DATAMONGO-1775 - Release version 1.10.8 (Ingalls SR8).

Update JavaDoc, enforce nullability constraints and add tests.

Original Pull Request: #501

.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

@@ -15,6 +15,7 @@ env:
     - PROFILE=mongo31
     - PROFILE=mongo32
     - PROFILE=mongo33
+    - PROFILE=mongo34
     - PROFILE=mongo34-next
 
 # Current MongoDB version is 2.4.2 as of 2016-04, see https://github.com/travis-ci/travis-ci/issues/3694
@@ -22,10 +23,13 @@ env:
 addons:
   apt:
     sources:
-    - mongodb-3.2-precise
+      - mongodb-upstart
+      - sourceline: 'deb [arch=amd64] http://repo.mongodb.org/apt/ubuntu precise/mongodb-org/3.4 multiverse'
+        key_url: 'https://www.mongodb.org/static/pgp/server-3.4.asc'
     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.

lombok.config

@@ -0,0 +1,2 @@
+lombok.nonNull.exceptionType = IllegalArgumentException
+lombok.log.fieldName = LOG

pom.xml

@@ -5,7 +5,7 @@
 
 	<groupId>org.springframework.data</groupId>
 	<artifactId>spring-data-mongodb-parent</artifactId>
-	<version>1.10.0.BUILD-SNAPSHOT</version>
+	<version>1.10.8.RELEASE</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>1.9.0.BUILD-SNAPSHOT</version>
+		<version>1.9.8.RELEASE</version>
 	</parent>
 
 	<modules>
@@ -28,9 +28,10 @@
 	<properties>
 		<project.type>multi</project.type>
 		<dist.id>spring-data-mongodb</dist.id>
-		<springdata.commons>1.13.0.BUILD-SNAPSHOT</springdata.commons>
+		<springdata.commons>1.13.8.RELEASE</springdata.commons>
 		<mongo>2.14.3</mongo>
 		<mongo.osgi>2.13.0</mongo.osgi>
+		<jmh.version>1.19</jmh.version>
 	</properties>
 
 	<developers>
@@ -178,11 +179,20 @@
 
 		</profile>
 
+		<profile>
+
+			<id>mongo34</id>
+			<properties>
+				<mongo>3.4.0</mongo>
+			</properties>
+
+		</profile>
+
 		<profile>
 
 			<id>mongo34-next</id>
 			<properties>
-				<mongo>3.4.0-SNAPSHOT</mongo>
+				<mongo>3.4.1-SNAPSHOT</mongo>
 			</properties>
 
 			<repositories>
@@ -207,6 +217,17 @@
 			</build>
 		</profile>
 
+		<profile>
+			<id>benchmarks</id>
+			<modules>
+				<module>spring-data-mongodb</module>
+				<module>spring-data-mongodb-cross-store</module>
+				<module>spring-data-mongodb-log4j</module>
+				<module>spring-data-mongodb-distribution</module>
+				<module>spring-data-mongodb-benchmarks</module>
+			</modules>
+		</profile>
+
 	</profiles>
 
 	<dependencies>
@@ -220,8 +241,8 @@
 
 	<repositories>
 		<repository>
-			<id>spring-libs-snapshot</id>
-			<url>https://repo.spring.io/libs-snapshot</url>
+			<id>spring-libs-release</id>
+			<url>https://repo.spring.io/libs-release</url>
 		</repository>
 	</repositories>
 

spring-data-mongodb-benchmarks/README.md

@@ -0,0 +1,76 @@
+# Benchmarks
+
+Benchmarks are based on [JMH](http://openjdk.java.net/projects/code-tools/jmh/).
+
+# Running Benchmarks
+
+Running benchmarks is disabled by default and can be activated via the `benchmarks` profile.
+To run the benchmarks with default settings use.
+
+```bash
+mvn -P benchmarks clean test
+```
+
+A basic report will be printed to the CLI.
+
+```bash
+# Run complete. Total time: 00:00:15
+
+Benchmark                                    Mode  Cnt        Score       Error  Units
+MappingMongoConverterBenchmark.readObject   thrpt   10  1920157,631 ± 64310,809  ops/s
+MappingMongoConverterBenchmark.writeObject  thrpt   10   782732,857 ± 53804,130  ops/s
+```
+
+## Running all Benchmarks of a specific class
+
+To run all Benchmarks of a specific class, just provide its simple class name via the `benchmark` command line argument.
+
+```bash
+mvn -P benchmarks clean test -D benchmark=MappingMongoConverterBenchmark
+```
+
+## Running a single Benchmark
+
+To run a single Benchmark provide its containing class simple name followed by `#` and the method name via the `benchmark` command line argument.
+
+```bash
+mvn -P benchmarks clean test -D benchmark=MappingMongoConverterBenchmark#readObjectWith2Properties
+```
+
+# Saving Benchmark Results
+
+A detailed benchmark report is stored in JSON format in the `/target/reports/performance` directory.
+To store the report in a different location use the `benchmarkReportDir` command line argument.
+
+## MongoDB
+
+Results can be directly piped to MongoDB by providing a valid [Connection String](https://docs.mongodb.com/manual/reference/connection-string/) via the `publishTo` command line argument.
+
+```bash
+mvn -P benchmarks clean test -D publishTo=mongodb://127.0.0.1:27017
+```
+
+NOTE: If the uri does not explicitly define a database the default `spring-data-mongodb-benchmarks` is used. 
+
+## HTTP Endpoint
+
+The benchmark report can also be posted as `application/json` to an HTTP Endpoint by providing a valid URl via the `publishTo` command line argument.
+
+```bash
+mvn -P benchmarks clean test -D publishTo=http://127.0.0.1:8080/capture-benchmarks
+```
+
+# Customizing Benchmarks
+
+Following options can be set via command line.
+
+Option | Default Value
+--- | ---
+warmupIterations | 10
+warmupTime | 1 (seconds)
+measurementIterations | 10
+measurementTime | 1 (seconds)
+forks | 1
+benchmarkReportDir | /target/reports/performance (always relative to project root dir)
+benchmark | .* (single benchmark via `classname#benchmark`)
+publishTo | \[not set\] (mongodb-uri or http-endpoint)

spring-data-mongodb-benchmarks/pom.xml

@@ -0,0 +1,112 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+		 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+
+	<modelVersion>4.0.0</modelVersion>
+
+	<parent>
+		<groupId>org.springframework.data</groupId>
+		<artifactId>spring-data-mongodb-parent</artifactId>
+		<version>1.10.8.RELEASE</version>
+		<relativePath>../pom.xml</relativePath>
+	</parent>
+
+	<artifactId>spring-data-mongodb-benchmarks</artifactId>
+	<packaging>jar</packaging>
+
+	<name>Spring Data MongoDB - Microbenchmarks</name>
+
+	<properties>
+		<!-- Skip tests by default; run only if -DskipTests=false is specified or benchmarks profile is activated  -->
+		<skipTests>true</skipTests>
+		<bundlor.enabled>false</bundlor.enabled>
+	</properties>
+
+	<dependencies>
+
+		<dependency>
+			<groupId>${project.groupId}</groupId>
+			<artifactId>spring-data-mongodb</artifactId>
+			<version>${project.version}</version>
+		</dependency>
+
+		<dependency>
+			<groupId>junit</groupId>
+			<artifactId>junit</artifactId>
+			<version>${junit}</version>
+			<scope>compile</scope>
+		</dependency>
+
+		<dependency>
+			<groupId>org.openjdk.jmh</groupId>
+			<artifactId>jmh-core</artifactId>
+			<version>${jmh.version}</version>
+		</dependency>
+
+		<dependency>
+			<groupId>org.openjdk.jmh</groupId>
+			<artifactId>jmh-generator-annprocess</artifactId>
+			<version>${jmh.version}</version>
+			<scope>provided</scope>
+		</dependency>
+
+	</dependencies>
+
+	<profiles>
+
+		<profile>
+			<id>benchmarks</id>
+			<properties>
+				<skipTests>false</skipTests>
+			</properties>
+		</profile>
+	</profiles>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>pl.project13.maven</groupId>
+				<artifactId>git-commit-id-plugin</artifactId>
+				<version>2.2.2</version>
+				<executions>
+					<execution>
+						<goals>
+							<goal>revision</goal>
+						</goals>
+					</execution>
+				</executions>
+			</plugin>
+			<plugin>
+				<artifactId>maven-jar-plugin</artifactId>
+				<executions>
+					<execution>
+						<id>default-jar</id>
+						<phase>never</phase>
+					</execution>
+				</executions>
+			</plugin>
+			<plugin>
+				<artifactId>maven-surefire-plugin</artifactId>
+				<configuration>
+					<testSourceDirectory>${project.build.sourceDirectory}</testSourceDirectory>
+					<testClassesDirectory>${project.build.outputDirectory}</testClassesDirectory>
+					<excludes>
+						<exclude>**/AbstractMicrobenchmark.java</exclude>
+						<exclude>**/*$*.class</exclude>
+						<exclude>**/generated/*.class</exclude>
+					</excludes>
+					<includes>
+						<include>**/*Benchmark*</include>
+					</includes>
+					<systemPropertyVariables>
+						<benchmarkReportDir>${project.build.directory}/reports/performance</benchmarkReportDir>
+						<project.version>${project.version}</project.version>
+						<git.dirty>${git.dirty}</git.dirty>
+						<git.commit.id>${git.commit.id}</git.commit.id>
+						<git.branch>${git.branch}</git.branch>
+					</systemPropertyVariables>
+				</configuration>
+			</plugin>
+		</plugins>
+	</build>
+</project>

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

@@ -0,0 +1,111 @@
+/*
+ * Copyright 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.convert;
+
+import static org.springframework.data.mongodb.core.query.Criteria.*;
+import static org.springframework.data.mongodb.core.query.Query.*;
+
+import lombok.Data;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.bson.types.ObjectId;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.TearDown;
+import org.springframework.data.annotation.Id;
+import org.springframework.data.mongodb.core.MongoTemplate;
+import org.springframework.data.mongodb.core.mapping.DBRef;
+import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.data.mongodb.microbenchmark.AbstractMicrobenchmark;
+
+import com.mongodb.MongoClient;
+import com.mongodb.ServerAddress;
+
+/**
+ * @author Christoph Strobl
+ */
+@State(Scope.Benchmark)
+public class DbRefMappingBenchmark extends AbstractMicrobenchmark {
+
+	private static final String DB_NAME = "dbref-loading-benchmark";
+
+	private MongoClient client;
+	private MongoTemplate template;
+
+	private Query queryObjectWithDBRef;
+	private Query queryObjectWithDBRefList;
+
+	@Setup
+	public void setUp() throws Exception {
+
+		client = new MongoClient(new ServerAddress());
+		template = new MongoTemplate(client, DB_NAME);
+
+		List<RefObject> refObjects = new ArrayList<RefObject>();
+		for (int i = 0; i < 1; i++) {
+			RefObject o = new RefObject();
+			template.save(o);
+			refObjects.add(o);
+		}
+
+		ObjectWithDBRef singleDBRef = new ObjectWithDBRef();
+		singleDBRef.ref = refObjects.iterator().next();
+		template.save(singleDBRef);
+
+		ObjectWithDBRef multipleDBRefs = new ObjectWithDBRef();
+		multipleDBRefs.refList = refObjects;
+		template.save(multipleDBRefs);
+
+		queryObjectWithDBRef = query(where("id").is(singleDBRef.id));
+		queryObjectWithDBRefList = query(where("id").is(multipleDBRefs.id));
+	}
+
+	@TearDown
+	public void tearDown() {
+
+		client.dropDatabase(DB_NAME);
+		client.close();
+	}
+
+	@Benchmark // DATAMONGO-1720
+	public ObjectWithDBRef readSingleDbRef() {
+		return template.findOne(queryObjectWithDBRef, ObjectWithDBRef.class);
+	}
+
+	@Benchmark // DATAMONGO-1720
+	public ObjectWithDBRef readMultipleDbRefs() {
+		return template.findOne(queryObjectWithDBRefList, ObjectWithDBRef.class);
+	}
+
+	@Data
+	static class ObjectWithDBRef {
+
+		private @Id ObjectId id;
+		private @DBRef RefObject ref;
+		private @DBRef List<RefObject> refList;
+	}
+
+	@Data
+	static class RefObject {
+
+		private @Id String id;
+		private String someValue;
+	}
+}

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

@@ -0,0 +1,182 @@
+/*
+ * Copyright 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.convert;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.Getter;
+import lombok.RequiredArgsConstructor;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+
+import org.bson.types.ObjectId;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.TearDown;
+import org.springframework.data.annotation.Id;
+import org.springframework.data.geo.Point;
+import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
+import org.springframework.data.mongodb.core.mapping.Field;
+import org.springframework.data.mongodb.core.mapping.MongoMappingContext;
+import org.springframework.data.mongodb.microbenchmark.AbstractMicrobenchmark;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.MongoClient;
+import com.mongodb.ServerAddress;
+import com.mongodb.util.JSON;
+
+/**
+ * @author Christoph Strobl
+ */
+@State(Scope.Benchmark)
+public class MappingMongoConverterBenchmark extends AbstractMicrobenchmark {
+
+	private static final String DB_NAME = "mapping-mongo-converter-benchmark";
+
+	private MongoClient client;
+	private MongoMappingContext mappingContext;
+	private MappingMongoConverter converter;
+	private BasicDBObject documentWith2Properties, documentWith2PropertiesAnd1Nested;
+	private Customer objectWith2PropertiesAnd1Nested;
+
+	private BasicDBObject documentWithFlatAndComplexPropertiesPlusListAndMap;
+	private SlightlyMoreComplexObject objectWithFlatAndComplexPropertiesPlusListAndMap;
+
+	@Setup
+	public void setUp() throws Exception {
+
+		client = new MongoClient(new ServerAddress());
+
+		this.mappingContext = new MongoMappingContext();
+		this.mappingContext.setInitialEntitySet(Collections.singleton(Customer.class));
+		this.mappingContext.afterPropertiesSet();
+
+		DbRefResolver dbRefResolver = new DefaultDbRefResolver(new SimpleMongoDbFactory(client, DB_NAME));
+
+		this.converter = new MappingMongoConverter(dbRefResolver, mappingContext);
+		this.converter.setCustomConversions(new CustomConversions(Collections.emptyList()));
+		this.converter.afterPropertiesSet();
+
+		// just a flat document
+		this.documentWith2Properties = new BasicDBObject("firstname", "Dave").append("lastname", "Matthews");
+
+		// document with a nested one
+		BasicDBObject address = new BasicDBObject("zipCode", "ABCDE").append("city", "Some Place");
+		this.documentWith2PropertiesAnd1Nested = new BasicDBObject("firstname", "Dave").//
+				append("lastname", "Matthews").//
+				append("address", address);
+
+		// object equivalent of documentWith2PropertiesAnd1Nested
+		this.objectWith2PropertiesAnd1Nested = new Customer("Dave", "Matthews", new Address("zipCode", "City"));
+
+		// a bit more challenging object with list & map conversion.
+		objectWithFlatAndComplexPropertiesPlusListAndMap = new SlightlyMoreComplexObject();
+		objectWithFlatAndComplexPropertiesPlusListAndMap.id = UUID.randomUUID().toString();
+		objectWithFlatAndComplexPropertiesPlusListAndMap.addressList = Arrays.asList(new Address("zip-1", "city-1"),
+				new Address("zip-2", "city-2"));
+		objectWithFlatAndComplexPropertiesPlusListAndMap.customer = objectWith2PropertiesAnd1Nested;
+		objectWithFlatAndComplexPropertiesPlusListAndMap.customerMap = new LinkedHashMap<String, Customer>();
+		objectWithFlatAndComplexPropertiesPlusListAndMap.customerMap.put("dave", objectWith2PropertiesAnd1Nested);
+		objectWithFlatAndComplexPropertiesPlusListAndMap.customerMap.put("deborah",
+				new Customer("Deborah Anne", "Dyer", new Address("?", "london")));
+		objectWithFlatAndComplexPropertiesPlusListAndMap.customerMap.put("eddie",
+				new Customer("Eddie", "Vedder", new Address("??", "Seattle")));
+		objectWithFlatAndComplexPropertiesPlusListAndMap.intOne = Integer.MIN_VALUE;
+		objectWithFlatAndComplexPropertiesPlusListAndMap.intTwo = Integer.MAX_VALUE;
+		objectWithFlatAndComplexPropertiesPlusListAndMap.location = new Point(-33.865143, 151.209900);
+		objectWithFlatAndComplexPropertiesPlusListAndMap.renamedField = "supercalifragilisticexpialidocious";
+		objectWithFlatAndComplexPropertiesPlusListAndMap.stringOne = "¯\\_(ツ)_/¯";
+		objectWithFlatAndComplexPropertiesPlusListAndMap.stringTwo = " (╯°□°）╯︵ ┻━┻";
+
+		// JSON equivalent of objectWithFlatAndComplexPropertiesPlusListAndMap
+		documentWithFlatAndComplexPropertiesPlusListAndMap = (BasicDBObject) JSON.parse(
+				"{ \"_id\" : \"517f6aee-e9e0-44f0-88ed-f3694a019f27\", \"intOne\" : -2147483648, \"intTwo\" : 2147483647, \"stringOne\" : \"¯\\\\_(ツ)_/¯\", \"stringTwo\" : \" (╯°□°）╯︵ ┻━┻\", \"explicit-field-name\" : \"supercalifragilisticexpialidocious\", \"location\" : { \"x\" : -33.865143, \"y\" : 151.2099 }, \"objectWith2PropertiesAnd1Nested\" : { \"firstname\" : \"Dave\", \"lastname\" : \"Matthews\", \"address\" : { \"zipCode\" : \"zipCode\", \"city\" : \"City\" } }, \"addressList\" : [{ \"zipCode\" : \"zip-1\", \"city\" : \"city-1\" }, { \"zipCode\" : \"zip-2\", \"city\" : \"city-2\" }], \"customerMap\" : { \"dave\" : { \"firstname\" : \"Dave\", \"lastname\" : \"Matthews\", \"address\" : { \"zipCode\" : \"zipCode\", \"city\" : \"City\" } }, \"deborah\" : { \"firstname\" : \"Deborah Anne\", \"lastname\" : \"Dyer\", \"address\" : { \"zipCode\" : \"?\", \"city\" : \"london\" } }, \"eddie\" : { \"firstname\" : \"Eddie\", \"lastname\" : \"Vedder\", \"address\" : { \"zipCode\" : \"??\", \"city\" : \"Seattle\" } } }, \"_class\" : \"org.springframework.data.mongodb.core.convert.MappingMongoConverterBenchmark$SlightlyMoreComplexObject\" }");
+
+	}
+
+	@TearDown
+	public void tearDown() {
+
+		client.dropDatabase(DB_NAME);
+		client.close();
+	}
+
+	@Benchmark // DATAMONGO-1720
+	public Customer readObjectWith2Properties() {
+		return converter.read(Customer.class, documentWith2Properties);
+	}
+
+	@Benchmark // DATAMONGO-1720
+	public Customer readObjectWith2PropertiesAnd1NestedObject() {
+		return converter.read(Customer.class, documentWith2PropertiesAnd1Nested);
+	}
+
+	@Benchmark // DATAMONGO-1720
+	public BasicDBObject writeObjectWith2PropertiesAnd1NestedObject() {
+
+		BasicDBObject sink = new BasicDBObject();
+		converter.write(objectWith2PropertiesAnd1Nested, sink);
+		return sink;
+	}
+
+	@Benchmark // DATAMONGO-1720
+	public Object readObjectWithListAndMapsOfComplexType() {
+		return converter.read(SlightlyMoreComplexObject.class, documentWithFlatAndComplexPropertiesPlusListAndMap);
+	}
+
+	@Benchmark // DATAMONGO-1720
+	public Object writeObjectWithListAndMapsOfComplexType() {
+
+		BasicDBObject sink = new BasicDBObject();
+		converter.write(objectWithFlatAndComplexPropertiesPlusListAndMap, sink);
+		return sink;
+	}
+
+	@Getter
+	@RequiredArgsConstructor
+	static class Customer {
+
+		private @Id ObjectId id;
+		private final String firstname, lastname;
+		private final Address address;
+	}
+
+	@Getter
+	@AllArgsConstructor
+	static class Address {
+		private String zipCode, city;
+	}
+
+	@Data
+	static class SlightlyMoreComplexObject {
+
+		@Id String id;
+		int intOne, intTwo;
+		String stringOne, stringTwo;
+		@Field("explicit-field-name") String renamedField;
+		Point location;
+		Customer customer;
+		List<Address> addressList;
+		Map<String, Customer> customerMap;
+	}
+}

spring-data-mongodb-benchmarks/src/main/java/org/springframework/data/mongodb/microbenchmark/AbstractMicrobenchmark.java

@@ -0,0 +1,329 @@
+/*
+ * Copyright 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.microbenchmark;
+
+import java.io.File;
+import java.io.IOException;
+import java.text.SimpleDateFormat;
+import java.util.Collection;
+import java.util.Date;
+
+import org.junit.Test;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.results.RunResult;
+import org.openjdk.jmh.results.format.ResultFormatType;
+import org.openjdk.jmh.runner.Runner;
+import org.openjdk.jmh.runner.options.ChainedOptionsBuilder;
+import org.openjdk.jmh.runner.options.OptionsBuilder;
+import org.openjdk.jmh.runner.options.TimeValue;
+import org.springframework.core.env.StandardEnvironment;
+import org.springframework.data.mongodb.microbenchmark.ResultsWriter.Utils;
+import org.springframework.util.CollectionUtils;
+import org.springframework.util.ResourceUtils;
+import org.springframework.util.StringUtils;
+
+/**
+ * @author Christoph Strobl
+ */
+@Warmup(iterations = AbstractMicrobenchmark.WARMUP_ITERATIONS)
+@Measurement(iterations = AbstractMicrobenchmark.MEASUREMENT_ITERATIONS)
+@Fork(AbstractMicrobenchmark.FORKS)
+@State(Scope.Thread)
+public class AbstractMicrobenchmark {
+
+	static final int WARMUP_ITERATIONS = 5;
+	static final int MEASUREMENT_ITERATIONS = 10;
+	static final int FORKS = 1;
+	static final String[] JVM_ARGS = { "-server", "-XX:+HeapDumpOnOutOfMemoryError", "-Xms1024m", "-Xmx1024m",
+			"-XX:MaxDirectMemorySize=1024m" };
+
+	private final StandardEnvironment environment = new StandardEnvironment();
+
+	/**
+	 * Run matching {@link org.openjdk.jmh.annotations.Benchmark} methods with options collected from
+	 * {@link org.springframework.core.env.Environment}.
+	 *
+	 * @throws Exception
+	 * @see #options(String)
+	 */
+	@Test
+	public void run() throws Exception {
+
+		String includes = includes();
+
+		if (!includes.contains(org.springframework.util.ClassUtils.getShortName(getClass()))) {
+			return;
+		}
+
+		publishResults(new Runner(options(includes).build()).run());
+	}
+
+	/**
+	 * Get the regex for all benchmarks to be included in the run. By default every benchmark within classes matching the
+	 * current ones short name. <br />
+	 * The {@literal benchmark} command line argument allows overriding the defaults using {@code #} as class / method
+	 * name separator.
+	 *
+	 * @return never {@literal null}.
+	 * @see org.springframework.util.ClassUtils#getShortName(Class)
+	 */
+	protected String includes() {
+
+		String tests = environment.getProperty("benchmark", String.class);
+
+		if (!StringUtils.hasText(tests)) {
+			return ".*" + org.springframework.util.ClassUtils.getShortName(getClass()) + ".*";
+		}
+
+		if (!tests.contains("#")) {
+			return ".*" + tests + ".*";
+		}
+
+		String[] args = tests.split("#");
+		return ".*" + args[0] + "." + args[1];
+	}
+
+	/**
+	 * Collect all options for the {@link Runner}.
+	 *
+	 * @param includes regex for matching benchmarks to be included in the run.
+	 * @return never {@literal null}.
+	 * @throws Exception
+	 */
+	protected ChainedOptionsBuilder options(String includes) throws Exception {
+
+		ChainedOptionsBuilder optionsBuilder = new OptionsBuilder().include(includes).jvmArgs(jvmArgs());
+
+		optionsBuilder = warmup(optionsBuilder);
+		optionsBuilder = measure(optionsBuilder);
+		optionsBuilder = forks(optionsBuilder);
+		optionsBuilder = report(optionsBuilder);
+
+		return optionsBuilder;
+	}
+
+	/**
+	 * JVM args to apply to {@link Runner} via its {@link org.openjdk.jmh.runner.options.Options}.
+	 *
+	 * @return {@link #JVM_ARGS} by default.
+	 */
+	protected String[] jvmArgs() {
+
+		String[] args = new String[JVM_ARGS.length];
+		System.arraycopy(JVM_ARGS, 0, args, 0, JVM_ARGS.length);
+		return args;
+	}
+
+	/**
+	 * Read {@code warmupIterations} property from {@link org.springframework.core.env.Environment}.
+	 *
+	 * @return -1 if not set.
+	 */
+	protected int getWarmupIterations() {
+		return environment.getProperty("warmupIterations", Integer.class, -1);
+	}
+
+	/**
+	 * Read {@code measurementIterations} property from {@link org.springframework.core.env.Environment}.
+	 *
+	 * @return -1 if not set.
+	 */
+	protected int getMeasurementIterations() {
+		return environment.getProperty("measurementIterations", Integer.class, -1);
+
+	}
+
+	/**
+	 * Read {@code forks} property from {@link org.springframework.core.env.Environment}.
+	 *
+	 * @return -1 if not set.
+	 */
+	protected int getForksCount() {
+		return environment.getProperty("forks", Integer.class, -1);
+	}
+
+	/**
+	 * Read {@code benchmarkReportDir} property from {@link org.springframework.core.env.Environment}.
+	 *
+	 * @return {@literal null} if not set.
+	 */
+	protected String getReportDirectory() {
+		return environment.getProperty("benchmarkReportDir");
+	}
+
+	/**
+	 * Read {@code measurementTime} property from {@link org.springframework.core.env.Environment}.
+	 *
+	 * @return -1 if not set.
+	 */
+	protected long getMeasurementTime() {
+		return environment.getProperty("measurementTime", Long.class, -1L);
+	}
+
+	/**
+	 * Read {@code warmupTime} property from {@link org.springframework.core.env.Environment}.
+	 *
+	 * @return -1 if not set.
+	 */
+	protected long getWarmupTime() {
+		return environment.getProperty("warmupTime", Long.class, -1L);
+	}
+
+	/**
+	 * {@code project.version_yyyy-MM-dd_ClassName.json} eg.
+	 * {@literal 1.11.0.BUILD-SNAPSHOT_2017-03-07_MappingMongoConverterBenchmark.json}
+	 *
+	 * @return
+	 */
+	protected String reportFilename() {
+
+		StringBuilder sb = new StringBuilder();
+
+		if (environment.containsProperty("project.version")) {
+
+			sb.append(environment.getProperty("project.version"));
+			sb.append("_");
+		}
+
+		sb.append(new SimpleDateFormat("yyyy-MM-dd").format(new Date()));
+		sb.append("_");
+		sb.append(org.springframework.util.ClassUtils.getShortName(getClass()));
+		sb.append(".json");
+		return sb.toString();
+	}
+
+	/**
+	 * Apply measurement options to {@link ChainedOptionsBuilder}.
+	 *
+	 * @param optionsBuilder must not be {@literal null}.
+	 * @return {@link ChainedOptionsBuilder} with options applied.
+	 * @see #getMeasurementIterations()
+	 * @see #getMeasurementTime()
+	 */
+	private ChainedOptionsBuilder measure(ChainedOptionsBuilder optionsBuilder) {
+
+		int measurementIterations = getMeasurementIterations();
+		long measurementTime = getMeasurementTime();
+
+		if (measurementIterations > 0) {
+			optionsBuilder = optionsBuilder.measurementIterations(measurementIterations);
+		}
+
+		if (measurementTime > 0) {
+			optionsBuilder = optionsBuilder.measurementTime(TimeValue.seconds(measurementTime));
+		}
+
+		return optionsBuilder;
+	}
+
+	/**
+	 * Apply warmup options to {@link ChainedOptionsBuilder}.
+	 *
+	 * @param optionsBuilder must not be {@literal null}.
+	 * @return {@link ChainedOptionsBuilder} with options applied.
+	 * @see #getWarmupIterations()
+	 * @see #getWarmupTime()
+	 */
+	private ChainedOptionsBuilder warmup(ChainedOptionsBuilder optionsBuilder) {
+
+		int warmupIterations = getWarmupIterations();
+		long warmupTime = getWarmupTime();
+
+		if (warmupIterations > 0) {
+			optionsBuilder = optionsBuilder.warmupIterations(warmupIterations);
+		}
+
+		if (warmupTime > 0) {
+			optionsBuilder = optionsBuilder.warmupTime(TimeValue.seconds(warmupTime));
+		}
+
+		return optionsBuilder;
+	}
+
+	/**
+	 * Apply forks option to {@link ChainedOptionsBuilder}.
+	 *
+	 * @param optionsBuilder must not be {@literal null}.
+	 * @return {@link ChainedOptionsBuilder} with options applied.
+	 * @see #getForksCount()
+	 */
+	private ChainedOptionsBuilder forks(ChainedOptionsBuilder optionsBuilder) {
+
+		int forks = getForksCount();
+
+		if (forks <= 0) {
+			return optionsBuilder;
+		}
+
+		return optionsBuilder.forks(forks);
+	}
+
+	/**
+	 * Apply report option to {@link ChainedOptionsBuilder}.
+	 *
+	 * @param optionsBuilder must not be {@literal null}.
+	 * @return {@link ChainedOptionsBuilder} with options applied.
+	 * @throws IOException if report file cannot be created.
+	 * @see #getReportDirectory()
+	 */
+	private ChainedOptionsBuilder report(ChainedOptionsBuilder optionsBuilder) throws IOException {
+
+		String reportDir = getReportDirectory();
+
+		if (!StringUtils.hasText(reportDir)) {
+			return optionsBuilder;
+		}
+
+		String reportFilePath = reportDir + (reportDir.endsWith(File.separator) ? "" : File.separator) + reportFilename();
+		File file = ResourceUtils.getFile(reportFilePath);
+
+		if (file.exists()) {
+			file.delete();
+		} else {
+
+			file.getParentFile().mkdirs();
+			file.createNewFile();
+		}
+
+		optionsBuilder.resultFormat(ResultFormatType.JSON);
+		optionsBuilder.result(reportFilePath);
+
+		return optionsBuilder;
+	}
+
+	/**
+	 * Publish results to an external system.
+	 *
+	 * @param results must not be {@literal null}.
+	 */
+	private void publishResults(Collection<RunResult> results) {
+
+		if (CollectionUtils.isEmpty(results) || !environment.containsProperty("publishTo")) {
+			return;
+		}
+
+		String uri = environment.getProperty("publishTo");
+		try {
+			Utils.forUri(uri).write(results);
+		} catch (Exception e) {
+			System.err.println(String.format("Cannot save benchmark results to '%s'. Error was %s.", uri, e));
+		}
+	}
+}

spring-data-mongodb-benchmarks/src/main/java/org/springframework/data/mongodb/microbenchmark/HttpResultsWriter.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright 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.microbenchmark;
+
+import lombok.SneakyThrows;
+
+import java.io.OutputStream;
+import java.net.HttpURLConnection;
+import java.net.URL;
+import java.net.URLConnection;
+import java.nio.charset.Charset;
+import java.util.Collection;
+
+import org.openjdk.jmh.results.RunResult;
+import org.springframework.core.env.StandardEnvironment;
+import org.springframework.util.CollectionUtils;
+
+/**
+ * {@link ResultsWriter} implementation of {@link URLConnection}.
+ *
+ * @since 2.0
+ */
+class HttpResultsWriter implements ResultsWriter {
+
+	private final String url;
+
+	HttpResultsWriter(String url) {
+		this.url = url;
+	}
+
+	@Override
+	@SneakyThrows
+	public void write(Collection<RunResult> results) {
+
+		if (CollectionUtils.isEmpty(results)) {
+			return;
+		}
+
+		StandardEnvironment env = new StandardEnvironment();
+
+		String projectVersion = env.getProperty("project.version", "unknown");
+		String gitBranch = env.getProperty("git.branch", "unknown");
+		String gitDirty = env.getProperty("git.dirty", "no");
+		String gitCommitId = env.getProperty("git.commit.id", "unknown");
+
+		HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
+		connection.setConnectTimeout(1000);
+		connection.setReadTimeout(1000);
+		connection.setDoOutput(true);
+		connection.setRequestMethod("POST");
+
+		connection.setRequestProperty("Content-Type", "application/json");
+		connection.addRequestProperty("X-Project-Version", projectVersion);
+		connection.addRequestProperty("X-Git-Branch", gitBranch);
+		connection.addRequestProperty("X-Git-Dirty", gitDirty);
+		connection.addRequestProperty("X-Git-Commit-Id", gitCommitId);
+
+		OutputStream output = null;
+		try {
+			output = connection.getOutputStream();
+			output.write(ResultsWriter.Utils.jsonifyResults(results).getBytes(Charset.forName("UTF-8")));
+		} finally {
+			if (output != null) {
+				output.close();
+			}
+		}
+
+		if (connection.getResponseCode() >= 400) {
+			throw new IllegalStateException(
+					String.format("Status %d %s", connection.getResponseCode(), connection.getResponseMessage()));
+		}
+	}
+}

spring-data-mongodb-benchmarks/src/main/java/org/springframework/data/mongodb/microbenchmark/MongoResultsWriter.java

@@ -0,0 +1,135 @@
+/*
+ * Copyright 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.microbenchmark;
+
+import java.net.UnknownHostException;
+import java.util.Collection;
+import java.util.Date;
+import java.util.List;
+
+import org.openjdk.jmh.results.RunResult;
+import org.springframework.core.env.StandardEnvironment;
+import org.springframework.util.ObjectUtils;
+import org.springframework.util.StringUtils;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.DB;
+import com.mongodb.MongoClient;
+import com.mongodb.MongoClientURI;
+import com.mongodb.util.JSON;
+
+/**
+ * MongoDB specific {@link ResultsWriter} implementation.
+ *
+ * @author Christoph Strobl
+ * @since 2.0
+ */
+class MongoResultsWriter implements ResultsWriter {
+
+	private final String uri;
+
+	MongoResultsWriter(String uri) {
+		this.uri = uri;
+	}
+
+	@Override
+	public void write(Collection<RunResult> results) {
+
+		Date now = new Date();
+		StandardEnvironment env = new StandardEnvironment();
+
+		String projectVersion = env.getProperty("project.version", "unknown");
+		String gitBranch = env.getProperty("git.branch", "unknown");
+		String gitDirty = env.getProperty("git.dirty", "no");
+		String gitCommitId = env.getProperty("git.commit.id", "unknown");
+
+		MongoClientURI uri = new MongoClientURI(this.uri);
+		MongoClient client = null;
+
+		try {
+			client = new MongoClient(uri);
+		} catch (UnknownHostException e) {
+			throw new RuntimeException(e);
+		}
+
+		String dbName = StringUtils.hasText(uri.getDatabase()) ? uri.getDatabase() : "spring-data-mongodb-benchmarks";
+		DB db = client.getDB(dbName);
+
+		for (BasicDBObject dbo : (List<BasicDBObject>) JSON.parse(Utils.jsonifyResults(results))) {
+
+			String collectionName = extractClass(dbo.get("benchmark").toString());
+
+			BasicDBObject sink = new BasicDBObject();
+			sink.append("_version", projectVersion);
+			sink.append("_branch", gitBranch);
+			sink.append("_commit", gitCommitId);
+			sink.append("_dirty", gitDirty);
+			sink.append("_method", extractBenchmarkName(dbo.get("benchmark").toString()));
+			sink.append("_date", now);
+			sink.append("_snapshot", projectVersion.toLowerCase().contains("snapshot"));
+
+			sink.putAll(dbo.toMap());
+
+			db.getCollection(collectionName).insert(fixDocumentKeys(sink));
+		}
+
+		client.close();
+	}
+
+	/**
+	 * Replace {@code .} by {@code ,}.
+	 *
+	 * @param doc
+	 * @return
+	 */
+	private BasicDBObject fixDocumentKeys(BasicDBObject doc) {
+
+		BasicDBObject sanitized = new BasicDBObject();
+
+		for (Object key : doc.keySet()) {
+
+			Object value = doc.get(key);
+			if (value instanceof BasicDBObject) {
+				value = fixDocumentKeys((BasicDBObject) value);
+			}
+
+			if (key instanceof String) {
+
+				String newKey = (String) key;
+				if (newKey.contains(".")) {
+					newKey = newKey.replace('.', ',');
+				}
+
+				sanitized.put(newKey, value);
+			} else {
+				sanitized.put(ObjectUtils.nullSafeToString(key).replace('.', ','), value);
+			}
+		}
+
+		return sanitized;
+	}
+
+	private static String extractClass(String source) {
+
+		String tmp = source.substring(0, source.lastIndexOf('.'));
+		return tmp.substring(tmp.lastIndexOf(".") + 1);
+	}
+
+	private static String extractBenchmarkName(String source) {
+		return source.substring(source.lastIndexOf(".") + 1);
+	}
+
+}

spring-data-mongodb-benchmarks/src/main/java/org/springframework/data/mongodb/microbenchmark/ResultsWriter.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 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.microbenchmark;
+
+import lombok.SneakyThrows;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.nio.charset.Charset;
+import java.util.Collection;
+
+import org.openjdk.jmh.results.RunResult;
+import org.openjdk.jmh.results.format.ResultFormatFactory;
+import org.openjdk.jmh.results.format.ResultFormatType;
+
+/**
+ * @author Christoph Strobl
+ * @since 2.0
+ */
+interface ResultsWriter {
+
+	/**
+	 * Write the {@link RunResult}s.
+	 *
+	 * @param results can be {@literal null}.
+	 */
+	void write(Collection<RunResult> results);
+
+	/* non Java8 hack */
+	class Utils {
+
+		/**
+		 * Get the uri specific {@link ResultsWriter}.
+		 *
+		 * @param uri must not be {@literal null}.
+		 * @return
+		 */
+		static ResultsWriter forUri(String uri) {
+			return uri.startsWith("mongodb:") ? new MongoResultsWriter(uri) : new HttpResultsWriter(uri);
+		}
+
+		/**
+		 * Convert {@link RunResult}s to JMH Json representation.
+		 *
+		 * @param results
+		 * @return json string representation of results.
+		 * @see org.openjdk.jmh.results.format.JSONResultFormat
+		 */
+		@SneakyThrows
+		static String jsonifyResults(Collection<RunResult> results) {
+
+			ByteArrayOutputStream baos = new ByteArrayOutputStream();
+			ResultFormatFactory.getInstance(ResultFormatType.JSON, new PrintStream(baos, true, "UTF-8")).writeOut(results);
+			return new String(baos.toByteArray(), Charset.forName("UTF-8"));
+		}
+	}
+
+}

spring-data-mongodb-benchmarks/src/main/resources/logback.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+
+	<appender name="console" class="ch.qos.logback.core.ConsoleAppender">
+		<encoder>
+			<pattern>%d %5p %40.40c:%4L - %m%n</pattern>
+		</encoder>
+	</appender>
+
+	<root level="error">
+		<appender-ref ref="console" />
+	</root>
+
+</configuration>

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

@@ -6,7 +6,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>1.10.0.BUILD-SNAPSHOT</version>
+		<version>1.10.8.RELEASE</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 
@@ -48,7 +48,7 @@
 		<dependency>
 			<groupId>org.springframework.data</groupId>
 			<artifactId>spring-data-mongodb</artifactId>
-			<version>1.10.0.BUILD-SNAPSHOT</version>
+			<version>1.10.8.RELEASE</version>
 		</dependency>
 
 		<dependency>

spring-data-mongodb-distribution/pom.xml

@@ -13,7 +13,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>1.10.0.BUILD-SNAPSHOT</version>
+		<version>1.10.8.RELEASE</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>1.10.0.BUILD-SNAPSHOT</version>
+		<version>1.10.8.RELEASE</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

@@ -11,7 +11,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>1.10.0.BUILD-SNAPSHOT</version>
+		<version>1.10.8.RELEASE</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/config/MappingMongoConverterParser.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.
@@ -361,7 +361,9 @@ 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/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.
@@ -129,6 +129,7 @@ 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/BulkOperations.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2016 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.
@@ -28,7 +28,7 @@ import com.mongodb.BulkWriteResult;
  * 2.6 and make use of low level bulk commands on the protocol level. This interface defines a fluent API to add
  * multiple single operations or list of similar operations in sequence which can then eventually be executed by calling
  * {@link #execute()}.
- * 
+ *
  * @author Tobias Trelle
  * @author Oliver Gierke
  * @since 1.9
@@ -49,7 +49,7 @@ public interface BulkOperations {
 
 	/**
 	 * Add a single insert to the bulk operation.
-	 * 
+	 *
 	 * @param documents the document to insert, must not be {@literal null}.
 	 * @return the current {@link BulkOperations} instance with the insert added, will never be {@literal null}.
 	 */
@@ -57,7 +57,7 @@ public interface BulkOperations {
 
 	/**
 	 * Add a list of inserts to the bulk operation.
-	 * 
+	 *
 	 * @param documents List of documents to insert, must not be {@literal null}.
 	 * @return the current {@link BulkOperations} instance with the insert added, will never be {@literal null}.
 	 */
@@ -65,7 +65,7 @@ public interface BulkOperations {
 
 	/**
 	 * Add a single update to the bulk operation. For the update request, only the first matching document is updated.
-	 * 
+	 *
 	 * @param query update criteria, must not be {@literal null}.
 	 * @param update {@link Update} operation to perform, must not be {@literal null}.
 	 * @return the current {@link BulkOperations} instance with the update added, will never be {@literal null}.
@@ -74,7 +74,7 @@ public interface BulkOperations {
 
 	/**
 	 * Add a list of updates to the bulk operation. For each update request, only the first matching document is updated.
-	 * 
+	 *
 	 * @param updates Update operations to perform.
 	 * @return the current {@link BulkOperations} instance with the update added, will never be {@literal null}.
 	 */
@@ -82,7 +82,7 @@ public interface BulkOperations {
 
 	/**
 	 * Add a single update to the bulk operation. For the update request, all matching documents are updated.
-	 * 
+	 *
 	 * @param query Update criteria.
 	 * @param update Update operation to perform.
 	 * @return the current {@link BulkOperations} instance with the update added, will never be {@literal null}.
@@ -91,7 +91,7 @@ public interface BulkOperations {
 
 	/**
 	 * Add a list of updates to the bulk operation. For each update request, all matching documents are updated.
-	 * 
+	 *
 	 * @param updates Update operations to perform.
 	 * @return The bulk operation.
 	 * @return the current {@link BulkOperations} instance with the update added, will never be {@literal null}.
@@ -101,7 +101,7 @@ public interface BulkOperations {
 	/**
 	 * Add a single upsert to the bulk operation. An upsert is an update if the set of matching documents is not empty,
 	 * else an insert.
-	 * 
+	 *
 	 * @param query Update criteria.
 	 * @param update Update operation to perform.
 	 * @return The bulk operation.
@@ -112,7 +112,7 @@ public interface BulkOperations {
 	/**
 	 * Add a list of upserts to the bulk operation. An upsert is an update if the set of matching documents is not empty,
 	 * else an insert.
-	 * 
+	 *
 	 * @param updates Updates/insert operations to perform.
 	 * @return The bulk operation.
 	 * @return the current {@link BulkOperations} instance with the update added, will never be {@literal null}.
@@ -121,7 +121,7 @@ public interface BulkOperations {
 
 	/**
 	 * Add a single remove operation to the bulk operation.
-	 * 
+	 *
 	 * @param remove the {@link Query} to select the documents to be removed, must not be {@literal null}.
 	 * @return the current {@link BulkOperations} instance with the removal added, will never be {@literal null}.
 	 */
@@ -129,7 +129,7 @@ public interface BulkOperations {
 
 	/**
 	 * Add a list of remove operations to the bulk operation.
-	 * 
+	 *
 	 * @param removes the remove operations to perform, must not be {@literal null}.
 	 * @return the current {@link BulkOperations} instance with the removal added, will never be {@literal null}.
 	 */
@@ -137,9 +137,9 @@ public interface BulkOperations {
 
 	/**
 	 * Execute all bulk operations using the default write concern.
-	 * 
+	 *
 	 * @return Result of the bulk operation providing counters for inserts/updates etc.
-	 * @throws {@link BulkOperationException} if an error occurred during bulk processing.
+	 * @throws org.springframework.data.mongodb.BulkOperationException if an error occurred during bulk processing.
 	 */
 	BulkWriteResult execute();
 }

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

@@ -15,16 +15,23 @@
  */
 package org.springframework.data.mongodb.core;
 
-import java.util.Arrays;
+import lombok.NonNull;
+import lombok.Value;
+
+import java.util.Collections;
 import java.util.List;
 
 import org.springframework.dao.DataAccessException;
 import org.springframework.dao.support.PersistenceExceptionTranslator;
+import org.springframework.data.mongodb.core.convert.QueryMapper;
+import org.springframework.data.mongodb.core.convert.UpdateMapper;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.data.mongodb.core.query.Update;
 import org.springframework.data.util.Pair;
 import org.springframework.util.Assert;
 
+import com.mongodb.BasicDBObject;
 import com.mongodb.BulkWriteException;
 import com.mongodb.BulkWriteOperation;
 import com.mongodb.BulkWriteRequestBuilder;
@@ -35,17 +42,18 @@ import com.mongodb.WriteConcern;
 
 /**
  * Default implementation for {@link BulkOperations}.
- * 
+ *
  * @author Tobias Trelle
  * @author Oliver Gierke
+ * @author Christoph Strobl
+ * @author Mark Paluch
  * @since 1.9
  */
 class DefaultBulkOperations implements BulkOperations {
 
 	private final MongoOperations mongoOperations;
-	private final BulkMode bulkMode;
 	private final String collectionName;
-	private final Class<?> entityType;
+	private final BulkOperationContext bulkOperationContext;
 
 	private PersistenceExceptionTranslator exceptionTranslator;
 	private WriteConcernResolver writeConcernResolver;
@@ -54,35 +62,32 @@ class DefaultBulkOperations implements BulkOperations {
 	private BulkWriteOperation bulk;
 
 	/**
-	 * Creates a new {@link DefaultBulkOperations} for the given {@link MongoOperations}, {@link BulkMode}, collection
-	 * name and {@link WriteConcern}.
-	 * 
-	 * @param mongoOperations The underlying {@link MongoOperations}, must not be {@literal null}.
-	 * @param bulkMode must not be {@literal null}.
-	 * @param collectionName Name of the collection to work on, must not be {@literal null} or empty.
-	 * @param entityType the entity type, can be {@literal null}.
+	 * Creates a new {@link DefaultBulkOperations} for the given {@link MongoOperations}, collection name and
+	 * {@link BulkOperationContext}.
+	 *
+	 * @param mongoOperations must not be {@literal null}.
+	 * @param collectionName must not be {@literal null}.
+	 * @param bulkOperationContext must not be {@literal null}.
+	 * @since 1.10.5
 	 */
-	DefaultBulkOperations(MongoOperations mongoOperations, BulkMode bulkMode, String collectionName,
-			Class<?> entityType) {
+	DefaultBulkOperations(MongoOperations mongoOperations, String collectionName,
+			BulkOperationContext bulkOperationContext) {
 
 		Assert.notNull(mongoOperations, "MongoOperations must not be null!");
-		Assert.notNull(bulkMode, "BulkMode must not be null!");
-		Assert.hasText(collectionName, "Collection name must not be null or empty!");
+		Assert.hasText(collectionName, "CollectionName must not be null nor empty!");
+		Assert.notNull(bulkOperationContext, "BulkOperationContext must not be null!");
 
 		this.mongoOperations = mongoOperations;
-		this.bulkMode = bulkMode;
 		this.collectionName = collectionName;
-		this.entityType = entityType;
-
+		this.bulkOperationContext = bulkOperationContext;
 		this.exceptionTranslator = new MongoExceptionTranslator();
 		this.writeConcernResolver = DefaultWriteConcernResolver.INSTANCE;
-
-		this.bulk = initBulkOperation();
+		this.bulk = getBulkWriteOptions(bulkOperationContext.getBulkMode());
 	}
 
 	/**
 	 * Configures the {@link PersistenceExceptionTranslator} to be used. Defaults to {@link MongoExceptionTranslator}.
-	 * 
+	 *
 	 * @param exceptionTranslator can be {@literal null}.
 	 */
 	public void setExceptionTranslator(PersistenceExceptionTranslator exceptionTranslator) {
@@ -91,7 +96,7 @@ class DefaultBulkOperations implements BulkOperations {
 
 	/**
 	 * Configures the {@link WriteConcernResolver} to be used. Defaults to {@link DefaultWriteConcernResolver}.
-	 * 
+	 *
 	 * @param writeConcernResolver can be {@literal null}.
 	 */
 	public void setWriteConcernResolver(WriteConcernResolver writeConcernResolver) {
@@ -101,10 +106,10 @@ class DefaultBulkOperations implements BulkOperations {
 
 	/**
 	 * Configures the default {@link WriteConcern} to be used. Defaults to {@literal null}.
-	 * 
+	 *
 	 * @param defaultWriteConcern can be {@literal null}.
 	 */
-	public void setDefaultWriteConcern(WriteConcern defaultWriteConcern) {
+	void setDefaultWriteConcern(WriteConcern defaultWriteConcern) {
 		this.defaultWriteConcern = defaultWriteConcern;
 	}
 
@@ -117,7 +122,15 @@ class DefaultBulkOperations implements BulkOperations {
 
 		Assert.notNull(document, "Document must not be null!");
 
-		bulk.insert((DBObject) mongoOperations.getConverter().convertToMongoType(document));
+		if (document instanceof DBObject) {
+
+			bulk.insert((DBObject) document);
+			return this;
+		}
+
+		DBObject sink = new BasicDBObject();
+		mongoOperations.getConverter().write(document, sink);
+		bulk.insert(sink);
 		return this;
 	}
 
@@ -148,7 +161,7 @@ class DefaultBulkOperations implements BulkOperations {
 		Assert.notNull(query, "Query must not be null!");
 		Assert.notNull(update, "Update must not be null!");
 
-		return updateOne(Arrays.asList(Pair.of(query, update)));
+		return updateOne(Collections.singletonList(Pair.of(query, update)));
 	}
 
 	/*
@@ -178,7 +191,7 @@ class DefaultBulkOperations implements BulkOperations {
 		Assert.notNull(query, "Query must not be null!");
 		Assert.notNull(update, "Update must not be null!");
 
-		return updateMulti(Arrays.asList(Pair.of(query, update)));
+		return updateMulti(Collections.singletonList(Pair.of(query, update)));
 	}
 
 	/*
@@ -229,7 +242,7 @@ class DefaultBulkOperations implements BulkOperations {
 
 		Assert.notNull(query, "Query must not be null!");
 
-		bulk.find(query.getQueryObject()).remove();
+		bulk.find(getMappedQuery(query.getQueryObject())).remove();
 
 		return this;
 	}
@@ -257,27 +270,25 @@ class DefaultBulkOperations implements BulkOperations {
 	@Override
 	public BulkWriteResult execute() {
 
-		MongoAction action = new MongoAction(defaultWriteConcern, MongoActionOperation.BULK, collectionName, entityType,
-				null, null);
+		MongoAction action = new MongoAction(defaultWriteConcern, MongoActionOperation.BULK, collectionName,
+				bulkOperationContext.getEntityType(), null, null);
 		WriteConcern writeConcern = writeConcernResolver.resolve(action);
 
 		try {
-
 			return writeConcern == null ? bulk.execute() : bulk.execute(writeConcern);
-
 		} catch (BulkWriteException o_O) {
 
 			DataAccessException toThrow = exceptionTranslator.translateExceptionIfPossible(o_O);
 			throw toThrow == null ? o_O : toThrow;
 
 		} finally {
-			this.bulk = initBulkOperation();
+			this.bulk = getBulkWriteOptions(bulkOperationContext.getBulkMode());
 		}
 	}
 
 	/**
 	 * Performs update and upsert bulk operations.
-	 * 
+	 *
 	 * @param query the {@link Query} to determine documents to update.
 	 * @param update the {@link Update} to perform, must not be {@literal null}.
 	 * @param upsert whether to upsert.
@@ -289,29 +300,37 @@ class DefaultBulkOperations implements BulkOperations {
 		Assert.notNull(query, "Query must not be null!");
 		Assert.notNull(update, "Update must not be null!");
 
-		BulkWriteRequestBuilder builder = bulk.find(query.getQueryObject());
+		BulkWriteRequestBuilder builder = bulk.find(getMappedQuery(query.getQueryObject()));
 
 		if (upsert) {
 
 			if (multi) {
-				builder.upsert().update(update.getUpdateObject());
+				builder.upsert().update(getMappedUpdate(update.getUpdateObject()));
 			} else {
-				builder.upsert().updateOne(update.getUpdateObject());
+				builder.upsert().updateOne(getMappedUpdate(update.getUpdateObject()));
 			}
 
 		} else {
 
 			if (multi) {
-				builder.update(update.getUpdateObject());
+				builder.update(getMappedUpdate(update.getUpdateObject()));
 			} else {
-				builder.updateOne(update.getUpdateObject());
+				builder.updateOne(getMappedUpdate(update.getUpdateObject()));
 			}
 		}
 
 		return this;
 	}
 
-	private final BulkWriteOperation initBulkOperation() {
+	private DBObject getMappedUpdate(DBObject update) {
+		return bulkOperationContext.getUpdateMapper().getMappedObject(update, bulkOperationContext.getEntity());
+	}
+
+	private DBObject getMappedQuery(DBObject query) {
+		return bulkOperationContext.getQueryMapper().getMappedObject(query, bulkOperationContext.getEntity());
+	}
+
+	private BulkWriteOperation getBulkWriteOptions(BulkMode bulkMode) {
 
 		DBCollection collection = mongoOperations.getCollection(collectionName);
 
@@ -324,4 +343,25 @@ class DefaultBulkOperations implements BulkOperations {
 
 		throw new IllegalStateException("BulkMode was null!");
 	}
+
+	/**
+	 * {@link BulkOperationContext} holds information about
+	 * {@link org.springframework.data.mongodb.core.BulkOperations.BulkMode} the entity in use as well as references to
+	 * {@link QueryMapper} and {@link UpdateMapper}.
+	 *
+	 * @author Christoph Strobl
+	 * @since 2.0
+	 */
+	@Value
+	static class BulkOperationContext {
+
+		@NonNull BulkMode bulkMode;
+		MongoPersistentEntity<?> entity;
+		@NonNull QueryMapper queryMapper;
+		@NonNull UpdateMapper updateMapper;
+
+		Class<?> getEntityType() {
+			return entity != null ? entity.getType() : null;
+		}
+	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/DefaultIndexOperations.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.
@@ -15,17 +15,15 @@
  */
 package org.springframework.data.mongodb.core;
 
-import static org.springframework.data.domain.Sort.Direction.*;
-
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
 
 import org.springframework.dao.DataAccessException;
+import org.springframework.data.mongodb.core.convert.QueryMapper;
 import org.springframework.data.mongodb.core.index.IndexDefinition;
-import org.springframework.data.mongodb.core.index.IndexField;
 import org.springframework.data.mongodb.core.index.IndexInfo;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.util.Assert;
 
 import com.mongodb.DBCollection;
@@ -42,12 +40,12 @@ import com.mongodb.MongoException;
  */
 public class DefaultIndexOperations implements IndexOperations {
 
-	private static final Double ONE = Double.valueOf(1);
-	private static final Double MINUS_ONE = Double.valueOf(-1);
-	private static final Collection<String> TWO_D_IDENTIFIERS = Arrays.asList("2d", "2dsphere");
+	private static final String PARTIAL_FILTER_EXPRESSION_KEY = "partialFilterExpression";
 
 	private final MongoOperations mongoOperations;
 	private final String collectionName;
+	private final QueryMapper mapper;
+	private final Class<?> type;
 
 	/**
 	 * Creates a new {@link DefaultIndexOperations}.
@@ -56,12 +54,26 @@ public class DefaultIndexOperations implements IndexOperations {
 	 * @param collectionName must not be {@literal null}.
 	 */
 	public DefaultIndexOperations(MongoOperations mongoOperations, String collectionName) {
+		this(mongoOperations, collectionName, null);
+	}
+
+	/**
+	 * Creates a new {@link DefaultIndexOperations}.
+	 *
+	 * @param mongoOperations must not be {@literal null}.
+	 * @param collectionName 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(MongoOperations mongoOperations, String collectionName, Class<?> type) {
 
 		Assert.notNull(mongoOperations, "MongoOperations must not be null!");
 		Assert.notNull(collectionName, "Collection name can not be null!");
 
 		this.mongoOperations = mongoOperations;
 		this.collectionName = collectionName;
+		this.mapper = new QueryMapper(mongoOperations.getConverter());
+		this.type = type;
 	}
 
 	/*
@@ -69,9 +81,20 @@ public class DefaultIndexOperations implements IndexOperations {
 	 * @see org.springframework.data.mongodb.core.IndexOperations#ensureIndex(org.springframework.data.mongodb.core.index.IndexDefinition)
 	 */
 	public void ensureIndex(final IndexDefinition indexDefinition) {
+
 		mongoOperations.execute(collectionName, new CollectionCallback<Object>() {
 			public Object doInCollection(DBCollection collection) throws MongoException, DataAccessException {
 				DBObject indexOptions = indexDefinition.getIndexOptions();
+
+				if (indexOptions != null && indexOptions.containsField(PARTIAL_FILTER_EXPRESSION_KEY)) {
+
+					Assert.isInstanceOf(DBObject.class, indexOptions.get(PARTIAL_FILTER_EXPRESSION_KEY));
+
+					indexOptions.put(PARTIAL_FILTER_EXPRESSION_KEY,
+							mapper.getMappedObject((DBObject) indexOptions.get(PARTIAL_FILTER_EXPRESSION_KEY),
+									lookupPersistentEntity(type, collectionName)));
+				}
+
 				if (indexOptions != null) {
 					collection.createIndex(indexDefinition.getIndexKeys(), indexOptions);
 				} else {
@@ -79,6 +102,24 @@ public class DefaultIndexOperations implements IndexOperations {
 				}
 				return null;
 			}
+
+			private MongoPersistentEntity<?> lookupPersistentEntity(Class<?> entityType, String collection) {
+
+				if (entityType != null) {
+					return mongoOperations.getConverter().getMappingContext().getPersistentEntity(entityType);
+				}
+
+				Collection<? extends MongoPersistentEntity<?>> entities = mongoOperations.getConverter().getMappingContext()
+						.getPersistentEntities();
+
+				for (MongoPersistentEntity<?> entity : entities) {
+					if (entity.getCollection().equals(collection)) {
+						return entity;
+					}
+				}
+
+				return null;
+			}
 		});
 	}
 
@@ -126,7 +167,9 @@ public class DefaultIndexOperations implements IndexOperations {
 	public List<IndexInfo> getIndexInfo() {
 
 		return mongoOperations.execute(collectionName, new CollectionCallback<List<IndexInfo>>() {
+
 			public List<IndexInfo> doInCollection(DBCollection collection) throws MongoException, DataAccessException {
+
 				List<DBObject> dbObjectList = collection.getIndexInfo();
 				return getIndexData(dbObjectList);
 			}
@@ -136,44 +179,7 @@ public class DefaultIndexOperations implements IndexOperations {
 				List<IndexInfo> indexInfoList = new ArrayList<IndexInfo>();
 
 				for (DBObject ix : dbObjectList) {
-
-					DBObject keyDbObject = (DBObject) ix.get("key");
-					int numberOfElements = keyDbObject.keySet().size();
-
-					List<IndexField> indexFields = new ArrayList<IndexField>(numberOfElements);
-
-					for (String key : keyDbObject.keySet()) {
-
-						Object value = keyDbObject.get(key);
-
-						if (TWO_D_IDENTIFIERS.contains(value)) {
-							indexFields.add(IndexField.geo(key));
-						} else if ("text".equals(value)) {
-
-							DBObject weights = (DBObject) 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.containsField("unique") ? (Boolean) ix.get("unique") : false;
-					boolean dropDuplicates = ix.containsField("dropDups") ? (Boolean) ix.get("dropDups") : false;
-					boolean sparse = ix.containsField("sparse") ? (Boolean) ix.get("sparse") : false;
-					String language = ix.containsField("default_language") ? (String) ix.get("default_language") : "";
-					indexInfoList.add(new IndexInfo(indexFields, name, unique, dropDuplicates, sparse, language));
+					indexInfoList.add(IndexInfo.indexInfoOf(ix));
 				}
 
 				return indexInfoList;

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/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.
@@ -27,7 +27,8 @@ import com.mongodb.Mongo;
  * Mongo server administration exposed via JMX annotations
  * 
  * @author Mark Pollack
- * @author Thomas Darimont
+ * @author Thomas Darimont
+ * @author Mark Paluch
  */
 @ManagedResource(description = "Mongo Admin Operations")
 public class MongoAdmin implements MongoAdminOperations {
@@ -35,10 +36,11 @@ public class MongoAdmin implements MongoAdminOperations {
 	private final Mongo mongo;
 	private String username;
 	private String password;
-	private String authenticationDatabaseName;
+	private String authenticationDatabaseName;
 
 	public MongoAdmin(Mongo mongo) {
-		Assert.notNull(mongo);
+
+		Assert.notNull(mongo, "Mongo must not be null!");
 		this.mongo = mongo;
 	}
 
@@ -84,16 +86,16 @@ public class MongoAdmin implements MongoAdminOperations {
 		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;
-	}
-
+	/**
+	 * 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);
+		return MongoDbUtils.getDB(mongo, databaseName, new UserCredentials(username, password), authenticationDatabaseName);
 	}
 }

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.
@@ -18,8 +18,10 @@ package org.springframework.data.mongodb.core;
 import javax.net.SocketFactory;
 import javax.net.ssl.SSLSocketFactory;
 
+import org.springframework.beans.DirectFieldAccessor;
 import org.springframework.beans.factory.config.AbstractFactoryBean;
 import org.springframework.data.mongodb.MongoDbFactory;
+import org.springframework.data.mongodb.util.MongoClientVersion;
 
 import com.mongodb.DBDecoderFactory;
 import com.mongodb.DBEncoderFactory;
@@ -30,7 +32,7 @@ import com.mongodb.WriteConcern;
 
 /**
  * A factory bean for construction of a {@link MongoClientOptions} instance.
- * 
+ *
  * @author Christoph Strobl
  * @author Oliver Gierke
  * @since 1.7
@@ -62,13 +64,14 @@ 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 = Integer.MIN_VALUE;
 
 	private boolean ssl;
 	private SSLSocketFactory sslSocketFactory;
 
 	/**
 	 * Set the {@link MongoClient} description.
-	 * 
+	 *
 	 * @param description
 	 */
 	public void setDescription(String description) {
@@ -77,7 +80,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the minimum number of connections per host.
-	 * 
+	 *
 	 * @param minConnectionsPerHost
 	 */
 	public void setMinConnectionsPerHost(int minConnectionsPerHost) {
@@ -87,7 +90,7 @@ 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 +101,7 @@ 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 +110,7 @@ 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 +119,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * The maximum idle time for a pooled connection.
-	 * 
+	 *
 	 * @param maxConnectionIdleTime
 	 */
 	public void setMaxConnectionIdleTime(int maxConnectionIdleTime) {
@@ -125,7 +128,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the maximum life time for a pooled connection.
-	 * 
+	 *
 	 * @param maxConnectionLifeTime
 	 */
 	public void setMaxConnectionLifeTime(int maxConnectionLifeTime) {
@@ -134,7 +137,7 @@ 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 +146,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the socket timeout. 0 is default and infinite.
-	 * 
+	 *
 	 * @param socketTimeout
 	 */
 	public void setSocketTimeout(int socketTimeout) {
@@ -152,7 +155,7 @@ 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 +164,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Set the {@link ReadPreference}.
-	 * 
+	 *
 	 * @param readPreference
 	 */
 	public void setReadPreference(ReadPreference readPreference) {
@@ -171,7 +174,7 @@ 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 +190,7 @@ 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 +200,7 @@ 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 +209,7 @@ 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 +218,7 @@ 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 +227,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	/**
 	 * Configures the name of the replica set.
-	 * 
+	 *
 	 * @param requiredReplicaSetName
 	 */
 	public void setRequiredReplicaSetName(String requiredReplicaSetName) {
@@ -233,7 +236,7 @@ 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) {
@@ -243,24 +246,41 @@ 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;
 	}
 
-	/* 
+	/**
+	 * 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() //
+		MongoClientOptions.Builder builder = MongoClientOptions.builder();
+
+		if (MongoClientVersion.isMongo3Driver() && serverSelectionTimeout != Integer.MIN_VALUE) {
+			new DirectFieldAccessor(builder).setPropertyValue("serverSelectionTimeout", serverSelectionTimeout);
+		}
+
+		return builder //
 				.alwaysUseMBeans(this.alwaysUseMBeans) //
 				.connectionsPerHost(this.connectionsPerHost) //
 				.connectTimeout(connectTimeout) //

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

@@ -1,6 +1,6 @@
 /*
  * 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
@@ -48,7 +48,7 @@ import com.mongodb.WriteResult;
  * 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
@@ -61,7 +61,7 @@ public interface MongoOperations {
 
 	/**
 	 * The collection name used for the specified class by this template.
-	 * 
+	 *
 	 * @param entityClass must not be {@literal null}.
 	 * @return
 	 */
@@ -71,7 +71,7 @@ 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 DBObject. 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.
 	 */
 	CommandResult executeCommand(String jsonCommand);
@@ -79,7 +79,7 @@ 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
 	 */
 	CommandResult executeCommand(DBObject command);
@@ -87,7 +87,7 @@ 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
 	 * @param options query options to use
 	 * @deprecated since 1.7. Please use {@link #executeCommand(DBObject, ReadPreference)}, as the MongoDB Java driver
@@ -99,7 +99,7 @@ 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
@@ -109,7 +109,7 @@ 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
@@ -121,7 +121,7 @@ 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>
@@ -132,7 +132,7 @@ 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
@@ -144,7 +144,7 @@ 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.
@@ -158,7 +158,7 @@ public interface MongoOperations {
 	 * href=http://www.mongodb.org/display/DOCS/Java+Driver+Concurrency>Java Driver Concurrency</a>}
 	 * <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 that specified the MongoDB actions to perform on the DB instance
 	 * @return a result object returned by the action or <tt>null</tt>
@@ -173,7 +173,7 @@ 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}.
@@ -187,7 +187,7 @@ 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}.
@@ -199,7 +199,7 @@ 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
 	 */
@@ -207,7 +207,7 @@ 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
@@ -216,7 +216,7 @@ public interface MongoOperations {
 
 	/**
 	 * Create an uncapped collection with the provided name.
-	 * 
+	 *
 	 * @param collectionName name of the collection
 	 * @return the created collection
 	 */
@@ -224,7 +224,7 @@ 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
@@ -233,7 +233,7 @@ public interface MongoOperations {
 
 	/**
 	 * A set of collection names.
-	 * 
+	 *
 	 * @return list of collection names
 	 */
 	Set<String> getCollectionNames();
@@ -242,7 +242,7 @@ 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.
 	 */
@@ -252,7 +252,7 @@ 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.
 	 */
@@ -262,7 +262,7 @@ 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.
 	 */
@@ -272,7 +272,7 @@ 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);
@@ -281,36 +281,39 @@ 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
 	 */
 	ScriptOperations scriptOps();
 
 	/**
-	 * Returns a new {@link BulkOperations} for the given collection.
-	 * 
+	 * Returns a new {@link BulkOperations} for the given collection. <br />
+	 * <strong>NOTE:</strong> Any additional support for field mapping, etc. is not available for {@literal update} or
+	 * {@literal remove} operations in bulk mode due to the lack of domain type information. Use
+	 * {@link #bulkOps(BulkMode, Class, String)} to get full type specific support.
+	 *
 	 * @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
@@ -319,7 +322,7 @@ 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.
@@ -328,7 +331,7 @@ 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.
@@ -344,7 +347,7 @@ 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
 	 */
@@ -358,7 +361,7 @@ 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
@@ -368,7 +371,7 @@ 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
@@ -383,7 +386,7 @@ 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
@@ -397,7 +400,7 @@ 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.
@@ -410,7 +413,7 @@ 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}.
@@ -421,7 +424,7 @@ 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
@@ -434,7 +437,7 @@ 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
@@ -447,7 +450,7 @@ public interface MongoOperations {
 
 	/**
 	 * 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
@@ -460,7 +463,7 @@ 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
@@ -474,7 +477,7 @@ 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
@@ -488,7 +491,7 @@ 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
@@ -505,7 +508,7 @@ 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
@@ -516,7 +519,7 @@ 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
@@ -534,7 +537,7 @@ 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.
@@ -551,7 +554,7 @@ 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.
@@ -561,8 +564,10 @@ public interface MongoOperations {
 	<T> T findOne(Query query, Class<T> entityClass, String collectionName);
 
 	/**
-	 * Determine result of given {@link Query} contains at least one element.
-	 * 
+	 * Determine result of given {@link Query} contains at least one element. <br />
+	 * <strong>NOTE:</strong> Any additional support for query/field mapping, etc. is not available due to the lack of
+	 * domain type information. Use {@link #exists(Query, Class, String)} to get full type specific support.
+	 *
 	 * @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
@@ -571,7 +576,7 @@ 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
@@ -580,7 +585,7 @@ 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.
@@ -596,7 +601,7 @@ 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.
@@ -612,7 +617,7 @@ 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.
@@ -624,7 +629,7 @@ 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.
@@ -634,7 +639,7 @@ 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
@@ -646,7 +651,7 @@ public interface MongoOperations {
 	/**
 	 * 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.
@@ -658,7 +663,7 @@ public interface MongoOperations {
 	/**
 	 * 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.
@@ -672,7 +677,7 @@ public interface MongoOperations {
 	 * 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.
@@ -686,7 +691,7 @@ public interface MongoOperations {
 	 * 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.
@@ -707,7 +712,7 @@ 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.
@@ -724,7 +729,7 @@ 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.
@@ -735,7 +740,7 @@ 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
@@ -745,8 +750,8 @@ 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)}.
-	 * 
+	 * onto document fields. Use {@link #count(Query, Class, String)} to get full type specific support.
+	 *
 	 * @param query
 	 * @param collectionName must not be {@literal null} or empty.
 	 * @return
@@ -757,7 +762,7 @@ 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.
@@ -778,7 +783,7 @@ 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);
@@ -790,7 +795,7 @@ 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
 	 */
@@ -798,7 +803,7 @@ 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
 	 */
@@ -806,7 +811,7 @@ 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
 	 */
@@ -815,7 +820,7 @@ 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);
@@ -832,7 +837,7 @@ 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);
@@ -849,7 +854,7 @@ 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
 	 */
@@ -858,7 +863,7 @@ 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
@@ -868,8 +873,10 @@ 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.
-	 * 
+	 * combining the query document and the update document. <br />
+	 * <strong>NOTE:</strong> Any additional support for field mapping, versions, etc. is not available due to the lack of
+	 * domain type information. Use {@link #upsert(Query, Update, Class, String)} to get full type specific support.
+	 *
 	 * @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.
@@ -881,7 +888,7 @@ 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
@@ -893,7 +900,7 @@ 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.
@@ -904,8 +911,10 @@ 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.
-	 * 
+	 * the provided updated document. <br />
+	 * <strong>NOTE:</strong> Any additional support for field mapping, versions, etc. is not available due to the lack of
+	 * domain type information. Use {@link #updateFirst(Query, Update, Class, String)} to get full type specific support.
+	 *
 	 * @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.
@@ -917,7 +926,7 @@ 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.
@@ -930,7 +939,7 @@ 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.
@@ -941,8 +950,10 @@ public interface MongoOperations {
 
 	/**
 	 * Updates all objects that are found in the specified collection that matches the query document criteria with the
-	 * provided updated document.
-	 * 
+	 * provided updated document. <br />
+	 * <strong>NOTE:</strong> Any additional support for field mapping, versions, etc. is not available due to the lack of
+	 * domain type information. Use {@link #updateMulti(Query, Update, Class, String)} to get full type specific support.
+	 *
 	 * @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.
@@ -954,7 +965,7 @@ 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.
@@ -966,14 +977,14 @@ public interface MongoOperations {
 
 	/**
 	 * Remove the given object from the collection by id.
-	 * 
+	 *
 	 * @param object
 	 */
 	WriteResult remove(Object object);
 
 	/**
 	 * Removes the given object from the given collection.
-	 * 
+	 *
 	 * @param object
 	 * @param collection must not be {@literal null} or empty.
 	 */
@@ -982,7 +993,7 @@ 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
 	 */
@@ -991,7 +1002,7 @@ 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
@@ -1000,18 +1011,22 @@ 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.
-	 * 
+	 * conversion/mapping done for any criteria using the id field. <br />
+	 * <strong>NOTE:</strong> Any additional support for field mapping is not available due to the lack of domain type
+	 * information. Use {@link #remove(Query, Class, String)} to get full type specific support.
+	 *
 	 * @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
 	 */
 	WriteResult remove(Query query, String collectionName);
 
 	/**
-	 * Returns and removes all documents form the specified collection that match the provided query.
-	 * 
-	 * @param query
-	 * @param collectionName
+	 * Returns and removes all documents form the specified collection that match the provided query. <br />
+	 * <strong>NOTE:</strong> Any additional support for field mapping is not available due to the lack of domain type
+	 * information. Use {@link #findAllAndRemove(Query, Class, String)} to get full type specific support.
+	 *
+	 * @param query must not be {@literal null}.
+	 * @param collectionName must not be {@literal null}.
 	 * @return
 	 * @since 1.5
 	 */
@@ -1019,7 +1034,7 @@ 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
@@ -1031,7 +1046,7 @@ 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
@@ -1042,7 +1057,7 @@ public interface MongoOperations {
 
 	/**
 	 * Returns the underlying {@link MongoConverter}.
-	 * 
+	 *
 	 * @return
 	 */
 	MongoConverter getConverter();

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.
@@ -61,12 +61,14 @@ import org.springframework.data.mapping.model.ConvertingPropertyAccessor;
 import org.springframework.data.mapping.model.MappingException;
 import org.springframework.data.mongodb.MongoDbFactory;
 import org.springframework.data.mongodb.core.BulkOperations.BulkMode;
+import org.springframework.data.mongodb.core.DefaultBulkOperations.BulkOperationContext;
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
 import org.springframework.data.mongodb.core.aggregation.AggregationOperationContext;
 import org.springframework.data.mongodb.core.aggregation.AggregationResults;
 import org.springframework.data.mongodb.core.aggregation.Fields;
 import org.springframework.data.mongodb.core.aggregation.TypeBasedAggregationOperationContext;
 import org.springframework.data.mongodb.core.aggregation.TypedAggregation;
+import org.springframework.data.mongodb.core.convert.CustomConversions;
 import org.springframework.data.mongodb.core.convert.DbRefResolver;
 import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver;
 import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
@@ -126,7 +128,7 @@ import com.mongodb.util.JSONParseException;
 
 /**
  * Primary implementation of {@link MongoOperations}.
- * 
+ *
  * @author Thomas Risberg
  * @author Graeme Rocher
  * @author Mark Pollack
@@ -141,6 +143,8 @@ import com.mongodb.util.JSONParseException;
  * @author Doménique Tilleuil
  * @author Niko Schmuck
  * @author Mark Paluch
+ * @author Laszlo Csontos
+ * @author Borislav Rangelov
  */
 @SuppressWarnings("deprecation")
 public class MongoTemplate implements MongoOperations, ApplicationContextAware {
@@ -177,7 +181,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	/**
 	 * Constructor used for a basic template configuration
-	 * 
+	 *
 	 * @param mongo must not be {@literal null}.
 	 * @param databaseName must not be {@literal null} or empty.
 	 */
@@ -188,7 +192,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * 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
@@ -199,7 +203,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	/**
 	 * Constructor used for a basic template configuration.
-	 * 
+	 *
 	 * @param mongoDbFactory must not be {@literal null}.
 	 */
 	public MongoTemplate(MongoDbFactory mongoDbFactory) {
@@ -208,13 +212,13 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	/**
 	 * Constructor used for a basic template configuration.
-	 * 
+	 *
 	 * @param mongoDbFactory must not be {@literal null}.
 	 * @param mongoConverter
 	 */
 	public MongoTemplate(MongoDbFactory mongoDbFactory, MongoConverter mongoConverter) {
 
-		Assert.notNull(mongoDbFactory);
+		Assert.notNull(mongoDbFactory, "MongoDbFactory must not be null!");
 
 		this.mongoDbFactory = mongoDbFactory;
 		this.exceptionTranslator = mongoDbFactory.getExceptionTranslator();
@@ -237,7 +241,7 @@ 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}.
-	 * 
+	 *
 	 * @param resultChecking
 	 */
 	public void setWriteResultChecking(WriteResultChecking resultChecking) {
@@ -248,7 +252,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	 * Configures the {@link WriteConcern} to be used with the template. If none is configured the {@link WriteConcern}
 	 * configured on the {@link MongoDbFactory} will apply. If you configured a {@link Mongo} instance no
 	 * {@link WriteConcern} will be used.
-	 * 
+	 *
 	 * @param writeConcern
 	 */
 	public void setWriteConcern(WriteConcern writeConcern) {
@@ -257,7 +261,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	/**
 	 * Configures the {@link WriteConcernResolver} to be used with the template.
-	 * 
+	 *
 	 * @param writeConcernResolver
 	 */
 	public void setWriteConcernResolver(WriteConcernResolver writeConcernResolver) {
@@ -267,7 +271,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * Used by @{link {@link #prepareCollection(DBCollection)} to set the {@link ReadPreference} before any operations are
 	 * performed.
-	 * 
+	 *
 	 * @param readPreference
 	 */
 	public void setReadPreference(ReadPreference readPreference) {
@@ -294,7 +298,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	 * they were registered for the current {@link MappingContext}. If no creator for the current {@link MappingContext}
 	 * can be found we manually add the internally created one as {@link ApplicationListener} to make sure indexes get
 	 * created appropriately for entity types persisted through this {@link MongoTemplate} instance.
-	 * 
+	 *
 	 * @param context must not be {@literal null}.
 	 */
 	private void prepareIndexCreator(ApplicationContext context) {
@@ -314,15 +318,15 @@ 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
 	 */
 	public MongoConverter getConverter() {
 		return this.mongoConverter;
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.MongoOperations#executeAsStream(org.springframework.data.mongodb.core.query.Query, java.lang.Class)
 	 */
@@ -332,7 +336,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 		return stream(query, entityType, determineCollectionName(entityType));
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.MongoOperations#stream(org.springframework.data.mongodb.core.query.Query, java.lang.Class, java.lang.String)
 	 */
@@ -428,7 +432,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * Execute a MongoDB query and iterate over the query results on a per-document basis with a
 	 * {@link DocumentCallbackHandler} using the provided CursorPreparer.
-	 * 
+	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
 	 *          specification, must not be {@literal null}.
 	 * @param collectionName name of the collection to retrieve the objects from
@@ -439,7 +443,7 @@ 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!");
 
 		DBObject queryObject = queryMapper.getMappedObject(query.getQueryObject(), null);
 		DBObject sortObject = query.getSortObject();
@@ -455,7 +459,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	public <T> T execute(DbCallback<T> action) {
 
-		Assert.notNull(action);
+		Assert.notNull(action, "DbCallbackmust not be null!");
 
 		try {
 			DB db = this.getDb();
@@ -471,7 +475,7 @@ 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 {
 			DBCollection collection = getAndPrepareCollection(getDb(), collectionName);
@@ -557,7 +561,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	}
 
 	public IndexOperations indexOps(Class<?> entityClass) {
-		return new DefaultIndexOperations(this, determineCollectionName(entityClass));
+		return new DefaultIndexOperations(this, determineCollectionName(entityClass), entityClass);
 	}
 
 	public BulkOperations bulkOps(BulkMode bulkMode, String collectionName) {
@@ -573,10 +577,10 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 		Assert.notNull(mode, "BulkMode must not be null!");
 		Assert.hasText(collectionName, "Collection name must not be null or empty!");
 
-		DefaultBulkOperations operations = new DefaultBulkOperations(this, mode, collectionName, entityType);
+		DefaultBulkOperations operations = new DefaultBulkOperations(this, collectionName,
+				new BulkOperationContext(mode, getPersistentEntity(entityType), queryMapper, updateMapper));
 
 		operations.setExceptionTranslator(exceptionTranslator);
-		operations.setWriteConcernResolver(writeConcernResolver);
 		operations.setDefaultWriteConcern(writeConcern);
 
 		return operations;
@@ -699,8 +703,8 @@ 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((DBObject) element));
@@ -749,7 +753,8 @@ 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));
 	}
 
@@ -763,7 +768,8 @@ 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 DBObject dbObject = query == null ? null
 				: queryMapper.getMappedObject(query.getQueryObject(),
 						entityClass == null ? null : mappingContext.getPersistentEntity(entityClass));
@@ -804,7 +810,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * Prepare the collection before any processing is done using it. This allows a convenient way to apply settings like
 	 * slaveOk() etc. Can be overridden in sub-classes.
-	 * 
+	 *
 	 * @param collection
 	 */
 	protected void prepareCollection(DBCollection collection) {
@@ -818,7 +824,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	 * settings in sub-classes. <br />
 	 * In case of using MongoDB Java driver version 3 the returned {@link WriteConcern} will be defaulted to
 	 * {@link WriteConcern#ACKNOWLEDGED} when {@link WriteResultChecking} is set to {@link WriteResultChecking#EXCEPTION}.
-	 * 
+	 *
 	 * @param writeConcern any WriteConcern already configured or null
 	 * @return The prepared WriteConcern or null
 	 */
@@ -842,11 +848,9 @@ 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);
 
 		DBObject dbDoc = toDbObject(objectToSave, writer);
 
@@ -934,15 +938,16 @@ 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<DBObject> dbObjectList = new ArrayList<DBObject>();
+
 		for (T o : batchToSave) {
 
 			initializeVersionProperty(o);
-			BasicDBObject dbDoc = new BasicDBObject();
-
 			maybeEmitEvent(new BeforeConvertEvent<T>(o, collectionName));
+
+			BasicDBObject dbDoc = new BasicDBObject();
 			writer.write(o, dbDoc);
 
 			maybeEmitEvent(new BeforeSaveEvent<T>(o, dbDoc, collectionName));
@@ -963,14 +968,14 @@ 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());
 
@@ -999,23 +1004,23 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 			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));
-
 			// Bump version number
 			convertingAccessor.setProperty(versionProperty, versionNumber.longValue() + 1);
 
+			maybeEmitEvent(new BeforeConvertEvent<T>(objectToSave, collectionName));
+			assertUpdateableIdIfNotSet(objectToSave);
+
 			BasicDBObject dbObject = new BasicDBObject();
 
-			maybeEmitEvent(new BeforeConvertEvent<T>(objectToSave, collectionName));
 			this.mongoConverter.write(objectToSave, dbObject);
 
 			maybeEmitEvent(new BeforeSaveEvent<T>(objectToSave, dbObject, collectionName));
 			Update update = Update.fromDBObject(dbObject, ID_FIELD);
 
+			// 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));
+
 			doUpdate(collectionName, query, update, objectToSave.getClass(), false, false);
 			maybeEmitEvent(new AfterSaveEvent<T>(objectToSave, dbObject, collectionName));
 		}
@@ -1023,9 +1028,8 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	protected <T> void doSave(String collectionName, T objectToSave, MongoWriter<T> writer) {
 
-		assertUpdateableIdIfNotSet(objectToSave);
-
 		maybeEmitEvent(new BeforeConvertEvent<T>(objectToSave, collectionName));
+		assertUpdateableIdIfNotSet(objectToSave);
 
 		DBObject dbDoc = toDbObject(objectToSave, writer);
 
@@ -1216,7 +1220,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	public WriteResult remove(Object object, String collection) {
 
-		Assert.hasText(collection);
+		Assert.hasText(collection, "Collection name must not be null or empty!");
 
 		if (object == null) {
 			return null;
@@ -1228,7 +1232,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * Returns {@link Entry} containing the field name of the id property as {@link Entry#getKey()} and the {@link Id}s
 	 * property value as its {@link Entry#getValue()}.
-	 * 
+	 *
 	 * @param object
 	 * @return
 	 */
@@ -1255,7 +1259,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	/**
 	 * Returns a {@link Query} for the given entity by its id.
-	 * 
+	 *
 	 * @param object must not be {@literal null}.
 	 * @return
 	 */
@@ -1267,7 +1271,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	/**
 	 * Returns a {@link Query} for the given entities by their ids.
-	 * 
+	 *
 	 * @param objects must not be {@literal null} or {@literal empty}.
 	 * @return
 	 */
@@ -1513,7 +1517,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	 */
 	@Override
 	public <T> List<T> findAllAndRemove(Query query, String collectionName) {
-		return findAndRemove(query, null, collectionName);
+		return (List<T>) findAllAndRemove(query, Object.class, collectionName);
 	}
 
 	/*
@@ -1538,7 +1542,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	 * Retrieve and remove all documents matching the given {@code query} by calling {@link #find(Query, Class, String)}
 	 * and {@link #remove(Query, Class, String)}, whereas the {@link Query} for {@link #remove(Query, Class, String)} is
 	 * constructed out of the find result.
-	 * 
+	 *
 	 * @param collectionName
 	 * @param query
 	 * @param entityClass
@@ -1578,7 +1582,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	/**
 	 * Returns the potentially mapped results of the given {@commandResult} contained some.
-	 * 
+	 *
 	 * @param outputType
 	 * @param commandResult
 	 * @return
@@ -1690,7 +1694,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	/**
 	 * Create the specified collection using the provided options
-	 * 
+	 *
 	 * @param collectionName
 	 * @param collectionOptions
 	 * @return the collection that was created
@@ -1711,7 +1715,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * Map the results of an ad-hoc query on the default MongoDB collection to an object using the template's converter.
 	 * The query document is specified as a standard {@link DBObject} and so is the fields specification.
-	 * 
+	 *
 	 * @param collectionName name of the collection to retrieve the objects from.
 	 * @param query the query document that specifies the criteria used to find a record.
 	 * @param fields the document that specifies the fields to be returned.
@@ -1736,7 +1740,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * Map the results of an ad-hoc query on the default MongoDB collection to a List using the template's converter. The
 	 * query document is specified as a standard DBObject and so is the fields specification.
-	 * 
+	 *
 	 * @param collectionName name of the collection to retrieve the objects from
 	 * @param query the query document that specifies the criteria used to find a record
 	 * @param fields the document that specifies the fields to be returned
@@ -1752,7 +1756,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	 * Map the results of an ad-hoc query on the default MongoDB collection to a List of the specified type. The object is
 	 * converted from the MongoDB native representation using an instance of {@see MongoConverter}. The query document is
 	 * specified as a standard DBObject and so is the fields specification.
-	 * 
+	 *
 	 * @param collectionName name of the collection to retrieve the objects from.
 	 * @param query the query document that specifies the criteria used to find a record.
 	 * @param fields the document that specifies the fields to be returned.
@@ -1805,7 +1809,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	 * The first document that matches the query is returned and also removed from the collection in the database.
 	 * <p/>
 	 * The query document is specified as a standard DBObject and so is the fields specification.
-	 * 
+	 *
 	 * @param collectionName name of the collection to retrieve the objects from
 	 * @param query the query document that specifies the criteria used to find a record
 	 * @param entityClass the parameterized type of the returned list.
@@ -1856,7 +1860,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	/**
 	 * Populates the id property of the saved object, if it's not set already.
-	 * 
+	 *
 	 * @param savedObject
 	 * @param id
 	 */
@@ -1906,7 +1910,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	 * <li>Execute the given {@link ConnectionCallback} for a {@link DBObject}.</li>
 	 * <li>Apply the given {@link DbObjectCallback} to each of the {@link DBObject}s to obtain the result.</li>
 	 * <ol>
-	 * 
+	 *
 	 * @param <T>
 	 * @param collectionCallback the callback to retrieve the {@link DBObject} with
 	 * @param objectCallback the {@link DbObjectCallback} to transform {@link DBObject}s into the actual domain type
@@ -1935,7 +1939,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	 * <li>Iterate over the {@link DBCursor} and applies the given {@link DbObjectCallback} to each of the
 	 * {@link DBObject}s collecting the actual result {@link List}.</li>
 	 * <ol>
-	 * 
+	 *
 	 * @param <T>
 	 * @param collectionCallback the callback to retrieve the {@link DBCursor} with
 	 * @param preparer the {@link CursorPreparer} to potentially modify the {@link DBCursor} before ireating over it
@@ -2042,7 +2046,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	/**
 	 * Handles {@link WriteResult} errors based on the configured {@link WriteResultChecking}.
-	 * 
+	 *
 	 * @param writeResult
 	 * @param query
 	 * @param operation
@@ -2086,7 +2090,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * 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}.
 	 */
@@ -2107,8 +2111,16 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	private static final MongoConverter getDefaultMongoConverter(MongoDbFactory factory) {
 
 		DbRefResolver dbRefResolver = new DefaultDbRefResolver(factory);
-		MappingMongoConverter converter = new MappingMongoConverter(dbRefResolver, new MongoMappingContext());
+		CustomConversions conversions = new CustomConversions(Collections.emptyList());
+
+		MongoMappingContext mappingContext = new MongoMappingContext();
+		mappingContext.setSimpleTypeHolder(conversions.getSimpleTypeHolder());
+		mappingContext.afterPropertiesSet();
+
+		MappingMongoConverter converter = new MappingMongoConverter(dbRefResolver, mappingContext);
+		converter.setCustomConversions(conversions);
 		converter.afterPropertiesSet();
+
 		return converter;
 	}
 
@@ -2124,7 +2136,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * Tries to convert the given {@link RuntimeException} into a {@link DataAccessException} but returns the original
 	 * exception if the conversation failed. Thus allows safe re-throwing of the return value.
-	 * 
+	 *
 	 * @param ex the exception to translate
 	 * @param exceptionTranslator the {@link PersistenceExceptionTranslator} to be used for translation
 	 * @return
@@ -2139,7 +2151,7 @@ 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)}.
@@ -2162,7 +2174,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * Simple {@link CollectionCallback} that takes a query {@link DBObject} plus an optional fields specification
 	 * {@link DBObject} and executes that against the {@link DBCollection}.
-	 * 
+	 *
 	 * @author Oliver Gierke
 	 * @author Thomas Risberg
 	 */
@@ -2196,7 +2208,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * Simple {@link CollectionCallback} that takes a query {@link DBObject} plus an optional fields specification
 	 * {@link DBObject} and executes that against the {@link DBCollection}.
-	 * 
+	 *
 	 * @author Oliver Gierke
 	 * @author Thomas Risberg
 	 */
@@ -2227,7 +2239,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * Simple {@link CollectionCallback} that takes a query {@link DBObject} plus an optional fields specification
 	 * {@link DBObject} and executes that against the {@link DBCollection}.
-	 * 
+	 *
 	 * @author Thomas Risberg
 	 */
 	private static class FindAndRemoveCallback implements CollectionCallback<DBObject> {
@@ -2272,7 +2284,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	/**
 	 * Simple internal callback to allow operations on a {@link DBObject}.
-	 * 
+	 *
 	 * @author Oliver Gierke
 	 * @author Thomas Darimont
 	 */
@@ -2285,7 +2297,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * Simple {@link DbObjectCallback} that will transform {@link DBObject} into the given target type using the given
 	 * {@link MongoReader}.
-	 * 
+	 *
 	 * @author Oliver Gierke
 	 * @author Christoph Strobl
 	 */
@@ -2297,8 +2309,9 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 		public ReadDbObjectCallback(EntityReader<? super T, DBObject> 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;
@@ -2431,7 +2444,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 	/**
 	 * {@link DbObjectCallback} that assumes a {@link GeoResult} to be created, delegates actual content unmarshalling to
 	 * a delegate and creates a {@link GeoResult} from the result.
-	 * 
+	 *
 	 * @author Oliver Gierke
 	 */
 	static class GeoNearResultDbObjectCallback<T> implements DbObjectCallback<GeoResult<T>> {
@@ -2442,11 +2455,13 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 		/**
 		 * Creates a new {@link GeoNearResultDbObjectCallback} using the given {@link DbObjectCallback} delegate for
 		 * {@link GeoResult} content unmarshalling.
-		 * 
+		 *
 		 * @param delegate must not be {@literal null}.
 		 */
 		public GeoNearResultDbObjectCallback(DbObjectCallback<T> delegate, Metric metric) {
-			Assert.notNull(delegate);
+
+			Assert.notNull(delegate, "DocumentCallback must not be null!");
+
 			this.delegate = delegate;
 			this.metric = metric;
 		}
@@ -2464,7 +2479,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 	/**
 	 * A {@link CloseableIterator} that is backed by a MongoDB {@link Cursor}.
-	 * 
+	 *
 	 * @since 1.7
 	 * @author Thomas Darimont
 	 */
@@ -2476,7 +2491,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 		/**
 		 * Creates a new {@link CloseableIterableCursorAdapter} backed by the given {@link Cursor}.
-		 * 
+		 *
 		 * @param cursor
 		 * @param exceptionTranslator
 		 * @param objectReadCallback
@@ -2524,7 +2539,11 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware {
 
 			Cursor c = cursor;
 			try {
-				c.close();
+
+				if (c != null) {
+					c.close();
+				}
+
 			} catch (RuntimeException ex) {
 				throw potentiallyConvertRuntimeException(ex, exceptionTranslator);
 			} finally {

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

@@ -0,0 +1,153 @@
+/*
+ * 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.springframework.util.ObjectUtils;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.DBObject;
+
+/**
+ * @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#toDbObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public DBObject toDbObject(AggregationOperationContext context) {
+		return toDbObject(this.value, context);
+	}
+
+	@SuppressWarnings("unchecked")
+	public DBObject toDbObject(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) {
+
+			DBObject dbo = new BasicDBObject();
+			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 BasicDBObject(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).toDbObject(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 +1,648 @@
+/*
+ * 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;
+
+import com.mongodb.DBObject;
+
+/**
+ * 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#toDbObject(java.lang.Object, org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		@SuppressWarnings("unchecked")
+		public DBObject toDbObject(Object value, AggregationOperationContext context) {
+
+			if (value instanceof List) {
+				if (((List) value).size() == 1) {
+					return super.toDbObject(((List<Object>) value).iterator().next(), context);
+				}
+			}
+
+			return super.toDbObject(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#toDbObject(java.lang.Object, org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		@SuppressWarnings("unchecked")
+		public DBObject toDbObject(Object value, AggregationOperationContext context) {
+
+			if (value instanceof List) {
+				if (((List) value).size() == 1) {
+					return super.toDbObject(((List<Object>) value).iterator().next(), context);
+				}
+			}
+
+			return super.toDbObject(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#toDbObject(java.lang.Object, org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		@SuppressWarnings("unchecked")
+		public DBObject toDbObject(Object value, AggregationOperationContext context) {
+
+			if (value instanceof List) {
+				if (((List) value).size() == 1) {
+					return super.toDbObject(((List<Object>) value).iterator().next(), context);
+				}
+			}
+
+			return super.toDbObject(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#toDbObject(java.lang.Object, org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		@SuppressWarnings("unchecked")
+		public DBObject toDbObject(Object value, AggregationOperationContext context) {
+
+			if (value instanceof List) {
+				if (((List) value).size() == 1) {
+					return super.toDbObject(((List<Object>) value).iterator().next(), context);
+				}
+			}
+
+			return super.toDbObject(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#toDbObject(java.lang.Object, org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		@SuppressWarnings("unchecked")
+		public DBObject toDbObject(Object value, AggregationOperationContext context) {
+
+			if (value instanceof List) {
+				if (((List) value).size() == 1) {
+					return super.toDbObject(((List<Object>) value).iterator().next(), context);
+				}
+			}
+
+			return super.toDbObject(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#toDbObject(java.lang.Object, org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		@SuppressWarnings("unchecked")
+		public DBObject toDbObject(Object value, AggregationOperationContext context) {
+
+			if (value instanceof List) {
+				if (((List) value).size() == 1) {
+					return super.toDbObject(((List<Object>) value).iterator().next(), context);
+				}
+			}
+
+			return super.toDbObject(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.
@@ -23,11 +23,18 @@ import java.util.List;
 
 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;
@@ -62,7 +69,7 @@ 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;
@@ -196,7 +203,7 @@ 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
@@ -215,6 +222,40 @@ 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+.
@@ -279,6 +320,18 @@ 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}.
 	 *
@@ -341,6 +394,17 @@ 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.
@@ -355,6 +419,73 @@ 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}.
 	 *
@@ -384,65 +515,13 @@ 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();
 	}
 
 	/**
@@ -498,24 +577,7 @@ public class Aggregation {
 	 */
 	public DBObject toDbObject(String inputCollectionName, AggregationOperationContext rootContext) {
 
-		AggregationOperationContext context = rootContext;
-		List<DBObject> operationDocuments = new ArrayList<DBObject>(operations.size());
-
-		for (AggregationOperation operation : operations) {
-
-			operationDocuments.add(operation.toDBObject(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<DBObject> operationDocuments = AggregationOperationRenderer.toDBObject(operations, rootContext);
 
 		DBObject command = new BasicDBObject("aggregate", inputCollectionName);
 		command.put("pipeline", operationDocuments);
@@ -531,50 +593,14 @@ public class Aggregation {
 	 */
 	@Override
 	public String toString() {
-		return SerializationUtils
-				.serializeToJsonSafely(toDbObject("__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.DBObject)
-		 */
-		@Override
-		public DBObject getMappedObject(DBObject dbObject) {
-			return dbObject;
-		}
-
-		/* 
-		 * (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(toDbObject("__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 {
 
@@ -607,7 +633,7 @@ 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

@@ -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.
@@ -29,11 +29,14 @@ import com.mongodb.DBObject;
  * 
  * @author Thomas Darimont
  * @author Oliver Gierke
- * @since 1.10
+ * @author Christoph Strobl
+ * @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 +55,7 @@ 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 +1,109 @@
+/*
+ * 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.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;
+
+import com.mongodb.DBObject;
+
+/**
+ * Rendering support for {@link AggregationOperation} into a {@link List} of {@link com.mongodb.DBObject}.
+ *
+ * @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 DBObject} representation.
+	 *
+	 * @param operations must not be {@literal null}.
+	 * @param context must not be {@literal null}.
+	 * @return the {@link List} of {@link DBObject}.
+	 */
+	static List<DBObject> toDBObject(List<AggregationOperation> operations, AggregationOperationContext rootContext) {
+
+		List<DBObject> operationDocuments = new ArrayList<DBObject>(operations.size());
+
+		AggregationOperationContext contextToUse = rootContext;
+
+		for (AggregationOperation operation : operations) {
+
+			operationDocuments.add(operation.toDBObject(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(com.mongodb.DBObject)
+		 */
+		@Override
+		public DBObject getMappedObject(DBObject dbObject) {
+			return dbObject;
+		}
+
+		/*
+		 * (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

@@ -21,7 +21,7 @@ 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

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2014 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 com.mongodb.DBObject;
  * @author Tobias Trelle
  * @author Oliver Gierke
  * @author Thomas Darimont
+ * @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, DBObject 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 +1,74 @@
+/*
+ * 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;
+
+import com.mongodb.DBObject;
+
+/**
+ * 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#toDbObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public DBObject toDbObject(AggregationOperationContext context) {
+		return (DBObject) 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 com.mongodb.BasicDBObject;
+import com.mongodb.DBObject;
+
+/**
+ * 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#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public DBObject toDBObject(AggregationOperationContext context) {
+
+		DBObject options = new BasicDBObject();
+
+		options.put("buckets", buckets);
+		options.putAll(super.toDBObject(context));
+
+		if (granularity != null) {
+			options.put("granularity", granularity);
+		}
+
+		return new BasicDBObject("$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 +1,227 @@
+/*
+ * 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 com.mongodb.BasicDBObject;
+import com.mongodb.DBObject;
+
+/**
+ * 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#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public DBObject toDBObject(AggregationOperationContext context) {
+
+		DBObject options = new BasicDBObject();
+
+		options.put("boundaries", context.getMappedObject(new BasicDBObject("$set", boundaries)).get("$set"));
+
+		if (defaultBucket != null) {
+			options.put("default", context.getMappedObject(new BasicDBObject("$set", defaultBucket)).get("$set"));
+		}
+
+		options.putAll(super.toDBObject(context));
+
+		return new BasicDBObject("$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 +1,680 @@
+/*
+ * 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 com.mongodb.BasicDBObject;
+import com.mongodb.DBObject;
+
+/**
+ * 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 DBObject toDbObject(AggregationOperationContext context) {
+				return new BasicDBObject("$sum", 1);
+			}
+		});
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public DBObject toDBObject(AggregationOperationContext context) {
+
+		DBObject dbObject = new BasicDBObject();
+
+		dbObject.put("groupBy", groupByExpression == null ? context.getReference(groupByField).toString()
+				: groupByExpression.toDbObject(context));
+
+		if (!outputs.isEmpty()) {
+			dbObject.put("output", outputs.toDbObject(context));
+		}
+
+		return dbObject;
+	}
+
+	/* (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#toDbObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public DBObject toDbObject(AggregationOperationContext context) {
+
+			DBObject dbObject = new BasicDBObject();
+
+			for (Output output : outputs) {
+				dbObject.put(output.getExposedField().getName(), output.toDbObject(context));
+			}
+
+			return dbObject;
+		}
+
+	}
+
+	/**
+	 * 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#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public DBObject toDbObject(AggregationOperationContext context) {
+
+			List<Object> operationArguments = getOperationArguments(context);
+			return new BasicDBObject(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).toDbObject(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#toDbObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public DBObject toDbObject(AggregationOperationContext context) {
+			return (DBObject) 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#toDbObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public DBObject toDbObject(AggregationOperationContext context) {
+			return expression.toDbObject(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

@@ -1,394 +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.springframework.dao.InvalidDataAccessApiUsageException;
-import org.springframework.data.mongodb.core.query.CriteriaDefinition;
-import org.springframework.util.Assert;
-import org.springframework.util.ClassUtils;
-
-import com.mongodb.BasicDBObject;
-import com.mongodb.DBObject;
-
-/**
- * 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 DBObject 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 DBObject 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(DBObject 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#toDbObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
-	 */
-	@Override
-	public DBObject toDbObject(AggregationOperationContext context) {
-
-		BasicDBObject condObject = new BasicDBObject();
-
-		condObject.append("if", resolveCriteria(context, condition));
-		condObject.append("then", resolveValue(context, thenValue));
-		condObject.append("else", resolveValue(context, otherwiseValue));
-
-		return new BasicDBObject("$cond", condObject);
-	}
-
-	private Object resolveValue(AggregationOperationContext context, Object value) {
-
-		if (value instanceof DBObject || value instanceof Field) {
-			return resolve(context, value);
-		}
-
-		if (value instanceof ConditionalOperator) {
-			return ((ConditionalOperator) value).toDbObject(context);
-		}
-
-		return context.getMappedObject(new BasicDBObject("$set", value)).get("$set");
-	}
-
-	private Object resolveCriteria(AggregationOperationContext context, Object value) {
-
-		if (value instanceof DBObject || value instanceof Field) {
-			return resolve(context, value);
-		}
-
-		if (value instanceof CriteriaDefinition) {
-
-			DBObject 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: DBObject, Field references, Criteria, got: %s", value));
-	}
-
-	private List<Object> getClauses(AggregationOperationContext context, DBObject 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 DBObject) {
-					args.addAll(getClauses(context, (DBObject) clause));
-				}
-			}
-
-			clauses.add(new BasicDBObject(key, args));
-
-		} else if (predicate instanceof DBObject) {
-
-			DBObject nested = (DBObject) predicate;
-
-			for (String s : nested.keySet()) {
-
-				if (!isKeyword(s)) {
-					continue;
-				}
-
-				List<Object> args = new ArrayList<Object>();
-				args.add("$" + key);
-				args.add(nested.get(s));
-				clauses.add(new BasicDBObject(s, args));
-			}
-
-		} else if (!isKeyword(key)) {
-
-			List<Object> args = new ArrayList<Object>();
-			args.add("$" + key);
-			args.add(predicate);
-			clauses.add(new BasicDBObject("$eq", args));
-		}
-
-		return clauses;
-	}
-
-	/**
-	 * Returns whether the given {@link String} is a MongoDB keyword.
-	 *
-	 * @param candidate
-	 * @return
-	 */
-	private boolean isKeyword(String candidate) {
-		return candidate.startsWith("$");
-	}
-
-	private Object resolve(AggregationOperationContext context, Object value) {
-
-		if (value instanceof DBObject) {
-			return context.getMappedObject((DBObject) 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(DBObject 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 DBObject}, 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 DBObject}, 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(com.mongodb.DBObject)
-		 */
-		@Override
-		public ConditionalExpressionBuilder when(DBObject 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 +1,978 @@
+/*
+ * 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.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;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.DBObject;
+
+/**
+ * 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#toDbObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public DBObject toDbObject(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).toDbObject(context));
+			} else {
+				list.add(condition);
+			}
+
+			list.add(resolve(value, context));
+
+			return new BasicDBObject("$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).toDbObject(context);
+			} else if (value instanceof DBObject) {
+				return value;
+			}
+
+			return context.getMappedObject(new BasicDBObject("$set", value)).get("$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 DBObject}, 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#toDbObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+			 */
+			@Override
+			public DBObject toDbObject(AggregationOperationContext context) {
+
+				DBObject dbo = new BasicDBObject("case", when.toDbObject(context));
+
+				if (then instanceof AggregationExpression) {
+					dbo.put("then", ((AggregationExpression) then).toDbObject(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 DBObject 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#toDbObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public DBObject toDbObject(AggregationOperationContext context) {
+
+			BasicDBObject condObject = new BasicDBObject();
+
+			condObject.append("if", resolveCriteria(context, condition));
+			condObject.append("then", resolveValue(context, thenValue));
+			condObject.append("else", resolveValue(context, otherwiseValue));
+
+			return new BasicDBObject("$cond", condObject);
+		}
+
+		private Object resolveValue(AggregationOperationContext context, Object value) {
+
+			if (value instanceof DBObject || value instanceof Field) {
+				return resolve(context, value);
+			}
+
+			if (value instanceof AggregationExpression) {
+				return ((AggregationExpression) value).toDbObject(context);
+			}
+
+			return context.getMappedObject(new BasicDBObject("$set", value)).get("$set");
+		}
+
+		private Object resolveCriteria(AggregationOperationContext context, Object value) {
+
+			if (value instanceof DBObject || value instanceof Field) {
+				return resolve(context, value);
+			}
+
+			if (value instanceof AggregationExpression) {
+				return ((AggregationExpression) value).toDbObject(context);
+			}
+
+			if (value instanceof CriteriaDefinition) {
+
+				DBObject 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: DBObject, Field references, Criteria, got: %s", value));
+		}
+
+		private List<Object> getClauses(AggregationOperationContext context, DBObject 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 DBObject) {
+						args.addAll(getClauses(context, (DBObject) clause));
+					}
+				}
+
+				clauses.add(new BasicDBObject(key, args));
+
+			} else if (predicate instanceof DBObject) {
+
+				DBObject nested = (DBObject) predicate;
+
+				for (String s : nested.keySet()) {
+
+					if (!isKeyword(s)) {
+						continue;
+					}
+
+					List<Object> args = new ArrayList<Object>();
+					args.add("$" + key);
+					args.add(nested.get(s));
+					clauses.add(new BasicDBObject(s, args));
+				}
+
+			} else if (!isKeyword(key)) {
+
+				List<Object> args = new ArrayList<Object>();
+				args.add("$" + key);
+				args.add(predicate);
+				clauses.add(new BasicDBObject("$eq", args));
+			}
+
+			return clauses;
+		}
+
+		/**
+		 * Returns whether the given {@link String} is a MongoDB keyword.
+		 *
+		 * @param candidate
+		 * @return
+		 */
+		private boolean isKeyword(String candidate) {
+			return candidate.startsWith("$");
+		}
+
+		private Object resolve(AggregationOperationContext context, Object value) {
+
+			if (value instanceof DBObject) {
+				return context.getMappedObject((DBObject) 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(DBObject 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(DBObject 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 DBObject}, 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 DBObject}, 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(com.mongodb.DBObject)
+			 */
+			@Override
+			public ConditionalExpressionBuilder when(DBObject 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 +1,82 @@
+/*
+ * 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.ExposedFields.ExposedField;
+import org.springframework.util.Assert;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.DBObject;
+
+/**
+ * Encapsulates the aggregation framework {@code $count}-operation. <br />
+ * We recommend to use the static factory method {@link Aggregation#count()} instead of creating instances of this class
+ * directly.
+ *
+ * @see <a href=
+ *      "https://docs.mongodb.com/manual/reference/operator/aggregation/count/#pipe._S_count">https://docs.mongodb.com/manual/reference/operator/aggregation/count/</a>
+ * @author Mark Paluch
+ * @since 1.10
+ */
+public class CountOperation implements FieldsExposingAggregationOperation {
+
+	private final String fieldName;
+
+	/**
+	 * Creates a new {@link CountOperation} given the {@link fieldName} field name.
+	 *
+	 * @param asFieldName must not be {@literal null} or empty.
+	 */
+	public CountOperation(String fieldName) {
+
+		Assert.hasText(fieldName, "Field name must not be null or empty!");
+		this.fieldName = fieldName;
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public DBObject toDBObject(AggregationOperationContext context) {
+		return new BasicDBObject("$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

@@ -16,6 +16,7 @@
 package org.springframework.data.mongodb.core.aggregation;
 
 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;
 
@@ -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 +1,228 @@
+/*
+ * 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 com.mongodb.BasicDBObject;
+import com.mongodb.DBObject;
+
+/**
+ * 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: $facet</a>
+ */
+public class FacetOperation implements FieldsExposingAggregationOperation {
+
+	/**
+	 * Empty (initial) {@link FacetOperation}.
+	 */
+	public static final FacetOperation EMPTY = new FacetOperation();
+
+	private final Facets facets;
+
+	/**
+	 * Creates a new {@link FacetOperation}.
+	 */
+	public FacetOperation() {
+		this(Facets.EMPTY);
+	}
+
+	private FacetOperation(Facets facets) {
+		this.facets = facets;
+	}
+
+	/**
+	 * Creates a new {@link FacetOperationBuilder} to append a new facet using {@literal operations}. <br />
+	 * {@link FacetOperationBuilder} takes a pipeline of {@link AggregationOperation} to categorize documents into a
+	 * single facet.
+	 *
+	 * @param operations must not be {@literal null} or empty.
+	 * @return
+	 */
+	public FacetOperationBuilder and(AggregationOperation... operations) {
+
+		Assert.notNull(operations, "AggregationOperations must not be null!");
+		Assert.notEmpty(operations, "AggregationOperations must not be empty!");
+
+		return new FacetOperationBuilder(facets, Arrays.asList(operations));
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public DBObject toDBObject(AggregationOperationContext context) {
+		return new BasicDBObject("$facet", facets.toDBObject(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;
+		}
+
+		DBObject toDBObject(AggregationOperationContext context) {
+
+			DBObject dbObject = new BasicDBObject(facets.size());
+
+			for (Facet facet : facets) {
+				dbObject.put(facet.getExposedField().getName(), facet.toDBObjects(context));
+			}
+
+			return dbObject;
+		}
+
+		/**
+		 * 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;
+		}
+
+		List<DBObject> toDBObjects(AggregationOperationContext context) {
+			return AggregationOperationRenderer.toDBObject(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 +1,411 @@
+/*
+ * 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.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;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.DBObject;
+
+/**
+ * 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, DBObject.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#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public DBObject toDBObject(AggregationOperationContext context) {
+
+		DBObject graphLookup = new BasicDBObject();
+
+		graphLookup.put("from", from);
+
+		List<Object> mappedStartWith = new ArrayList<Object>(startWith.size());
+
+		for (Object startWithElement : startWith) {
+
+			if (startWithElement instanceof AggregationExpression) {
+				mappedStartWith.add(((AggregationExpression) startWithElement).toDbObject(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 BasicDBObject("$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 DBObject} 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 2013-2015 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.
@@ -19,12 +19,10 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
-import java.util.Locale;
 
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference;
 import org.springframework.util.Assert;
-import org.springframework.util.StringUtils;
 
 import com.mongodb.BasicDBObject;
 import com.mongodb.DBObject;
@@ -35,11 +33,14 @@ import com.mongodb.DBObject;
  * 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
+ * @author Sergey Shcherbakov
  * @since 1.3
+ * @see <a href="https://docs.mongodb.org/manual/reference/aggregation/group/">MongoDB Aggregation Framework: $group</a>
  */
 public class GroupOperation implements FieldsExposingAggregationOperation {
 
@@ -155,6 +156,21 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 		return sum(reference, null);
 	}
 
+	/**
+	 * Generates an {@link GroupOperationBuilder} for an {@code $sum}-expression for the given
+	 * {@link AggregationExpression}.
+	 *
+	 * @param expr must not be {@literal null}.
+	 * @return new instance of {@link GroupOperationBuilder}. Never {@literal null}.
+	 * @throws IllegalArgumentException when {@code expr} is {@literal null}.
+	 * @since 1.10.8
+	 */
+	public GroupOperationBuilder sum(AggregationExpression expr) {
+
+		Assert.notNull(expr, "Expr must not be null!");
+		return newBuilder(GroupOps.SUM, null, expr);
+	}
+
 	private GroupOperationBuilder sum(String reference, Object value) {
 		return newBuilder(GroupOps.SUM, reference, value);
 	}
@@ -194,7 +210,8 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	}
 
 	/**
-	 * Generates an {@link GroupOperationBuilder} for an {@code $last}-expression for the given {@link AggregationExpression}.
+	 * Generates an {@link GroupOperationBuilder} for an {@code $last}-expression for the given
+	 * {@link AggregationExpression}.
 	 * 
 	 * @param expr
 	 * @return
@@ -214,7 +231,8 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	}
 
 	/**
-	 * Generates an {@link GroupOperationBuilder} for a {@code $first}-expression for the given {@link AggregationExpression}.
+	 * Generates an {@link GroupOperationBuilder} for a {@code $first}-expression for the given
+	 * {@link AggregationExpression}.
 	 * 
 	 * @param expr
 	 * @return
@@ -234,7 +252,8 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	}
 
 	/**
-	 * Generates an {@link GroupOperationBuilder} for an {@code $avg}-expression for the given {@link AggregationExpression}.
+	 * Generates an {@link GroupOperationBuilder} for an {@code $avg}-expression for the given
+	 * {@link AggregationExpression}.
 	 * 
 	 * @param expr
 	 * @return
@@ -278,7 +297,8 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	}
 
 	/**
-	 * Generates an {@link GroupOperationBuilder} for an {@code $min}-expression that for the given {@link AggregationExpression}.
+	 * Generates an {@link GroupOperationBuilder} for an {@code $min}-expression that for the given
+	 * {@link AggregationExpression}.
 	 * 
 	 * @param expr
 	 * @return
@@ -298,7 +318,8 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	}
 
 	/**
-	 * Generates an {@link GroupOperationBuilder} for an {@code $max}-expression that for the given {@link AggregationExpression}.
+	 * Generates an {@link GroupOperationBuilder} for an {@code $max}-expression that for the given
+	 * {@link AggregationExpression}.
 	 * 
 	 * @param expr
 	 * @return
@@ -307,6 +328,53 @@ 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));
 	}
@@ -371,21 +439,18 @@ 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

@@ -1,197 +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.springframework.util.Assert;
-
-import com.mongodb.BasicDBObject;
-import com.mongodb.DBObject;
-
-/**
- * Encapsulates the aggregation framework {@code $ifNull} operator. Replacement values can be either {@link Field field
- * references}, values of simple MongoDB types or values that can be converted to a simple MongoDB type.
- *
- * @see http://docs.mongodb.com/manual/reference/operator/aggregation/ifNull/
- * @author Mark Paluch
- * @since 1.10
- */
-public class IfNullOperator implements AggregationExpression {
-
-	private final Field field;
-	private final Object value;
-
-	/**
-	 * Creates a new {@link IfNullOperator} for the given {@link Field} and replacement {@code value}.
-	 *
-	 * @param field must not be {@literal null}.
-	 * @param value must not be {@literal null}.
-	 */
-	public IfNullOperator(Field field, Object value) {
-
-		Assert.notNull(field, "Field must not be null!");
-		Assert.notNull(value, "'Replacement-value' must not be null!");
-
-		this.field = field;
-		this.value = value;
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.core.aggregation.AggregationExpression#toDbObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
-	 */
-	@Override
-	public DBObject toDbObject(AggregationOperationContext context) {
-
-		List<Object> list = new ArrayList<Object>();
-
-		list.add(context.getReference(field).toString());
-		list.add(resolve(value, context));
-
-		return new BasicDBObject("$ifNull", list);
-	}
-
-	private Object resolve(Object value, AggregationOperationContext context) {
-
-		if (value instanceof Field) {
-			return context.getReference((Field) value).toString();
-		} else if (value instanceof DBObject) {
-			return value;
-		}
-
-		return context.getMappedObject(new BasicDBObject("$set", value)).get("$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 DBObject}, 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 2013-2015 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.
@@ -26,10 +26,10 @@ import com.mongodb.DBObject;
  * 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
  * @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.
@@ -29,8 +29,8 @@ import com.mongodb.DBObject;
  * @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.
@@ -28,11 +28,11 @@ import com.mongodb.DBObject;
  * {@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 +1,73 @@
+/*
+ * 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.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExpressionFieldReference;
+import org.springframework.util.Assert;
+
+import com.mongodb.DBObject;
+
+/**
+ * {@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(com.mongodb.DBObject)
+	 */
+	@Override
+	public DBObject getMappedObject(DBObject dbObject) {
+		return delegate.getMappedObject(dbObject);
+	}
+
+	/*
+	 * (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.
@@ -25,8 +25,8 @@ 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
+ * @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.
@@ -17,12 +17,16 @@ 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.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;
 
 import com.mongodb.BasicDBObject;
@@ -37,13 +41,13 @@ import com.mongodb.DBObject;
  * 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 {
 
@@ -243,22 +247,22 @@ 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);
 	}
 
 	/**
@@ -462,10 +466,10 @@ 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));
 		}
 
 		/*
@@ -473,10 +477,10 @@ 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));
 		}
 
 		/**
@@ -528,6 +532,20 @@ 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.
 		 * 
@@ -553,6 +571,20 @@ 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.
 		 * 
@@ -579,6 +611,20 @@ 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.
@@ -596,7 +642,7 @@ 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
 		 */
@@ -606,6 +652,20 @@ 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 />
 		 *
@@ -616,6 +676,85 @@ 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 />
@@ -641,7 +780,453 @@ 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#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
 		 */
@@ -697,6 +1282,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * 
 		 * @author Oliver Gierke
 		 * @author Thomas Darimont
+		 * @author Mark Paluch
 		 */
 		static class FieldProjection extends Projection {
 
@@ -715,7 +1301,7 @@ 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;
@@ -822,10 +1408,21 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			protected List<Object> getOperationArguments(AggregationOperationContext context) {
 
 				List<Object> result = new ArrayList<Object>(values.size());
-				result.add(context.getReference(getField().getName()).toString());
+				result.add(context.getReference(getField()).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).toDbObject(context));
+					} else {
+						result.add(element);
+					}
 				}
 
 				return result;

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

@@ -0,0 +1,573 @@
+/*
+ * 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.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
+import org.springframework.expression.spel.ast.Projection;
+import org.springframework.util.Assert;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.DBObject;
+
+/**
+ * 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: $replaceRoot</a>
+ */
+public class ReplaceRootOperation implements FieldsExposingAggregationOperation {
+
+	private final Replacement replacement;
+
+	/**
+	 * Creates a new {@link ReplaceRootOperation} given the {@link Field} field name.
+	 *
+	 * @param field must not be {@literal null} or empty.
+	 */
+	public ReplaceRootOperation(Field field) {
+		this(new FieldReplacement(field));
+	}
+
+	/**
+	 * Creates a new {@link ReplaceRootOperation} given the {@link AggregationExpression} pointing to a document.
+	 *
+	 * @param aggregationExpression must not be {@literal null}.
+	 */
+	public ReplaceRootOperation(AggregationExpression aggregationExpression) {
+		this(new AggregationExpressionReplacement(aggregationExpression));
+	}
+
+	/**
+	 * Creates a new {@link ReplaceRootOperation} given the {@link Replacement}.
+	 *
+	 * @param replacement must not be {@literal null}.
+	 */
+	public ReplaceRootOperation(Replacement replacement) {
+
+		Assert.notNull(replacement, "Replacement must not be null!");
+		this.replacement = replacement;
+	}
+
+	/**
+	 * Creates a new {@link ReplaceRootDocumentOperationBuilder}.
+	 *
+	 * @return a new {@link ReplaceRootDocumentOperationBuilder}.
+	 */
+	public static ReplaceRootOperationBuilder builder() {
+		return new ReplaceRootOperationBuilder();
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public DBObject toDBObject(AggregationOperationContext context) {
+		return new BasicDBObject("$replaceRoot", new BasicDBObject("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 dbObject}. <br />
+		 * {@link ReplaceRootOperation} can be populated with individual entries and derive its values from other, existing
+		 * documents.
+		 *
+		 * @param dbObject must not be {@literal null}.
+		 * @return the final {@link ReplaceRootOperation}.
+		 */
+		public ReplaceRootOperation withDocument(DBObject dbObject) {
+
+			Assert.notNull(dbObject, "DBObject must not be null!");
+
+			return new ReplaceRootDocumentOperation().andValuesOf(dbObject);
+		}
+	}
+
+	/**
+	 * 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 DBObject toDocumentExpression(AggregationOperationContext context) {
+			return aggregationExpression.toDbObject(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 DBObject toDocumentExpression(AggregationOperationContext context) {
+
+			DBObject dbObject = new BasicDBObject();
+
+			for (ReplacementContributor replacement : replacements) {
+				dbObject.putAll(replacement.toDbObject(context));
+			}
+
+			return dbObject;
+		}
+
+		/**
+		 * 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 DBObject} contributor for document replacement.
+	 *
+	 * @author Mark Paluch
+	 */
+	private interface ReplacementContributor extends AggregationExpression {
+
+		/**
+		 * Renders the current {@link ReplacementContributor} into a {@link DBObject} based on the given
+		 * {@link AggregationOperationContext}.
+		 *
+		 * @param context will never be {@literal null}.
+		 * @return
+		 */
+		DBObject toDbObject(AggregationOperationContext context);
+	}
+
+	/**
+	 * {@link ReplacementContributor} to contribute multiple fields based on the input {@literal value}. <br />
+	 * The value object is mapped into a MongoDB {@link DBObject}.
+	 *
+	 * @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#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public DBObject toDbObject(AggregationOperationContext context) {
+
+			if (value instanceof DBObject) {
+				return (DBObject) value;
+			}
+
+			return (DBObject) context.getMappedObject(new BasicDBObject("$set", value)).get("$set");
+		}
+	}
+
+	/**
+	 * Base class for {@link ReplacementContributor} implementations to contribute a single {@literal field} Typically
+	 * used to construct a composite document that should contain the resulting key-value pair.
+	 *
+	 * @author Mark Paluch
+	 */
+	private abstract static class FieldContributorSupport implements ReplacementContributor {
+
+		private final ExposedField field;
+
+		/**
+		 * Creates new {@link FieldContributorSupport} for the given {@link Field}.
+		 *
+		 * @param field must not be {@literal null}.
+		 */
+		public FieldContributorSupport(Field field) {
+
+			Assert.notNull(field, "Field must not be null!");
+			this.field = new ExposedField(field, true);
+		}
+
+		/**
+		 * @return the {@link ExposedField}.
+		 */
+		public ExposedField getField() {
+			return field;
+		}
+	}
+
+	/**
+	 * {@link ReplacementContributor} to contribute a single {@literal field} and {@literal value}. The {@literal value}
+	 * is mapped to a MongoDB {@link DBObject} and can be a singular value, a list or subdocument.
+	 *
+	 * @author Mark Paluch
+	 */
+	private static class ValueFieldContributor extends FieldContributorSupport {
+
+		private final Object value;
+
+		/**
+		 * Creates new {@link Projection} for the given {@link Field}.
+		 *
+		 * @param field must not be {@literal null}.
+		 * @param value must not be {@literal null}.
+		 */
+		public ValueFieldContributor(Field field, Object value) {
+
+			super(field);
+
+			Assert.notNull(value, "Value must not be null!");
+
+			this.value = value;
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.ReplaceRootOperation.ReplacementContributor#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public DBObject toDbObject(AggregationOperationContext context) {
+
+			Object mappedValue = value instanceof BasicDBObject ? value
+					: context.getMappedObject(new BasicDBObject("$set", value)).get("$set");
+
+			return new BasicDBObject(getField().getTarget(), mappedValue);
+		}
+	}
+
+	/**
+	 * {@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#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public DBObject toDbObject(AggregationOperationContext context) {
+			return new BasicDBObject(getField().getTarget(), aggregationExpression.toDbObject(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.
@@ -26,10 +26,10 @@ import com.mongodb.DBObject;
  * 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
  * @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 2013-2015 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.
@@ -30,10 +30,10 @@ import com.mongodb.DBObject;
  * 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
  * @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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2014 the original author or authors.
+ * Copyright 2013-2016 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.
@@ -26,19 +26,26 @@ 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;
 
 import com.mongodb.BasicDBList;
 import com.mongodb.BasicDBObject;
@@ -48,6 +55,7 @@ import com.mongodb.DBObject;
  * Renders the AST of a SpEL expression as a MongoDB Aggregation Framework projection expression.
  * 
  * @author Thomas Darimont
+ * @author Christoph Strobl
  */
 class SpelExpressionTransformer implements AggregationExpressionTransformer {
 
@@ -69,6 +77,8 @@ 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);
 	}
@@ -131,8 +141,8 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 	 * @author Thomas Darimont
 	 * @author Oliver Gierke
 	 */
-	private static abstract class ExpressionNodeConversion<T extends ExpressionNode> implements
-			AggregationExpressionTransformer {
+	private static abstract class ExpressionNodeConversion<T extends ExpressionNode>
+			implements AggregationExpressionTransformer {
 
 		private final AggregationExpressionTransformer transformer;
 		private final Class<? extends ExpressionNode> nodeType;
@@ -235,8 +245,17 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 		protected Object convert(AggregationExpressionTransformationContext<OperatorNode> context) {
 
 			OperatorNode currentNode = context.getCurrentNode();
-
 			DBObject 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()) {
@@ -271,7 +290,8 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 			return nextDbObject;
 		}
 
-		private Object convertUnaryMinusOp(ExpressionTransformationContextSupport<OperatorNode> context, Object leftResult) {
+		private Object convertUnaryMinusOp(ExpressionTransformationContextSupport<OperatorNode> context,
+				Object leftResult) {
 
 			Object result = leftResult instanceof Number ? leftResult
 					: new BasicDBObject("$multiply", dbList(-1, leftResult));
@@ -289,7 +309,7 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 		 */
 		@Override
 		protected boolean supports(ExpressionNode node) {
-			return node.isMathematicalOperation();
+			return node.isMathematicalOperation() || node.isLogicalOperator();
 		}
 	}
 
@@ -462,13 +482,33 @@ 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)) {
+
+				DBObject dbo = new BasicDBObject();
+
+				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 = dbList(argList.toArray());
 			}
 
-			return context.addToPreviousOrReturn(new BasicDBObject(node.getMethodName(), dbList(args.toArray())));
+			return context.addToPreviousOrReturn(new BasicDBObject(methodReference.getMongoOperator(), args));
 		}
 	}
 
@@ -510,4 +550,81 @@ 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 BasicDBObject(node.getMongoOperator(), dbList(args.toArray())));
+		}
+
+		/*
+		 * (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) {
+			return context.getCurrentNode().getValue();
+		}
+
+		/*
+		 * (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 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.
@@ -22,6 +22,7 @@ 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 com.mongodb.DBObject;
  * property references into document field names.
  * 
  * @author Oliver Gierke
+ * @author Mark Paluch
  * @since 1.3
  */
 public class TypeBasedAggregationOperationContext implements AggregationOperationContext {
@@ -95,9 +97,9 @@ public class TypeBasedAggregationOperationContext implements AggregationOperatio
 
 		PersistentPropertyPath<MongoPersistentProperty> propertyPath = mappingContext.getPersistentPropertyPath(
 				field.getTarget(), type);
-		Field mappedField = field(propertyPath.getLeafProperty().getName(),
+		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.
@@ -27,12 +27,12 @@ import com.mongodb.DBObject;
  * 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 +1,391 @@
+/*
+ * 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.springframework.data.mongodb.core.aggregation.VariableOperators.Let.ExpressionVariable;
+import org.springframework.util.Assert;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.DBObject;
+
+/**
+ * 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#toDbObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public DBObject toDbObject(final AggregationOperationContext context) {
+			return toMap(ExposedFields.synthetic(Fields.fields(itemVariableName)), context);
+		}
+
+		private DBObject toMap(ExposedFields exposedFields, AggregationOperationContext context) {
+
+			BasicDBObject map = new BasicDBObject();
+			InheritingExposedFieldsAggregationOperationContext operationContext = new InheritingExposedFieldsAggregationOperationContext(
+					exposedFields, context);
+
+			BasicDBObject input;
+			if (sourceArray instanceof Field) {
+				input = new BasicDBObject("input", context.getReference((Field) sourceArray).toString());
+			} else {
+				input = new BasicDBObject("input", ((AggregationExpression) sourceArray).toDbObject(context));
+			}
+
+			map.putAll(context.getMappedObject(input));
+			map.put("as", itemVariableName);
+			map.put("in",
+					functionToApply.toDbObject(new NestedDelegatingExpressionAggregationOperationContext(operationContext)));
+
+			return new BasicDBObject("$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 $vars}.
+		 *
+		 * @param variables must not be {@literal null}.
+		 * @return
+		 */
+		public static LetBuilder define(final ExpressionVariable... variables) {
+
+			Assert.notNull(variables, "Variables must not be null!");
+
+			return new LetBuilder() {
+
+				@Override
+				public Let andApply(final AggregationExpression expression) {
+
+					Assert.notNull(expression, "Expression must not be null!");
+					return new Let(Arrays.asList(variables), expression);
+				}
+			};
+		}
+
+		public interface LetBuilder {
+
+			/**
+			 * Define the {@link AggregationExpression} to evaluate.
+			 *
+			 * @param expression must not be {@literal null}.
+			 * @return
+			 */
+			Let andApply(AggregationExpression expression);
+		}
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AggregationExpression#toDbObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public DBObject toDbObject(final AggregationOperationContext context) {
+			return toLet(ExposedFields.synthetic(Fields.fields(getVariableNames())), context);
+		}
+
+		private String[] getVariableNames() {
+
+			String[] varNames = new String[this.vars.size()];
+			for (int i = 0; i < this.vars.size(); i++) {
+				varNames[i] = this.vars.get(i).variableName;
+			}
+
+			return varNames;
+		}
+
+		private DBObject toLet(ExposedFields exposedFields, AggregationOperationContext context) {
+
+			DBObject letExpression = new BasicDBObject();
+			DBObject mappedVars = new BasicDBObject();
+			InheritingExposedFieldsAggregationOperationContext operationContext = new InheritingExposedFieldsAggregationOperationContext(
+					exposedFields, context);
+
+			for (ExpressionVariable var : this.vars) {
+				mappedVars.putAll(getMappedVariable(var, context));
+			}
+
+			letExpression.put("vars", mappedVars);
+			letExpression.put("in", getMappedIn(operationContext));
+
+			return new BasicDBObject("$let", letExpression);
+		}
+
+		private DBObject getMappedVariable(ExpressionVariable var, AggregationOperationContext context) {
+
+			return new BasicDBObject(var.variableName, var.expression instanceof AggregationExpression
+					? ((AggregationExpression) var.expression).toDbObject(context) : var.expression);
+		}
+
+		private Object getMappedIn(AggregationOperationContext context) {
+			return expression.toDbObject(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(DBObject 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.
@@ -56,6 +56,7 @@ import org.springframework.util.Assert;
  * @author Oliver Gierke
  * @author Thomas Darimont
  * @author Christoph Strobl
+ * @author Mark Paluch
  */
 public class CustomConversions {
 
@@ -88,7 +89,7 @@ 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>();
@@ -345,8 +346,8 @@ public class CustomConversions {
 	private static 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;

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

@@ -25,7 +25,9 @@ import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
@@ -46,7 +48,6 @@ import org.springframework.util.Assert;
 import org.springframework.util.ReflectionUtils;
 
 import com.mongodb.BasicDBObject;
-import com.mongodb.BasicDBObjectBuilder;
 import com.mongodb.DB;
 import com.mongodb.DBObject;
 import com.mongodb.DBRef;
@@ -62,6 +63,8 @@ import com.mongodb.DBRef;
  */
 public class DefaultDbRefResolver implements DbRefResolver {
 
+	private static final String ID = "_id";
+
 	private final MongoDbFactory mongoDbFactory;
 	private final PersistenceExceptionTranslator exceptionTranslator;
 	private final ObjenesisStd objenesis;
@@ -144,10 +147,37 @@ public class DefaultDbRefResolver implements DbRefResolver {
 			ids.add(ref.getId());
 		}
 
+		Map<Object, DBObject> documentsById = getDocumentsById(ids, collection);
+		List<DBObject> result = new ArrayList<DBObject>(ids.size());
+
+		for (Object id : ids) {
+			result.add(documentsById.get(id));
+		}
+
+		return result;
+	}
+
+	/**
+	 * Returns all documents with the given ids contained in the given collection mapped by their ids.
+	 * 
+	 * @param ids must not be {@literal null}.
+	 * @param collection must not be {@literal null} or empty.
+	 * @return
+	 */
+	private Map<Object, DBObject> getDocumentsById(List<Object> ids, String collection) {
+
+		Assert.notNull(ids, "Ids must not be null!");
+		Assert.hasText(collection, "Collection must not be null or empty!");
+
 		DB db = mongoDbFactory.getDb();
-		List<DBObject> result = db.getCollection(collection)
-				.find(new BasicDBObjectBuilder().add("_id", new BasicDBObject("$in", ids)).get()).toArray();
-		Collections.sort(result, new DbRefByReferencePositionComparator(ids));
+		BasicDBObject query = new BasicDBObject(ID, new BasicDBObject("$in", ids));
+		List<DBObject> documents = db.getCollection(collection).find(query).toArray();
+		Map<Object, DBObject> result = new HashMap<Object, DBObject>(documents.size());
+
+		for (DBObject document : documents) {
+			result.put(document.get(ID), document);
+		}
+
 		return result;
 	}
 
@@ -316,6 +346,8 @@ public class DefaultDbRefResolver implements DbRefResolver {
 				return null;
 			}
 
+			ReflectionUtils.makeAccessible(method);
+
 			return method.invoke(target, args);
 		}
 
@@ -467,7 +499,7 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		 */
 		@Override
 		public int compare(DBObject o1, DBObject o2) {
-			return Integer.compare(reference.indexOf(o1.get("_id")), reference.indexOf(o2.get("_id")));
+			return Integer.compare(reference.indexOf(o1.get(ID)), reference.indexOf(o2.get(ID)));
 		}
 	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/GeoConverters.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.
@@ -41,6 +41,7 @@ import org.springframework.data.mongodb.core.geo.GeoJsonPolygon;
 import org.springframework.data.mongodb.core.geo.Sphere;
 import org.springframework.data.mongodb.core.query.GeoCommand;
 import org.springframework.util.Assert;
+import org.springframework.util.NumberUtils;
 import org.springframework.util.ObjectUtils;
 
 import com.mongodb.BasicDBList;
@@ -53,6 +54,7 @@ import com.mongodb.DBObject;
  * @author Thomas Darimont
  * @author Oliver Gierke
  * @author Christoph Strobl
+ * @author Thiago Diniz da Silveira
  * @since 1.5
  */
 abstract class GeoConverters {
@@ -121,7 +123,7 @@ abstract class GeoConverters {
 				return DbObjectToGeoJsonPointConverter.INSTANCE.convert(source);
 			}
 
-			return new Point((Double) source.get("x"), (Double) source.get("y"));
+			return new Point(toPrimitiveDoubleValue(source.get("x")), toPrimitiveDoubleValue(source.get("y")));
 		}
 	}
 
@@ -255,9 +257,12 @@ abstract class GeoConverters {
 			}
 
 			DBObject center = (DBObject) source.get("center");
-			Double radius = (Double) source.get("radius");
+			Number radius = (Number) source.get("radius");
 
-			Distance distance = new Distance(radius);
+			Assert.notNull(center, "Center must not be null!");
+			Assert.notNull(radius, "Radius must not be null!");
+
+			Distance distance = new Distance(toPrimitiveDoubleValue(radius));
 
 			if (source.containsField("metric")) {
 
@@ -267,9 +272,6 @@ abstract class GeoConverters {
 				distance = distance.in(Metrics.valueOf(metricString));
 			}
 
-			Assert.notNull(center, "Center must not be null!");
-			Assert.notNull(radius, "Radius must not be null!");
-
 			return new Circle(DbObjectToPointConverter.INSTANCE.convert(center), distance);
 		}
 	}
@@ -326,9 +328,12 @@ abstract class GeoConverters {
 			}
 
 			DBObject center = (DBObject) source.get("center");
-			Double radius = (Double) source.get("radius");
+			Number radius = (Number) source.get("radius");
 
-			Distance distance = new Distance(radius);
+			Assert.notNull(center, "Center must not be null!");
+			Assert.notNull(radius, "Radius must not be null!");
+
+			Distance distance = new Distance(toPrimitiveDoubleValue(radius));
 
 			if (source.containsField("metric")) {
 
@@ -338,9 +343,6 @@ abstract class GeoConverters {
 				distance = distance.in(Metrics.valueOf(metricString));
 			}
 
-			Assert.notNull(center, "Center must not be null!");
-			Assert.notNull(radius, "Radius must not be null!");
-
 			return new Sphere(DbObjectToPointConverter.INSTANCE.convert(center), distance);
 		}
 	}
@@ -600,7 +602,7 @@ abstract class GeoConverters {
 					String.format("Cannot convert type '%s' to Point.", source.get("type")));
 
 			List<Number> dbl = (List<Number>) source.get("coordinates");
-			return new GeoJsonPoint(dbl.get(0).doubleValue(), dbl.get(1).doubleValue());
+			return new GeoJsonPoint(toPrimitiveDoubleValue(dbl.get(0)), toPrimitiveDoubleValue(dbl.get(1)));
 		}
 	}
 
@@ -834,7 +836,8 @@ abstract class GeoConverters {
 
 			List<Number> coordinatesList = (List<Number>) point;
 
-			points.add(new GeoJsonPoint(coordinatesList.get(0).doubleValue(), coordinatesList.get(1).doubleValue()));
+			points.add(new GeoJsonPoint(toPrimitiveDoubleValue(coordinatesList.get(0)),
+					toPrimitiveDoubleValue(coordinatesList.get(1))));
 		}
 		return points;
 	}
@@ -849,4 +852,10 @@ abstract class GeoConverters {
 	static GeoJsonPolygon toGeoJsonPolygon(BasicDBList dbList) {
 		return new GeoJsonPolygon(toListOfPoint((BasicDBList) dbList.get(0)));
 	}
+
+	private static double toPrimitiveDoubleValue(Object value) {
+
+		Assert.isInstanceOf(Number.class, value, "Argument must be a Number.");
+		return NumberUtils.convertNumberToTargetClass((Number) value, Double.class).doubleValue();
+	}
 }

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

@@ -1,11 +1,11 @@
 /*
- * Copyright 2011-2016 by the original author(s).
+ * 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
  *
- *     http://www.apache.org/licenses/LICENSE-2.0
+ *      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,
@@ -28,6 +28,7 @@ import java.util.Set;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+
 import org.springframework.beans.BeansException;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
@@ -73,7 +74,7 @@ import com.mongodb.DBRef;
 /**
  * {@link MongoConverter} that uses a {@link MappingContext} to do sophisticated mapping of domain objects to
  * {@link DBObject}.
- * 
+ *
  * @author Oliver Gierke
  * @author Jon Brisbin
  * @author Patrik Wasik
@@ -100,8 +101,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Creates a new {@link MappingMongoConverter} given the new {@link DbRefResolver} and {@link MappingContext}.
-	 * 
-	 * @param mongoDbFactory must not be {@literal null}.
+	 *
+	 * @param dbRefResolver must not be {@literal null}.
 	 * @param mappingContext must not be {@literal null}.
 	 */
 	public MappingMongoConverter(DbRefResolver dbRefResolver,
@@ -122,7 +123,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Creates a new {@link MappingMongoConverter} given the new {@link MongoDbFactory} and {@link MappingContext}.
-	 * 
+	 *
 	 * @deprecated use the constructor taking a {@link DbRefResolver} instead.
 	 * @param mongoDbFactory must not be {@literal null}.
 	 * @param mappingContext must not be {@literal null}.
@@ -138,12 +139,13 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * converter and how to lookup type information from {@link DBObject}s when reading them. Uses a
 	 * {@link DefaultMongoTypeMapper} by default. Setting this to {@literal null} will reset the {@link TypeMapper} to the
 	 * default one.
-	 * 
+	 *
 	 * @param typeMapper the typeMapper to set
 	 */
 	public void setTypeMapper(MongoTypeMapper typeMapper) {
 		this.typeMapper = typeMapper == null
-				? new DefaultMongoTypeMapper(DefaultMongoTypeMapper.DEFAULT_TYPE_KEY, mappingContext) : typeMapper;
+				? new DefaultMongoTypeMapper(DefaultMongoTypeMapper.DEFAULT_TYPE_KEY, mappingContext)
+				: typeMapper;
 	}
 
 	/*
@@ -160,7 +162,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * any translation but rather reject a {@link Map} with keys containing dots causing the conversion for the entire
 	 * object to fail. If further customization of the translation is needed, have a look at
 	 * {@link #potentiallyEscapeMapKey(String)} as well as {@link #potentiallyUnescapeMapKey(String)}.
-	 * 
+	 *
 	 * @param mapKeyDotReplacement the mapKeyDotReplacement to set
 	 */
 	public void setMapKeyDotReplacement(String mapKeyDotReplacement) {
@@ -315,32 +317,32 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		return result;
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.convert.MongoWriter#toDBRef(java.lang.Object, org.springframework.data.mongodb.core.mapping.MongoPersistentProperty)
 	 */
-	public DBRef toDBRef(Object object, MongoPersistentProperty referingProperty) {
+	public DBRef toDBRef(Object object, MongoPersistentProperty referringProperty) {
 
 		org.springframework.data.mongodb.core.mapping.DBRef annotation = null;
 
-		if (referingProperty != null) {
-			annotation = referingProperty.getDBRef();
+		if (referringProperty != null) {
+			annotation = referringProperty.getDBRef();
 			Assert.isTrue(annotation != null, "The referenced property has to be mapped with @DBRef!");
 		}
 
-		// @see DATAMONGO-913
+		// DATAMONGO-913
 		if (object instanceof LazyLoadingProxy) {
 			return ((LazyLoadingProxy) object).toDBRef();
 		}
 
-		return createDBRef(object, referingProperty);
+		return createDBRef(object, referringProperty);
 	}
 
 	/**
 	 * Root entry method into write conversion. Adds a type discriminator to the {@link DBObject}. Shouldn't be called for
 	 * nested conversions.
-	 * 
-	 * @see org.springframework.data.mongodb.core.core.convert.MongoWriter#write(java.lang.Object, com.mongodb.DBObject)
+	 *
+	 * @see org.springframework.data.mongodb.core.convert.MongoWriter#write(java.lang.Object, com.mongodb.DBObject)
 	 */
 	public void write(final Object obj, final DBObject dbo) {
 
@@ -363,7 +365,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Internal write conversion method which should be used for nested invocations.
-	 * 
+	 *
 	 * @param obj
 	 * @param dbo
 	 */
@@ -483,7 +485,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			DBRef dbRefObj = null;
 
 			/*
-			 * If we already have a LazyLoadingProxy, we use it's cached DBRef value instead of 
+			 * If we already have a LazyLoadingProxy, we use it's cached DBRef value instead of
 			 * unnecessarily initializing it only to convert it to a DBRef a few instructions later.
 			 */
 			if (obj instanceof LazyLoadingProxy) {
@@ -519,7 +521,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		addCustomTypeKeyIfNecessary(ClassTypeInformation.from(prop.getRawType()), obj, propDbObj);
 
 		MongoPersistentEntity<?> entity = isSubtype(prop.getType(), obj.getClass())
-				? mappingContext.getPersistentEntity(obj.getClass()) : mappingContext.getPersistentEntity(type);
+				? mappingContext.getPersistentEntity(obj.getClass())
+				: mappingContext.getPersistentEntity(type);
 
 		writeInternal(obj, propDbObj, entity);
 		accessor.put(prop, propDbObj);
@@ -533,7 +536,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * Returns given object as {@link Collection}. Will return the {@link Collection} as is if the source is a
 	 * {@link Collection} already, will convert an array into a {@link Collection} or simply create a single element
 	 * collection for everything else.
-	 * 
+	 *
 	 * @param source
 	 * @return
 	 */
@@ -548,7 +551,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Writes the given {@link Collection} using the given {@link MongoPersistentProperty} information.
-	 * 
+	 *
 	 * @param collection must not be {@literal null}.
 	 * @param property must not be {@literal null}.
 	 * @return
@@ -576,7 +579,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Writes the given {@link Map} using the given {@link MongoPersistentProperty} information.
-	 * 
+	 *
 	 * @param map must not {@literal null}.
 	 * @param property must not be {@literal null}.
 	 * @return
@@ -612,7 +615,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Populates the given {@link BasicDBList} with values from the given {@link Collection}.
-	 * 
+	 *
 	 * @param source the collection to create a {@link BasicDBList} for, must not be {@literal null}.
 	 * @param type the {@link TypeInformation} to consider or {@literal null} if unknown.
 	 * @param sink the {@link BasicDBList} to write to.
@@ -642,7 +645,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Writes the given {@link Map} to the given {@link DBObject} considering the given {@link TypeInformation}.
-	 * 
+	 *
 	 * @param obj must not be {@literal null}.
 	 * @param dbo must not be {@literal null}.
 	 * @param propertyType must not be {@literal null}.
@@ -681,7 +684,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	/**
 	 * Prepares the given {@link Map} key to be converted into a {@link String}. Will invoke potentially registered custom
 	 * conversions and escape dots from the result as they're not supported as {@link Map} key in MongoDB.
-	 * 
+	 *
 	 * @param key must not be {@literal null}.
 	 * @return
 	 */
@@ -696,7 +699,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	/**
 	 * Potentially replaces dots in the given map key with the configured map key replacement if configured or aborts
 	 * conversion if none is configured.
-	 * 
+	 *
 	 * @see #setMapKeyDotReplacement(String)
 	 * @param source
 	 * @return
@@ -719,7 +722,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Returns a {@link String} representation of the given {@link Map} key
-	 * 
+	 *
 	 * @param key
 	 * @return
 	 */
@@ -730,13 +733,14 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 
 		return conversions.hasCustomWriteTarget(key.getClass(), String.class)
-				? (String) getPotentiallyConvertedSimpleWrite(key) : key.toString();
+				? (String) getPotentiallyConvertedSimpleWrite(key)
+				: key.toString();
 	}
 
 	/**
 	 * Translates the map key replacements in the given key just read with a dot in case a map key replacement has been
 	 * configured.
-	 * 
+	 *
 	 * @param source
 	 * @return
 	 */
@@ -766,7 +770,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Writes the given simple value to the given {@link DBObject}. Will store enum names for enum values.
-	 * 
+	 *
 	 * @param value
 	 * @param dbObject must not be {@literal null}.
 	 * @param key must not be {@literal null}.
@@ -783,7 +787,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	/**
 	 * Checks whether we have a custom conversion registered for the given value into an arbitrary simple Mongo type.
 	 * Returns the converted value if so. If not, we perform special enum handling or simply return the value as is.
-	 * 
+	 *
 	 * @param value
 	 * @return
 	 */
@@ -805,7 +809,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	/**
 	 * Checks whether we have a custom conversion for the given simple object. Converts the given value if so, applies
 	 * {@link Enum} handling or returns the value as is.
-	 * 
+	 *
 	 * @param value
 	 * @param target must not be {@literal null}.
 	 * @return
@@ -830,7 +834,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	protected DBRef createDBRef(Object target, MongoPersistentProperty property) {
 
-		Assert.notNull(target);
+		Assert.notNull(target, "Target object must not be null!");
 
 		if (target instanceof DBRef) {
 			return (DBRef) target;
@@ -878,7 +882,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Reads the given {@link BasicDBList} into a collection of the given {@link TypeInformation}.
-	 * 
+	 *
 	 * @param targetType must not be {@literal null}.
 	 * @param sourceValue must not be {@literal null}.
 	 * @param path must not be {@literal null}.
@@ -892,10 +896,6 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 		Class<?> collectionType = targetType.getType();
 
-		if (sourceValue.isEmpty()) {
-			return getPotentiallyConvertedSimpleRead(new HashSet<Object>(), collectionType);
-		}
-
 		TypeInformation<?> componentType = targetType.getComponentType();
 		Class<?> rawComponentType = componentType == null ? null : componentType.getType();
 
@@ -903,8 +903,15 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		Collection<Object> items = targetType.getType().isArray() ? new ArrayList<Object>()
 				: CollectionFactory.createCollection(collectionType, rawComponentType, sourceValue.size());
 
+		if (sourceValue.isEmpty()) {
+			return getPotentiallyConvertedSimpleRead(items, collectionType);
+		}
+
 		if (!DBRef.class.equals(rawComponentType) && isCollectionOfDbRefWhereBulkFetchIsPossible(sourceValue)) {
-			return bulkReadAndConvertDBRefs((List<DBRef>) (List) (sourceValue), componentType, path, rawComponentType);
+
+			List<Object> objects = bulkReadAndConvertDBRefs((List<DBRef>)(List) sourceValue, componentType, path,
+					rawComponentType);
+			return getPotentiallyConvertedSimpleRead(objects, targetType.getType());
 		}
 
 		for (Object dbObjItem : sourceValue) {
@@ -925,7 +932,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Reads the given {@link DBObject} into a {@link Map}. will recursively resolve nested {@link Map}s as well.
-	 * 
+	 *
 	 * @param type the {@link Map} {@link TypeInformation} to be used to unmarshall this {@link DBObject}.
 	 * @param dbObject must not be {@literal null}
 	 * @param path must not be {@literal null}
@@ -1027,7 +1034,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			for (Entry<Object, Object> entry : ((Map<Object, Object>) obj).entrySet()) {
 
 				TypeInformation<? extends Object> valueTypeHint = typeHint != null && typeHint.getMapValueType() != null
-						? typeHint.getMapValueType() : typeHint;
+						? typeHint.getMapValueType()
+						: typeHint;
 
 				converted.put(getPotentiallyConvertedSimpleWrite(entry.getKey()).toString(),
 						convertToMongoType(entry.getValue(), valueTypeHint));
@@ -1070,7 +1078,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Removes the type information from the entire conversion result.
-	 * 
+	 *
 	 * @param object
 	 * @param recursively whether to apply the removal recursively
 	 * @return
@@ -1131,22 +1139,22 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		/**
 		 * Creates a new {@link MongoDbPropertyValueProvider} for the given source, {@link SpELExpressionEvaluator} and
 		 * {@link ObjectPath}.
-		 * 
+		 *
 		 * @param source must not be {@literal null}.
 		 * @param evaluator must not be {@literal null}.
 		 * @param path can be {@literal null}.
 		 */
 		public MongoDbPropertyValueProvider(DBObject source, SpELExpressionEvaluator evaluator, ObjectPath path) {
 
-			Assert.notNull(source);
-			Assert.notNull(evaluator);
+			Assert.notNull(source, "DBObject must not be null!");
+			Assert.notNull(evaluator, "SpELExpressionEvaluator must not be null!");
 
 			this.source = new DBObjectAccessor(source);
 			this.evaluator = evaluator;
 			this.path = path;
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.convert.PropertyValueProvider#getPropertyValue(org.springframework.data.mapping.PersistentProperty)
 		 */
@@ -1166,7 +1174,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	/**
 	 * Extension of {@link SpELExpressionParameterValueProvider} to recursively trigger value conversion on the raw
 	 * resolved SpEL value.
-	 * 
+	 *
 	 * @author Oliver Gierke
 	 */
 	private class ConverterAwareSpELExpressionParameterValueProvider
@@ -1176,7 +1184,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 		/**
 		 * Creates a new {@link ConverterAwareSpELExpressionParameterValueProvider}.
-		 * 
+		 *
 		 * @param evaluator must not be {@literal null}.
 		 * @param conversionService must not be {@literal null}.
 		 * @param delegate must not be {@literal null}.
@@ -1189,7 +1197,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			this.path = path;
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mapping.model.SpELExpressionParameterValueProvider#potentiallyConvertSpelValue(java.lang.Object, org.springframework.data.mapping.PreferredConstructor.Parameter)
 		 */
@@ -1224,11 +1232,11 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			return (T) dbref;
 		}
 
-		Object object = dbref == null ? null : path.getPathItem(dbref.getId(), dbref.getCollectionName());
-		return (T) (object != null ? object : readAndConvertDBRef(dbref, type, path, rawType));
+		T object = dbref == null ? null : path.getPathItem(dbref.getId(), dbref.getCollectionName(), (Class<T>) rawType);
+		return object != null ? object : (T) readAndConvertDBRef(dbref, type, path, rawType);
 	}
 
-	private <T> T readAndConvertDBRef(DBRef dbref, TypeInformation<?> type, ObjectPath path, final Class<?> rawType) {
+	private <T> T readAndConvertDBRef(DBRef dbref, TypeInformation<?> type, ObjectPath path, Class<?> rawType) {
 
 		List<T> result = bulkReadAndConvertDBRefs(Collections.singletonList(dbref), type, path, rawType);
 		return CollectionUtils.isEmpty(result) ? null : result.iterator().next();
@@ -1258,7 +1266,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 
 		List<DBObject> referencedRawDocuments = dbrefs.size() == 1
-				? Collections.singletonList(readRef(dbrefs.iterator().next())) : bulkReadRefs(dbrefs);
+				? Collections.singletonList(readRef(dbrefs.iterator().next()))
+				: bulkReadRefs(dbrefs);
 		String collectionName = dbrefs.iterator().next().getCollectionName();
 
 		List<T> targeList = new ArrayList<T>(dbrefs.size());
@@ -1293,7 +1302,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Performs the fetch operation for the given {@link DBRef}.
-	 * 
+	 *
 	 * @param ref
 	 * @return
 	 */
@@ -1314,7 +1323,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 	/**
 	 * Returns whether the given {@link Iterable} contains {@link DBRef} instances all pointing to the same collection.
-	 * 
+	 *
 	 * @param source must not be {@literal null}.
 	 * @return
 	 */
@@ -1343,7 +1352,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	/**
 	 * Marker class used to indicate we have a non root document object here that might be used within an update - so we
 	 * need to preserve type hints for potential nested elements but need to remove it on top level.
-	 * 
+	 *
 	 * @author Christoph Strobl
 	 * @since 1.8
 	 */

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

@@ -28,6 +28,7 @@ import java.util.Stack;
 import java.util.regex.Pattern;
 
 import org.springframework.data.domain.Example;
+import org.springframework.data.domain.ExampleMatcher;
 import org.springframework.data.domain.ExampleMatcher.NullHandler;
 import org.springframework.data.domain.ExampleMatcher.PropertyValueTransformer;
 import org.springframework.data.domain.ExampleMatcher.StringMatcher;
@@ -41,6 +42,7 @@ import org.springframework.data.repository.core.support.ExampleMatcherAccessor;
 import org.springframework.data.repository.query.parser.Part.Type;
 import org.springframework.data.util.TypeInformation;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
@@ -48,9 +50,13 @@ import com.mongodb.BasicDBObject;
 import com.mongodb.DBObject;
 
 /**
+ * Mapper from {@link Example} to a query {@link DBObject}.
+ *
  * @author Christoph Strobl
  * @author Mark Paluch
  * @since 1.8
+ * @see Example
+ * @see org.springframework.data.domain.ExampleMatcher
  */
 public class MongoExampleMapper {
 
@@ -58,6 +64,11 @@ public class MongoExampleMapper {
 	private final MongoConverter converter;
 	private final Map<StringMatcher, Type> stringMatcherPartMapping = new HashMap<StringMatcher, Type>();
 
+	/**
+	 * Create a new {@link MongoTypeMapper} given {@link MongoConverter}.
+	 *
+	 * @param converter must not be {@literal null}.
+	 */
 	public MongoExampleMapper(MongoConverter converter) {
 
 		this.converter = converter;
@@ -99,8 +110,10 @@ public class MongoExampleMapper {
 
 		DBObject reference = (DBObject) converter.convertToMongoType(example.getProbe());
 
-		if (entity.hasIdProperty() && entity.getIdentifierAccessor(example.getProbe()).getIdentifier() == null) {
-			reference.removeField(entity.getIdProperty().getFieldName());
+		if (entity.hasIdProperty() && ClassUtils.isAssignable(entity.getType(), example.getProbeType())) {
+			if (entity.getIdentifierAccessor(example.getProbe()).getIdentifier() == null) {
+				reference.removeField(entity.getIdProperty().getFieldName());
+			}
 		}
 
 		ExampleMatcherAccessor matcherAccessor = new ExampleMatcherAccessor(example.getMatcher());
@@ -111,80 +124,7 @@ public class MongoExampleMapper {
 				: new BasicDBObject(SerializationUtils.flattenMap(reference));
 		DBObject result = example.getMatcher().isAllMatching() ? flattened : orConcatenate(flattened);
 
-		this.converter.getTypeMapper().writeTypeRestrictions(result, getTypesToMatch(example));
-
-		return result;
-	}
-
-	private static DBObject orConcatenate(DBObject source) {
-
-		List<DBObject> foo = new ArrayList<DBObject>(source.keySet().size());
-
-		for (String key : source.keySet()) {
-			foo.add(new BasicDBObject(key, source.get(key)));
-		}
-
-		return new BasicDBObject("$or", foo);
-	}
-
-	private Set<Class<?>> getTypesToMatch(Example<?> example) {
-
-		Set<Class<?>> types = new HashSet<Class<?>>();
-
-		for (TypeInformation<?> reference : mappingContext.getManagedTypes()) {
-			if (example.getProbeType().isAssignableFrom(reference.getType())) {
-				types.add(reference.getType());
-			}
-		}
-
-		return types;
-	}
-
-	private String getMappedPropertyPath(String path, Class<?> probeType) {
-
-		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(probeType);
-
-		Iterator<String> parts = Arrays.asList(path.split("\\.")).iterator();
-
-		final Stack<MongoPersistentProperty> stack = new Stack<MongoPersistentProperty>();
-
-		List<String> resultParts = new ArrayList<String>();
-
-		while (parts.hasNext()) {
-
-			final String part = parts.next();
-			MongoPersistentProperty prop = entity.getPersistentProperty(part);
-
-			if (prop == null) {
-
-				entity.doWithProperties(new PropertyHandler<MongoPersistentProperty>() {
-
-					@Override
-					public void doWithPersistentProperty(MongoPersistentProperty property) {
-
-						if (property.getFieldName().equals(part)) {
-							stack.push(property);
-						}
-					}
-				});
-
-				if (stack.isEmpty()) {
-					return "";
-				}
-				prop = stack.pop();
-			}
-
-			resultParts.add(prop.getName());
-
-			if (prop.isEntity() && mappingContext.hasPersistentEntityFor(prop.getActualType())) {
-				entity = mappingContext.getPersistentEntity(prop.getActualType());
-			} else {
-				break;
-			}
-		}
-
-		return StringUtils.collectionToDelimitedString(resultParts, ".");
-
+		return updateTypeRestrictions(result, example);
 	}
 
 	private void applyPropertySpecs(String path, DBObject source, Class<?> probeType,
@@ -246,7 +186,102 @@ public class MongoExampleMapper {
 		}
 	}
 
-	private boolean isEmptyIdProperty(Entry<String, Object> entry) {
+	private String getMappedPropertyPath(String path, Class<?> probeType) {
+
+		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(probeType);
+
+		Iterator<String> parts = Arrays.asList(path.split("\\.")).iterator();
+
+		final Stack<MongoPersistentProperty> stack = new Stack<MongoPersistentProperty>();
+
+		List<String> resultParts = new ArrayList<String>();
+
+		while (parts.hasNext()) {
+
+			final String part = parts.next();
+			MongoPersistentProperty prop = entity.getPersistentProperty(part);
+
+			if (prop == null) {
+
+				entity.doWithProperties(new PropertyHandler<MongoPersistentProperty>() {
+
+					@Override
+					public void doWithPersistentProperty(MongoPersistentProperty property) {
+
+						if (property.getFieldName().equals(part)) {
+							stack.push(property);
+						}
+					}
+				});
+
+				if (stack.isEmpty()) {
+					return "";
+				}
+
+				prop = stack.pop();
+			}
+
+			resultParts.add(prop.getName());
+
+			if (prop.isEntity() && mappingContext.hasPersistentEntityFor(prop.getActualType())) {
+				entity = mappingContext.getPersistentEntity(prop.getActualType());
+			} else {
+				break;
+			}
+		}
+
+		return StringUtils.collectionToDelimitedString(resultParts, ".");
+	}
+
+	private DBObject updateTypeRestrictions(DBObject query, Example example) {
+
+		DBObject result = new BasicDBObject();
+
+		if (isTypeRestricting(example.getMatcher())) {
+
+			result.putAll(query);
+			this.converter.getTypeMapper().writeTypeRestrictions(result, getTypesToMatch(example));
+			return result;
+		}
+
+		for (String key : query.keySet()) {
+			if (!this.converter.getTypeMapper().isTypeKey(key)) {
+				result.put(key, query.get(key));
+			}
+		}
+
+		return result;
+	}
+
+	private boolean isTypeRestricting(ExampleMatcher matcher) {
+
+		if (matcher.getIgnoredPaths().isEmpty()) {
+			return true;
+		}
+
+		for (String path : matcher.getIgnoredPaths()) {
+			if (this.converter.getTypeMapper().isTypeKey(path)) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+
+	private Set<Class<?>> getTypesToMatch(Example<?> example) {
+
+		Set<Class<?>> types = new HashSet<Class<?>>();
+
+		for (TypeInformation<?> reference : mappingContext.getManagedTypes()) {
+			if (example.getProbeType().isAssignableFrom(reference.getType())) {
+				types.add(reference.getType());
+			}
+		}
+
+		return types;
+	}
+
+	private static boolean isEmptyIdProperty(Entry<String, Object> entry) {
 		return entry.getKey().equals("_id") && entry.getValue() == null;
 	}
 
@@ -272,4 +307,15 @@ public class MongoExampleMapper {
 			dbo.put("$options", "i");
 		}
 	}
+
+	private static DBObject orConcatenate(DBObject source) {
+
+		List<DBObject> or = new ArrayList<DBObject>(source.keySet().size());
+
+		for (String key : source.keySet()) {
+			or.add(new BasicDBObject(key, source.get(key)));
+		}
+
+		return new BasicDBObject("$or", or);
+	}
 }

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

@@ -15,12 +15,16 @@
  */
 package org.springframework.data.mongodb.core.convert;
 
+import lombok.Value;
+
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
 import com.mongodb.DBObject;
@@ -30,16 +34,18 @@ import com.mongodb.DBObject;
  * when resolving more nested objects. This allows to avoid re-resolving object instances that are logically equivalent
  * to already resolved ones.
  * <p>
- * An immutable ordered set of target objects for {@link DBObject} to {@link Object} conversions. Object paths can be
- * constructed by the {@link #toObjectPath(Object)} method and extended via {@link #push(Object)}.
- * 
+ * An immutable ordered set of target objects for {@link DBObject} to {@link Object} conversions. Object paths
+ * can be extended via {@link #push(Object, MongoPersistentEntity, Object)}.
+ *
  * @author Thomas Darimont
  * @author Oliver Gierke
+ * @author Mark Paluch
+ * @author Christoph Strobl
  * @since 1.6
  */
 class ObjectPath {
 
-	public static final ObjectPath ROOT = new ObjectPath();
+	static final ObjectPath ROOT = new ObjectPath();
 
 	private final List<ObjectPathItem> items;
 
@@ -50,7 +56,7 @@ class ObjectPath {
 	/**
 	 * Creates a new {@link ObjectPath} from the given parent {@link ObjectPath} by adding the provided
 	 * {@link ObjectPathItem} to it.
-	 * 
+	 *
 	 * @param parent can be {@literal null}.
 	 * @param item
 	 */
@@ -68,9 +74,9 @@ class ObjectPath {
 	 * @param object must not be {@literal null}.
 	 * @param entity must not be {@literal null}.
 	 * @param id must not be {@literal null}.
-	 * @return
+	 * @return new instance of {@link ObjectPath}.
 	 */
-	public ObjectPath push(Object object, MongoPersistentEntity<?> entity, Object id) {
+	ObjectPath push(Object object, MongoPersistentEntity<?> entity, Object id) {
 
 		Assert.notNull(object, "Object must not be null!");
 		Assert.notNull(entity, "MongoPersistentEntity must not be null!");
@@ -80,14 +86,15 @@ class ObjectPath {
 	}
 
 	/**
-	 * Returns the object with the given id and stored in the given collection if it's contained in the {@link ObjectPath}
-	 * .
-	 * 
+	 * Returns the object with the given id and stored in the given collection if it's contained in the* {@link ObjectPath}.
+	 *
 	 * @param id must not be {@literal null}.
 	 * @param collection must not be {@literal null} or empty.
 	 * @return
+	 * @deprecated use {@link #getPathItem(Object, String, Class)}.
 	 */
-	public Object getPathItem(Object id, String collection) {
+	@Deprecated
+	Object getPathItem(Object id, String collection) {
 
 		Assert.notNull(id, "Id must not be null!");
 		Assert.hasText(collection, "Collection name must not be null!");
@@ -96,11 +103,7 @@ class ObjectPath {
 
 			Object object = item.getObject();
 
-			if (object == null) {
-				continue;
-			}
-
-			if (item.getIdValue() == null) {
+			if (object == null || item.getIdValue() == null) {
 				continue;
 			}
 
@@ -112,16 +115,49 @@ class ObjectPath {
 		return null;
 	}
 
+	/**
+	 * Get the object with given {@literal id}, stored in the {@literal collection} that is assignable to the given
+	 * {@literal type} or {@literal null} if no match found.
+	 *
+	 * @param id must not be {@literal null}.
+	 * @param collection must not be {@literal null} or empty.
+	 * @param type must not be {@literal null}.
+	 * @return {@literal null} when no match found.
+	 * @since 2.0
+	 */
+	<T> T getPathItem(Object id, String collection, Class<T> type) {
+
+		Assert.notNull(id, "Id must not be null!");
+		Assert.hasText(collection, "Collection name must not be null!");
+		Assert.notNull(type, "Type must not be null!");
+
+		for (ObjectPathItem item : items) {
+
+			Object object = item.getObject();
+
+			if (object == null || item.getIdValue() == null) {
+				continue;
+			}
+
+			if (collection.equals(item.getCollection()) && id.equals(item.getIdValue())
+					&& ClassUtils.isAssignable(type, object.getClass())) {
+				return type.cast(object);
+			}
+		}
+
+		return null;
+	}
+
 	/**
 	 * Returns the current object of the {@link ObjectPath} or {@literal null} if the path is empty.
-	 * 
+	 *
 	 * @return
 	 */
-	public Object getCurrentObject() {
+	Object getCurrentObject() {
 		return items.isEmpty() ? null : items.get(items.size() - 1).getObject();
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see java.lang.Object#toString()
 	 */
@@ -135,7 +171,7 @@ class ObjectPath {
 		List<String> strings = new ArrayList<String>(items.size());
 
 		for (ObjectPathItem item : items) {
-			strings.add(item.object.toString());
+			strings.add(ObjectUtils.nullSafeToString(item.object));
 		}
 
 		return StringUtils.collectionToDelimitedString(strings, " -> ");
@@ -143,40 +179,16 @@ class ObjectPath {
 
 	/**
 	 * An item in an {@link ObjectPath}.
-	 * 
+	 *
 	 * @author Thomas Darimont
 	 * @author Oliver Gierke
+	 * @author Mark Paluch
 	 */
+	@Value
 	private static class ObjectPathItem {
 
-		private final Object object;
-		private final Object idValue;
-		private final String collection;
-
-		/**
-		 * Creates a new {@link ObjectPathItem}.
-		 * 
-		 * @param object
-		 * @param idValue
-		 * @param collection
-		 */
-		ObjectPathItem(Object object, Object idValue, String collection) {
-
-			this.object = object;
-			this.idValue = idValue;
-			this.collection = collection;
-		}
-
-		public Object getObject() {
-			return object;
-		}
-
-		public Object getIdValue() {
-			return idValue;
-		}
-
-		public String getCollection() {
-			return collection;
-		}
+		Object object;
+		Object idValue;
+		String collection;
 	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/QueryMapper.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.
@@ -82,7 +82,7 @@ public class QueryMapper {
 	 */
 	public QueryMapper(MongoConverter converter) {
 
-		Assert.notNull(converter);
+		Assert.notNull(converter, "MongoConverter must not be null!");
 
 		this.conversionService = converter.getConversionService();
 		this.converter = converter;

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/convert/UpdateMapper.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.
@@ -15,9 +15,12 @@
  */
 package org.springframework.data.mongodb.core.convert;
 
+import java.util.Collection;
 import java.util.Map.Entry;
 
 import org.springframework.core.convert.converter.Converter;
+import org.springframework.data.domain.Sort;
+import org.springframework.data.domain.Sort.Order;
 import org.springframework.data.mapping.Association;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
@@ -37,6 +40,7 @@ import com.mongodb.DBObject;
  * @author Thomas Darimont
  * @author Oliver Gierke
  * @author Christoph Strobl
+ * @author Mark Paluch
  */
 public class UpdateMapper extends QueryMapper {
 
@@ -130,11 +134,23 @@ public class UpdateMapper extends QueryMapper {
 	}
 
 	private DBObject getMappedValue(Field field, Modifier modifier) {
+		return new BasicDBObject(modifier.getKey(), getMappedModifier(field, modifier));
+	}
+
+	private Object getMappedModifier(Field field, Modifier modifier) {
+
+		Object value = modifier.getValue();
+
+		if (value instanceof Sort) {
+
+			DBObject sortObject = getSortObject((Sort) value);
+			return field == null || field.getPropertyEntity() == null ? sortObject
+					: getMappedSort(sortObject, field.getPropertyEntity());
+		}
 
 		TypeInformation<?> typeHint = field == null ? ClassTypeInformation.OBJECT : field.getTypeHint();
 
-		Object value = converter.convertToMongoType(modifier.getValue(), typeHint);
-		return new BasicDBObject(modifier.getKey(), value);
+		return converter.convertToMongoType(value, typeHint);
 	}
 
 	private TypeInformation<?> getTypeHintForEntity(Object source, MongoPersistentEntity<?> entity) {
@@ -146,6 +162,10 @@ public class UpdateMapper extends QueryMapper {
 			return info;
 		}
 
+		if (source instanceof Collection) {
+			return NESTED_DOCUMENT;
+		}
+
 		if (!type.equals(source.getClass())) {
 			return info;
 		}
@@ -153,6 +173,17 @@ public class UpdateMapper extends QueryMapper {
 		return NESTED_DOCUMENT;
 	}
 
+	public DBObject getSortObject(Sort sort) {
+
+		DBObject dbo = new BasicDBObject();
+
+		for (Order order : sort) {
+			dbo.put(order.getProperty(), order.isAscending() ? 1 : -1);
+		}
+
+		return dbo;
+	}
+
 	/* 
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.convert.QueryMapper#createPropertyField(org.springframework.data.mongodb.core.mapping.MongoPersistentEntity, java.lang.String, org.springframework.data.mapping.context.MappingContext)

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/geo/GeoJson.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.
@@ -27,7 +27,7 @@ public interface GeoJson<T extends Iterable<?>> {
 	 * String value representing the type of the {@link GeoJson} object.
 	 * 
 	 * @return will never be {@literal null}.
-	 * @see http://geojson.org/geojson-spec.html#geojson-objects
+	 * @see <a href="http://geojson.org/geojson-spec.html#geojson-objects">http://geojson.org/geojson-spec.html#geojson-objects</a>
 	 */
 	String getType();
 
@@ -36,7 +36,7 @@ public interface GeoJson<T extends Iterable<?>> {
 	 * determined by {@link #getType()} of geometry.
 	 * 
 	 * @return will never be {@literal null}.
-	 * @see http://geojson.org/geojson-spec.html#geometry-objects
+	 * @see <a href="http://geojson.org/geojson-spec.html#geometry-objects">http://geojson.org/geojson-spec.html#geometry-objects</a>
 	 */
 	T getCoordinates();
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/geo/GeoJsonGeometryCollection.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.
@@ -27,7 +27,7 @@ import org.springframework.util.ObjectUtils;
  * 
  * @author Christoph Strobl
  * @since 1.7
- * @see http://geojson.org/geojson-spec.html#geometry-collection
+ * @see <a href="http://geojson.org/geojson-spec.html#geometry-collection">http://geojson.org/geojson-spec.html#geometry-collection</a>
  */
 public class GeoJsonGeometryCollection implements GeoJson<Iterable<GeoJson<?>>> {
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/geo/GeoJsonLineString.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.
@@ -24,7 +24,7 @@ import org.springframework.data.geo.Point;
  * 
  * @author Christoph Strobl
  * @since 1.7
- * @see http://geojson.org/geojson-spec.html#linestring
+ * @see <a href="http://geojson.org/geojson-spec.html#linestring">http://geojson.org/geojson-spec.html#linestring</a>
  */
 public class GeoJsonLineString extends GeoJsonMultiPoint {
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/geo/GeoJsonMultiLineString.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.
@@ -28,7 +28,7 @@ import org.springframework.util.ObjectUtils;
  * 
  * @author Christoph Strobl
  * @since 1.7
- * @see http://geojson.org/geojson-spec.html#multilinestring
+ * @see <a href="http://geojson.org/geojson-spec.html#multilinestring">http://geojson.org/geojson-spec.html#multilinestring</a>
  */
 public class GeoJsonMultiLineString implements GeoJson<Iterable<GeoJsonLineString>> {
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/geo/GeoJsonMultiPoint.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.
@@ -29,7 +29,7 @@ import org.springframework.util.ObjectUtils;
  * 
  * @author Christoph Strobl
  * @since 1.7
- * @see http://geojson.org/geojson-spec.html#multipoint
+ * @see <a href="http://geojson.org/geojson-spec.html#multipoint">http://geojson.org/geojson-spec.html#multipoint</a>
  */
 public class GeoJsonMultiPoint implements GeoJson<Iterable<Point>> {
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/geo/GeoJsonPoint.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.
@@ -25,7 +25,7 @@ import org.springframework.data.geo.Point;
  * 
  * @author Christoph Strobl
  * @since 1.7
- * @see http://geojson.org/geojson-spec.html#point
+ * @see <a href="http://geojson.org/geojson-spec.html#point">http://geojson.org/geojson-spec.html#point</a>
  */
 public class GeoJsonPoint extends Point implements GeoJson<List<Double>> {
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2016 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.
@@ -31,7 +31,7 @@ import org.springframework.util.Assert;
  *
  * @author Christoph Strobl
  * @since 1.7
- * @see http://geojson.org/geojson-spec.html#polygon
+ * @see <a href="http://geojson.org/geojson-spec.html#polygon">http://geojson.org/geojson-spec.html#polygon</a>
  */
 public class GeoJsonPolygon extends Polygon implements GeoJson<List<GeoJsonLineString>> {
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 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.
@@ -29,6 +29,7 @@ import org.springframework.util.Assert;
  * Represents a geospatial sphere value.
  * 
  * @author Thomas Darimont
+ * @author Mark Paluch
  * @since 1.5
  */
 public class Sphere implements Shape {
@@ -46,8 +47,8 @@ public class Sphere implements Shape {
 	@PersistenceConstructor
 	public Sphere(Point center, Distance radius) {
 
-		Assert.notNull(center);
-		Assert.notNull(radius);
+		Assert.notNull(center, "Center point must not be null!");
+		Assert.notNull(radius, "Radius must not be null!");
 		Assert.isTrue(radius.getValue() >= 0, "Radius must not be negative!");
 
 		this.center = center;

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/index/CompoundIndex.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.
@@ -54,22 +54,22 @@ public @interface CompoundIndex {
 	IndexDirection direction() default IndexDirection.ASCENDING;
 
 	/**
-	 * @see http://docs.mongodb.org/manual/core/index-unique/
 	 * @return
+	 * @see <a href="https://docs.mongodb.org/manual/core/index-unique/">https://docs.mongodb.org/manual/core/index-unique/</a>
 	 */
 	boolean unique() default false;
 
 	/**
 	 * If set to true index will skip over any document that is missing the indexed field.
 	 * 
-	 * @see http://docs.mongodb.org/manual/core/index-sparse/
 	 * @return
+	 * @see <a href="https://docs.mongodb.org/manual/core/index-sparse/">https://docs.mongodb.org/manual/core/index-sparse/</a>
 	 */
 	boolean sparse() default false;
 
 	/**
-	 * @see http://docs.mongodb.org/manual/core/index-creation/#index-creation-duplicate-dropping
 	 * @return
+	 * @see <a href="https://docs.mongodb.org/manual/core/index-creation/#index-creation-duplicate-dropping">https://docs.mongodb.org/manual/core/index-creation/#index-creation-duplicate-dropping</a>
 	 */
 	boolean dropDups() default false;
 
@@ -139,8 +139,8 @@ public @interface CompoundIndex {
 	/**
 	 * If {@literal true} the index will be created in the background.
 	 * 
-	 * @see http://docs.mongodb.org/manual/core/indexes/#background-construction
 	 * @return
+	 * @see <a href="https://docs.mongodb.org/manual/core/indexes/#background-construction">https://docs.mongodb.org/manual/core/indexes/#background-construction</a>
 	 */
 	boolean background() default false;
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2014 the original author or authors.
+ * Copyright 2010-2016 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.
@@ -39,6 +39,7 @@ public class GeospatialIndex implements IndexDefinition {
 	private GeoSpatialIndexType type = GeoSpatialIndexType.GEO_2D;
 	private Double bucketSize = 1.0;
 	private String additionalField;
+	private IndexFilter filter;
 
 	/**
 	 * Creates a new {@link GeospatialIndex} for the given field.
@@ -119,6 +120,22 @@ public class GeospatialIndex implements IndexDefinition {
 		return this;
 	}
 
+
+	/**
+	 * Only index the documents in a collection that meet a specified {@link IndexFilter filter expression}.
+	 *
+	 * @param filter can be {@literal null}.
+	 * @return
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/core/index-partial/">https://docs.mongodb.com/manual/core/index-partial/</a>
+	 * @since 1.10
+	 */
+	public GeospatialIndex partial(IndexFilter filter) {
+
+		this.filter = filter;
+		return this;
+	}
+
 	public DBObject getIndexKeys() {
 
 		DBObject dbo = new BasicDBObject();
@@ -186,6 +203,10 @@ public class GeospatialIndex implements IndexDefinition {
 				break;
 		}
 
+		if (filter != null) {
+			dbo.put("partialFilterExpression", filter.getFilterObject());
+		}
+
 		return dbo;
 	}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2015 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.
@@ -63,6 +63,8 @@ public class Index implements IndexDefinition {
 
 	private long expire = -1;
 
+	private IndexFilter filter;
+
 	public Index() {}
 
 	public Index(String key, Direction direction) {
@@ -107,8 +109,8 @@ public class Index implements IndexDefinition {
 	/**
 	 * Reject all documents that contain a duplicate value for the indexed field.
 	 * 
-	 * @see http://docs.mongodb.org/manual/core/index-unique/
 	 * @return
+	 * @see <a href="https://docs.mongodb.org/manual/core/index-unique/">https://docs.mongodb.org/manual/core/index-unique/</a>
 	 */
 	public Index unique() {
 		this.unique = true;
@@ -118,8 +120,8 @@ public class Index implements IndexDefinition {
 	/**
 	 * Skip over any document that is missing the indexed field.
 	 * 
-	 * @see http://docs.mongodb.org/manual/core/index-sparse/
 	 * @return
+	 * @see <a href="https://docs.mongodb.org/manual/core/index-sparse/">https://docs.mongodb.org/manual/core/index-sparse/</a>
 	 */
 	public Index sparse() {
 		this.sparse = true;
@@ -165,9 +167,9 @@ public class Index implements IndexDefinition {
 	}
 
 	/**
-	 * @see http://docs.mongodb.org/manual/core/index-creation/#index-creation-duplicate-dropping
 	 * @param duplicates
 	 * @return
+	 * @see <a href="http://docs.mongodb.org/manual/core/index-creation/#index-creation-duplicate-dropping">http://docs.mongodb.org/manual/core/index-creation/#index-creation-duplicate-dropping</a>
 	 */
 	public Index unique(Duplicates duplicates) {
 		if (duplicates == Duplicates.DROP) {
@@ -176,6 +178,21 @@ public class Index implements IndexDefinition {
 		return unique();
 	}
 
+	/**
+	 * Only index the documents in a collection that meet a specified {@link IndexFilter filter expression}.
+	 *
+	 * @param filter can be {@literal null}.
+	 * @return
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/core/index-partial/">https://docs.mongodb.com/manual/core/index-partial/</a>
+	 * @since 1.10
+	 */
+	public Index partial(IndexFilter filter) {
+
+		this.filter = filter;
+		return this;
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.index.IndexDefinition#getIndexKeys()
@@ -213,6 +230,9 @@ public class Index implements IndexDefinition {
 			dbo.put("expireAfterSeconds", expire);
 		}
 
+		if (filter != null) {
+			dbo.put("partialFilterExpression", filter.getFilterObject());
+		}
 		return dbo;
 	}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2014 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.
@@ -44,8 +44,13 @@ public final class IndexField {
 
 	private IndexField(String key, Direction direction, Type type, Float weight) {
 
-		Assert.hasText(key);
-		Assert.isTrue(direction != null ^ (Type.GEO.equals(type) || Type.TEXT.equals(type)));
+		Assert.hasText(key, "Key must not be null or empty");
+
+		if (Type.GEO.equals(type) || Type.TEXT.equals(type)) {
+			Assert.isTrue(direction == null, "Geo/Text indexes must not have a direction!");
+		} else {
+			Assert.notNull(direction, "Default indexes require a direction");
+		}
 
 		this.key = key;
 		this.direction = direction;
@@ -58,17 +63,21 @@ public final class IndexField {
 	 * 
 	 * @deprecated use {@link #create(String, Direction)}.
 	 * @param key must not be {@literal null} or emtpy.
-	 * @param direction must not be {@literal null}.
+	 * @param order must not be {@literal null}.
 	 * @return
 	 */
 	@Deprecated
 	public static IndexField create(String key, Order order) {
-		Assert.notNull(order);
+		
+		Assert.notNull(order, "Order must not be null!");
+
 		return new IndexField(key, order.toDirection(), Type.DEFAULT);
 	}
 
 	public static IndexField create(String key, Direction order) {
-		Assert.notNull(order);
+		
+		Assert.notNull(order, "Direction must not be null!");
+
 		return new IndexField(key, order, Type.DEFAULT);
 	}
 
@@ -128,7 +137,7 @@ public final class IndexField {
 	}
 
 	/**
-	 * Returns wheter the {@link IndexField} is a text index field.
+	 * Returns whether the {@link IndexField} is a text index field.
 	 * 
 	 * @return true if type is {@link Type#TEXT}
 	 * @since 1.6
@@ -158,7 +167,7 @@ public final class IndexField {
 				&& this.type == that.type;
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see java.lang.Object#hashCode()
 	 */
@@ -173,7 +182,7 @@ public final class IndexField {
 		return result;
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see java.lang.Object#toString()
 	 */