-					}
-				});
+		return customWriteTargetTypes.computeIfAbsent(new ConvertiblePair(sourceType, requestedTargetType),
+				it -> getCustomTarget(sourceType, requestedTargetType, writingPairs)).orElse(null);
 	}
 
 	/**
@@ -323,14 +313,8 @@ public class CustomConversions {
 			return null;
 		}
 
-		return getOrCreateAndCache(new ConvertiblePair(sourceType, requestedTargetType), customReadTargetTypes,
-				new Producer() {
-
-					@Override
-					public Class<?> get() {
-						return getCustomTarget(sourceType, requestedTargetType, readingPairs);
-					}
-				});
+		return customReadTargetTypes.computeIfAbsent(new ConvertiblePair(sourceType, requestedTargetType),
+				it -> getCustomTarget(sourceType, requestedTargetType, readingPairs)).orElse(null);
 	}
 
 	/**
@@ -342,54 +326,26 @@ public class CustomConversions {
 	 * @param pairs must not be {@literal null}.
 	 * @return
 	 */
-	private static Class<?> getCustomTarget(Class<?> sourceType, Class<?> requestedTargetType,
+	private static Optional<Class<?>> getCustomTarget(Class<?> sourceType, Class<?> requestedTargetType,
 			Collection<ConvertiblePair> pairs) {
 
-		Assert.notNull(sourceType);
-		Assert.notNull(pairs);
+		Assert.notNull(sourceType, "Source Class must not be null!");
+		Assert.notNull(pairs, "Collection of ConvertiblePair must not be null!");
 
 		if (requestedTargetType != null && pairs.contains(new ConvertiblePair(sourceType, requestedTargetType))) {
-			return requestedTargetType;
+			return Optional.of(requestedTargetType);
 		}
 
 		for (ConvertiblePair typePair : pairs) {
 			if (typePair.getSourceType().isAssignableFrom(sourceType)) {
 				Class<?> targetType = typePair.getTargetType();
 				if (requestedTargetType == null || targetType.isAssignableFrom(requestedTargetType)) {
-					return targetType;
+					return Optional.of(targetType);
 				}
 			}
 		}
 
-		return null;
-	}
-
-	/**
-	 * Will try to find a value for the given key in the given cache or produce one using the given {@link Producer} and
-	 * store it in the cache.
-	 * 
-	 * @param key the key to lookup a potentially existing value, must not be {@literal null}.
-	 * @param cache the cache to find the value in, must not be {@literal null}.
-	 * @param producer the {@link Producer} to create values to cache, must not be {@literal null}.
-	 * @return
-	 */
-	private static <T> Class<?> getOrCreateAndCache(T key, Map<T, CacheValue<Class<?>>> cache, Producer producer) {
-
-		CacheValue<Class<?>> cacheValue = cache.get(key);
-
-		if (cacheValue != null) {
-			return cacheValue.getValue();
-		}
-
-		Class<?> type = producer.get();
-		cache.put(key, CacheValue.<Class<?>> ofNullable(type));
-
-		return type;
-	}
-
-	private interface Producer {
-
-		Class<?> get();
+		return Optional.empty();
 	}
 
 	@WritingConverter

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/DbRefResolver.java

@@ -17,6 +17,7 @@ package org.springframework.data.mongodb.core.convert;
 
 import org.bson.Document;
 import java.util.List;
+import java.util.Optional;
 
 import org.springframework.dao.InvalidDataAccessApiUsageException;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
@@ -45,7 +46,7 @@ public interface DbRefResolver {
 	 * @param callback will never be {@literal null}.
 	 * @return
 	 */
-	Object resolveDbRef(MongoPersistentProperty property, DBRef dbref, DbRefResolverCallback callback,
+	Optional<Object> resolveDbRef(MongoPersistentProperty property, DBRef dbref, DbRefResolverCallback callback,
 			DbRefProxyHandler proxyHandler);
 
 	/**

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/DefaultDbRefProxyHandler.java

@@ -61,8 +61,9 @@ class DefaultDbRefProxyHandler implements DbRefProxyHandler {
 			return proxy;
 		}
 
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(property);
-		MongoPersistentProperty idProperty = entity.getIdProperty();
+		MongoPersistentEntity<?> entity = mappingContext.getRequiredPersistentEntity(property);
+		MongoPersistentProperty idProperty = entity.getIdProperty()
+				.orElseThrow(() -> new IllegalStateException("Couldn't find identifier property!"));
 
 		if (idProperty.usePropertyAccess()) {
 			return proxy;

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/DefaultDbRefResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,6 +26,7 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
+import java.util.Optional;
 
 import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
@@ -45,9 +46,11 @@ import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
 import org.springframework.objenesis.ObjenesisStd;
 import org.springframework.util.Assert;
 import org.springframework.util.ReflectionUtils;
+import org.springframework.util.StringUtils;
 
 import com.mongodb.DBRef;
 import com.mongodb.client.MongoDatabase;
+import com.mongodb.client.model.Filters;
 
 /**
  * A {@link DbRefResolver} that resolves {@link org.springframework.data.mongodb.core.mapping.DBRef}s by delegating to a
@@ -84,17 +87,17 @@ public class DefaultDbRefResolver implements DbRefResolver {
 	 * @see org.springframework.data.mongodb.core.convert.DbRefResolver#resolveDbRef(org.springframework.data.mongodb.core.mapping.MongoPersistentProperty, org.springframework.data.mongodb.core.convert.DbRefResolverCallback)
 	 */
 	@Override
-	public Object resolveDbRef(MongoPersistentProperty property, DBRef dbref, DbRefResolverCallback callback,
+	public Optional<Object> resolveDbRef(MongoPersistentProperty property, DBRef dbref, DbRefResolverCallback callback,
 			DbRefProxyHandler handler) {
 
 		Assert.notNull(property, "Property must not be null!");
 		Assert.notNull(callback, "Callback must not be null!");
 
 		if (isLazyDbRef(property)) {
-			return createLazyLoadingProxy(property, dbref, callback, handler);
+			return Optional.of(createLazyLoadingProxy(property, dbref, callback, handler));
 		}
 
-		return callback.resolve(property);
+		return Optional.ofNullable(callback.resolve(property));
 	}
 
 	/* 
@@ -104,6 +107,11 @@ public class DefaultDbRefResolver implements DbRefResolver {
 	@Override
 	public DBRef createDbRef(org.springframework.data.mongodb.core.mapping.DBRef annotation,
 			MongoPersistentEntity<?> entity, Object id) {
+
+		if (annotation != null && StringUtils.hasText(annotation.db())) {
+			return new DBRef(annotation.db(), entity.getCollection(), id);
+		}
+
 		return new DBRef(entity.getCollection(), id);
 	}
 
@@ -113,7 +121,11 @@ public class DefaultDbRefResolver implements DbRefResolver {
 	 */
 	@Override
 	public Document fetch(DBRef dbRef) {
-		return ReflectiveDBRefResolver.fetch(mongoDbFactory, dbRef);
+
+		StringUtils.hasText(dbRef.getDatabaseName());
+		return (StringUtils.hasText(dbRef.getDatabaseName()) ? mongoDbFactory.getDb(dbRef.getDatabaseName())
+				: mongoDbFactory.getDb()).getCollection(dbRef.getCollectionName(), Document.class)
+						.find(Filters.eq("_id", dbRef.getId())).first();
 	}
 
 	/*
@@ -146,7 +158,7 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		MongoDatabase db = mongoDbFactory.getDb();
 		List<Document> result = new ArrayList<>();
 		db.getCollection(collection).find(new Document("_id", new Document("$in", ids))).into(result);
-		Collections.sort(result, new DbRefByReferencePositionComparator(ids));
+		result.sort(new DbRefByReferencePositionComparator(ids));
 		return result;
 	}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/DefaultDbRefResolverCallback.java

@@ -57,6 +57,6 @@ class DefaultDbRefResolverCallback implements DbRefResolverCallback {
 	 */
 	@Override
 	public Object resolve(MongoPersistentProperty property) {
-		return resolver.getValueInternal(property, surroundingObject, evaluator, path);
+		return resolver.getValueInternal(property, surroundingObject, evaluator, path).orElse(null);
 	}
 }