Release version 3.2 M2 (2021.0.0).

See #3521

.github/PULL_REQUEST_TEMPLATE.md

@@ -6,7 +6,6 @@ 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).

.github/workflows/project.yml

@@ -0,0 +1,47 @@
+# GitHub Actions to automate GitHub issues for Spring Data Project Management
+
+name: Spring Data GitHub Issues
+
+on:
+  issues:
+    types: [opened, edited, reopened]
+  issue_comment:
+    types: [created]
+  pull_request_target:
+    types: [opened, edited, reopened]
+
+jobs:
+  Inbox:
+    runs-on: ubuntu-latest
+    if: github.repository_owner == 'spring-projects' && (github.event.action == 'opened' || github.event.action == 'reopened') && github.event.pull_request == null
+    steps:
+      - name: Create or Update Issue Card
+        uses: peter-evans/create-or-update-project-card@v1.1.2
+        with:
+          project-name: 'Spring Data'
+          column-name: 'Inbox'
+          project-location: 'spring-projects'
+          token: ${{ secrets.GH_ISSUES_TOKEN_SPRING_DATA }}
+  Pull-Request:
+    runs-on: ubuntu-latest
+    if: github.repository_owner == 'spring-projects' && (github.event.action == 'opened' || github.event.action == 'reopened') && github.event.pull_request != null
+    steps:
+      - name: Create or Update Pull Request Card
+        uses: peter-evans/create-or-update-project-card@v1.1.2
+        with:
+          project-name: 'Spring Data'
+          column-name: 'Review pending'
+          project-location: 'spring-projects'
+          issue-number: ${{ github.event.pull_request.number }}
+          token: ${{ secrets.GH_ISSUES_TOKEN_SPRING_DATA }}
+  Feedback-Provided:
+    runs-on: ubuntu-latest
+    if: github.repository_owner == 'spring-projects' && github.event.action == 'created' && contains(join(github.event.issue.labels.*.name, ', '), 'waiting-for-feedback')
+    steps:
+      - name: Update Project Card
+        uses: peter-evans/create-or-update-project-card@v1.1.2
+        with:
+          project-name: 'Spring Data'
+          column-name: 'Feedback provided'
+          project-location: 'spring-projects'
+          token: ${{ secrets.GH_ISSUES_TOKEN_SPRING_DATA }}

CODE_OF_CONDUCT.adoc

@@ -1,27 +0,0 @@
-= Contributor Code of Conduct
-
-As contributors and maintainers of this project, and in the interest of fostering an open and welcoming community, we pledge to respect all people who contribute through reporting issues, posting feature requests, updating documentation, submitting pull requests or patches, and other activities.
-
-We are committed to making participation in this project a harassment-free experience for everyone, regardless of level of experience, gender, gender identity and expression, sexual orientation, disability, personal appearance, body size, race, ethnicity, age, religion, or nationality.
-
-Examples of unacceptable behavior by participants include:
-
-* The use of sexualized language or imagery
-* Personal attacks
-* Trolling or insulting/derogatory comments
-* Public or private harassment
-* Publishing other's private information, such as physical or electronic addresses,
-  without explicit permission
-* Other unethical or unprofessional conduct
-
-Project maintainers have the right and responsibility to remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned to this Code of Conduct, or to ban temporarily or permanently any contributor for other behaviors that they deem inappropriate, threatening, offensive, or harmful.
-
-By adopting this Code of Conduct, project maintainers commit themselves to fairly and consistently applying these principles to every aspect of managing this project. Project maintainers who do not follow or enforce the Code of Conduct may be permanently removed from the project team.
-
-This Code of Conduct applies both within project spaces and in public spaces when an individual is representing the project or its community.
-
-Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by contacting a project maintainer at spring-code-of-conduct@pivotal.io.
-All complaints will be reviewed and investigated and will result in a response that is deemed necessary and appropriate to the circumstances.
-Maintainers are obligated to maintain confidentiality with regard to the reporter of an incident.
-
-This Code of Conduct is adapted from the https://contributor-covenant.org[Contributor Covenant], version 1.3.0, available at https://contributor-covenant.org/version/1/3/0/[contributor-covenant.org/version/1/3/0/].

Jenkinsfile

@@ -3,7 +3,7 @@ pipeline {
 
 	triggers {
 		pollSCM 'H/10 * * * *'
-		upstream(upstreamProjects: "spring-data-commons/2.3.x", threshold: hudson.model.Result.SUCCESS)
+		upstream(upstreamProjects: "spring-data-commons/master", threshold: hudson.model.Result.SUCCESS)
 	}
 
 	options {
@@ -46,16 +46,16 @@ pipeline {
 						}
 					}
 				}
-				stage('Publish JDK 14 + MongoDB 4.2') {
+				stage('Publish JDK 15 + MongoDB 4.2') {
 					when {
-						changeset "ci/openjdk14-mongodb-4.2/**"
+						changeset "ci/openjdk15-mongodb-4.2/**"
 					}
 					agent { label 'data' }
 					options { timeout(time: 30, unit: 'MINUTES') }
 
 					steps {
 						script {
-							def image = docker.build("springci/spring-data-openjdk14-with-mongodb-4.2.0", "ci/openjdk14-mongodb-4.2/")
+							def image = docker.build("springci/spring-data-openjdk15-with-mongodb-4.2.0", "ci/openjdk15-mongodb-4.2/")
 							docker.withRegistry('', 'hub.docker.com-springbuildmaster') {
 								image.push()
 							}
@@ -68,7 +68,7 @@ pipeline {
 		stage("test: baseline (jdk8)") {
 			when {
 				anyOf {
-					branch '3.0.x'
+					branch 'master'
 					not { triggeredBy 'UpstreamCause' }
 				}
 			}
@@ -76,9 +76,6 @@ pipeline {
 				label 'data'
 			}
 			options { timeout(time: 30, unit: 'MINUTES') }
-			environment {
-				ARTIFACTORY = credentials('02bd1690-b54f-4c9f-819d-a77cb7a9822c')
-			}
 			steps {
 				script {
 					docker.withRegistry('', 'hub.docker.com-springbuildmaster') {
@@ -88,7 +85,7 @@ pipeline {
 							sh 'sleep 10'
 							sh 'mongo --eval "rs.initiate({_id: \'rs0\', members:[{_id: 0, host: \'127.0.0.1:27017\'}]});"'
 							sh 'sleep 15'
-							sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw -s settings.xml clean dependency:list test -Duser.name=jenkins -Dsort -U -B'
+							sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw clean dependency:list test -Duser.name=jenkins -Dsort -U -B'
 						}
 					}
 				}
@@ -97,8 +94,8 @@ pipeline {
 
 		stage("Test other configurations") {
 			when {
-				anyOf {
-					branch '3.0.x'
+				allOf {
+					branch 'master'
 					not { triggeredBy 'UpstreamCause' }
 				}
 			}
@@ -108,9 +105,6 @@ pipeline {
 						label 'data'
 					}
 					options { timeout(time: 30, unit: 'MINUTES') }
-					environment {
-						ARTIFACTORY = credentials('02bd1690-b54f-4c9f-819d-a77cb7a9822c')
-					}
 					steps {
 						script {
 							docker.withRegistry('', 'hub.docker.com-springbuildmaster') {
@@ -120,7 +114,7 @@ pipeline {
 									sh 'sleep 10'
 									sh 'mongo --eval "rs.initiate({_id: \'rs0\', members:[{_id: 0, host: \'127.0.0.1:27017\'}]});"'
 									sh 'sleep 15'
-									sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw -s settings.xml clean dependency:list test -Duser.name=jenkins -Dsort -U -B'
+									sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw clean dependency:list test -Duser.name=jenkins -Dsort -U -B'
 								}
 							}
 						}
@@ -132,9 +126,6 @@ pipeline {
 						label 'data'
 					}
 					options { timeout(time: 30, unit: 'MINUTES') }
-					environment {
-						ARTIFACTORY = credentials('02bd1690-b54f-4c9f-819d-a77cb7a9822c')
-					}
 					steps {
 						script {
 							docker.withRegistry('', 'hub.docker.com-springbuildmaster') {
@@ -144,21 +135,18 @@ pipeline {
 									sh 'sleep 10'
 									sh 'mongo --eval "rs.initiate({_id: \'rs0\', members:[{_id: 0, host: \'127.0.0.1:27017\'}]});"'
 									sh 'sleep 15'
-									sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw -s settings.xml clean dependency:list test -Duser.name=jenkins -Dsort -U -B'
+									sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw clean dependency:list test -Duser.name=jenkins -Dsort -U -B'
 								}
 							}
 						}
 					}
 				}
 
-				stage("test: baseline (jdk14)") {
+				stage("test: baseline (jdk15)") {
 					agent {
 						label 'data'
 					}
 					options { timeout(time: 30, unit: 'MINUTES') }
-					environment {
-						ARTIFACTORY = credentials('02bd1690-b54f-4c9f-819d-a77cb7a9822c')
-					}
 					steps {
 						script {
 							docker.withRegistry('', 'hub.docker.com-springbuildmaster') {
@@ -168,7 +156,7 @@ pipeline {
 									sh 'sleep 10'
 									sh 'mongo --eval "rs.initiate({_id: \'rs0\', members:[{_id: 0, host: \'127.0.0.1:27017\'}]});"'
 									sh 'sleep 15'
-									sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw -s settings.xml -Pjava11 clean dependency:list test -Duser.name=jenkins -Dsort -U -B'
+									sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw -Pjava11 clean dependency:list test -Duser.name=jenkins -Dsort -U -B'
 								}
 							}
 						}
@@ -180,7 +168,7 @@ pipeline {
 		stage('Release to artifactory') {
 			when {
 				anyOf {
-					branch '3.0.x'
+					branch 'master'
 					not { triggeredBy 'UpstreamCause' }
 				}
 			}
@@ -197,7 +185,7 @@ pipeline {
 				script {
 					docker.withRegistry('', 'hub.docker.com-springbuildmaster') {
 						docker.image('adoptopenjdk/openjdk8:latest').inside('-v $HOME:/tmp/jenkins-home') {
-							sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw -s settings.xml -Pci,artifactory ' +
+							sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw -Pci,artifactory ' +
 									'-Dartifactory.server=https://repo.spring.io ' +
 									"-Dartifactory.username=${ARTIFACTORY_USR} " +
 									"-Dartifactory.password=${ARTIFACTORY_PSW} " +
@@ -213,7 +201,7 @@ pipeline {
 
 		stage('Publish documentation') {
 			when {
-				branch '3.0.x'
+				branch 'master'
 			}
 			agent {
 				label 'data'
@@ -228,7 +216,7 @@ pipeline {
 				script {
 					docker.withRegistry('', 'hub.docker.com-springbuildmaster') {
 						docker.image('adoptopenjdk/openjdk8:latest').inside('-v $HOME:/tmp/jenkins-home') {
-							sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw -s settings.xml -Pci,distribute ' +
+							sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw -Pci,distribute ' +
 									'-Dartifactory.server=https://repo.spring.io ' +
 									"-Dartifactory.username=${ARTIFACTORY_USR} " +
 									"-Dartifactory.password=${ARTIFACTORY_PSW} " +

LICENSE.txt

@@ -1,202 +0,0 @@
-
-                                 Apache License
-                           Version 2.0, January 2004
-                        https://www.apache.org/licenses/
-
-   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
-
-   1. Definitions.
-
-      "License" shall mean the terms and conditions for use, reproduction,
-      and distribution as defined by Sections 1 through 9 of this document.
-
-      "Licensor" shall mean the copyright owner or entity authorized by
-      the copyright owner that is granting the License.
-
-      "Legal Entity" shall mean the union of the acting entity and all
-      other entities that control, are controlled by, or are under common
-      control with that entity. For the purposes of this definition,
-      "control" means (i) the power, direct or indirect, to cause the
-      direction or management of such entity, whether by contract or
-      otherwise, or (ii) ownership of fifty percent (50%) or more of the
-      outstanding shares, or (iii) beneficial ownership of such entity.
-
-      "You" (or "Your") shall mean an individual or Legal Entity
-      exercising permissions granted by this License.
-
-      "Source" form shall mean the preferred form for making modifications,
-      including but not limited to software source code, documentation
-      source, and configuration files.
-
-      "Object" form shall mean any form resulting from mechanical
-      transformation or translation of a Source form, including but
-      not limited to compiled object code, generated documentation,
-      and conversions to other media types.
-
-      "Work" shall mean the work of authorship, whether in Source or
-      Object form, made available under the License, as indicated by a
-      copyright notice that is included in or attached to the work
-      (an example is provided in the Appendix below).
-
-      "Derivative Works" shall mean any work, whether in Source or Object
-      form, that is based on (or derived from) the Work and for which the
-      editorial revisions, annotations, elaborations, or other modifications
-      represent, as a whole, an original work of authorship. For the purposes
-      of this License, Derivative Works shall not include works that remain
-      separable from, or merely link (or bind by name) to the interfaces of,
-      the Work and Derivative Works thereof.
-
-      "Contribution" shall mean any work of authorship, including
-      the original version of the Work and any modifications or additions
-      to that Work or Derivative Works thereof, that is intentionally
-      submitted to Licensor for inclusion in the Work by the copyright owner
-      or by an individual or Legal Entity authorized to submit on behalf of
-      the copyright owner. For the purposes of this definition, "submitted"
-      means any form of electronic, verbal, or written communication sent
-      to the Licensor or its representatives, including but not limited to
-      communication on electronic mailing lists, source code control systems,
-      and issue tracking systems that are managed by, or on behalf of, the
-      Licensor for the purpose of discussing and improving the Work, but
-      excluding communication that is conspicuously marked or otherwise
-      designated in writing by the copyright owner as "Not a Contribution."
-
-      "Contributor" shall mean Licensor and any individual or Legal Entity
-      on behalf of whom a Contribution has been received by Licensor and
-      subsequently incorporated within the Work.
-
-   2. Grant of Copyright License. Subject to the terms and conditions of
-      this License, each Contributor hereby grants to You a perpetual,
-      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
-      copyright license to reproduce, prepare Derivative Works of,
-      publicly display, publicly perform, sublicense, and distribute the
-      Work and such Derivative Works in Source or Object form.
-
-   3. Grant of Patent License. Subject to the terms and conditions of
-      this License, each Contributor hereby grants to You a perpetual,
-      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
-      (except as stated in this section) patent license to make, have made,
-      use, offer to sell, sell, import, and otherwise transfer the Work,
-      where such license applies only to those patent claims licensable
-      by such Contributor that are necessarily infringed by their
-      Contribution(s) alone or by combination of their Contribution(s)
-      with the Work to which such Contribution(s) was submitted. If You
-      institute patent litigation against any entity (including a
-      cross-claim or counterclaim in a lawsuit) alleging that the Work
-      or a Contribution incorporated within the Work constitutes direct
-      or contributory patent infringement, then any patent licenses
-      granted to You under this License for that Work shall terminate
-      as of the date such litigation is filed.
-
-   4. Redistribution. You may reproduce and distribute copies of the
-      Work or Derivative Works thereof in any medium, with or without
-      modifications, and in Source or Object form, provided that You
-      meet the following conditions:
-
-      (a) You must give any other recipients of the Work or
-          Derivative Works a copy of this License; and
-
-      (b) You must cause any modified files to carry prominent notices
-          stating that You changed the files; and
-
-      (c) You must retain, in the Source form of any Derivative Works
-          that You distribute, all copyright, patent, trademark, and
-          attribution notices from the Source form of the Work,
-          excluding those notices that do not pertain to any part of
-          the Derivative Works; and
-
-      (d) If the Work includes a "NOTICE" text file as part of its
-          distribution, then any Derivative Works that You distribute must
-          include a readable copy of the attribution notices contained
-          within such NOTICE file, excluding those notices that do not
-          pertain to any part of the Derivative Works, in at least one
-          of the following places: within a NOTICE text file distributed
-          as part of the Derivative Works; within the Source form or
-          documentation, if provided along with the Derivative Works; or,
-          within a display generated by the Derivative Works, if and
-          wherever such third-party notices normally appear. The contents
-          of the NOTICE file are for informational purposes only and
-          do not modify the License. You may add Your own attribution
-          notices within Derivative Works that You distribute, alongside
-          or as an addendum to the NOTICE text from the Work, provided
-          that such additional attribution notices cannot be construed
-          as modifying the License.
-
-      You may add Your own copyright statement to Your modifications and
-      may provide additional or different license terms and conditions
-      for use, reproduction, or distribution of Your modifications, or
-      for any such Derivative Works as a whole, provided Your use,
-      reproduction, and distribution of the Work otherwise complies with
-      the conditions stated in this License.
-
-   5. Submission of Contributions. Unless You explicitly state otherwise,
-      any Contribution intentionally submitted for inclusion in the Work
-      by You to the Licensor shall be under the terms and conditions of
-      this License, without any additional terms or conditions.
-      Notwithstanding the above, nothing herein shall supersede or modify
-      the terms of any separate license agreement you may have executed
-      with Licensor regarding such Contributions.
-
-   6. Trademarks. This License does not grant permission to use the trade
-      names, trademarks, service marks, or product names of the Licensor,
-      except as required for reasonable and customary use in describing the
-      origin of the Work and reproducing the content of the NOTICE file.
-
-   7. Disclaimer of Warranty. Unless required by applicable law or
-      agreed to in writing, Licensor provides the Work (and each
-      Contributor provides its Contributions) on an "AS IS" BASIS,
-      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
-      implied, including, without limitation, any warranties or conditions
-      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
-      PARTICULAR PURPOSE. You are solely responsible for determining the
-      appropriateness of using or redistributing the Work and assume any
-      risks associated with Your exercise of permissions under this License.
-
-   8. Limitation of Liability. In no event and under no legal theory,
-      whether in tort (including negligence), contract, or otherwise,
-      unless required by applicable law (such as deliberate and grossly
-      negligent acts) or agreed to in writing, shall any Contributor be
-      liable to You for damages, including any direct, indirect, special,
-      incidental, or consequential damages of any character arising as a
-      result of this License or out of the use or inability to use the
-      Work (including but not limited to damages for loss of goodwill,
-      work stoppage, computer failure or malfunction, or any and all
-      other commercial damages or losses), even if such Contributor
-      has been advised of the possibility of such damages.
-
-   9. Accepting Warranty or Additional Liability. While redistributing
-      the Work or Derivative Works thereof, You may choose to offer,
-      and charge a fee for, acceptance of support, warranty, indemnity,
-      or other liability obligations and/or rights consistent with this
-      License. However, in accepting such obligations, You may act only
-      on Your own behalf and on Your sole responsibility, not on behalf
-      of any other Contributor, and only if You agree to indemnify,
-      defend, and hold each Contributor harmless for any liability
-      incurred by, or claims asserted against, such Contributor by reason
-      of your accepting any such warranty or additional liability.
-
-   END OF TERMS AND CONDITIONS
-
-   APPENDIX: How to apply the Apache License to your work.
-
-      To apply the Apache License to your work, attach the following
-      boilerplate notice, with the fields enclosed by brackets "{}"
-      replaced with your own identifying information. (Don't include
-      the brackets!)  The text should be enclosed in the appropriate
-      comment syntax for the file format. We also recommend that a
-      file or class name and description of purpose be included on the
-      same "printed page" as the copyright notice for easier
-      identification within third-party archives.
-
-   Copyright {yyyy} {name of copyright owner}
-
-   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
-
-       https://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.

README.adoc

@@ -10,7 +10,7 @@ Key functional areas of Spring Data MongoDB are a POJO centric model for interac
 
 == Code of Conduct
 
-This project is governed by the link:CODE_OF_CONDUCT.adoc[Spring Code of Conduct]. By participating, you are expected to uphold this code of conduct. Please report unacceptable behavior to spring-code-of-conduct@pivotal.io.
+This project is governed by the https://github.com/spring-projects/.github/blob/e3cc2ff230d8f1dca06535aa6b5a4a23815861d4/CODE_OF_CONDUCT.md[Spring Code of Conduct]. By participating, you are expected to uphold this code of conduct. Please report unacceptable behavior to spring-code-of-conduct@pivotal.io.
 
 == Getting Started
 

ci/openjdk15-mongodb-4.2/Dockerfile

@@ -1,4 +1,4 @@
-FROM adoptopenjdk/openjdk14:latest
+FROM adoptopenjdk/openjdk15:latest
 
 ENV TZ=Etc/UTC
 ENV DEBIAN_FRONTEND=noninteractive

pom.xml

@@ -5,7 +5,7 @@
 
 	<groupId>org.springframework.data</groupId>
 	<artifactId>spring-data-mongodb-parent</artifactId>
-	<version>3.0.10.BUILD-SNAPSHOT</version>
+	<version>3.2.0-M2</version>
 	<packaging>pom</packaging>
 
 	<name>Spring Data MongoDB</name>
@@ -15,7 +15,7 @@
 	<parent>
 		<groupId>org.springframework.data.build</groupId>
 		<artifactId>spring-data-parent</artifactId>
-		<version>2.3.10.BUILD-SNAPSHOT</version>
+		<version>2.5.0-M2</version>
 	</parent>
 
 	<modules>
@@ -26,8 +26,8 @@
 	<properties>
 		<project.type>multi</project.type>
 		<dist.id>spring-data-mongodb</dist.id>
-		<springdata.commons>2.3.10.BUILD-SNAPSHOT</springdata.commons>
-		<mongo>4.0.6</mongo>
+		<springdata.commons>2.5.0-M2</springdata.commons>
+		<mongo>4.1.1</mongo>
 		<mongo.reactivestreams>${mongo}</mongo.reactivestreams>
 		<jmh.version>1.19</jmh.version>
 	</properties>
@@ -134,8 +134,8 @@
 
 	<repositories>
 		<repository>
-			<id>spring-libs-snapshot</id>
-			<url>https://repo.spring.io/libs-snapshot</url>
+			<id>spring-libs-milestone</id>
+			<url>https://repo.spring.io/libs-milestone</url>
 		</repository>
 		<repository>
 			<id>sonatype-libs-snapshot</id>
@@ -158,6 +158,11 @@
 			<id>spring-libs-milestone</id>
 			<url>https://repo.spring.io/libs-milestone</url>
 		</pluginRepository>
+		<pluginRepository>
+			<id>bintray-plugins</id>
+			<name>bintray-plugins</name>
+			<url>https://jcenter.bintray.com</url>
+		</pluginRepository>
 	</pluginRepositories>
 
 </project>

settings.xml

@@ -1,29 +0,0 @@
-<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
-          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-          xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0
-                      https://maven.apache.org/xsd/settings-1.0.0.xsd">
-
-	<servers>
-		<server>
-			<id>spring-plugins-release</id>
-			<username>${env.ARTIFACTORY_USR}</username>
-			<password>${env.ARTIFACTORY_PSW}</password>
-		</server>
-		<server>
-			<id>spring-libs-snapshot</id>
-			<username>${env.ARTIFACTORY_USR}</username>
-			<password>${env.ARTIFACTORY_PSW}</password>
-		</server>
-		<server>
-			<id>spring-libs-milestone</id>
-			<username>${env.ARTIFACTORY_USR}</username>
-			<password>${env.ARTIFACTORY_PSW}</password>
-		</server>
-		<server>
-			<id>spring-libs-release</id>
-			<username>${env.ARTIFACTORY_USR}</username>
-			<password>${env.ARTIFACTORY_PSW}</password>
-		</server>
-	</servers>
-
-</settings>

spring-data-mongodb-benchmarks/pom.xml

@@ -7,7 +7,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>3.0.10.BUILD-SNAPSHOT</version>
+		<version>3.2.0-M2</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb-distribution/pom.xml

@@ -14,7 +14,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>3.0.10.BUILD-SNAPSHOT</version>
+		<version>3.2.0-M2</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb/pom.xml

@@ -11,7 +11,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>3.0.10.BUILD-SNAPSHOT</version>
+		<version>3.2.0-M2</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 
@@ -136,6 +136,13 @@
 			<optional>true</optional>
 		</dependency>
 
+		<dependency>
+			<groupId>io.reactivex.rxjava3</groupId>
+			<artifactId>rxjava</artifactId>
+			<version>${rxjava3}</version>
+			<optional>true</optional>
+		</dependency>
+
 		<!-- CDI -->
 		<!-- Dependency order required to build against CDI 1.0 and test with CDI 2.0 -->
 		<dependency>
@@ -192,7 +199,14 @@
 		<dependency>
 			<groupId>org.hibernate</groupId>
 			<artifactId>hibernate-validator</artifactId>
-			<version>5.2.4.Final</version>
+			<version>5.4.3.Final</version>
+			<scope>test</scope>
+		</dependency>
+
+		<dependency>
+			<groupId>org.glassfish</groupId>
+			<artifactId>javax.el</artifactId>
+			<version>3.0.1-b11</version>
 			<scope>test</scope>
 		</dependency>
 

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

@@ -61,8 +61,8 @@ public @interface EnableMongoAuditing {
 	boolean modifyOnCreate() default true;
 
 	/**
-	 * Configures a {@link DateTimeProvider} bean name that allows customizing the {@link org.joda.time.DateTime} to be
-	 * used for setting creation and modification dates.
+	 * Configures a {@link DateTimeProvider} bean name that allows customizing the timestamp to be used for setting
+	 * creation and modification dates.
 	 *
 	 * @return empty {@link String} by default.
 	 */

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

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2020-2021 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
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.config;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Inherited;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.springframework.context.annotation.Import;
+import org.springframework.data.auditing.DateTimeProvider;
+import org.springframework.data.domain.ReactiveAuditorAware;
+
+/**
+ * Annotation to enable auditing in MongoDB using reactive infrastructure via annotation configuration.
+ *
+ * @author Mark Paluch
+ * @since 3.1
+ */
+@Inherited
+@Documented
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+@Import(ReactiveMongoAuditingRegistrar.class)
+public @interface EnableReactiveMongoAuditing {
+
+	/**
+	 * Configures the {@link ReactiveAuditorAware} bean to be used to lookup the current principal.
+	 *
+	 * @return empty {@link String} by default.
+	 */
+	String auditorAwareRef() default "";
+
+	/**
+	 * Configures whether the creation and modification dates are set. Defaults to {@literal true}.
+	 *
+	 * @return {@literal true} by default.
+	 */
+	boolean setDates() default true;
+
+	/**
+	 * Configures whether the entity shall be marked as modified on creation. Defaults to {@literal true}.
+	 *
+	 * @return {@literal true} by default.
+	 */
+	boolean modifyOnCreate() default true;
+
+	/**
+	 * Configures a {@link DateTimeProvider} bean name that allows customizing the timestamp to be used for setting
+	 * creation and modification dates.
+	 *
+	 * @return empty {@link String} by default.
+	 */
+	String dateTimeProviderRef() default "";
+}

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

@@ -17,7 +17,6 @@ package org.springframework.data.mongodb.config;
 
 import java.lang.annotation.Annotation;
 
-import org.springframework.beans.factory.FactoryBean;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.support.AbstractBeanDefinition;
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
@@ -28,14 +27,8 @@ import org.springframework.data.auditing.IsNewAwareAuditingHandler;
 import org.springframework.data.auditing.config.AuditingBeanDefinitionRegistrarSupport;
 import org.springframework.data.auditing.config.AuditingConfiguration;
 import org.springframework.data.config.ParsingUtils;
-import org.springframework.data.mapping.context.MappingContext;
-import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
-import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
-import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
 import org.springframework.data.mongodb.core.mapping.event.AuditingEntityCallback;
-import org.springframework.data.mongodb.core.mapping.event.ReactiveAuditingEntityCallback;
 import org.springframework.util.Assert;
-import org.springframework.util.ClassUtils;
 
 /**
  * {@link ImportBeanDefinitionRegistrar} to enable {@link EnableMongoAuditing} annotation.
@@ -46,9 +39,6 @@ import org.springframework.util.ClassUtils;
  */
 class MongoAuditingRegistrar extends AuditingBeanDefinitionRegistrarSupport {
 
-	private static boolean PROJECT_REACTOR_AVAILABLE = ClassUtils.isPresent("reactor.core.publisher.Mono",
-			MongoAuditingRegistrar.class.getClassLoader());
-
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.auditing.config.AuditingBeanDefinitionRegistrarSupport#getAnnotation()
@@ -91,7 +81,7 @@ class MongoAuditingRegistrar extends AuditingBeanDefinitionRegistrarSupport {
 
 		BeanDefinitionBuilder builder = BeanDefinitionBuilder.rootBeanDefinition(IsNewAwareAuditingHandler.class);
 
-		BeanDefinitionBuilder definition = BeanDefinitionBuilder.genericBeanDefinition(MongoMappingContextLookup.class);
+		BeanDefinitionBuilder definition = BeanDefinitionBuilder.genericBeanDefinition(PersistentEntitiesFactoryBean.class);
 		definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_CONSTRUCTOR);
 
 		builder.addConstructorArgValue(definition.getBeanDefinition());
@@ -116,68 +106,6 @@ class MongoAuditingRegistrar extends AuditingBeanDefinitionRegistrarSupport {
 
 		registerInfrastructureBeanWithId(listenerBeanDefinitionBuilder.getBeanDefinition(),
 				AuditingEntityCallback.class.getName(), registry);
-
-		if (PROJECT_REACTOR_AVAILABLE) {
-			registerReactiveAuditingEntityCallback(registry, auditingHandlerDefinition.getSource());
-		}
 	}
 
-	private void registerReactiveAuditingEntityCallback(BeanDefinitionRegistry registry, Object source) {
-
-		BeanDefinitionBuilder builder = BeanDefinitionBuilder.rootBeanDefinition(ReactiveAuditingEntityCallback.class);
-
-		builder.addConstructorArgValue(ParsingUtils.getObjectFactoryBeanDefinition(getAuditingHandlerBeanName(), registry));
-		builder.getRawBeanDefinition().setSource(source);
-
-		registerInfrastructureBeanWithId(builder.getBeanDefinition(), ReactiveAuditingEntityCallback.class.getName(),
-				registry);
-	}
-
-	/**
-	 * Simple helper to be able to wire the {@link MappingContext} from a {@link MappingMongoConverter} bean available in
-	 * the application context.
-	 *
-	 * @author Oliver Gierke
-	 */
-	static class MongoMappingContextLookup
-			implements FactoryBean<MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty>> {
-
-		private final MappingMongoConverter converter;
-
-		/**
-		 * Creates a new {@link MongoMappingContextLookup} for the given {@link MappingMongoConverter}.
-		 *
-		 * @param converter must not be {@literal null}.
-		 */
-		public MongoMappingContextLookup(MappingMongoConverter converter) {
-			this.converter = converter;
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.springframework.beans.factory.FactoryBean#getObject()
-		 */
-		@Override
-		public MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> getObject() throws Exception {
-			return converter.getMappingContext();
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.springframework.beans.factory.FactoryBean#getObjectType()
-		 */
-		@Override
-		public Class<?> getObjectType() {
-			return MappingContext.class;
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see org.springframework.beans.factory.FactoryBean#isSingleton()
-		 */
-		@Override
-		public boolean isSingleton() {
-			return true;
-		}
-	}
 }

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

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2020-2021 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
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.config;
+
+import org.springframework.beans.factory.FactoryBean;
+import org.springframework.data.mapping.context.PersistentEntities;
+import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
+
+/**
+ * Simple helper to be able to wire the {@link PersistentEntities} from a {@link MappingMongoConverter} bean available
+ * in the application context.
+ *
+ * @author Oliver Gierke
+ * @author Mark Paluch
+ * @author Christoph Strobl
+ * @since 3.1
+ */
+class PersistentEntitiesFactoryBean implements FactoryBean<PersistentEntities> {
+
+	private final MappingMongoConverter converter;
+
+	/**
+	 * Creates a new {@link PersistentEntitiesFactoryBean} for the given {@link MappingMongoConverter}.
+	 *
+	 * @param converter must not be {@literal null}.
+	 */
+	public PersistentEntitiesFactoryBean(MappingMongoConverter converter) {
+		this.converter = converter;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.beans.factory.FactoryBean#getObject()
+	 */
+	@Override
+	public PersistentEntities getObject() {
+		return PersistentEntities.of(converter.getMappingContext());
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.beans.factory.FactoryBean#getObjectType()
+	 */
+	@Override
+	public Class<?> getObjectType() {
+		return PersistentEntities.class;
+	}
+}

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

@@ -0,0 +1,97 @@
+/*
+ * Copyright 2020-2021 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
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.config;
+
+import java.lang.annotation.Annotation;
+
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.support.AbstractBeanDefinition;
+import org.springframework.beans.factory.support.BeanDefinitionBuilder;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
+import org.springframework.core.type.AnnotationMetadata;
+import org.springframework.data.auditing.ReactiveIsNewAwareAuditingHandler;
+import org.springframework.data.auditing.config.AuditingBeanDefinitionRegistrarSupport;
+import org.springframework.data.auditing.config.AuditingConfiguration;
+import org.springframework.data.config.ParsingUtils;
+import org.springframework.data.mongodb.core.mapping.event.ReactiveAuditingEntityCallback;
+import org.springframework.util.Assert;
+
+/**
+ * {@link ImportBeanDefinitionRegistrar} to enable {@link EnableReactiveMongoAuditing} annotation.
+ *
+ * @author Mark Paluch
+ * @since 3.1
+ */
+class ReactiveMongoAuditingRegistrar extends AuditingBeanDefinitionRegistrarSupport {
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.auditing.config.AuditingBeanDefinitionRegistrarSupport#getAnnotation()
+	 */
+	@Override
+	protected Class<? extends Annotation> getAnnotation() {
+		return EnableReactiveMongoAuditing.class;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.auditing.config.AuditingBeanDefinitionRegistrarSupport#getAuditingHandlerBeanName()
+	 */
+	@Override
+	protected String getAuditingHandlerBeanName() {
+		return "reactiveMongoAuditingHandler";
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.auditing.config.AuditingBeanDefinitionRegistrarSupport#getAuditHandlerBeanDefinitionBuilder(org.springframework.data.auditing.config.AuditingConfiguration)
+	 */
+	@Override
+	protected BeanDefinitionBuilder getAuditHandlerBeanDefinitionBuilder(AuditingConfiguration configuration) {
+
+		Assert.notNull(configuration, "AuditingConfiguration must not be null!");
+
+		BeanDefinitionBuilder builder = BeanDefinitionBuilder.rootBeanDefinition(ReactiveIsNewAwareAuditingHandler.class);
+
+		BeanDefinitionBuilder definition = BeanDefinitionBuilder.genericBeanDefinition(PersistentEntitiesFactoryBean.class);
+		definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_CONSTRUCTOR);
+
+		builder.addConstructorArgValue(definition.getBeanDefinition());
+		return configureDefaultAuditHandlerAttributes(configuration, builder);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.auditing.config.AuditingBeanDefinitionRegistrarSupport#registerAuditListener(org.springframework.beans.factory.config.BeanDefinition, org.springframework.beans.factory.support.BeanDefinitionRegistry)
+	 */
+	@Override
+	protected void registerAuditListenerBeanDefinition(BeanDefinition auditingHandlerDefinition,
+			BeanDefinitionRegistry registry) {
+
+		Assert.notNull(auditingHandlerDefinition, "BeanDefinition must not be null!");
+		Assert.notNull(registry, "BeanDefinitionRegistry must not be null!");
+
+		BeanDefinitionBuilder builder = BeanDefinitionBuilder.rootBeanDefinition(ReactiveAuditingEntityCallback.class);
+
+		builder.addConstructorArgValue(ParsingUtils.getObjectFactoryBeanDefinition(getAuditingHandlerBeanName(), registry));
+		builder.getRawBeanDefinition().setSource(auditingHandlerDefinition.getSource());
+
+		registerInfrastructureBeanWithId(builder.getBeanDefinition(), ReactiveAuditingEntityCallback.class.getName(),
+				registry);
+	}
+
+}

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

@@ -15,8 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.AllArgsConstructor;
-
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
@@ -30,6 +28,7 @@ import org.springframework.data.mongodb.core.aggregation.AggregationOperation;
 import org.springframework.data.mongodb.core.aggregation.AggregationOperationContext;
 import org.springframework.data.mongodb.core.aggregation.AggregationOptions;
 import org.springframework.data.mongodb.core.aggregation.CountOperation;
+import org.springframework.data.mongodb.core.aggregation.RelaxedTypeBasedAggregationOperationContext;
 import org.springframework.data.mongodb.core.aggregation.TypeBasedAggregationOperationContext;
 import org.springframework.data.mongodb.core.aggregation.TypedAggregation;
 import org.springframework.data.mongodb.core.convert.QueryMapper;
@@ -49,12 +48,18 @@ import org.springframework.util.ObjectUtils;
  * @author Mark Paluch
  * @since 2.1
  */
-@AllArgsConstructor
 class AggregationUtil {
 
 	QueryMapper queryMapper;
 	MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext;
 
+	AggregationUtil(QueryMapper queryMapper,
+			MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext) {
+
+		this.queryMapper = queryMapper;
+		this.mappingContext = mappingContext;
+	}
+
 	/**
 	 * Prepare the {@link AggregationOperationContext} for a given aggregation by either returning the context itself it
 	 * is not {@literal null}, create a {@link TypeBasedAggregationOperationContext} if the aggregation contains type
@@ -71,12 +76,17 @@ class AggregationUtil {
 			return context;
 		}
 
-		if (aggregation instanceof TypedAggregation) {
-			return new TypeBasedAggregationOperationContext(((TypedAggregation) aggregation).getInputType(), mappingContext,
-					queryMapper);
+		if (!(aggregation instanceof TypedAggregation)) {
+			return new RelaxedTypeBasedAggregationOperationContext(Object.class, mappingContext, queryMapper);
 		}
 
-		return Aggregation.DEFAULT_CONTEXT;
+		Class<?> inputType = ((TypedAggregation) aggregation).getInputType();
+
+		if (aggregation.getPipeline().containsUnionWith()) {
+			return new RelaxedTypeBasedAggregationOperationContext(inputType, mappingContext, queryMapper);
+		}
+
+		return new TypeBasedAggregationOperationContext(inputType, mappingContext, queryMapper);
 	}
 
 	/**
@@ -88,7 +98,7 @@ class AggregationUtil {
 	 */
 	List<Document> createPipeline(Aggregation aggregation, AggregationOperationContext context) {
 
-		if (!ObjectUtils.nullSafeEquals(context, Aggregation.DEFAULT_CONTEXT)) {
+		if (ObjectUtils.nullSafeEquals(context, Aggregation.DEFAULT_CONTEXT)) {
 			return aggregation.toPipeline(context);
 		}
 

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

@@ -15,8 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.EqualsAndHashCode;
-
 import java.time.Instant;
 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
 
@@ -27,6 +25,7 @@ import org.springframework.data.mongodb.core.convert.MongoConverter;
 import org.springframework.data.mongodb.core.messaging.Message;
 import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
+import org.springframework.util.ObjectUtils;
 
 import com.mongodb.client.model.changestream.ChangeStreamDocument;
 import com.mongodb.client.model.changestream.OperationType;
@@ -39,7 +38,6 @@ import com.mongodb.client.model.changestream.OperationType;
  * @author Mark Paluch
  * @since 2.1
  */
-@EqualsAndHashCode
 public class ChangeStreamEvent<T> {
 
 	@SuppressWarnings("rawtypes") //
@@ -187,8 +185,8 @@ public class ChangeStreamEvent<T> {
 			return CONVERTED_UPDATER.compareAndSet(this, null, result) ? result : CONVERTED_UPDATER.get(this);
 		}
 
-		throw new IllegalArgumentException(String.format("No converter found capable of converting %s to %s",
-				fullDocument.getClass(), targetType));
+		throw new IllegalArgumentException(
+				String.format("No converter found capable of converting %s to %s", fullDocument.getClass(), targetType));
 	}
 
 	/*
@@ -199,4 +197,27 @@ public class ChangeStreamEvent<T> {
 	public String toString() {
 		return "ChangeStreamEvent {" + "raw=" + raw + ", targetType=" + targetType + '}';
 	}
+
+	@Override
+	public boolean equals(Object o) {
+
+		if (this == o)
+			return true;
+		if (o == null || getClass() != o.getClass())
+			return false;
+
+		ChangeStreamEvent<?> that = (ChangeStreamEvent<?>) o;
+
+		if (!ObjectUtils.nullSafeEquals(this.raw, that.raw)) {
+			return false;
+		}
+		return ObjectUtils.nullSafeEquals(this.targetType, that.targetType);
+	}
+
+	@Override
+	public int hashCode() {
+		int result = raw != null ? raw.hashCode() : 0;
+		result = 31 * result + ObjectUtils.nullSafeHashCode(targetType);
+		return result;
+	}
 }

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

@@ -15,8 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.EqualsAndHashCode;
-
 import java.time.Instant;
 import java.util.Arrays;
 import java.util.Optional;
@@ -25,7 +23,6 @@ import org.bson.BsonDocument;
 import org.bson.BsonTimestamp;
 import org.bson.BsonValue;
 import org.bson.Document;
-
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
 import org.springframework.data.mongodb.core.query.Collation;
 import org.springframework.lang.Nullable;
@@ -45,7 +42,6 @@ import com.mongodb.client.model.changestream.FullDocument;
  * @author Mark Paluch
  * @since 2.1
  */
-@EqualsAndHashCode
 public class ChangeStreamOptions {
 
 	private @Nullable Object filter;
@@ -156,6 +152,44 @@ public class ChangeStreamOptions {
 						+ ObjectUtils.nullSafeClassName(timestamp));
 	}
 
+	@Override
+	public boolean equals(Object o) {
+		if (this == o)
+			return true;
+		if (o == null || getClass() != o.getClass())
+			return false;
+
+		ChangeStreamOptions that = (ChangeStreamOptions) o;
+
+		if (!ObjectUtils.nullSafeEquals(this.filter, that.filter)) {
+			return false;
+		}
+		if (!ObjectUtils.nullSafeEquals(this.resumeToken, that.resumeToken)) {
+			return false;
+		}
+		if (!ObjectUtils.nullSafeEquals(this.fullDocumentLookup, that.fullDocumentLookup)) {
+			return false;
+		}
+		if (!ObjectUtils.nullSafeEquals(this.collation, that.collation)) {
+			return false;
+		}
+		if (!ObjectUtils.nullSafeEquals(this.resumeTimestamp, that.resumeTimestamp)) {
+			return false;
+		}
+		return resume == that.resume;
+	}
+
+	@Override
+	public int hashCode() {
+		int result = ObjectUtils.nullSafeHashCode(filter);
+		result = 31 * result + ObjectUtils.nullSafeHashCode(resumeToken);
+		result = 31 * result + ObjectUtils.nullSafeHashCode(fullDocumentLookup);
+		result = 31 * result + ObjectUtils.nullSafeHashCode(collation);
+		result = 31 * result + ObjectUtils.nullSafeHashCode(resumeTimestamp);
+		result = 31 * result + ObjectUtils.nullSafeHashCode(resume);
+		return result;
+	}
+
 	/**
 	 * @author Christoph Strobl
 	 * @since 2.2

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

@@ -15,8 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.RequiredArgsConstructor;
-
 import java.util.Optional;
 
 import org.springframework.data.mongodb.core.query.Collation;
@@ -312,7 +310,6 @@ public class CollectionOptions {
 	 * @author Andreas Zink
 	 * @since 2.1
 	 */
-	@RequiredArgsConstructor
 	public static class ValidationOptions {
 
 		private static final ValidationOptions NONE = new ValidationOptions(null, null, null);
@@ -321,6 +318,13 @@ public class CollectionOptions {
 		private final @Nullable ValidationLevel validationLevel;
 		private final @Nullable ValidationAction validationAction;
 
+		public ValidationOptions(Validator validator, ValidationLevel validationLevel, ValidationAction validationAction) {
+
+			this.validator = validator;
+			this.validationLevel = validationLevel;
+			this.validationAction = validationAction;
+		}
+
 		/**
 		 * Create an empty {@link ValidationOptions}.
 		 *

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

@@ -15,9 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.NonNull;
-import lombok.Value;
-
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -27,8 +24,9 @@ import java.util.stream.Collectors;
 import org.bson.Document;
 import org.bson.conversions.Bson;
 import org.springframework.context.ApplicationEventPublisher;
-import org.springframework.dao.support.PersistenceExceptionTranslator;
+import org.springframework.dao.DataIntegrityViolationException;
 import org.springframework.data.mapping.callback.EntityCallbacks;
+import org.springframework.data.mongodb.BulkOperationException;
 import org.springframework.data.mongodb.core.convert.QueryMapper;
 import org.springframework.data.mongodb.core.convert.UpdateMapper;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
@@ -47,7 +45,9 @@ import org.springframework.data.mongodb.core.query.UpdateDefinition.ArrayFilter;
 import org.springframework.data.util.Pair;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
+import com.mongodb.MongoBulkWriteException;
 import com.mongodb.WriteConcern;
 import com.mongodb.bulk.BulkWriteResult;
 import com.mongodb.client.MongoCollection;
@@ -64,6 +64,7 @@ import com.mongodb.client.model.*;
  * @author Jens Schauder
  * @author Michail Nikolaev
  * @author Roman Puchkovskiy
+ * @author Jacob Botuck
  * @since 1.9
  */
 class DefaultBulkOperations implements BulkOperations {
@@ -73,7 +74,6 @@ class DefaultBulkOperations implements BulkOperations {
 	private final BulkOperationContext bulkOperationContext;
 	private final List<SourceAwareWriteModelHolder> models = new ArrayList<>();
 
-	private PersistenceExceptionTranslator exceptionTranslator;
 	private @Nullable WriteConcern defaultWriteConcern;
 
 	private BulkWriteOptions bulkOptions;
@@ -97,19 +97,9 @@ class DefaultBulkOperations implements BulkOperations {
 		this.mongoOperations = mongoOperations;
 		this.collectionName = collectionName;
 		this.bulkOperationContext = bulkOperationContext;
-		this.exceptionTranslator = new MongoExceptionTranslator();
 		this.bulkOptions = getBulkWriteOptions(bulkOperationContext.getBulkMode());
 	}
 
-	/**
-	 * Configures the {@link PersistenceExceptionTranslator} to be used. Defaults to {@link MongoExceptionTranslator}.
-	 *
-	 * @param exceptionTranslator can be {@literal null}.
-	 */
-	public void setExceptionTranslator(@Nullable PersistenceExceptionTranslator exceptionTranslator) {
-		this.exceptionTranslator = exceptionTranslator == null ? new MongoExceptionTranslator() : exceptionTranslator;
-	}
-
 	/**
 	 * Configures the default {@link WriteConcern} to be used. Defaults to {@literal null}.
 	 *
@@ -316,11 +306,26 @@ class DefaultBulkOperations implements BulkOperations {
 			collection = collection.withWriteConcern(defaultWriteConcern);
 		}
 
-		return collection.bulkWrite( //
-				models.stream() //
-						.map(this::extractAndMapWriteModel) //
-						.collect(Collectors.toList()), //
-				bulkOptions);
+		try {
+
+			return collection.bulkWrite( //
+					models.stream() //
+							.map(this::extractAndMapWriteModel) //
+							.collect(Collectors.toList()), //
+					bulkOptions);
+		} catch (RuntimeException ex) {
+
+			if (ex instanceof MongoBulkWriteException) {
+
+				MongoBulkWriteException mongoBulkWriteException = (MongoBulkWriteException) ex;
+				if (mongoBulkWriteException.getWriteConcernError() != null) {
+					throw new DataIntegrityViolationException(ex.getMessage(), ex);
+				}
+				throw new BulkOperationException(ex.getMessage(), mongoBulkWriteException);
+			}
+
+			throw ex;
+		}
 	}
 
 	private WriteModel<Document> extractAndMapWriteModel(SourceAwareWriteModelHolder it) {
@@ -547,15 +552,93 @@ class DefaultBulkOperations implements BulkOperations {
 	 * @author Christoph Strobl
 	 * @since 2.0
 	 */
-	@Value
-	static class BulkOperationContext {
+	static final class BulkOperationContext {
 
-		@NonNull BulkMode bulkMode;
-		@NonNull Optional<? extends MongoPersistentEntity<?>> entity;
-		@NonNull QueryMapper queryMapper;
-		@NonNull UpdateMapper updateMapper;
-		ApplicationEventPublisher eventPublisher;
-		EntityCallbacks entityCallbacks;
+		private final BulkMode bulkMode;
+		private final Optional<? extends MongoPersistentEntity<?>> entity;
+		private final QueryMapper queryMapper;
+		private final UpdateMapper updateMapper;
+		private final ApplicationEventPublisher eventPublisher;
+		private final EntityCallbacks entityCallbacks;
+
+		BulkOperationContext(BulkOperations.BulkMode bulkMode, Optional<? extends MongoPersistentEntity<?>> entity,
+				QueryMapper queryMapper, UpdateMapper updateMapper, ApplicationEventPublisher eventPublisher,
+				EntityCallbacks entityCallbacks) {
+
+			this.bulkMode = bulkMode;
+			this.entity = entity;
+			this.queryMapper = queryMapper;
+			this.updateMapper = updateMapper;
+			this.eventPublisher = eventPublisher;
+			this.entityCallbacks = entityCallbacks;
+		}
+
+		public BulkMode getBulkMode() {
+			return this.bulkMode;
+		}
+
+		public Optional<? extends MongoPersistentEntity<?>> getEntity() {
+			return this.entity;
+		}
+
+		public QueryMapper getQueryMapper() {
+			return this.queryMapper;
+		}
+
+		public UpdateMapper getUpdateMapper() {
+			return this.updateMapper;
+		}
+
+		public ApplicationEventPublisher getEventPublisher() {
+			return this.eventPublisher;
+		}
+
+		public EntityCallbacks getEntityCallbacks() {
+			return this.entityCallbacks;
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (this == o)
+				return true;
+			if (o == null || getClass() != o.getClass())
+				return false;
+
+			BulkOperationContext that = (BulkOperationContext) o;
+
+			if (bulkMode != that.bulkMode)
+				return false;
+			if (!ObjectUtils.nullSafeEquals(this.entity, that.entity)) {
+				return false;
+			}
+			if (!ObjectUtils.nullSafeEquals(this.queryMapper, that.queryMapper)) {
+				return false;
+			}
+			if (!ObjectUtils.nullSafeEquals(this.updateMapper, that.updateMapper)) {
+				return false;
+			}
+			if (!ObjectUtils.nullSafeEquals(this.eventPublisher, that.eventPublisher)) {
+				return false;
+			}
+			return ObjectUtils.nullSafeEquals(this.entityCallbacks, that.entityCallbacks);
+		}
+
+		@Override
+		public int hashCode() {
+			int result = bulkMode != null ? bulkMode.hashCode() : 0;
+			result = 31 * result + ObjectUtils.nullSafeHashCode(entity);
+			result = 31 * result + ObjectUtils.nullSafeHashCode(queryMapper);
+			result = 31 * result + ObjectUtils.nullSafeHashCode(updateMapper);
+			result = 31 * result + ObjectUtils.nullSafeHashCode(eventPublisher);
+			result = 31 * result + ObjectUtils.nullSafeHashCode(entityCallbacks);
+			return result;
+		}
+
+		public String toString() {
+			return "DefaultBulkOperations.BulkOperationContext(bulkMode=" + this.getBulkMode() + ", entity="
+					+ this.getEntity() + ", queryMapper=" + this.getQueryMapper() + ", updateMapper=" + this.getUpdateMapper()
+					+ ", eventPublisher=" + this.getEventPublisher() + ", entityCallbacks=" + this.getEntityCallbacks() + ")";
+		}
 	}
 
 	/**
@@ -564,10 +647,50 @@ class DefaultBulkOperations implements BulkOperations {
 	 * @since 2.2
 	 * @author Christoph Strobl
 	 */
-	@Value
-	private static class SourceAwareWriteModelHolder {
+	private static final class SourceAwareWriteModelHolder {
 
-		Object source;
-		WriteModel<Document> model;
+		private final Object source;
+		private final WriteModel<Document> model;
+
+		SourceAwareWriteModelHolder(Object source, WriteModel<Document> model) {
+
+			this.source = source;
+			this.model = model;
+		}
+
+		public Object getSource() {
+			return this.source;
+		}
+
+		public WriteModel<Document> getModel() {
+			return this.model;
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (this == o)
+				return true;
+			if (o == null || getClass() != o.getClass())
+				return false;
+
+			SourceAwareWriteModelHolder that = (SourceAwareWriteModelHolder) o;
+
+			if (!ObjectUtils.nullSafeEquals(this.source, that.source)) {
+				return false;
+			}
+			return ObjectUtils.nullSafeEquals(this.model, that.model);
+		}
+
+		@Override
+		public int hashCode() {
+			int result = ObjectUtils.nullSafeHashCode(model);
+			result = 31 * result + ObjectUtils.nullSafeHashCode(source);
+			return result;
+		}
+
+		public String toString() {
+			return "DefaultBulkOperations.SourceAwareWriteModelHolder(source=" + this.getSource() + ", model="
+					+ this.getModel() + ")";
+		}
 	}
 }

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

@@ -15,10 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.AccessLevel;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-
 import java.util.Collection;
 import java.util.Map;
 import java.util.Optional;
@@ -55,12 +51,15 @@ import org.springframework.util.MultiValueMap;
  * @see MongoTemplate
  * @see ReactiveMongoTemplate
  */
-@RequiredArgsConstructor
 class EntityOperations {
 
 	private static final String ID_FIELD = "_id";
 
-	private final @NonNull MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> context;
+	private final MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> context;
+
+	EntityOperations(MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> context) {
+		this.context = context;
+	}
 
 	/**
 	 * Creates a new {@link Entity} for the given bean.
@@ -69,7 +68,7 @@ class EntityOperations {
 	 * @return new instance of {@link Entity}.
 	 */
 	@SuppressWarnings({ "unchecked", "rawtypes" })
-	public <T> Entity<T> forEntity(T entity) {
+	<T> Entity<T> forEntity(T entity) {
 
 		Assert.notNull(entity, "Bean must not be null!");
 
@@ -92,7 +91,7 @@ class EntityOperations {
 	 * @return new instance of {@link AdaptibleEntity}.
 	 */
 	@SuppressWarnings({ "unchecked", "rawtypes" })
-	public <T> AdaptibleEntity<T> forEntity(T entity, ConversionService conversionService) {
+	<T> AdaptibleEntity<T> forEntity(T entity, ConversionService conversionService) {
 
 		Assert.notNull(entity, "Bean must not be null!");
 		Assert.notNull(conversionService, "ConversionService must not be null!");
@@ -346,11 +345,14 @@ class EntityOperations {
 		Number getVersion();
 	}
 
-	@RequiredArgsConstructor
 	private static class UnmappedEntity<T extends Map<String, Object>> implements AdaptibleEntity<T> {
 
 		private final T map;
 
+		protected UnmappedEntity(T map) {
+			this.map = map;
+		}
+
 		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#getIdPropertyName()
@@ -460,7 +462,7 @@ class EntityOperations {
 
 	private static class SimpleMappedEntity<T extends Map<String, Object>> extends UnmappedEntity<T> {
 
-		SimpleMappedEntity(T map) {
+		protected SimpleMappedEntity(T map) {
 			super(map);
 		}
 
@@ -483,12 +485,19 @@ class EntityOperations {
 		}
 	}
 
-	@RequiredArgsConstructor(access = AccessLevel.PROTECTED)
 	private static class MappedEntity<T> implements Entity<T> {
 
-		private final @NonNull MongoPersistentEntity<?> entity;
-		private final @NonNull IdentifierAccessor idAccessor;
-		private final @NonNull PersistentPropertyAccessor<T> propertyAccessor;
+		private final MongoPersistentEntity<?> entity;
+		private final IdentifierAccessor idAccessor;
+		private final PersistentPropertyAccessor<T> propertyAccessor;
+
+		protected MappedEntity(MongoPersistentEntity<?> entity, IdentifierAccessor idAccessor,
+				PersistentPropertyAccessor<T> propertyAccessor) {
+
+			this.entity = entity;
+			this.idAccessor = idAccessor;
+			this.propertyAccessor = propertyAccessor;
+		}
 
 		private static <T> MappedEntity<T> of(T bean,
 				MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> context) {
@@ -759,11 +768,12 @@ class EntityOperations {
 	 * {@link TypedOperations} for generic entities that are not represented with {@link PersistentEntity} (e.g. custom
 	 * conversions).
 	 */
-	@RequiredArgsConstructor
 	enum UntypedOperations implements TypedOperations<Object> {
 
 		INSTANCE;
 
+		UntypedOperations() {}
+
 		@SuppressWarnings({ "unchecked", "rawtypes" })
 		public static <T> TypedOperations<T> instance() {
 			return (TypedOperations) INSTANCE;
@@ -798,10 +808,13 @@ class EntityOperations {
 	 *
 	 * @param <T>
 	 */
-	@RequiredArgsConstructor
 	static class TypedEntityOperations<T> implements TypedOperations<T> {
 
-		private final @NonNull MongoPersistentEntity<T> entity;
+		private final MongoPersistentEntity<T> entity;
+
+		protected TypedEntityOperations(MongoPersistentEntity<T> entity) {
+			this.entity = entity;
+		}
 
 		/*
 		 * (non-Javadoc)

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

@@ -15,16 +15,10 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.AccessLevel;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-import lombok.experimental.FieldDefaults;
-
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
 import org.springframework.data.mongodb.core.aggregation.AggregationResults;
 import org.springframework.data.mongodb.core.aggregation.TypedAggregation;
 import org.springframework.data.util.CloseableIterator;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -35,10 +29,13 @@ import org.springframework.util.StringUtils;
  * @author Mark Paluch
  * @since 2.0
  */
-@RequiredArgsConstructor
 class ExecutableAggregationOperationSupport implements ExecutableAggregationOperation {
 
-	private final @NonNull MongoTemplate template;
+	private final MongoTemplate template;
+
+	ExecutableAggregationOperationSupport(MongoTemplate template) {
+		this.template = template;
+	}
 
 	/*
 	 * (non-Javadoc)
@@ -56,15 +53,21 @@ class ExecutableAggregationOperationSupport implements ExecutableAggregationOper
 	 * @author Christoph Strobl
 	 * @since 2.0
 	 */
-	@RequiredArgsConstructor
-	@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
 	static class ExecutableAggregationSupport<T>
 			implements AggregationWithAggregation<T>, ExecutableAggregation<T>, TerminatingAggregation<T> {
 
-		@NonNull MongoTemplate template;
-		@NonNull Class<T> domainType;
-		@Nullable Aggregation aggregation;
-		@Nullable String collection;
+		private final MongoTemplate template;
+		private final Class<T> domainType;
+		private final Aggregation aggregation;
+		private final String collection;
+
+		public ExecutableAggregationSupport(MongoTemplate template, Class<T> domainType, Aggregation aggregation,
+				String collection) {
+			this.template = template;
+			this.domainType = domainType;
+			this.aggregation = aggregation;
+			this.collection = collection;
+		}
 
 		/*
 		 * (non-Javadoc)

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

@@ -15,12 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import com.mongodb.ReadPreference;
-import lombok.AccessLevel;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-import lombok.experimental.FieldDefaults;
-
 import java.util.List;
 import java.util.Optional;
 import java.util.stream.Stream;
@@ -37,6 +31,7 @@ import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
+import com.mongodb.ReadPreference;
 import com.mongodb.client.FindIterable;
 
 /**
@@ -46,12 +41,15 @@ import com.mongodb.client.FindIterable;
  * @author Mark Paluch
  * @since 2.0
  */
-@RequiredArgsConstructor
 class ExecutableFindOperationSupport implements ExecutableFindOperation {
 
 	private static final Query ALL_QUERY = new Query();
 
-	private final @NonNull MongoTemplate template;
+	private final MongoTemplate template;
+
+	ExecutableFindOperationSupport(MongoTemplate template) {
+		this.template = template;
+	}
 
 	/*
 	 * (non-Javadoc)
@@ -70,16 +68,23 @@ class ExecutableFindOperationSupport implements ExecutableFindOperation {
 	 * @author Christoph Strobl
 	 * @since 2.0
 	 */
-	@RequiredArgsConstructor
-	@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
 	static class ExecutableFindSupport<T>
 			implements ExecutableFind<T>, FindWithCollection<T>, FindWithProjection<T>, FindWithQuery<T> {
 
-		@NonNull MongoTemplate template;
-		@NonNull Class<?> domainType;
-		Class<T> returnType;
-		@Nullable String collection;
-		Query query;
+		private final MongoTemplate template;
+		private final Class<?> domainType;
+		private final Class<T> returnType;
+		@Nullable private final String collection;
+		private final Query query;
+
+		ExecutableFindSupport(MongoTemplate template, Class<?> domainType, Class<T> returnType,
+				String collection, Query query) {
+			this.template = template;
+			this.domainType = domainType;
+			this.returnType = returnType;
+			this.collection = collection;
+			this.query = query;
+		}
 
 		/*
 		 * (non-Javadoc)

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

@@ -15,11 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.AccessLevel;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-import lombok.experimental.FieldDefaults;
-
 import java.util.ArrayList;
 import java.util.Collection;
 
@@ -37,10 +32,13 @@ import com.mongodb.bulk.BulkWriteResult;
  * @author Mark Paluch
  * @since 2.0
  */
-@RequiredArgsConstructor
 class ExecutableInsertOperationSupport implements ExecutableInsertOperation {
 
-	private final @NonNull MongoTemplate template;
+	private final MongoTemplate template;
+
+	ExecutableInsertOperationSupport(MongoTemplate template) {
+		this.template = template;
+	}
 
 	/*
 	 * (non-Javadoc)
@@ -58,14 +56,20 @@ class ExecutableInsertOperationSupport implements ExecutableInsertOperation {
 	 * @author Christoph Strobl
 	 * @since 2.0
 	 */
-	@RequiredArgsConstructor
-	@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
 	static class ExecutableInsertSupport<T> implements ExecutableInsert<T> {
 
-		@NonNull MongoTemplate template;
-		@NonNull Class<T> domainType;
-		@Nullable String collection;
-		@Nullable BulkMode bulkMode;
+		private final MongoTemplate template;
+		private final Class<T> domainType;
+		@Nullable private final String collection;
+		@Nullable private final BulkMode bulkMode;
+
+		ExecutableInsertSupport(MongoTemplate template, Class<T> domainType, String collection, BulkMode bulkMode) {
+
+			this.template = template;
+			this.domainType = domainType;
+			this.collection = collection;
+			this.bulkMode = bulkMode;
+		}
 
 		/*
 		 * (non-Javadoc)

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

@@ -15,9 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-
 import java.util.List;
 
 import org.springframework.data.mongodb.core.mapreduce.MapReduceOptions;
@@ -32,12 +29,17 @@ import org.springframework.util.StringUtils;
  * @author Christoph Strobl
  * @since 2.1
  */
-@RequiredArgsConstructor
 class ExecutableMapReduceOperationSupport implements ExecutableMapReduceOperation {
 
 	private static final Query ALL_QUERY = new Query();
 
-	private final @NonNull MongoTemplate template;
+	private final MongoTemplate template;
+
+	ExecutableMapReduceOperationSupport(MongoTemplate template) {
+
+		Assert.notNull(template, "Template must not be null!");
+		this.template = template;
+	}
 
 	/*
 	 * (non-Javascript)

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

@@ -15,11 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.AccessLevel;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-import lombok.experimental.FieldDefaults;
-
 import java.util.List;
 
 import org.springframework.data.mongodb.core.query.Query;
@@ -36,12 +31,15 @@ import com.mongodb.client.result.DeleteResult;
  * @author Mark Paluch
  * @since 2.0
  */
-@RequiredArgsConstructor
 class ExecutableRemoveOperationSupport implements ExecutableRemoveOperation {
 
 	private static final Query ALL_QUERY = new Query();
 
-	private final @NonNull MongoTemplate tempate;
+	private final MongoTemplate tempate;
+
+	public ExecutableRemoveOperationSupport(MongoTemplate tempate) {
+		this.tempate = tempate;
+	}
 
 	/*
 	 * (non-Javadoc)
@@ -59,14 +57,19 @@ class ExecutableRemoveOperationSupport implements ExecutableRemoveOperation {
 	 * @author Christoph Strobl
 	 * @since 2.0
 	 */
-	@RequiredArgsConstructor
-	@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
 	static class ExecutableRemoveSupport<T> implements ExecutableRemove<T>, RemoveWithCollection<T> {
 
-		@NonNull MongoTemplate template;
-		@NonNull Class<T> domainType;
-		Query query;
-		@Nullable String collection;
+		private final MongoTemplate template;
+		private final Class<T> domainType;
+		private final Query query;
+		@Nullable private final String collection;
+
+		public ExecutableRemoveSupport(MongoTemplate template, Class<T> domainType, Query query, String collection) {
+			this.template = template;
+			this.domainType = domainType;
+			this.query = query;
+			this.collection = collection;
+		}
 
 		/*
 		 * (non-Javadoc)

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

@@ -15,11 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.AccessLevel;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-import lombok.experimental.FieldDefaults;
-
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.data.mongodb.core.query.UpdateDefinition;
 import org.springframework.lang.Nullable;
@@ -35,12 +30,15 @@ import com.mongodb.client.result.UpdateResult;
  * @author Mark Paluch
  * @since 2.0
  */
-@RequiredArgsConstructor
 class ExecutableUpdateOperationSupport implements ExecutableUpdateOperation {
 
 	private static final Query ALL_QUERY = new Query();
 
-	private final @NonNull MongoTemplate template;
+	private final MongoTemplate template;
+
+	ExecutableUpdateOperationSupport(MongoTemplate template) {
+		this.template = template;
+	}
 
 	/*
 	 * (non-Javadoc)
@@ -58,21 +56,34 @@ class ExecutableUpdateOperationSupport implements ExecutableUpdateOperation {
 	 * @author Christoph Strobl
 	 * @since 2.0
 	 */
-	@RequiredArgsConstructor
-	@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
 	static class ExecutableUpdateSupport<T>
 			implements ExecutableUpdate<T>, UpdateWithCollection<T>, UpdateWithQuery<T>, TerminatingUpdate<T>,
 			FindAndReplaceWithOptions<T>, TerminatingFindAndReplace<T>, FindAndReplaceWithProjection<T> {
 
-		@NonNull MongoTemplate template;
-		@NonNull Class domainType;
-		Query query;
-		@Nullable UpdateDefinition update;
-		@Nullable String collection;
-		@Nullable FindAndModifyOptions findAndModifyOptions;
-		@Nullable FindAndReplaceOptions findAndReplaceOptions;
-		@Nullable Object replacement;
-		@NonNull Class<T> targetType;
+		private final MongoTemplate template;
+		private final Class domainType;
+		private final Query query;
+		@Nullable private final UpdateDefinition update;
+		@Nullable private final String collection;
+		@Nullable private final FindAndModifyOptions findAndModifyOptions;
+		@Nullable private final FindAndReplaceOptions findAndReplaceOptions;
+		@Nullable private final Object replacement;
+		private final Class<T> targetType;
+
+		ExecutableUpdateSupport(MongoTemplate template, Class domainType, Query query, UpdateDefinition update,
+				String collection, FindAndModifyOptions findAndModifyOptions, FindAndReplaceOptions findAndReplaceOptions,
+				Object replacement, Class<T> targetType) {
+
+			this.template = template;
+			this.domainType = domainType;
+			this.query = query;
+			this.update = update;
+			this.collection = collection;
+			this.findAndModifyOptions = findAndModifyOptions;
+			this.findAndReplaceOptions = findAndReplaceOptions;
+			this.replacement = replacement;
+			this.targetType = targetType;
+		}
 
 		/*
 		 * (non-Javadoc)

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

@@ -15,9 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.Getter;
-import lombok.RequiredArgsConstructor;
-
 import java.util.Collection;
 import java.util.List;
 
@@ -27,8 +24,6 @@ import org.springframework.data.mongodb.core.query.Update;
 import org.springframework.data.mongodb.core.query.UpdateDefinition;
 import org.springframework.data.util.StreamUtils;
 
-import com.mongodb.client.model.Filters;
-
 /**
  * A MongoDB document in its mapped state. I.e. after a source document has been mapped using mapping information of the
  * entity the source document was supposed to represent.
@@ -36,13 +31,20 @@ import com.mongodb.client.model.Filters;
  * @author Oliver Gierke
  * @since 2.1
  */
-@RequiredArgsConstructor(staticName = "of")
 public class MappedDocument {
 
 	private static final String ID_FIELD = "_id";
 	private static final Document ID_ONLY_PROJECTION = new Document(ID_FIELD, 1);
 
-	private final @Getter Document document;
+	private final Document document;
+
+	private MappedDocument(Document document) {
+		this.document = document;
+	}
+
+	public static MappedDocument of(Document document) {
+		return new MappedDocument(document);
+	}
 
 	public static Document getIdOnlyProjection() {
 		return ID_ONLY_PROJECTION;
@@ -91,6 +93,10 @@ public class MappedDocument {
 		return new MappedUpdate(Update.fromDocument(document, ID_FIELD));
 	}
 
+	public Document getDocument() {
+		return this.document;
+	}
+
 	/**
 	 * An {@link UpdateDefinition} that indicates that the {@link #getUpdateObject() update object} has already been
 	 * mapped to the specific domain type.

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

@@ -15,8 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.Value;
-
 import org.springframework.aop.framework.ProxyFactory;
 import org.springframework.dao.DataAccessException;
 import org.springframework.dao.support.PersistenceExceptionTranslator;
@@ -24,6 +22,7 @@ import org.springframework.data.mongodb.MongoDatabaseFactory;
 import org.springframework.data.mongodb.SessionAwareMethodInterceptor;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 import com.mongodb.ClientSessionOptions;
 import com.mongodb.WriteConcern;
@@ -171,11 +170,15 @@ public abstract class MongoDatabaseFactorySupport<C> implements MongoDatabaseFac
 	 * @author Christoph Strobl
 	 * @since 2.1
 	 */
-	@Value
-	static class ClientSessionBoundMongoDbFactory implements MongoDatabaseFactory {
+	static final class ClientSessionBoundMongoDbFactory implements MongoDatabaseFactory {
 
-		ClientSession session;
-		MongoDatabaseFactory delegate;
+		private final ClientSession session;
+		private final MongoDatabaseFactory delegate;
+
+		public ClientSessionBoundMongoDbFactory(ClientSession session, MongoDatabaseFactory delegate) {
+			this.session = session;
+			this.delegate = delegate;
+		}
 
 		/*
 		 * (non-Javadoc)
@@ -256,5 +259,40 @@ public abstract class MongoDatabaseFactorySupport<C> implements MongoDatabaseFac
 
 			return targetType.cast(factory.getProxy(target.getClass().getClassLoader()));
 		}
+
+		public ClientSession getSession() {
+			return this.session;
+		}
+
+		public MongoDatabaseFactory getDelegate() {
+			return this.delegate;
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (this == o)
+				return true;
+			if (o == null || getClass() != o.getClass())
+				return false;
+
+			ClientSessionBoundMongoDbFactory that = (ClientSessionBoundMongoDbFactory) o;
+
+			if (!ObjectUtils.nullSafeEquals(this.session, that.session)) {
+				return false;
+			}
+			return ObjectUtils.nullSafeEquals(this.delegate, that.delegate);
+		}
+
+		@Override
+		public int hashCode() {
+			int result = ObjectUtils.nullSafeHashCode(this.session);
+			result = 31 * result + ObjectUtils.nullSafeHashCode(this.delegate);
+			return result;
+		}
+
+		public String toString() {
+			return "MongoDatabaseFactorySupport.ClientSessionBoundMongoDbFactory(session=" + this.getSession() + ", delegate="
+					+ this.getDelegate() + ")";
+		}
 	}
 }

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

@@ -21,7 +21,6 @@ import java.util.HashSet;
 import java.util.Set;
 
 import org.bson.BsonInvalidOperationException;
-
 import org.springframework.dao.DataAccessException;
 import org.springframework.dao.DataAccessResourceFailureException;
 import org.springframework.dao.DataIntegrityViolationException;
@@ -40,7 +39,6 @@ import org.springframework.util.ClassUtils;
 import com.mongodb.MongoBulkWriteException;
 import com.mongodb.MongoException;
 import com.mongodb.MongoServerException;
-import com.mongodb.MongoSocketException;
 import com.mongodb.bulk.BulkWriteError;
 
 /**
@@ -51,7 +49,6 @@ import com.mongodb.bulk.BulkWriteError;
  * @author Oliver Gierke
  * @author Michal Vich
  * @author Christoph Strobl
- * @author Brice Vandeputte
  */
 public class MongoExceptionTranslator implements PersistenceExceptionTranslator {
 
@@ -81,10 +78,6 @@ public class MongoExceptionTranslator implements PersistenceExceptionTranslator
 			throw new InvalidDataAccessApiUsageException(ex.getMessage(), ex);
 		}
 
-		if (ex instanceof MongoSocketException) {
-			return new DataAccessResourceFailureException(ex.getMessage(), ex);
-		}
-
 		String exception = ClassUtils.getShortName(ClassUtils.getUserClass(ex.getClass()));
 
 		if (DUPLICATE_KEY_EXCEPTIONS.contains(exception)) {

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

@@ -1184,6 +1184,29 @@ public interface MongoOperations extends FluentMongoOperations {
 	 */
 	long count(Query query, String collectionName);
 
+	/**
+	 * Estimate the number of documents, in the collection {@link #getCollectionName(Class) identified by the given type},
+	 * based on collection statistics.
+	 *
+	 * @param entityClass must not be {@literal null}.
+	 * @return the estimated number of documents.
+	 * @since 3.1
+	 */
+	default long estimatedCount(Class<?> entityClass) {
+
+		Assert.notNull(entityClass, "Entity class must not be null!");
+		return estimatedCount(getCollectionName(entityClass));
+	}
+
+	/**
+	 * Estimate the number of documents in the given collection based on collection statistics.
+	 *
+	 * @param collectionName must not be {@literal null}.
+	 * @return the estimated number of documents.
+	 * @since 3.1
+	 */
+	long estimatedCount(String collectionName);
+
 	/**
 	 * 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}. <br />

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

@@ -17,11 +17,6 @@ package org.springframework.data.mongodb.core;
 
 import static org.springframework.data.mongodb.core.query.SerializationUtils.*;
 
-import lombok.AccessLevel;
-import lombok.AllArgsConstructor;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-
 import java.io.IOException;
 import java.math.BigDecimal;
 import java.math.RoundingMode;
@@ -160,6 +155,8 @@ import com.mongodb.client.result.UpdateResult;
  * @author Cimon Lucas
  * @author Michael J. Simons
  * @author Roman Puchkovskiy
+ * @author Yadhukrishna S Pai
+ * @author Anton Barkan
  */
 public class MongoTemplate implements MongoOperations, ApplicationContextAware, IndexOperationsProvider {
 
@@ -763,7 +760,6 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 				new BulkOperationContext(mode, Optional.ofNullable(getPersistentEntity(entityType)), queryMapper, updateMapper,
 						eventPublisher, entityCallbacks));
 
-		operations.setExceptionTranslator(exceptionTranslator);
 		operations.setDefaultWriteConcern(writeConcern);
 
 		return operations;
@@ -1140,6 +1136,19 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 				collection -> collection.countDocuments(CountQuery.of(filter).toQueryDocument(), options));
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.MongoOperations#estimatedCount(java.lang.String)
+	 */
+	@Override
+	public long estimatedCount(String collectionName) {
+		return doEstimatedCount(collectionName, new EstimatedDocumentCountOptions());
+	}
+
+	protected long doEstimatedCount(String collectionName, EstimatedDocumentCountOptions options) {
+		return execute(collectionName, collection -> collection.estimatedDocumentCount(options));
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.MongoOperations#insert(java.lang.Object)
@@ -1969,9 +1978,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 
 		Assert.notNull(aggregation, "Aggregation pipeline must not be null!");
 
-		AggregationOperationContext context = new TypeBasedAggregationOperationContext(aggregation.getInputType(),
-				mappingContext, queryMapper);
-		return aggregate(aggregation, inputCollectionName, outputType, context);
+		return aggregate(aggregation, inputCollectionName, outputType, null);
 	}
 
 	/* (non-Javadoc)
@@ -2141,6 +2148,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 			}
 
 			options.getComment().ifPresent(aggregateIterable::comment);
+			options.getHint().ifPresent(aggregateIterable::hint);
 
 			if (options.hasExecutionTimeLimit()) {
 				aggregateIterable = aggregateIterable.maxTime(options.getMaxTime().toMillis(), TimeUnit.MILLISECONDS);
@@ -2199,6 +2207,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 			}
 
 			options.getComment().ifPresent(cursor::comment);
+			options.getHint().ifPresent(cursor::hint);
 
 			Class<?> domainType = aggregation instanceof TypedAggregation ? ((TypedAggregation) aggregation).getInputType()
 					: null;
@@ -2961,12 +2970,17 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	 * @author Christoph Strobl
 	 * @since 2.0
 	 */
-	@RequiredArgsConstructor
 	private class ExistsCallback implements CollectionCallback<Boolean> {
 
 		private final Document mappedQuery;
 		private final com.mongodb.client.model.Collation collation;
 
+		ExistsCallback(Document mappedQuery, com.mongodb.client.model.Collation collation) {
+
+			this.mappedQuery = mappedQuery;
+			this.collation = collation;
+		}
+
 		@Override
 		public Boolean doInCollection(MongoCollection<Document> collection) throws MongoException, DataAccessException {
 
@@ -2988,7 +3002,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		private final Document sort;
 		private final Optional<Collation> collation;
 
-		public FindAndRemoveCallback(Document query, Document fields, Document sort, @Nullable Collation collation) {
+		FindAndRemoveCallback(Document query, Document fields, Document sort, @Nullable Collation collation) {
 
 			this.query = query;
 			this.fields = fields;
@@ -3014,8 +3028,9 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		private final List<Document> arrayFilters;
 		private final FindAndModifyOptions options;
 
-		public FindAndModifyCallback(Document query, Document fields, Document sort, Object update,
-				List<Document> arrayFilters, FindAndModifyOptions options) {
+		FindAndModifyCallback(Document query, Document fields, Document sort, Object update, List<Document> arrayFilters,
+				FindAndModifyOptions options) {
+
 			this.query = query;
 			this.fields = fields;
 			this.sort = sort;
@@ -3124,13 +3139,19 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	 * @author Christoph Strobl
 	 * @author Roman Puchkovskiy
 	 */
-	@RequiredArgsConstructor
 	private class ReadDocumentCallback<T> implements DocumentCallback<T> {
 
-		private final @NonNull EntityReader<? super T, Bson> reader;
-		private final @NonNull Class<T> type;
+		private final EntityReader<? super T, Bson> reader;
+		private final Class<T> type;
 		private final String collectionName;
 
+		ReadDocumentCallback(EntityReader<? super T, Bson> reader, Class<T> type, String collectionName) {
+
+			this.reader = reader;
+			this.type = type;
+			this.collectionName = collectionName;
+		}
+
 		@Nullable
 		public T doWith(@Nullable Document document) {
 
@@ -3158,13 +3179,21 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	 * @param <T>
 	 * @since 2.0
 	 */
-	@RequiredArgsConstructor
 	private class ProjectingReadCallback<S, T> implements DocumentCallback<T> {
 
-		private final @NonNull EntityReader<Object, Bson> reader;
-		private final @NonNull Class<S> entityType;
-		private final @NonNull Class<T> targetType;
-		private final @NonNull String collectionName;
+		private final EntityReader<Object, Bson> reader;
+		private final Class<S> entityType;
+		private final Class<T> targetType;
+		private final String collectionName;
+
+		ProjectingReadCallback(EntityReader<Object, Bson> reader, Class<S> entityType, Class<T> targetType,
+				String collectionName) {
+
+			this.reader = reader;
+			this.entityType = entityType;
+			this.targetType = targetType;
+			this.collectionName = collectionName;
+		}
 
 		/*
 		 * (non-Javadoc)
@@ -3200,7 +3229,7 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		private final Query query;
 		private final @Nullable Class<?> type;
 
-		public QueryCursorPreparer(Query query, @Nullable Class<?> type) {
+		QueryCursorPreparer(Query query, @Nullable Class<?> type) {
 
 			this.query = query;
 			this.type = type;
@@ -3261,6 +3290,10 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 						cursorToUse = cursorToUse.batchSize(meta.getCursorBatchSize());
 					}
 
+					if (meta.getAllowDiskUse() != null) {
+						cursorToUse = cursorToUse.allowDiskUse(meta.getAllowDiskUse());
+					}
+
 					for (Meta.CursorOption option : meta.getFlags()) {
 
 						switch (option) {
@@ -3344,7 +3377,6 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 	 * @author Thomas Darimont
 	 * @since 1.7
 	 */
-	@AllArgsConstructor(access = AccessLevel.PACKAGE)
 	static class CloseableIterableCursorAdapter<T> implements CloseableIterator<T> {
 
 		private volatile @Nullable MongoCursor<Document> cursor;
@@ -3358,14 +3390,22 @@ public class MongoTemplate implements MongoOperations, ApplicationContextAware,
 		 * @param exceptionTranslator
 		 * @param objectReadCallback
 		 */
-		public CloseableIterableCursorAdapter(MongoIterable<Document> cursor,
-				PersistenceExceptionTranslator exceptionTranslator, DocumentCallback<T> objectReadCallback) {
+		CloseableIterableCursorAdapter(MongoIterable<Document> cursor, PersistenceExceptionTranslator exceptionTranslator,
+				DocumentCallback<T> objectReadCallback) {
 
 			this.cursor = cursor.iterator();
 			this.exceptionTranslator = exceptionTranslator;
 			this.objectReadCallback = objectReadCallback;
 		}
 
+		CloseableIterableCursorAdapter(MongoCursor<Document> cursor, PersistenceExceptionTranslator exceptionTranslator,
+				DocumentCallback<T> objectReadCallback) {
+
+			this.cursor = cursor;
+			this.exceptionTranslator = exceptionTranslator;
+			this.objectReadCallback = objectReadCallback;
+		}
+
 		@Override
 		public boolean hasNext() {
 

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

@@ -15,9 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.AccessLevel;
-import lombok.RequiredArgsConstructor;
-
 import org.bson.Document;
 import org.springframework.data.mapping.SimplePropertyHandler;
 import org.springframework.data.mapping.context.MappingContext;
@@ -33,11 +30,14 @@ import org.springframework.util.ClassUtils;
  * @author Christoph Strobl
  * @since 2.1
  */
-@RequiredArgsConstructor(access = AccessLevel.PACKAGE)
 class PropertyOperations {
 
 	private final MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext;
 
+	PropertyOperations(MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext) {
+		this.mappingContext = mappingContext;
+	}
+
 	/**
 	 * For cases where {@code fields} is {@link Document#isEmpty() empty} include only fields that are required for
 	 * creating the projection (target) type if the {@code targetType} is a {@literal DTO projection} or a

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

@@ -658,8 +658,7 @@ class QueryOperations {
 					: mappedDocument != null ? mappedDocument.getDocument() : getMappedUpdate(domainType);
 
 			Document filterWithShardKey = new Document(filter);
-			getMappedShardKeyFields(domainType)
-					.forEach(key -> filterWithShardKey.putIfAbsent(key, BsonUtils.resolveValue(shardKeySource, key)));
+			getMappedShardKeyFields(domainType).forEach(key -> filterWithShardKey.putIfAbsent(key, shardKeySource.get(key)));
 
 			return filterWithShardKey;
 		}
@@ -708,10 +707,9 @@ class QueryOperations {
 		 */
 		List<Document> getUpdatePipeline(@Nullable Class<?> domainType) {
 
-			AggregationOperationContext context = domainType != null
-					? new RelaxedTypeBasedAggregationOperationContext(domainType, mappingContext, queryMapper)
-					: Aggregation.DEFAULT_CONTEXT;
+			Class<?> type = domainType != null ? domainType : Object.class;
 
+			AggregationOperationContext context = new RelaxedTypeBasedAggregationOperationContext(type, mappingContext, queryMapper);
 			return aggregationUtil.createPipeline((AggregationUpdate) update, context);
 		}
 

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

@@ -15,10 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.AccessLevel;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-import lombok.experimental.FieldDefaults;
 import reactor.core.publisher.Flux;
 
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
@@ -62,15 +58,22 @@ class ReactiveAggregationOperationSupport implements ReactiveAggregationOperatio
 		return new ReactiveAggregationSupport<>(template, domainType, null, null);
 	}
 
-	@RequiredArgsConstructor
-	@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
 	static class ReactiveAggregationSupport<T>
 			implements AggregationOperationWithAggregation<T>, ReactiveAggregation<T>, TerminatingAggregationOperation<T> {
 
-		@NonNull ReactiveMongoTemplate template;
-		@NonNull Class<T> domainType;
-		Aggregation aggregation;
-		String collection;
+		private final ReactiveMongoTemplate template;
+		private final Class<T> domainType;
+		private final Aggregation aggregation;
+		private final String collection;
+
+		ReactiveAggregationSupport(ReactiveMongoTemplate template, Class<T> domainType, Aggregation aggregation,
+				String collection) {
+
+			this.template = template;
+			this.domainType = domainType;
+			this.aggregation = aggregation;
+			this.collection = collection;
+		}
 
 		/*
 		 * (non-Javadoc)

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

@@ -15,15 +15,10 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.AccessLevel;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-import lombok.experimental.FieldDefaults;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 import org.bson.Document;
-
 import org.springframework.dao.IncorrectResultSizeDataAccessException;
 import org.springframework.data.mongodb.core.query.NearQuery;
 import org.springframework.data.mongodb.core.query.Query;
@@ -39,12 +34,15 @@ import org.springframework.util.StringUtils;
  * @author Christoph Strobl
  * @since 2.0
  */
-@RequiredArgsConstructor
 class ReactiveFindOperationSupport implements ReactiveFindOperation {
 
 	private static final Query ALL_QUERY = new Query();
 
-	private final @NonNull ReactiveMongoTemplate template;
+	private final ReactiveMongoTemplate template;
+
+	ReactiveFindOperationSupport(ReactiveMongoTemplate template) {
+		this.template = template;
+	}
 
 	/*
 	 * (non-Javadoc)
@@ -64,16 +62,24 @@ class ReactiveFindOperationSupport implements ReactiveFindOperation {
 	 * @author Christoph Strobl
 	 * @since 2.0
 	 */
-	@RequiredArgsConstructor
-	@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
 	static class ReactiveFindSupport<T>
 			implements ReactiveFind<T>, FindWithCollection<T>, FindWithProjection<T>, FindWithQuery<T> {
 
-		@NonNull ReactiveMongoTemplate template;
-		@NonNull Class<?> domainType;
-		Class<T> returnType;
-		String collection;
-		Query query;
+		private final ReactiveMongoTemplate template;
+		private final Class<?> domainType;
+		private final Class<T> returnType;
+		private final String collection;
+		private final Query query;
+
+		ReactiveFindSupport(ReactiveMongoTemplate template, Class<?> domainType, Class<T> returnType,
+				String collection, Query query) {
+
+			this.template = template;
+			this.domainType = domainType;
+			this.returnType = returnType;
+			this.collection = collection;
+			this.query = query;
+		}
 
 		/*
 		 * (non-Javadoc)

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

@@ -15,10 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.AccessLevel;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-import lombok.experimental.FieldDefaults;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
@@ -34,10 +30,13 @@ import org.springframework.util.StringUtils;
  * @author Christoph Strobl
  * @since 2.0
  */
-@RequiredArgsConstructor
 class ReactiveInsertOperationSupport implements ReactiveInsertOperation {
 
-	private final @NonNull ReactiveMongoTemplate template;
+	private final ReactiveMongoTemplate template;
+
+	ReactiveInsertOperationSupport(ReactiveMongoTemplate template) {
+		this.template = template;
+	}
 
 	/*
 	 * (non-Javadoc)
@@ -51,13 +50,18 @@ class ReactiveInsertOperationSupport implements ReactiveInsertOperation {
 		return new ReactiveInsertSupport<>(template, domainType, null);
 	}
 
-	@RequiredArgsConstructor
-	@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
 	static class ReactiveInsertSupport<T> implements ReactiveInsert<T> {
 
-		@NonNull ReactiveMongoTemplate template;
-		@NonNull Class<T> domainType;
-		String collection;
+		private final ReactiveMongoTemplate template;
+		private final Class<T> domainType;
+		private final String collection;
+
+		ReactiveInsertSupport(ReactiveMongoTemplate template, Class<T> domainType, String collection) {
+
+			this.template = template;
+			this.domainType = domainType;
+			this.collection = collection;
+		}
 
 		/*
 		 * (non-Javadoc)

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

@@ -15,8 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
 import reactor.core.publisher.Flux;
 
 import org.springframework.data.mongodb.core.mapreduce.MapReduceOptions;
@@ -31,12 +29,15 @@ import org.springframework.util.StringUtils;
  * @author Christoph Strobl
  * @since 2.1
  */
-@RequiredArgsConstructor
 class ReactiveMapReduceOperationSupport implements ReactiveMapReduceOperation {
 
 	private static final Query ALL_QUERY = new Query();
 
-	private final @NonNull ReactiveMongoTemplate template;
+	private final ReactiveMongoTemplate template;
+
+	ReactiveMapReduceOperationSupport(ReactiveMongoTemplate template) {
+		this.template = template;
+	}
 
 	/*
 	 * (non-Javascript)

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

@@ -15,11 +15,15 @@
  */
 package org.springframework.data.mongodb.core;
 
-import org.reactivestreams.Publisher;
-import org.springframework.util.Assert;
 import reactor.core.publisher.Mono;
 import reactor.util.context.Context;
 
+import java.util.function.Function;
+
+import org.reactivestreams.Publisher;
+
+import org.springframework.util.Assert;
+
 import com.mongodb.reactivestreams.client.ClientSession;
 
 /**
@@ -29,7 +33,7 @@ import com.mongodb.reactivestreams.client.ClientSession;
  * @author Christoph Strobl
  * @author Mark Paluch
  * @since 2.1
- * @see Mono#subscriberContext()
+ * @see Mono#deferContextual(Function)
  * @see Context
  */
 public class ReactiveMongoContext {
@@ -46,8 +50,14 @@ public class ReactiveMongoContext {
 	 */
 	public static Mono<ClientSession> getSession() {
 
-		return Mono.subscriberContext().filter(ctx -> ctx.hasKey(SESSION_KEY))
-				.flatMap(ctx -> ctx.<Mono<ClientSession>> get(SESSION_KEY));
+		return Mono.deferContextual(ctx -> {
+
+			if (ctx.hasKey(SESSION_KEY)) {
+				return ctx.<Mono<ClientSession>> get(SESSION_KEY);
+			}
+
+			return Mono.empty();
+		});
 	}
 
 	/**

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

@@ -980,6 +980,29 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 */
 	Mono<Long> count(Query query, @Nullable Class<?> entityClass, String collectionName);
 
+	/**
+	 * Estimate the number of documents, in the collection {@link #getCollectionName(Class) identified by the given type},
+	 * based on collection statistics.
+	 *
+	 * @param entityClass must not be {@literal null}.
+	 * @return a {@link Mono} emitting the estimated number of documents.
+	 * @since 3.1
+	 */
+	default Mono<Long> estimatedCount(Class<?> entityClass) {
+
+		Assert.notNull(entityClass, "Entity class must not be null!");
+		return estimatedCount(getCollectionName(entityClass));
+	}
+
+	/**
+	 * Estimate the number of documents in the given collection based on collection statistics.
+	 *
+	 * @param collectionName must not be {@literal null}.
+	 * @return a {@link Mono} emitting the estimated number of documents.
+	 * @since 3.1
+	 */
+	Mono<Long> estimatedCount(String collectionName);
+
 	/**
 	 * Insert the object into the collection for the entity type of the object to save.
 	 * <p/>

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

@@ -17,9 +17,7 @@ package org.springframework.data.mongodb.core;
 
 import static org.springframework.data.mongodb.core.query.SerializationUtils.*;
 
-import lombok.AccessLevel;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
+import org.springframework.data.mongodb.core.aggregation.RelaxedTypeBasedAggregationOperationContext;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.util.function.Tuple2;
@@ -120,16 +118,7 @@ import com.mongodb.CursorType;
 import com.mongodb.MongoException;
 import com.mongodb.ReadPreference;
 import com.mongodb.WriteConcern;
-import com.mongodb.client.model.CountOptions;
-import com.mongodb.client.model.CreateCollectionOptions;
-import com.mongodb.client.model.DeleteOptions;
-import com.mongodb.client.model.FindOneAndDeleteOptions;
-import com.mongodb.client.model.FindOneAndReplaceOptions;
-import com.mongodb.client.model.FindOneAndUpdateOptions;
-import com.mongodb.client.model.ReplaceOptions;
-import com.mongodb.client.model.ReturnDocument;
-import com.mongodb.client.model.UpdateOptions;
-import com.mongodb.client.model.ValidationOptions;
+import com.mongodb.client.model.*;
 import com.mongodb.client.model.changestream.FullDocument;
 import com.mongodb.client.result.DeleteResult;
 import com.mongodb.client.result.InsertOneResult;
@@ -158,6 +147,7 @@ import com.mongodb.reactivestreams.client.MongoDatabase;
  * @author Christoph Strobl
  * @author Roman Puchkovskiy
  * @author Mathieu Ouellet
+ * @author Yadhukrishna S Pai
  * @since 2.0
  */
 public class ReactiveMongoTemplate implements ReactiveMongoOperations, ApplicationContextAware {
@@ -584,7 +574,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 				ReactiveMongoTemplate.this);
 
 		return Flux.from(action.doInSession(operations)) //
-				.subscriberContext(ctx -> ReactiveMongoContext.setSession(ctx, Mono.just(session)));
+				.contextWrite(ctx -> ReactiveMongoContext.setSession(ctx, Mono.just(session)));
 	}
 
 	/*
@@ -1035,6 +1025,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		}
 
 		options.getComment().ifPresent(cursor::comment);
+		options.getHint().ifPresent(cursor::hint);
 
 		Optionals.firstNonEmpty(options::getCollation, () -> operations.forType(inputType).getCollation()) //
 				.map(Collation::toMongoCollation) //
@@ -1258,6 +1249,15 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		});
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#estimatedCount(java.lang.String)
+	 */
+	@Override
+	public Mono<Long> estimatedCount(String collectionName) {
+		return doEstimatedCount(collectionName, new EstimatedDocumentCountOptions());
+	}
+
 	/**
 	 * Run the actual count operation against the collection with given name.
 	 *
@@ -1272,6 +1272,11 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 				collection -> collection.countDocuments(CountQuery.of(filter).toQueryDocument(), options));
 	}
 
+	protected Mono<Long> doEstimatedCount(String collectionName, EstimatedDocumentCountOptions options) {
+
+		return createMono(collectionName, collection -> collection.estimatedDocumentCount(options));
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#insert(reactor.core.publisher.Mono)
@@ -2108,7 +2113,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 			AggregationOperationContext context = agg instanceof TypedAggregation
 					? new TypeBasedAggregationOperationContext(((TypedAggregation<?>) agg).getInputType(),
 							getConverter().getMappingContext(), queryMapper)
-					: Aggregation.DEFAULT_CONTEXT;
+					: new RelaxedTypeBasedAggregationOperationContext(Object.class, mappingContext, queryMapper);
 
 			return agg.toPipeline(new PrefixingDelegatingAggregationOperationContext(context, "fullDocument",
 					Arrays.asList("operationType", "fullDocument", "documentKey", "updateDescription", "ns")));
@@ -2418,8 +2423,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * @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.
 	 * @param entityClass the parameterized type of the returned list.
-	 * @param preparer allows for customization of the {@link com.mongodb.client.FindIterable} used when iterating over the result set, (apply
-	 *          limits, skips and so on).
+	 * @param preparer allows for customization of the {@link com.mongodb.client.FindIterable} used when iterating over
+	 *          the result set, (apply limits, skips and so on).
 	 * @return the {@link List} of converted objects.
 	 */
 	protected <T> Flux<T> doFind(String collectionName, Document query, Document fields, Class<T> entityClass,
@@ -2893,7 +2898,6 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 *
 	 * @author Mark Paluch
 	 */
-	@RequiredArgsConstructor
 	private static class FindCallback implements ReactiveCollectionQueryCallback<Document> {
 
 		private final @Nullable Document query;
@@ -2903,6 +2907,12 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 			this(query, null);
 		}
 
+		FindCallback(Document query, Document fields) {
+
+			this.query = query;
+			this.fields = fields;
+		}
+
 		@Override
 		public FindPublisher<Document> doInCollection(MongoCollection<Document> collection) {
 
@@ -2956,7 +2966,6 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	/**
 	 * @author Mark Paluch
 	 */
-	@RequiredArgsConstructor
 	private static class FindAndModifyCallback implements ReactiveCollectionCallback<Document> {
 
 		private final Document query;
@@ -2966,6 +2975,17 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		private final List<Document> arrayFilters;
 		private final FindAndModifyOptions options;
 
+		FindAndModifyCallback(Document query, Document fields, Document sort, Object update, List<Document> arrayFilters,
+				FindAndModifyOptions options) {
+
+			this.query = query;
+			this.fields = fields;
+			this.sort = sort;
+			this.update = update;
+			this.arrayFilters = arrayFilters;
+			this.options = options;
+		}
+
 		@Override
 		public Publisher<Document> doInCollection(MongoCollection<Document> collection)
 				throws MongoException, DataAccessException {
@@ -3021,7 +3041,6 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * @author Christoph Strobl
 	 * @since 2.1
 	 */
-	@RequiredArgsConstructor(access = AccessLevel.PACKAGE)
 	private static class FindAndReplaceCallback implements ReactiveCollectionCallback<Document> {
 
 		private final Document query;
@@ -3031,6 +3050,17 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		private final @Nullable com.mongodb.client.model.Collation collation;
 		private final FindAndReplaceOptions options;
 
+		FindAndReplaceCallback(Document query, Document fields, Document sort, Document update,
+				com.mongodb.client.model.Collation collation, FindAndReplaceOptions options) {
+
+			this.query = query;
+			this.fields = fields;
+			this.sort = sort;
+			this.update = update;
+			this.collation = collation;
+			this.options = options;
+		}
+
 		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.ReactiveCollectionCallback#doInCollection(com.mongodb.reactivestreams.client.MongoCollection)
@@ -3147,13 +3177,20 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * @author Roman Puchkovskiy
 	 * @since 2.0
 	 */
-	@RequiredArgsConstructor
 	private class ProjectingReadCallback<S, T> implements DocumentCallback<T> {
 
-		private final @NonNull EntityReader<Object, Bson> reader;
-		private final @NonNull Class<S> entityType;
-		private final @NonNull Class<T> targetType;
-		private final @NonNull String collectionName;
+		private final EntityReader<Object, Bson> reader;
+		private final Class<S> entityType;
+		private final Class<T> targetType;
+		private final String collectionName;
+
+		ProjectingReadCallback(EntityReader<Object, Bson> reader, Class<S> entityType, Class<T> targetType,
+				String collectionName) {
+			this.reader = reader;
+			this.entityType = entityType;
+			this.targetType = targetType;
+			this.collectionName = collectionName;
+		}
 
 		@SuppressWarnings("unchecked")
 		public Mono<T> doWith(Document document) {
@@ -3292,6 +3329,10 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 					if (meta.getCursorBatchSize() != null) {
 						findPublisherToUse = findPublisherToUse.batchSize(meta.getCursorBatchSize());
 					}
+
+					if (meta.getAllowDiskUse() != null) {
+						findPublisherToUse = findPublisherToUse.allowDiskUse(meta.getAllowDiskUse());
+					}
 				}
 
 			} catch (RuntimeException e) {
@@ -3374,11 +3415,14 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		}
 	}
 
-	@RequiredArgsConstructor
 	class IndexCreatorEventListener implements ApplicationListener<MappingContextEvent<?, ?>> {
 
 		final Consumer<Throwable> subscriptionExceptionHandler;
 
+		public IndexCreatorEventListener(Consumer<Throwable> subscriptionExceptionHandler) {
+			this.subscriptionExceptionHandler = subscriptionExceptionHandler;
+		}
+
 		@Override
 		public void onApplicationEvent(MappingContextEvent<?, ?> event) {
 

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

@@ -15,10 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.AccessLevel;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-import lombok.experimental.FieldDefaults;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
@@ -35,12 +31,15 @@ import com.mongodb.client.result.DeleteResult;
  * @author Christoph Strobl
  * @since 2.0
  */
-@RequiredArgsConstructor
 class ReactiveRemoveOperationSupport implements ReactiveRemoveOperation {
 
 	private static final Query ALL_QUERY = new Query();
 
-	private final @NonNull ReactiveMongoTemplate tempate;
+	private final ReactiveMongoTemplate tempate;
+
+	ReactiveRemoveOperationSupport(ReactiveMongoTemplate tempate) {
+		this.tempate = tempate;
+	}
 
 	/*
 	 * (non-Javadoc)
@@ -54,14 +53,20 @@ class ReactiveRemoveOperationSupport implements ReactiveRemoveOperation {
 		return new ReactiveRemoveSupport<>(tempate, domainType, ALL_QUERY, null);
 	}
 
-	@RequiredArgsConstructor
-	@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
 	static class ReactiveRemoveSupport<T> implements ReactiveRemove<T>, RemoveWithCollection<T> {
 
-		@NonNull ReactiveMongoTemplate template;
-		@NonNull Class<T> domainType;
-		Query query;
-		String collection;
+		private final ReactiveMongoTemplate template;
+		private final Class<T> domainType;
+		private final Query query;
+		private final String collection;
+
+		ReactiveRemoveSupport(ReactiveMongoTemplate template, Class<T> domainType, Query query, String collection) {
+
+			this.template = template;
+			this.domainType = domainType;
+			this.query = query;
+			this.collection = collection;
+		}
 
 		/*
 		 * (non-Javadoc)

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

@@ -15,13 +15,10 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.AccessLevel;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-import lombok.experimental.FieldDefaults;
 import reactor.core.publisher.Mono;
 
 import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.data.mongodb.core.query.UpdateDefinition;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
@@ -35,12 +32,15 @@ import com.mongodb.client.result.UpdateResult;
  * @author Christoph Strobl
  * @since 2.0
  */
-@RequiredArgsConstructor
 class ReactiveUpdateOperationSupport implements ReactiveUpdateOperation {
 
 	private static final Query ALL_QUERY = new Query();
 
-	private final @NonNull ReactiveMongoTemplate template;
+	private final ReactiveMongoTemplate template;
+
+	ReactiveUpdateOperationSupport(ReactiveMongoTemplate template) {
+		this.template = template;
+	}
 
 	/*
 	 * (non-Javadoc)
@@ -54,21 +54,34 @@ class ReactiveUpdateOperationSupport implements ReactiveUpdateOperation {
 		return new ReactiveUpdateSupport<>(template, domainType, ALL_QUERY, null, null, null, null, null, domainType);
 	}
 
-	@RequiredArgsConstructor
-	@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
 	static class ReactiveUpdateSupport<T>
 			implements ReactiveUpdate<T>, UpdateWithCollection<T>, UpdateWithQuery<T>, TerminatingUpdate<T>,
 			FindAndReplaceWithOptions<T>, FindAndReplaceWithProjection<T>, TerminatingFindAndReplace<T> {
 
-		@NonNull ReactiveMongoTemplate template;
-		@NonNull Class<?> domainType;
-		Query query;
-		org.springframework.data.mongodb.core.query.UpdateDefinition update;
-		@Nullable String collection;
-		@Nullable FindAndModifyOptions findAndModifyOptions;
-		@Nullable FindAndReplaceOptions findAndReplaceOptions;
-		@Nullable Object replacement;
-		@NonNull Class<T> targetType;
+		private final ReactiveMongoTemplate template;
+		private final Class<?> domainType;
+		private final Query query;
+		private final org.springframework.data.mongodb.core.query.UpdateDefinition update;
+		@Nullable private final String collection;
+		@Nullable private final FindAndModifyOptions findAndModifyOptions;
+		@Nullable private final FindAndReplaceOptions findAndReplaceOptions;
+		@Nullable private final Object replacement;
+		private final Class<T> targetType;
+
+		ReactiveUpdateSupport(ReactiveMongoTemplate template, Class<?> domainType, Query query, UpdateDefinition update,
+				String collection, FindAndModifyOptions findAndModifyOptions, FindAndReplaceOptions findAndReplaceOptions,
+				Object replacement, Class<T> targetType) {
+
+			this.template = template;
+			this.domainType = domainType;
+			this.query = query;
+			this.update = update;
+			this.collection = collection;
+			this.findAndModifyOptions = findAndModifyOptions;
+			this.findAndReplaceOptions = findAndReplaceOptions;
+			this.replacement = replacement;
+			this.targetType = targetType;
+		}
 
 		/*
 		 * (non-Javadoc)
@@ -123,7 +136,9 @@ class ReactiveUpdateOperationSupport implements ReactiveUpdateOperation {
 
 			String collectionName = getCollectionName();
 
-			return template.findAndModify(query, update, findAndModifyOptions != null ? findAndModifyOptions : FindAndModifyOptions.none(), targetType, collectionName);
+			return template.findAndModify(query, update,
+					findAndModifyOptions != null ? findAndModifyOptions : FindAndModifyOptions.none(), targetType,
+					collectionName);
 		}
 
 		/*

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

@@ -15,7 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import lombok.Value;
 import reactor.core.publisher.Mono;
 
 import org.bson.codecs.configuration.CodecRegistry;
@@ -27,6 +26,7 @@ import org.springframework.data.mongodb.ReactiveMongoDatabaseFactory;
 import org.springframework.data.mongodb.SessionAwareMethodInterceptor;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 import com.mongodb.ClientSessionOptions;
 import com.mongodb.ConnectionString;
@@ -175,11 +175,16 @@ public class SimpleReactiveMongoDatabaseFactory implements DisposableBean, React
 	 * @author Christoph Strobl
 	 * @since 2.1
 	 */
-	@Value
-	static class ClientSessionBoundMongoDbFactory implements ReactiveMongoDatabaseFactory {
+	static final class ClientSessionBoundMongoDbFactory implements ReactiveMongoDatabaseFactory {
 
-		ClientSession session;
-		ReactiveMongoDatabaseFactory delegate;
+		private final ClientSession session;
+		private final ReactiveMongoDatabaseFactory delegate;
+
+		ClientSessionBoundMongoDbFactory(ClientSession session, ReactiveMongoDatabaseFactory delegate) {
+
+			this.session = session;
+			this.delegate = delegate;
+		}
 
 		/*
 		 * (non-Javadoc)
@@ -268,5 +273,40 @@ public class SimpleReactiveMongoDatabaseFactory implements DisposableBean, React
 
 			return targetType.cast(factory.getProxy(target.getClass().getClassLoader()));
 		}
+
+		public ClientSession getSession() {
+			return this.session;
+		}
+
+		public ReactiveMongoDatabaseFactory getDelegate() {
+			return this.delegate;
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (this == o)
+				return true;
+			if (o == null || getClass() != o.getClass())
+				return false;
+
+			ClientSessionBoundMongoDbFactory that = (ClientSessionBoundMongoDbFactory) o;
+
+			if (!ObjectUtils.nullSafeEquals(this.session, that.session)) {
+				return false;
+			}
+			return ObjectUtils.nullSafeEquals(this.delegate, that.delegate);
+		}
+
+		@Override
+		public int hashCode() {
+			int result = ObjectUtils.nullSafeHashCode(this.session);
+			result = 31 * result + ObjectUtils.nullSafeHashCode(this.delegate);
+			return result;
+		}
+
+		public String toString() {
+			return "SimpleReactiveMongoDatabaseFactory.ClientSessionBoundMongoDbFactory(session=" + this.getSession()
+					+ ", delegate=" + this.getDelegate() + ")";
+		}
 	}
 }

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

@@ -29,8 +29,11 @@ import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
 /**
+ * Support class for {@link AggregationExpression} implementations.
+ *
  * @author Christoph Strobl
  * @author Matt Morrissette
+ * @author Mark Paluch
  * @since 1.10
  */
 abstract class AbstractAggregationExpression implements AggregationExpression {
@@ -49,7 +52,6 @@ abstract class AbstractAggregationExpression implements AggregationExpression {
 		return toDocument(this.value, context);
 	}
 
-	@SuppressWarnings("unchecked")
 	public Document toDocument(Object value, AggregationOperationContext context) {
 		return new Document(getMongoMethod(), unpack(value, context));
 	}
@@ -101,17 +103,19 @@ abstract class AbstractAggregationExpression implements AggregationExpression {
 		return value;
 	}
 
+	@SuppressWarnings("unchecked")
 	protected List<Object> append(Object value, Expand expandList) {
 
 		if (this.value instanceof List) {
 
-			List<Object> clone = new ArrayList<Object>((List) this.value);
+			List<Object> clone = new ArrayList<>((List<Object>) this.value);
 
 			if (value instanceof Collection && Expand.EXPAND_VALUES.equals(expandList)) {
 				clone.addAll((Collection<?>) value);
 			} else {
 				clone.add(value);
 			}
+
 			return clone;
 		}
 
@@ -129,25 +133,72 @@ abstract class AbstractAggregationExpression implements AggregationExpression {
 		return append(value, Expand.EXPAND_VALUES);
 	}
 
-	@SuppressWarnings("unchecked")
-	protected java.util.Map<String, Object> append(String key, Object value) {
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	protected Map<String, Object> append(String key, Object value) {
 
 		Assert.isInstanceOf(Map.class, this.value, "Value must be a type of Map!");
 
-		java.util.Map<String, Object> clone = new LinkedHashMap<>((java.util.Map) this.value);
+		Map<String, Object> clone = new LinkedHashMap<>((java.util.Map) this.value);
 		clone.put(key, value);
 		return clone;
 
 	}
 
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	protected Map<String, Object> remove(String key) {
+
+		Assert.isInstanceOf(Map.class, this.value, "Value must be a type of Map!");
+
+		Map<String, Object> clone = new LinkedHashMap<>((java.util.Map) this.value);
+		clone.remove(key);
+		return clone;
+	}
+
+	/**
+	 * Append the given key at the position in the underlying {@link LinkedHashMap}.
+	 *
+	 * @param index
+	 * @param key
+	 * @param value
+	 * @return
+	 * @since 3.1
+	 */
+	@SuppressWarnings({ "unchecked" })
+	protected Map<String, Object> appendAt(int index, String key, Object value) {
+
+		Assert.isInstanceOf(Map.class, this.value, "Value must be a type of Map!");
+
+		Map<String, Object> clone = new LinkedHashMap<>();
+
+		int i = 0;
+		for (Map.Entry<String, Object> entry : ((Map<String, Object>) this.value).entrySet()) {
+
+			if (i == index) {
+				clone.put(key, value);
+			}
+			if (!entry.getKey().equals(key)) {
+				clone.put(entry.getKey(), entry.getValue());
+			}
+			i++;
+		}
+		if (i <= index) {
+			clone.put(key, value);
+		}
+		return clone;
+
+	}
+
+	@SuppressWarnings({ "rawtypes" })
 	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<>(Collections.singletonList(value));
 	}
 
@@ -177,7 +228,7 @@ abstract class AbstractAggregationExpression implements AggregationExpression {
 
 		Assert.isInstanceOf(Map.class, this.value, "Value must be a type of Map!");
 
-		return (T) ((java.util.Map<String, Object>) this.value).get(key);
+		return (T) ((Map<String, Object>) this.value).get(key);
 	}
 
 	/**
@@ -187,11 +238,11 @@ abstract class AbstractAggregationExpression implements AggregationExpression {
 	 * @return
 	 */
 	@SuppressWarnings("unchecked")
-	protected java.util.Map<String, Object> argumentMap() {
+	protected Map<String, Object> argumentMap() {
 
 		Assert.isInstanceOf(Map.class, this.value, "Value must be a type of Map!");
 
-		return Collections.unmodifiableMap((java.util.Map) value);
+		return Collections.unmodifiableMap((java.util.Map<String, Object>) value);
 	}
 
 	/**
@@ -208,7 +259,7 @@ abstract class AbstractAggregationExpression implements AggregationExpression {
 			return false;
 		}
 
-		return ((java.util.Map<String, Object>) this.value).containsKey(key);
+		return ((Map<String, Object>) this.value).containsKey(key);
 	}
 
 	protected abstract String getMongoMethod();

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

@@ -32,6 +32,7 @@ import org.springframework.util.Assert;
  * @author Oliver Gierke
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Yadhukrishna S Pai
  * @see Aggregation#withOptions(AggregationOptions)
  * @see TypedAggregation#withOptions(AggregationOptions)
  * @since 1.6
@@ -45,12 +46,14 @@ public class AggregationOptions {
 	private static final String COLLATION = "collation";
 	private static final String COMMENT = "comment";
 	private static final String MAX_TIME = "maxTimeMS";
+	private static final String HINT = "hint";
 
 	private final boolean allowDiskUse;
 	private final boolean explain;
 	private final Optional<Document> cursor;
 	private final Optional<Collation> collation;
 	private final Optional<String> comment;
+	private final Optional<Document> hint;
 	private Duration maxTime = Duration.ZERO;
 	private ResultOptions resultOptions = ResultOptions.READ;
 
@@ -71,13 +74,13 @@ public class AggregationOptions {
 	 * @param allowDiskUse whether to off-load intensive sort-operations to disk.
 	 * @param explain whether to get the execution plan for the aggregation instead of the actual results.
 	 * @param cursor can be {@literal null}, used to pass additional options (such as {@code batchSize}) to the
-	 * aggregation.
+	 *          aggregation.
 	 * @param collation collation for string comparison. Can be {@literal null}.
 	 * @since 2.0
 	 */
 	public AggregationOptions(boolean allowDiskUse, boolean explain, @Nullable Document cursor,
 			@Nullable Collation collation) {
-		this(allowDiskUse, explain, cursor, collation, null);
+		this(allowDiskUse, explain, cursor, collation, null, null);
 	}
 
 	/**
@@ -86,19 +89,37 @@ public class AggregationOptions {
 	 * @param allowDiskUse whether to off-load intensive sort-operations to disk.
 	 * @param explain whether to get the execution plan for the aggregation instead of the actual results.
 	 * @param cursor can be {@literal null}, used to pass additional options (such as {@code batchSize}) to the
-	 * aggregation.
+	 *          aggregation.
 	 * @param collation collation for string comparison. Can be {@literal null}.
 	 * @param comment execution comment. Can be {@literal null}.
 	 * @since 2.2
 	 */
 	public AggregationOptions(boolean allowDiskUse, boolean explain, @Nullable Document cursor,
 			@Nullable Collation collation, @Nullable String comment) {
+		this(allowDiskUse, explain, cursor, collation, comment, null);
+	}
+
+	/**
+	 * Creates a new {@link AggregationOptions}.
+	 *
+	 * @param allowDiskUse whether to off-load intensive sort-operations to disk.
+	 * @param explain whether to get the execution plan for the aggregation instead of the actual results.
+	 * @param cursor can be {@literal null}, used to pass additional options (such as {@code batchSize}) to the
+	 *          aggregation.
+	 * @param collation collation for string comparison. Can be {@literal null}.
+	 * @param comment execution comment. Can be {@literal null}.
+	 * @param hint can be {@literal null}, used to provide an index that would be forcibly used by query optimizer.
+	 * @since 3.1
+	 */
+	private AggregationOptions(boolean allowDiskUse, boolean explain, @Nullable Document cursor,
+			@Nullable Collation collation, @Nullable String comment, @Nullable Document hint) {
 
 		this.allowDiskUse = allowDiskUse;
 		this.explain = explain;
 		this.cursor = Optional.ofNullable(cursor);
 		this.collation = Optional.ofNullable(collation);
 		this.comment = Optional.ofNullable(comment);
+		this.hint = Optional.ofNullable(hint);
 	}
 
 	/**
@@ -130,8 +151,9 @@ public class AggregationOptions {
 		Collation collation = document.containsKey(COLLATION) ? Collation.from(document.get(COLLATION, Document.class))
 				: null;
 		String comment = document.getString(COMMENT);
+		Document hint = document.get(HINT, Document.class);
 
-		AggregationOptions options = new AggregationOptions(allowDiskUse, explain, cursor, collation, comment);
+		AggregationOptions options = new AggregationOptions(allowDiskUse, explain, cursor, collation, comment, hint);
 		if (document.containsKey(MAX_TIME)) {
 			options.maxTime = Duration.ofMillis(document.getLong(MAX_TIME));
 		}
@@ -212,6 +234,16 @@ public class AggregationOptions {
 		return comment;
 	}
 
+	/**
+	 * Get the hint used to to fulfill the aggregation.
+	 *
+	 * @return never {@literal null}.
+	 * @since 3.1
+	 */
+	public Optional<Document> getHint() {
+		return hint;
+	}
+
 	/**
 	 * @return the time limit for processing. {@link Duration#ZERO} is used for the default unbounded behavior.
 	 * @since 3.0
@@ -248,6 +280,10 @@ public class AggregationOptions {
 			result.put(EXPLAIN, explain);
 		}
 
+		if (result.containsKey(HINT)) {
+			hint.ifPresent(val -> result.append(HINT, val));
+		}
+
 		if (!result.containsKey(CURSOR)) {
 			cursor.ifPresent(val -> result.put(CURSOR, val));
 		}
@@ -277,6 +313,7 @@ public class AggregationOptions {
 		cursor.ifPresent(val -> document.put(CURSOR, val));
 		collation.ifPresent(val -> document.append(COLLATION, val.toDocument()));
 		comment.ifPresent(val -> document.append(COMMENT, val));
+		hint.ifPresent(val -> document.append(HINT, val));
 
 		if (hasExecutionTimeLimit()) {
 			document.append(MAX_TIME, maxTime.toMillis());
@@ -318,6 +355,7 @@ public class AggregationOptions {
 		private @Nullable Document cursor;
 		private @Nullable Collation collation;
 		private @Nullable String comment;
+		private @Nullable Document hint;
 		private @Nullable Duration maxTime;
 		private @Nullable ResultOptions resultOptions;
 
@@ -396,11 +434,24 @@ public class AggregationOptions {
 			return this;
 		}
 
+		/**
+		 * Define a hint that is used by query optimizer to to fulfill the aggregation.
+		 *
+		 * @param hint can be {@literal null}.
+		 * @return this.
+		 * @since 3.1
+		 */
+		public Builder hint(@Nullable Document hint) {
+
+			this.hint = hint;
+			return this;
+		}
+
 		/**
 		 * Set the time limit for processing.
 		 *
 		 * @param maxTime {@link Duration#ZERO} is used for the default unbounded behavior. {@link Duration#isNegative()
-		 * Negative} values will be ignored.
+		 *          Negative} values will be ignored.
 		 * @return this.
 		 * @since 3.0
 		 */
@@ -431,7 +482,7 @@ public class AggregationOptions {
 		 */
 		public AggregationOptions build() {
 
-			AggregationOptions options = new AggregationOptions(allowDiskUse, explain, cursor, collation, comment);
+			AggregationOptions options = new AggregationOptions(allowDiskUse, explain, cursor, collation, comment, hint);
 			if (maxTime != null) {
 				options.maxTime = maxTime;
 			}

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

@@ -18,6 +18,7 @@ package org.springframework.data.mongodb.core.aggregation;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.function.Predicate;
 
 import org.bson.Document;
 import org.springframework.util.Assert;
@@ -26,6 +27,7 @@ import org.springframework.util.Assert;
  * The {@link AggregationPipeline} holds the collection of {@link AggregationOperation aggregation stages}.
  *
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @since 3.0.2
  */
 public class AggregationPipeline {
@@ -45,6 +47,8 @@ public class AggregationPipeline {
 	 * @param aggregationOperations must not be {@literal null}.
 	 */
 	public AggregationPipeline(List<AggregationOperation> aggregationOperations) {
+
+		Assert.notNull(aggregationOperations, "AggregationOperations must not be null!");
 		pipeline = new ArrayList<>(aggregationOperations);
 	}
 
@@ -82,30 +86,77 @@ public class AggregationPipeline {
 	 */
 	public boolean isOutOrMerge() {
 
-		if (pipeline.isEmpty()) {
+		if (isEmpty()) {
 			return false;
 		}
 
-		String operator = pipeline.get(pipeline.size() - 1).getOperator();
-		return operator.equals("$out") || operator.equals("$merge");
+		AggregationOperation operation = pipeline.get(pipeline.size() - 1);
+		return isOut(operation) || isMerge(operation);
 	}
 
 	void verify() {
 
 		// check $out/$merge is the last operation if it exists
-		for (AggregationOperation aggregationOperation : pipeline) {
+		for (AggregationOperation operation : pipeline) {
 
-			if (aggregationOperation instanceof OutOperation && !isLast(aggregationOperation)) {
+			if (isOut(operation) && !isLast(operation)) {
 				throw new IllegalArgumentException("The $out operator must be the last stage in the pipeline.");
 			}
 
-			if (aggregationOperation instanceof MergeOperation && !isLast(aggregationOperation)) {
+			if (isMerge(operation) && !isLast(operation)) {
 				throw new IllegalArgumentException("The $merge operator must be the last stage in the pipeline.");
 			}
 		}
 	}
 
+	/**
+	 * Return whether this aggregation pipeline defines a {@code $unionWith} stage that may contribute documents from
+	 * other collections. Checking for presence of union stages is useful when attempting to determine the aggregation
+	 * element type for mapping metadata computation.
+	 *
+	 * @return {@literal true} the aggregation pipeline makes use of {@code $unionWith}.
+	 * @since 3.1
+	 */
+	public boolean containsUnionWith() {
+		return containsOperation(AggregationPipeline::isUnionWith);
+	}
+
+	/**
+	 * @return {@literal true} if the pipeline does not contain any stages.
+	 * @since 3.1
+	 */
+	public boolean isEmpty() {
+		return pipeline.isEmpty();
+	}
+
+	private boolean containsOperation(Predicate<AggregationOperation> predicate) {
+
+		if (isEmpty()) {
+			return false;
+		}
+
+		for (AggregationOperation element : pipeline) {
+			if (predicate.test(element)) {
+				return true;
+			}
+		}
+
+		return false;
+	}
+
 	private boolean isLast(AggregationOperation aggregationOperation) {
 		return pipeline.indexOf(aggregationOperation) == pipeline.size() - 1;
 	}
+
+	private static boolean isUnionWith(AggregationOperation operator) {
+		return operator instanceof UnionWithOperation || operator.getOperator().equals("$unionWith");
+	}
+
+	private static boolean isMerge(AggregationOperation operator) {
+		return operator instanceof MergeOperation || operator.getOperator().equals("$merge");
+	}
+
+	private static boolean isOut(AggregationOperation operator) {
+		return operator instanceof OutOperation || operator.getOperator().equals("$out");
+	}
 }

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

@@ -104,7 +104,7 @@ public class BucketOperation extends BucketOperationSupport<BucketOperation, Buc
 		return new Document(getOperator(), options);
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#getOperator()
 	 */

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

@@ -1835,7 +1835,7 @@ public class DateOperators {
 		 * @param millisecond must not be {@literal null}.
 		 * @return new instance.
 		 * @throws IllegalArgumentException if given {@literal millisecond} is {@literal null}
-		 * @deprecated since 3.0.7, use {@link #millisecond(Object)} instead.
+		 * @deprecated since 3.2, use {@link #millisecond(Object)} instead.
 		 */
 		@Deprecated
 		default T milliseconds(Object millisecond) {
@@ -1849,7 +1849,7 @@ public class DateOperators {
 		 * @param millisecond must not be {@literal null}.
 		 * @return new instance.
 		 * @throws IllegalArgumentException if given {@literal millisecond} is {@literal null}
-		 * @since 3.0.7
+		 * @since 3.2
 		 */
 		T millisecond(Object millisecond);
 
@@ -1859,7 +1859,7 @@ public class DateOperators {
 		 * @param fieldReference must not be {@literal null}.
 		 * @return new instance.
 		 * @throws IllegalArgumentException if given {@literal fieldReference} is {@literal null}.
-		 * @deprecated since 3.0.7,use {@link #millisecondOf(String)} instead.
+		 * @deprecated since 3.2,use {@link #millisecondOf(String)} instead.
 		 */
 		@Deprecated
 		default T millisecondsOf(String fieldReference) {
@@ -1872,7 +1872,7 @@ public class DateOperators {
 		 * @param fieldReference must not be {@literal null}.
 		 * @return new instance.
 		 * @throws IllegalArgumentException if given {@literal fieldReference} is {@literal null}.
-		 * @since 3.0.7
+		 * @since 3.2
 		 */
 		default T millisecondOf(String fieldReference) {
 			return milliseconds(Fields.field(fieldReference));
@@ -1884,7 +1884,7 @@ public class DateOperators {
 		 * @param expression must not be {@literal null}.
 		 * @return new instance.
 		 * @throws IllegalArgumentException if given {@literal expression} is {@literal null}.
-		 * @deprecated since 3.0.7, use {@link #millisecondOf(AggregationExpression)} instead.
+		 * @deprecated since 3.2, use {@link #millisecondOf(AggregationExpression)} instead.
 		 */
 		@Deprecated
 		default T millisecondsOf(AggregationExpression expression) {
@@ -1897,7 +1897,7 @@ public class DateOperators {
 		 * @param expression must not be {@literal null}.
 		 * @return new instance.
 		 * @throws IllegalArgumentException if given {@literal expression} is {@literal null}.
-		 * @since 3.0.7
+		 * @since 3.2
 		 */
 		default T millisecondOf(AggregationExpression expression) {
 			return milliseconds(expression);

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

@@ -149,4 +149,12 @@ class ExposedFieldsAggregationOperationContext implements AggregationOperationCo
 		}
 		return null;
 	}
+
+	/**
+	 * @return obtain the root context used to resolve references.
+	 * @since 3.1
+	 */
+	AggregationOperationContext getRootContext() {
+		return rootContext;
+	}
 }

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

@@ -23,6 +23,7 @@ import java.util.List;
 import org.bson.Document;
 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.ScriptOperators.Accumulator;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
@@ -375,6 +376,17 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 		return newBuilder(GroupOps.STD_DEV_POP, null, expr);
 	}
 
+	/**
+	 * Generates an {@link GroupOperationBuilder} for an {@code $accumulator}-expression.
+	 *
+	 * @param accumulator must not be {@literal null}.
+	 * @return never {@literal null}.
+	 * @since 3.2
+	 */
+	public GroupOperationBuilder accumulate(Accumulator accumulator) {
+		return new GroupOperationBuilder(this, new Operation(accumulator));
+	}
+
 	private GroupOperationBuilder newBuilder(Keyword keyword, @Nullable String reference, @Nullable Object value) {
 		return new GroupOperationBuilder(this, new Operation(keyword, null, reference, value));
 	}
@@ -465,12 +477,16 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	static class Operation implements AggregationOperation {
 
-		private final Keyword op;
+		private final @Nullable Keyword op;
 		private final @Nullable String key;
 		private final @Nullable String reference;
 		private final @Nullable Object value;
 
-		public Operation(Keyword op, @Nullable String key, @Nullable String reference, @Nullable Object value) {
+		Operation(AggregationExpression expression) {
+			this(null, null, null, expression);
+		}
+
+		public Operation(@Nullable Keyword op, @Nullable String key, @Nullable String reference, @Nullable Object value) {
 
 			this.op = op;
 			this.key = key;
@@ -487,7 +503,12 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 		}
 
 		public Document toDocument(AggregationOperationContext context) {
-			return new Document(key, new Document(op.toString(), getValue(context)));
+
+			Object value = getValue(context);
+			if(op == null && value instanceof Document) {
+				return new Document(key, value);
+			}
+			return new Document(key, new Document(op.toString(), value));
 		}
 
 		public Object getValue(AggregationOperationContext context) {

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

@@ -52,7 +52,7 @@ public class LimitOperation implements AggregationOperation {
 		return new Document(getOperator(), Long.valueOf(maxElements));
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#getOperator()
 	 */

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

@@ -0,0 +1,587 @@
+/*
+ * Copyright 2020-2021 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
+ *
+ *      https://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 java.util.Map;
+
+import org.springframework.data.mongodb.core.aggregation.ScriptOperators.Accumulator.AccumulatorBuilder;
+import org.springframework.data.mongodb.core.aggregation.ScriptOperators.Accumulator.AccumulatorInitBuilder;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
+
+/**
+ * Gateway to {@literal $function} and {@literal $accumulator} aggregation operations.
+ * <p />
+ * Using {@link ScriptOperators} as part of the {@link Aggregation} requires MongoDB server to have
+ * <a href="https://docs.mongodb.com/master/core/server-side-javascript/">server-side JavaScript</a> execution
+ * <a href="https://docs.mongodb.com/master/reference/configuration-options/#security.javascriptEnabled">enabled</a>.
+ *
+ * @author Christoph Strobl
+ * @author Mark Paluch
+ * @since 3.1
+ */
+public class ScriptOperators {
+
+	/**
+	 * Create a custom aggregation
+	 * <a href="https://docs.mongodb.com/master/reference/operator/aggregation/function/">$function<a /> in JavaScript.
+	 *
+	 * @param body The function definition. Must not be {@literal null}.
+	 * @return new instance of {@link Function}.
+	 */
+	public static Function function(String body) {
+		return Function.function(body);
+	}
+
+	/**
+	 * Create a custom <a href="https://docs.mongodb.com/master/reference/operator/aggregation/accumulator/">$accumulator
+	 * operator</a> in Javascript.
+	 *
+	 * @return new instance of {@link AccumulatorInitBuilder}.
+	 */
+	public static AccumulatorInitBuilder accumulatorBuilder() {
+		return new AccumulatorBuilder();
+	}
+
+	/**
+	 * {@link Function} defines a custom aggregation
+	 * <a href="https://docs.mongodb.com/master/reference/operator/aggregation/function/">$function</a> in JavaScript.
+	 * <p />
+	 * <code class="java">
+	 * {
+	 *   $function: {
+	 *     body: ...,
+	 *     args: ...,
+	 *     lang: "js"
+	 *   }
+	 * }
+	 * </code>
+	 * <p />
+	 * {@link Function} cannot be used as part of {@link org.springframework.data.mongodb.core.schema.MongoJsonSchema
+	 * schema} validation query expression. <br />
+	 * <b>NOTE:</b> <a href="https://docs.mongodb.com/master/core/server-side-javascript/">Server-Side JavaScript</a>
+	 * execution must be
+	 * <a href="https://docs.mongodb.com/master/reference/configuration-options/#security.javascriptEnabled">enabled</a>
+	 *
+	 * @see <a href="https://docs.mongodb.com/master/reference/operator/aggregation/function/">MongoDB Documentation:
+	 *      $function</a>
+	 */
+	public static class Function extends AbstractAggregationExpression {
+
+		private Function(Map<String, Object> values) {
+			super(values);
+		}
+
+		/**
+		 * Create a new {@link Function} with the given function definition.
+		 *
+		 * @param body must not be {@literal null}.
+		 * @return new instance of {@link Function}.
+		 */
+		public static Function function(String body) {
+
+			Assert.notNull(body, "Function body must not be null!");
+
+			Map<String, Object> function = new LinkedHashMap<>(2);
+			function.put(Fields.BODY.toString(), body);
+			function.put(Fields.ARGS.toString(), Collections.emptyList());
+			function.put(Fields.LANG.toString(), "js");
+
+			return new Function(function);
+		}
+
+		/**
+		 * Set the arguments passed to the function body.
+		 *
+		 * @param args the arguments passed to the function body. Leave empty if the function does not take any arguments.
+		 * @return new instance of {@link Function}.
+		 */
+		public Function args(Object... args) {
+			return args(Arrays.asList(args));
+		}
+
+		/**
+		 * Set the arguments passed to the function body.
+		 *
+		 * @param args the arguments passed to the function body. Leave empty if the function does not take any arguments.
+		 * @return new instance of {@link Function}.
+		 */
+		public Function args(List<Object> args) {
+
+			Assert.notNull(args, "Args must not be null! Use an empty list instead.");
+
+			return new Function(appendAt(1, Fields.ARGS.toString(), args));
+		}
+
+		/**
+		 * The language used in the body.
+		 *
+		 * @param lang must not be {@literal null} nor empty.
+		 * @return new instance of {@link Function}.
+		 */
+		public Function lang(String lang) {
+
+			Assert.hasText(lang, "Lang must not be null nor empty! The default would be 'js'.");
+
+			return new Function(appendAt(2, Fields.LANG.toString(), lang));
+		}
+
+		@Nullable
+		List<Object> getArgs() {
+			return get(Fields.ARGS.toString());
+		}
+
+		String getBody() {
+			return get(Fields.BODY.toString());
+		}
+
+		String getLang() {
+			return get(Fields.LANG.toString());
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$function";
+		}
+
+		enum Fields {
+
+			BODY, ARGS, LANG;
+
+			@Override
+			public String toString() {
+				return name().toLowerCase();
+			}
+		}
+	}
+
+	/**
+	 * {@link Accumulator} defines a custom aggregation
+	 * <a href="https://docs.mongodb.com/master/reference/operator/aggregation/accumulator/">$accumulator operator</a>,
+	 * one that maintains its state (e.g. totals, maximums, minimums, and related data) as documents progress through the
+	 * pipeline, in JavaScript.
+	 * <p />
+	 * <code class="java">
+	 * {
+	 *   $accumulator: {
+	 *     init: ...,
+	 *     intArgs: ...,
+	 *     accumulate: ...,
+	 *     accumulateArgs: ...,
+	 *     merge: ...,
+	 *     finalize: ...,
+	 *     lang: "js"
+	 *   }
+	 * }
+	 * </code>
+	 * <p />
+	 * {@link Accumulator} can be used as part of {@link GroupOperation $group}, {@link BucketOperation $bucket} and
+	 * {@link BucketAutoOperation $bucketAuto} pipeline stages. <br />
+	 * <b>NOTE:</b> <a href="https://docs.mongodb.com/master/core/server-side-javascript/">Server-Side JavaScript</a>
+	 * execution must be
+	 * <a href="https://docs.mongodb.com/master/reference/configuration-options/#security.javascriptEnabled">enabled</a>
+	 *
+	 * @see <a href="https://docs.mongodb.com/master/reference/operator/aggregation/accumulator/">MongoDB Documentation:
+	 *      $accumulator</a>
+	 */
+	public static class Accumulator extends AbstractAggregationExpression {
+
+		private Accumulator(Map<String, Object> value) {
+			super(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$accumulator";
+		}
+
+		enum Fields {
+
+			ACCUMULATE("accumulate"), //
+			ACCUMULATE_ARGS("accumulateArgs"), //
+			FINALIZE("finalize"), //
+			INIT("init"), //
+			INIT_ARGS("initArgs"), //
+			LANG("lang"), //
+			MERGE("merge"); //
+
+			private String field;
+
+			Fields(String field) {
+				this.field = field;
+			}
+
+			@Override
+			public String toString() {
+				return field;
+			}
+		}
+
+		public interface AccumulatorInitBuilder {
+
+			/**
+			 * Define the {@code init} {@link Function} for the {@link Accumulator accumulators} initial state. The function
+			 * receives its arguments from the {@link Function#args(Object...) initArgs} array expression.
+			 * <p />
+			 * <code class="java">
+			 * function(initArg1, initArg2, ...) {
+			 *   ...
+			 *   return initialState
+			 * }
+			 * </code>
+			 *
+			 * @param function must not be {@literal null}.
+			 * @return this.
+			 */
+			default AccumulatorAccumulateBuilder init(Function function) {
+				return init(function.getBody()).initArgs(function.getArgs());
+			}
+
+			/**
+			 * Define the {@code init} function for the {@link Accumulator accumulators} initial state. The function receives
+			 * its arguments from the {@link AccumulatorInitArgsBuilder#initArgs(Object...)} array expression.
+			 * <p />
+			 * <code class="java">
+			 * function(initArg1, initArg2, ...) {
+			 *   ...
+			 *   return initialState
+			 * }
+			 * </code>
+			 *
+			 * @param function must not be {@literal null}.
+			 * @return this.
+			 */
+			AccumulatorInitArgsBuilder init(String function);
+
+			/**
+			 * The language used in the {@code $accumulator} code.
+			 *
+			 * @param lang must not be {@literal null}. Default is {@literal js}.
+			 * @return this.
+			 */
+			AccumulatorInitBuilder lang(String lang);
+		}
+
+		public interface AccumulatorInitArgsBuilder extends AccumulatorAccumulateBuilder {
+
+			/**
+			 * Define the optional {@code initArgs} for the {@link AccumulatorInitBuilder#init(String)} function.
+			 *
+			 * @param args must not be {@literal null}.
+			 * @return this.
+			 */
+			default AccumulatorAccumulateBuilder initArgs(Object... args) {
+				return initArgs(Arrays.asList(args));
+			}
+
+			/**
+			 * Define the optional {@code initArgs} for the {@link AccumulatorInitBuilder#init(String)} function.
+			 *
+			 * @param args must not be {@literal null}.
+			 * @return this.
+			 */
+			AccumulatorAccumulateBuilder initArgs(List<Object> args);
+		}
+
+		public interface AccumulatorAccumulateBuilder {
+
+			/**
+			 * Set the {@code accumulate} {@link Function} that updates the state for each document. The functions first
+			 * argument is the current {@code state}, additional arguments can be defined via {@link Function#args(Object...)
+			 * accumulateArgs}.
+			 * <p />
+			 * <code class="java">
+			 * function(state, accumArg1, accumArg2, ...) {
+			 *   ...
+			 *   return newState
+			 * }
+			 * </code>
+			 *
+			 * @param function must not be {@literal null}.
+			 * @return this.
+			 */
+			default AccumulatorMergeBuilder accumulate(Function function) {
+				return accumulate(function.getBody()).accumulateArgs(function.getArgs());
+			}
+
+			/**
+			 * Set the {@code accumulate} function that updates the state for each document. The functions first argument is
+			 * the current {@code state}, additional arguments can be defined via
+			 * {@link AccumulatorAccumulateArgsBuilder#accumulateArgs(Object...)}.
+			 * <p />
+			 * <code class="java">
+			 * function(state, accumArg1, accumArg2, ...) {
+			 *   ...
+			 *   return newState
+			 * }
+			 * </code>
+			 *
+			 * @param function must not be {@literal null}.
+			 * @return this.
+			 */
+			AccumulatorAccumulateArgsBuilder accumulate(String function);
+		}
+
+		public interface AccumulatorAccumulateArgsBuilder extends AccumulatorMergeBuilder {
+
+			/**
+			 * Define additional {@code accumulateArgs} for the {@link AccumulatorAccumulateBuilder#accumulate(String)}
+			 * function.
+			 *
+			 * @param args must not be {@literal null}.
+			 * @return this.
+			 */
+			default AccumulatorMergeBuilder accumulateArgs(Object... args) {
+				return accumulateArgs(Arrays.asList(args));
+			}
+
+			/**
+			 * Define additional {@code accumulateArgs} for the {@link AccumulatorAccumulateBuilder#accumulate(String)}
+			 * function.
+			 *
+			 * @param args must not be {@literal null}.
+			 * @return this.
+			 */
+			AccumulatorMergeBuilder accumulateArgs(List<Object> args);
+		}
+
+		public interface AccumulatorMergeBuilder {
+
+			/**
+			 * Set the {@code merge} function used to merge two internal states. <br />
+			 * This might be required because the operation is run on a sharded cluster or when the operator exceeds its
+			 * memory limit.
+			 * <p />
+			 * <code class="java">
+			 * function(state1, state2) {
+			 *   ...
+			 *   return newState
+			 * }
+			 * </code>
+			 *
+			 * @param function must not be {@literal null}.
+			 * @return this.
+			 */
+			AccumulatorFinalizeBuilder merge(String function);
+		}
+
+		public interface AccumulatorFinalizeBuilder {
+
+			/**
+			 * Set the {@code finalize} function used to update the result of the accumulation when all documents have been
+			 * processed.
+			 * <p />
+			 * <code class="java">
+			 * function(state) {
+			 *   ...
+			 *   return finalState
+			 * }
+			 * </code>
+			 *
+			 * @param function must not be {@literal null}.
+			 * @return new instance of {@link Accumulator}.
+			 */
+			Accumulator finalize(String function);
+
+			/**
+			 * Build the {@link Accumulator} object without specifying a {@link #finalize(String) finalize function}.
+			 *
+			 * @return new instance of {@link Accumulator}.
+			 */
+			Accumulator build();
+		}
+
+		static class AccumulatorBuilder
+				implements AccumulatorInitBuilder, AccumulatorInitArgsBuilder, AccumulatorAccumulateBuilder,
+				AccumulatorAccumulateArgsBuilder, AccumulatorMergeBuilder, AccumulatorFinalizeBuilder {
+
+			private List<Object> initArgs;
+			private String initFunction;
+			private List<Object> accumulateArgs;
+			private String accumulateFunction;
+			private String mergeFunction;
+			private String finalizeFunction;
+			private String lang = "js";
+
+			/**
+			 * Define the {@code init} function for the {@link Accumulator accumulators} initial state. The function receives
+			 * its arguments from the {@link #initArgs(Object...)} array expression.
+			 * <p />
+			 * <code class="java">
+			 * function(initArg1, initArg2, ...) {
+			 *   ...
+			 *   return initialState
+			 * }
+			 * </code>
+			 *
+			 * @param function must not be {@literal null}.
+			 * @return this.
+			 */
+			@Override
+			public AccumulatorBuilder init(String function) {
+
+				this.initFunction = function;
+				return this;
+			}
+
+			/**
+			 * Define the optional {@code initArgs} for the {@link #init(String)} function.
+			 *
+			 * @param function must not be {@literal null}.
+			 * @return this.
+			 */
+			@Override
+			public AccumulatorBuilder initArgs(List<Object> args) {
+
+				Assert.notNull(args, "Args must not be null");
+
+				this.initArgs = new ArrayList<>(args);
+				return this;
+			}
+
+			/**
+			 * Set the {@code accumulate} function that updates the state for each document. The functions first argument is
+			 * the current {@code state}, additional arguments can be defined via {@link #accumulateArgs(Object...)}.
+			 * <p />
+			 * <code class="java">
+			 * function(state, accumArg1, accumArg2, ...) {
+			 *   ...
+			 *   return newState
+			 * }
+			 * </code>
+			 *
+			 * @param function must not be {@literal null}.
+			 * @return this.
+			 */
+			@Override
+			public AccumulatorBuilder accumulate(String function) {
+
+				Assert.notNull(function, "Accumulate function must not be null");
+
+				this.accumulateFunction = function;
+				return this;
+			}
+
+			/**
+			 * Define additional {@code accumulateArgs} for the {@link #accumulate(String)} function.
+			 *
+			 * @param args must not be {@literal null}.
+			 * @return this.
+			 */
+			@Override
+			public AccumulatorBuilder accumulateArgs(List<Object> args) {
+
+				Assert.notNull(args, "Args must not be null");
+
+				this.accumulateArgs = new ArrayList<>(args);
+				return this;
+			}
+
+			/**
+			 * Set the {@code merge} function used to merge two internal states. <br />
+			 * This might be required because the operation is run on a sharded cluster or when the operator exceeds its
+			 * memory limit.
+			 * <p />
+			 * <code class="java">
+			 * function(state1, state2) {
+			 *   ...
+			 *   return newState
+			 * }
+			 * </code>
+			 *
+			 * @param function must not be {@literal null}.
+			 * @return this.
+			 */
+			@Override
+			public AccumulatorBuilder merge(String function) {
+
+				Assert.notNull(function, "Merge function must not be null");
+
+				this.mergeFunction = function;
+				return this;
+			}
+
+			/**
+			 * The language used in the {@code $accumulator} code.
+			 *
+			 * @param lang must not be {@literal null}. Default is {@literal js}.
+			 * @return this.
+			 */
+			public AccumulatorBuilder lang(String lang) {
+
+				Assert.hasText(lang, "Lang must not be null nor empty! The default would be 'js'.");
+
+				this.lang = lang;
+				return this;
+			}
+
+			/**
+			 * Set the {@code finalize} function used to update the result of the accumulation when all documents have been
+			 * processed.
+			 * <p />
+			 * <code class="java">
+			 * function(state) {
+			 *   ...
+			 *   return finalState
+			 * }
+			 * </code>
+			 *
+			 * @param function must not be {@literal null}.
+			 * @return new instance of {@link Accumulator}.
+			 */
+			@Override
+			public Accumulator finalize(String function) {
+
+				Assert.notNull(function, "Finalize function must not be null");
+
+				this.finalizeFunction = function;
+
+				Map<String, Object> args = createArgumentMap();
+				args.put(Fields.FINALIZE.toString(), finalizeFunction);
+
+				return new Accumulator(args);
+			}
+
+			@Override
+			public Accumulator build() {
+				return new Accumulator(createArgumentMap());
+			}
+
+			private Map<String, Object> createArgumentMap() {
+
+				Map<String, Object> args = new LinkedHashMap<>();
+				args.put(Fields.INIT.toString(), initFunction);
+				if (!CollectionUtils.isEmpty(initArgs)) {
+					args.put(Fields.INIT_ARGS.toString(), initArgs);
+				}
+				args.put(Fields.ACCUMULATE.toString(), accumulateFunction);
+				if (!CollectionUtils.isEmpty(accumulateArgs)) {
+					args.put(Fields.ACCUMULATE_ARGS.toString(), accumulateArgs);
+				}
+				args.put(Fields.MERGE.toString(), mergeFunction);
+				args.put(Fields.LANG.toString(), lang);
+
+				return args;
+			}
+		}
+	}
+}

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

@@ -78,7 +78,7 @@ public class SortByCountOperation implements AggregationOperation {
 				: groupByExpression.toDocument(context));
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#getOperator()
 	 */

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

@@ -21,6 +21,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 import org.bson.Document;
+import org.springframework.data.mapping.PersistentEntity;
 import org.springframework.data.mapping.PersistentPropertyPath;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.DirectFieldReference;
@@ -29,6 +30,7 @@ import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldRefe
 import org.springframework.data.mongodb.core.convert.QueryMapper;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+import org.springframework.data.util.Lazy;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
@@ -46,6 +48,7 @@ public class TypeBasedAggregationOperationContext implements AggregationOperatio
 	private final Class<?> type;
 	private final MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext;
 	private final QueryMapper mapper;
+	private final Lazy<MongoPersistentEntity<?>> entity;
 
 	/**
 	 * Creates a new {@link TypeBasedAggregationOperationContext} for the given type, {@link MappingContext} and
@@ -65,6 +68,7 @@ public class TypeBasedAggregationOperationContext implements AggregationOperatio
 		this.type = type;
 		this.mappingContext = mappingContext;
 		this.mapper = mapper;
+		this.entity = Lazy.of(() -> mappingContext.getPersistentEntity(type));
 	}
 
 	/*
@@ -133,15 +137,32 @@ public class TypeBasedAggregationOperationContext implements AggregationOperatio
 	 */
 	@Override
 	public AggregationOperationContext continueOnMissingFieldReference() {
+		return continueOnMissingFieldReference(type);
+	}
+
+	/**
+	 * This toggle allows the {@link AggregationOperationContext context} to use any given field name without checking for
+	 * its existence. Typically the {@link AggregationOperationContext} fails when referencing unknown fields, those that
+	 * are not present in one of the previous stages or the input source, throughout the pipeline.
+	 *
+	 * @param type The domain type to map fields to.
+	 * @return a more relaxed {@link AggregationOperationContext}.
+	 * @since 3.1
+	 */
+	public AggregationOperationContext continueOnMissingFieldReference(Class<?> type) {
 		return new RelaxedTypeBasedAggregationOperationContext(type, mappingContext, mapper);
 	}
 
 	protected FieldReference getReferenceFor(Field field) {
 
+		if(entity.getNullable() == null) {
+			return new DirectFieldReference(new ExposedField(field, true));
+		}
+
 		PersistentPropertyPath<MongoPersistentProperty> propertyPath = mappingContext
-				.getPersistentPropertyPath(field.getTarget(), type);
+					.getPersistentPropertyPath(field.getTarget(), type);
 		Field mappedField = field(field.getName(),
-				propertyPath.toDotPath(MongoPersistentProperty.PropertyToFieldNameConverter.INSTANCE));
+					propertyPath.toDotPath(MongoPersistentProperty.PropertyToFieldNameConverter.INSTANCE));
 
 		return new DirectFieldReference(new ExposedField(mappedField, true));
 	}

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

@@ -0,0 +1,164 @@
+/*
+ * Copyright 2020-2021 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
+ *
+ *      https://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.List;
+
+import org.bson.Document;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+
+/**
+ * The <a href="https://docs.mongodb.com/master/reference/operator/aggregation/unionWith/">$unionWith</a> aggregation
+ * stage (available since MongoDB 4.4) performs a union of two collections by combining pipeline results, potentially
+ * containing duplicates, into a single result set that is handed over to the next stage. <br />
+ * In order to remove duplicates it is possible to append a {@link GroupOperation} right after
+ * {@link UnionWithOperation}.
+ * <p />
+ * If the {@link UnionWithOperation} uses a
+ * <a href="https://docs.mongodb.com/master/reference/operator/aggregation/unionWith/#unionwith-pipeline">pipeline</a>
+ * to process documents, field names within the pipeline will be treated as is. In order to map domain type property
+ * names to actual field names (considering potential {@link org.springframework.data.mongodb.core.mapping.Field}
+ * annotations) make sure the enclosing aggregation is a {@link TypedAggregation} and provide the target type for the
+ * {@code $unionWith} stage via {@link #mapFieldsTo(Class)}.
+ *
+ * @author Christoph Strobl
+ * @see <a href="https://docs.mongodb.com/master/reference/operator/aggregation/unionWith/">Aggregation Pipeline Stage:
+ *      $unionWith</a>
+ * @since 3.1
+ */
+public class UnionWithOperation implements AggregationOperation {
+
+	private final String collection;
+
+	private final @Nullable AggregationPipeline pipeline;
+
+	private final @Nullable Class<?> domainType;
+
+	public UnionWithOperation(String collection, @Nullable AggregationPipeline pipeline, @Nullable Class<?> domainType) {
+
+		Assert.notNull(collection, "Collection must not be null!");
+
+		this.collection = collection;
+		this.pipeline = pipeline;
+		this.domainType = domainType;
+	}
+
+	/**
+	 * Set the name of the collection from which pipeline results should be included in the result set.<br />
+	 * The collection name is used to set the {@code coll} parameter of {@code $unionWith}.
+	 *
+	 * @param collection the MongoDB collection name. Must not be {@literal null}.
+	 * @return new instance of {@link UnionWithOperation}.
+	 * @throws IllegalArgumentException if the required argument is {@literal null}.
+	 */
+	public static UnionWithOperation unionWith(String collection) {
+		return new UnionWithOperation(collection, null, null);
+	}
+
+	/**
+	 * Set the {@link AggregationPipeline} to apply to the specified collection. The pipeline corresponds to the optional
+	 * {@code pipeline} field of the {@code $unionWith} aggregation stage and is used to compute the documents going into
+	 * the result set.
+	 *
+	 * @param pipeline the {@link AggregationPipeline} that computes the documents. Must not be {@literal null}.
+	 * @return new instance of {@link UnionWithOperation}.
+	 * @throws IllegalArgumentException if the required argument is {@literal null}.
+	 */
+	public UnionWithOperation pipeline(AggregationPipeline pipeline) {
+		return new UnionWithOperation(collection, pipeline, domainType);
+	}
+
+	/**
+	 * Set the aggregation pipeline stages to apply to the specified collection. The pipeline corresponds to the optional
+	 * {@code pipeline} field of the {@code $unionWith} aggregation stage and is used to compute the documents going into
+	 * the result set.
+	 *
+	 * @param aggregationStages the aggregation pipeline stages that compute the documents. Must not be {@literal null}.
+	 * @return new instance of {@link UnionWithOperation}.
+	 * @throws IllegalArgumentException if the required argument is {@literal null}.
+	 */
+	public UnionWithOperation pipeline(List<AggregationOperation> aggregationStages) {
+		return new UnionWithOperation(collection, new AggregationPipeline(aggregationStages), domainType);
+	}
+
+	/**
+	 * Set the aggregation pipeline stages to apply to the specified collection. The pipeline corresponds to the optional
+	 * {@code pipeline} field of the {@code $unionWith} aggregation stage and is used to compute the documents going into
+	 * the result set.
+	 *
+	 * @param aggregationStages the aggregation pipeline stages that compute the documents. Must not be {@literal null}.
+	 * @return new instance of {@link UnionWithOperation}.
+	 * @throws IllegalArgumentException if the required argument is {@literal null}.
+	 */
+	public UnionWithOperation pipeline(AggregationOperation... aggregationStages) {
+		return new UnionWithOperation(collection, new AggregationPipeline(Arrays.asList(aggregationStages)), domainType);
+	}
+
+	/**
+	 * Set domain type used for field name mapping of property references used by the {@link AggregationPipeline}.
+	 * Remember to also use a {@link TypedAggregation} in the outer pipeline.<br />
+	 * If not set, field names used within {@link AggregationOperation pipeline operations} are taken as is.
+	 *
+	 * @param domainType the domain type to map field names used in pipeline operations to. Must not be {@literal null}.
+	 * @return new instance of {@link UnionWithOperation}.
+	 * @throws IllegalArgumentException if the required argument is {@literal null}.
+	 */
+	public UnionWithOperation mapFieldsTo(Class<?> domainType) {
+
+		Assert.notNull(domainType, "DomainType must not be null!");
+		return new UnionWithOperation(collection, pipeline, domainType);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+	 */
+	@Override
+	public Document toDocument(AggregationOperationContext context) {
+
+		Document $unionWith = new Document("coll", collection);
+		if (pipeline == null || pipeline.isEmpty()) {
+			return new Document(getOperator(), $unionWith);
+		}
+
+		$unionWith.append("pipeline", pipeline.toDocuments(computeContext(context)));
+		return new Document(getOperator(), $unionWith);
+	}
+
+	private AggregationOperationContext computeContext(AggregationOperationContext source) {
+
+		if (source instanceof TypeBasedAggregationOperationContext) {
+			return ((TypeBasedAggregationOperationContext) source).continueOnMissingFieldReference(domainType != null ? domainType : Object.class);
+		}
+
+		if (source instanceof ExposedFieldsAggregationOperationContext) {
+			return computeContext(((ExposedFieldsAggregationOperationContext) source).getRootContext());
+		}
+
+		return source;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#getOperator()
+	 */
+	@Override
+	public String getOperator() {
+		return "$unionWith";
+	}
+}

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

@@ -108,7 +108,7 @@ public class UnwindOperation
 		return new Document(getOperator(), unwindArgs);
 	}
 
-	/*
+	/* 
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#getOperator()
 	 */

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

@@ -17,16 +17,17 @@ package org.springframework.data.mongodb.core.convert;
 
 import java.util.Arrays;
 import java.util.Iterator;
+import java.util.Map;
 
 import org.bson.Document;
 import org.bson.conversions.Bson;
-
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
 import org.springframework.data.mongodb.util.BsonUtils;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
+import com.mongodb.BasicDBObject;
 import com.mongodb.DBObject;
 
 /**
@@ -109,7 +110,28 @@ class DocumentAccessor {
 	 */
 	@Nullable
 	public Object get(MongoPersistentProperty property) {
-		return BsonUtils.resolveValue(document, property.getFieldName());
+
+		String fieldName = property.getFieldName();
+		Map<String, Object> map = BsonUtils.asMap(document);
+
+		if (!fieldName.contains(".")) {
+			return map.get(fieldName);
+		}
+
+		Iterator<String> parts = Arrays.asList(fieldName.split("\\.")).iterator();
+		Map<String, Object> source = map;
+		Object result = null;
+
+		while (source != null && parts.hasNext()) {
+
+			result = source.get(parts.next());
+
+			if (parts.hasNext()) {
+				source = getAsMap(result);
+			}
+		}
+
+		return result;
 	}
 
 	/**
@@ -135,7 +157,71 @@ class DocumentAccessor {
 
 		Assert.notNull(property, "Property must not be null!");
 
-		return BsonUtils.hasValue(document, property.getFieldName());
+		String fieldName = property.getFieldName();
+
+
+		if (this.document instanceof Document) {
+
+			if (((Document) this.document).containsKey(fieldName)) {
+				return true;
+			}
+		} else if (this.document instanceof DBObject) {
+			if (((DBObject) this.document).containsField(fieldName)) {
+				return true;
+			}
+		}
+
+		if (!fieldName.contains(".")) {
+			return false;
+		}
+
+		String[] parts = fieldName.split("\\.");
+		Map<String, Object> source;
+
+		if (this.document instanceof Document) {
+			source = ((Document) this.document);
+		} else {
+			source = ((DBObject) this.document).toMap();
+		}
+
+		Object result = null;
+
+		for (int i = 1; i < parts.length; i++) {
+
+			result = source.get(parts[i - 1]);
+			source = getAsMap(result);
+
+			if (source == null) {
+				return false;
+			}
+		}
+
+		return source.containsKey(parts[parts.length - 1]);
+	}
+
+	/**
+	 * Returns the given source object as map, i.e. {@link Document}s and maps as is or {@literal null} otherwise.
+	 *
+	 * @param source can be {@literal null}.
+	 * @return can be {@literal null}.
+	 */
+	@Nullable
+	@SuppressWarnings("unchecked")
+	private static Map<String, Object> getAsMap(Object source) {
+
+		if (source instanceof Document) {
+			return (Document) source;
+		}
+
+		if (source instanceof BasicDBObject) {
+			return (BasicDBObject) source;
+		}
+
+		if (source instanceof Map) {
+			return (Map<String, Object>) source;
+		}
+
+		return null;
 	}
 
 	/**

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

@@ -1152,8 +1152,7 @@ public class QueryMapper {
 
 		private boolean isPathToJavaLangClassProperty(PropertyPath path) {
 
-			if ((path.getType() == Class.class || path.getType().equals(Object.class))
-					&& path.getLeafProperty().getType() == Class.class) {
+			if (path.getType().equals(Class.class) && path.getLeafProperty().getOwningType().getType().equals(Class.class)) {
 				return true;
 			}
 			return false;
@@ -1262,9 +1261,9 @@ public class QueryMapper {
 
 					String partial = iterator.next();
 
-					boolean isPositional = isPositionalParameter(partial) && property.isCollectionLike();
+					boolean isPositional = (isPositionalParameter(partial) && (property.isMap() || property.isCollectionLike()));
 
-					if (isPositional || property.isMap()) {
+					if (isPositional) {
 						mappedName.append(".").append(partial);
 					}
 

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

@@ -16,7 +16,7 @@
 package org.springframework.data.mongodb.core.geo;
 
 /**
- * Interface definition for structures defined in <a href="https://geojson.org/">GeoJSON</a> format.
+ * Interface definition for structures defined in <a href="https://geojson.org/>GeoJSON</a> format.
  *
  * @author Christoph Strobl
  * @since 1.7

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

@@ -46,6 +46,7 @@ import java.lang.annotation.Target;
  * @author Philipp Schneider
  * @author Johno Crawford
  * @author Christoph Strobl
+ * @author Dave Perryman
  */
 @Target({ ElementType.TYPE })
 @Documented
@@ -95,7 +96,8 @@ public @interface CompoundIndex {
 	boolean unique() default false;
 
 	/**
-	 * If set to true index will skip over any document that is missing the indexed field.
+	 * If set to true index will skip over any document that is missing the indexed field. <br />
+	 * Must not be used with {@link #partialFilter()}.
 	 *
 	 * @return {@literal false} by default.
 	 * @see <a href=
@@ -170,4 +172,14 @@ public @interface CompoundIndex {
 	 */
 	boolean background() default false;
 
+	/**
+	 * Only index the documents in a collection that meet a specified {@link IndexFilter filter expression}. <br />
+	 * Must not be used with {@link #sparse() sparse = true}.
+	 *
+	 * @return empty by default.
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/core/index-partial/">https://docs.mongodb.com/manual/core/index-partial/</a>
+	 * @since 3.1
+	 */
+	String partialFilter() default "";
 }

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

@@ -53,7 +53,8 @@ public @interface Indexed {
 	IndexDirection direction() default IndexDirection.ASCENDING;
 
 	/**
-	 * If set to true index will skip over any document that is missing the indexed field.
+	 * If set to true index will skip over any document that is missing the indexed field. <br />
+	 * Must not be used with {@link #partialFilter()}.
 	 *
 	 * @return {@literal false} by default.
 	 * @see <a href=
@@ -170,4 +171,15 @@ public @interface Indexed {
 	 * @since 2.2
 	 */
 	String expireAfter() default "";
+
+	/**
+	 * Only index the documents in a collection that meet a specified {@link IndexFilter filter expression}. <br />
+	 * Must not be used with {@link #sparse() sparse = true}.
+	 *
+	 * @return empty by default.
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/core/index-partial/">https://docs.mongodb.com/manual/core/index-partial/</a>
+	 * @since 3.1
+	 */
+	String partialFilter() default "";
 }

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

@@ -15,10 +15,6 @@
  */
 package org.springframework.data.mongodb.core.index;
 
-import lombok.AccessLevel;
-import lombok.EqualsAndHashCode;
-import lombok.RequiredArgsConstructor;
-
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -33,7 +29,6 @@ import java.util.stream.Collectors;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-
 import org.springframework.dao.InvalidDataAccessApiUsageException;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.mapping.Association;
@@ -51,6 +46,7 @@ import org.springframework.data.mongodb.core.mapping.BasicMongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.Document;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+import org.springframework.data.mongodb.util.BsonUtils;
 import org.springframework.data.spel.EvaluationContextProvider;
 import org.springframework.data.util.TypeInformation;
 import org.springframework.expression.EvaluationContext;
@@ -74,6 +70,7 @@ import org.springframework.util.StringUtils;
  * @author Thomas Darimont
  * @author Martin Macko
  * @author Mark Paluch
+ * @author Dave Perryman
  * @since 1.5
  */
 public class MongoPersistentEntityIndexResolver implements IndexResolver {
@@ -385,6 +382,10 @@ public class MongoPersistentEntityIndexResolver implements IndexResolver {
 			indexDefinition.background();
 		}
 
+		if (StringUtils.hasText(index.partialFilter())) {
+			indexDefinition.partial(evaluatePartialFilter(index.partialFilter(), entity));
+		}
+
 		return new IndexDefinitionHolder(dotPath, indexDefinition, collection);
 	}
 
@@ -474,9 +475,25 @@ public class MongoPersistentEntityIndexResolver implements IndexResolver {
 			}
 		}
 
+		if (StringUtils.hasText(index.partialFilter())) {
+			indexDefinition.partial(evaluatePartialFilter(index.partialFilter(), persistentProperty.getOwner()));
+		}
+
 		return new IndexDefinitionHolder(dotPath, indexDefinition, collection);
 	}
 
+	private PartialIndexFilter evaluatePartialFilter(String filterExpression, PersistentEntity<?,?> entity) {
+
+		Object result = evaluate(filterExpression, getEvaluationContextForProperty(entity));
+
+		if (result instanceof org.bson.Document) {
+			return PartialIndexFilter.of((org.bson.Document) result);
+		}
+
+		return PartialIndexFilter.of(BsonUtils.parse(filterExpression, null));
+	}
+
+
 	/**
 	 * Creates {@link HashedIndex} wrapped in {@link IndexDefinitionHolder} out of {@link HashIndexed} for a given
 	 * {@link MongoPersistentProperty}.
@@ -733,8 +750,6 @@ public class MongoPersistentEntityIndexResolver implements IndexResolver {
 		 * @author Christoph Strobl
 		 * @author Mark Paluch
 		 */
-		@RequiredArgsConstructor(access = AccessLevel.PRIVATE)
-		@EqualsAndHashCode
 		static class Path {
 
 			private static final Path EMPTY = new Path(Collections.emptyList(), false);
@@ -742,6 +757,11 @@ public class MongoPersistentEntityIndexResolver implements IndexResolver {
 			private final List<PersistentProperty<?>> elements;
 			private final boolean cycle;
 
+			private Path(List<PersistentProperty<?>> elements, boolean cycle) {
+				this.elements = elements;
+				this.cycle = cycle;
+			}
+
 			/**
 			 * @return an empty {@link Path}.
 			 * @since 1.10.8
@@ -843,6 +863,28 @@ public class MongoPersistentEntityIndexResolver implements IndexResolver {
 
 				return builder.toString();
 			}
+
+			@Override
+			public boolean equals(Object o) {
+				if (this == o)
+					return true;
+				if (o == null || getClass() != o.getClass())
+					return false;
+
+				Path that = (Path) o;
+
+				if (this.cycle != that.cycle) {
+					return false;
+				}
+				return ObjectUtils.nullSafeEquals(this.elements, that.elements);
+			}
+
+			@Override
+			public int hashCode() {
+				int result = ObjectUtils.nullSafeHashCode(elements);
+				result = 31 * result + (cycle ? 1 : 0);
+				return result;
+			}
 		}
 	}
 

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

@@ -16,14 +16,8 @@
 package org.springframework.data.mongodb.core.index;
 
 import org.bson.Document;
-
-import lombok.AccessLevel;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-
 import org.springframework.data.mongodb.core.query.CriteriaDefinition;
-
-import com.mongodb.DBObject;
+import org.springframework.util.Assert;
 
 /**
  * {@link IndexFilter} implementation for usage with plain {@link Document} as well as {@link CriteriaDefinition} filter
@@ -32,10 +26,16 @@ import com.mongodb.DBObject;
  * @author Christoph Strobl
  * @since 1.10
  */
-@RequiredArgsConstructor(access = AccessLevel.PRIVATE)
 public class PartialIndexFilter implements IndexFilter {
 
-	private final @NonNull Object filterExpression;
+	private final Object filterExpression;
+
+	private PartialIndexFilter(Object filterExpression) {
+
+		Assert.notNull(filterExpression, "FilterExpression must not be null!");
+
+		this.filterExpression = filterExpression;
+	}
 
 	/**
 	 * Create new {@link PartialIndexFilter} for given {@link Document filter expression}.

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

@@ -41,7 +41,7 @@ public @interface Document {
 	 * The collection the document representing the entity is supposed to be stored in. If not configured, a default
 	 * collection name will be derived from the type's name. The attribute supports SpEL expressions to dynamically
 	 * calculate the collection to based on a per operation basis.
-	 *
+	 * 
 	 * @return the name of the collection to be used.
 	 */
 	@AliasFor("collection")
@@ -51,7 +51,7 @@ public @interface Document {
 	 * The collection the document representing the entity is supposed to be stored in. If not configured, a default
 	 * collection name will be derived from the type's name. The attribute supports SpEL expressions to dynamically
 	 * calculate the collection to based on a per operation basis.
-	 *
+	 * 
 	 * @return the name of the collection to be used.
 	 */
 	@AliasFor("value")

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/event/MongoMappingEvent.java

@@ -77,7 +77,7 @@ public class MongoMappingEvent<T> extends ApplicationEvent {
 
 	/**
 	 * Allows client code to change the underlying source instance by applying the given {@link Function}.
-	 *
+	 * 
 	 * @param mapper the {@link Function} to apply, will only be applied if the source is not {@literal null}.
 	 * @since 2.1
 	 */

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/mapping/event/ReactiveAuditingEntityCallback.java

@@ -15,13 +15,12 @@
  */
 package org.springframework.data.mongodb.core.mapping.event;
 
-import reactor.core.publisher.Mono;
-
 import org.reactivestreams.Publisher;
+
 import org.springframework.beans.factory.ObjectFactory;
 import org.springframework.core.Ordered;
 import org.springframework.data.auditing.AuditingHandler;
-import org.springframework.data.auditing.IsNewAwareAuditingHandler;
+import org.springframework.data.auditing.ReactiveIsNewAwareAuditingHandler;
 import org.springframework.data.mapping.callback.EntityCallback;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.util.Assert;
@@ -34,7 +33,7 @@ import org.springframework.util.Assert;
  */
 public class ReactiveAuditingEntityCallback implements ReactiveBeforeConvertCallback<Object>, Ordered {
 
-	private final ObjectFactory<IsNewAwareAuditingHandler> auditingHandlerFactory;
+	private final ObjectFactory<ReactiveIsNewAwareAuditingHandler> auditingHandlerFactory;
 
 	/**
 	 * Creates a new {@link ReactiveAuditingEntityCallback} using the given {@link MappingContext} and
@@ -42,7 +41,7 @@ public class ReactiveAuditingEntityCallback implements ReactiveBeforeConvertCall
 	 *
 	 * @param auditingHandlerFactory must not be {@literal null}.
 	 */
-	public ReactiveAuditingEntityCallback(ObjectFactory<IsNewAwareAuditingHandler> auditingHandlerFactory) {
+	public ReactiveAuditingEntityCallback(ObjectFactory<ReactiveIsNewAwareAuditingHandler> auditingHandlerFactory) {
 
 		Assert.notNull(auditingHandlerFactory, "IsNewAwareAuditingHandler must not be null!");
 		this.auditingHandlerFactory = auditingHandlerFactory;
@@ -54,7 +53,7 @@ public class ReactiveAuditingEntityCallback implements ReactiveBeforeConvertCall
 	 */
 	@Override
 	public Publisher<Object> onBeforeConvert(Object entity, String collection) {
-		return Mono.just(auditingHandlerFactory.getObject().markAudited(entity));
+		return auditingHandlerFactory.getObject().markAudited(entity);
 	}
 
 	/*

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

@@ -15,8 +15,6 @@
  */
 package org.springframework.data.mongodb.core.messaging;
 
-import lombok.AllArgsConstructor;
-
 import java.time.Instant;
 import java.util.Arrays;
 import java.util.Collections;
@@ -217,12 +215,17 @@ class ChangeStreamTask extends CursorReadingTask<ChangeStreamDocument<Document>,
 	 *
 	 * @since 2.1
 	 */
-	@AllArgsConstructor
 	static class ChangeStreamEventMessage<T> implements Message<ChangeStreamDocument<Document>, T> {
 
 		private final ChangeStreamEvent<T> delegate;
 		private final MessageProperties messageProperties;
 
+		ChangeStreamEventMessage(ChangeStreamEvent<T> delegate, MessageProperties messageProperties) {
+
+			this.delegate = delegate;
+			this.messageProperties = messageProperties;
+		}
+
 		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.messaging.Message#getRaw()

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

@@ -15,10 +15,6 @@
  */
 package org.springframework.data.mongodb.core.messaging;
 
-import lombok.AccessLevel;
-import lombok.EqualsAndHashCode;
-import lombok.RequiredArgsConstructor;
-
 import java.time.Duration;
 import java.util.LinkedHashMap;
 import java.util.Map;
@@ -34,6 +30,7 @@ import org.springframework.data.mongodb.core.messaging.SubscriptionRequest.Reque
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ErrorHandler;
+import org.springframework.util.ObjectUtils;
 
 /**
  * Simple {@link Executor} based {@link MessageListenerContainer} implementation for running {@link Task tasks} like
@@ -259,7 +256,6 @@ public class DefaultMessageListenerContainer implements MessageListenerContainer
 	 * @author Christoph Strobl
 	 * @since 2.1
 	 */
-	@EqualsAndHashCode
 	static class TaskSubscription implements Subscription {
 
 		private final Task task;
@@ -286,19 +282,39 @@ public class DefaultMessageListenerContainer implements MessageListenerContainer
 		public void cancel() throws DataAccessResourceFailureException {
 			task.cancel();
 		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (this == o)
+				return true;
+			if (o == null || getClass() != o.getClass())
+				return false;
+
+			TaskSubscription that = (TaskSubscription) o;
+
+			return ObjectUtils.nullSafeEquals(this.task, that.task);
+		}
+
+		@Override
+		public int hashCode() {
+			return ObjectUtils.nullSafeHashCode(task);
+		}
 	}
 
 	/**
 	 * @author Christoph Strobl
 	 * @since 2.1
 	 */
-	@RequiredArgsConstructor(access = AccessLevel.PACKAGE)
 	private static class DecoratingLoggingErrorHandler implements ErrorHandler {
 
 		private final Log logger = LogFactory.getLog(DecoratingLoggingErrorHandler.class);
 
 		private final ErrorHandler delegate;
 
+		DecoratingLoggingErrorHandler(ErrorHandler delegate) {
+			this.delegate = delegate;
+		}
+
 		@Override
 		public void handleError(Throwable t) {
 

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

@@ -15,8 +15,6 @@
  */
 package org.springframework.data.mongodb.core.messaging;
 
-import lombok.ToString;
-
 import org.bson.Document;
 import org.springframework.data.mongodb.core.convert.MongoConverter;
 import org.springframework.util.ClassUtils;
@@ -26,7 +24,6 @@ import org.springframework.util.ClassUtils;
  * @author Mark Paluch
  * @since 2.1
  */
-@ToString(of = { "delegate", "targetType" })
 class LazyMappingDelegatingMessage<S, T> implements Message<S, T> {
 
 	private final Message<S, ?> delegate;
@@ -82,4 +79,8 @@ class LazyMappingDelegatingMessage<S, T> implements Message<S, T> {
 	public MessageProperties getProperties() {
 		return delegate.getProperties();
 	}
+
+	public String toString() {
+		return "LazyMappingDelegatingMessage(delegate=" + this.delegate + ", targetType=" + this.targetType + ")";
+	}
 }

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

@@ -15,11 +15,9 @@
  */
 package org.springframework.data.mongodb.core.messaging;
 
-import lombok.EqualsAndHashCode;
-import lombok.ToString;
-
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 /**
  * General message abstraction for any type of Event / Message published by MongoDB server to the client. This might be
@@ -65,8 +63,6 @@ public interface Message<S, T> {
 	 * @author Christoph Strobl
 	 * @since 2.1
 	 */
-	@ToString
-	@EqualsAndHashCode
 	class MessageProperties {
 
 		private static final MessageProperties EMPTY = new MessageProperties();
@@ -111,6 +107,34 @@ public interface Message<S, T> {
 			return new MessagePropertiesBuilder();
 		}
 
+		@Override
+		public boolean equals(Object o) {
+			if (this == o)
+				return true;
+			if (o == null || getClass() != o.getClass())
+				return false;
+
+			MessageProperties that = (MessageProperties) o;
+
+			if (!ObjectUtils.nullSafeEquals(this.databaseName, that.databaseName)) {
+				return false;
+			}
+
+			return ObjectUtils.nullSafeEquals(this.collectionName, that.collectionName);
+		}
+
+		@Override
+		public int hashCode() {
+			int result = ObjectUtils.nullSafeHashCode(databaseName);
+			result = 31 * result + ObjectUtils.nullSafeHashCode(collectionName);
+			return result;
+		}
+
+		public String toString() {
+			return "Message.MessageProperties(databaseName=" + this.getDatabaseName() + ", collectionName="
+					+ this.getCollectionName() + ")";
+		}
+
 		/**
 		 * Builder for {@link MessageProperties}.
 		 *

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

@@ -15,11 +15,9 @@
  */
 package org.springframework.data.mongodb.core.messaging;
 
-import lombok.EqualsAndHashCode;
-import lombok.ToString;
-
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 /**
  * Trivial {@link Message} implementation.
@@ -27,8 +25,6 @@ import org.springframework.util.Assert;
  * @author Christoph Strobl
  * @since 2.1
  */
-@EqualsAndHashCode
-@ToString
 class SimpleMessage<S, T> implements Message<S, T> {
 
 	private @Nullable final S raw;
@@ -75,4 +71,35 @@ class SimpleMessage<S, T> implements Message<S, T> {
 	public MessageProperties getProperties() {
 		return properties;
 	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o)
+			return true;
+		if (o == null || getClass() != o.getClass())
+			return false;
+
+		SimpleMessage<?, ?> that = (SimpleMessage<?, ?>) o;
+
+		if (!ObjectUtils.nullSafeEquals(this.raw, that.raw)) {
+			return false;
+		}
+		if (!ObjectUtils.nullSafeEquals(this.body, that.body)) {
+			return false;
+		}
+		return ObjectUtils.nullSafeEquals(this.properties, that.properties);
+	}
+
+	@Override
+	public int hashCode() {
+		int result = ObjectUtils.nullSafeHashCode(raw);
+		result = 31 * result + ObjectUtils.nullSafeHashCode(body);
+		result = 31 * result + ObjectUtils.nullSafeHashCode(properties);
+		return result;
+	}
+
+	public String toString() {
+		return "SimpleMessage(raw=" + this.getRaw() + ", body=" + this.getBody() + ", properties=" + this.getProperties()
+				+ ")";
+	}
 }

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

@@ -67,6 +67,7 @@ public class BasicUpdate extends Update {
 	}
 
 	@Override
+	@Deprecated
 	public Update pushAll(String key, Object[] values) {
 		Document keyValue = new Document();
 		keyValue.put(key, values);

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

@@ -15,11 +15,6 @@
  */
 package org.springframework.data.mongodb.core.query;
 
-import lombok.AccessLevel;
-import lombok.AllArgsConstructor;
-import lombok.Getter;
-import lombok.RequiredArgsConstructor;
-
 import java.util.Locale;
 import java.util.Optional;
 
@@ -515,8 +510,6 @@ public class Collation {
 	 *
 	 * @since 2.0
 	 */
-	@AllArgsConstructor(access = AccessLevel.PACKAGE)
-	@Getter
 	static class ICUComparisonLevel implements ComparisonLevel {
 
 		private final int level;
@@ -526,6 +519,24 @@ public class Collation {
 		ICUComparisonLevel(int level) {
 			this(level, Optional.empty(), Optional.empty());
 		}
+
+		ICUComparisonLevel(int level, Optional<CaseFirst> caseFirst, Optional<Boolean> caseLevel) {
+			this.level = level;
+			this.caseFirst = caseFirst;
+			this.caseLevel = caseLevel;
+		}
+
+		public int getLevel() {
+			return this.level;
+		}
+
+		public Optional<CaseFirst> getCaseFirst() {
+			return this.caseFirst;
+		}
+
+		public Optional<Boolean> getCaseLevel() {
+			return this.caseLevel;
+		}
 	}
 
 	/**
@@ -650,7 +661,6 @@ public class Collation {
 	/**
 	 * @since 2.0
 	 */
-	@RequiredArgsConstructor(access = AccessLevel.PRIVATE)
 	public static class CaseFirst {
 
 		private static final CaseFirst UPPER = new CaseFirst("upper");
@@ -659,6 +669,10 @@ public class Collation {
 
 		private final String state;
 
+		private CaseFirst(String state) {
+			this.state = state;
+		}
+
 		/**
 		 * Sort uppercase before lowercase.
 		 *
@@ -690,7 +704,6 @@ public class Collation {
 	/**
 	 * @since 2.0
 	 */
-	@RequiredArgsConstructor(access = AccessLevel.PACKAGE)
 	public static class Alternate {
 
 		private static final Alternate NON_IGNORABLE = new Alternate("non-ignorable", Optional.empty());
@@ -698,6 +711,11 @@ public class Collation {
 		final String alternate;
 		final Optional<String> maxVariable;
 
+		Alternate(String alternate, Optional<String> maxVariable) {
+			this.alternate = alternate;
+			this.maxVariable = maxVariable;
+		}
+
 		/**
 		 * Consider Whitespace and punctuation as base characters.
 		 *
@@ -761,12 +779,17 @@ public class Collation {
 	 * @see <a href="http://site.icu-project.org">ICU - International Components for Unicode</a>
 	 * @since 2.0
 	 */
-	@RequiredArgsConstructor(access = AccessLevel.PRIVATE)
 	public static class CollationLocale {
 
 		private final String language;
 		private final Optional<String> variant;
 
+		private CollationLocale(String language, Optional<String> variant) {
+
+			this.language = language;
+			this.variant = variant;
+		}
+
 		/**
 		 * Create new {@link CollationLocale} for given language.
 		 *

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

@@ -20,10 +20,8 @@ import static org.springframework.util.ObjectUtils.*;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.List;
-import java.util.Map;
 import java.util.Map.Entry;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
@@ -60,7 +58,6 @@ import com.mongodb.BasicDBList;
  * @author Christoph Strobl
  * @author Mark Paluch
  * @author Andreas Zink
- * @author Clément Petit
  */
 public class Criteria implements CriteriaDefinition {
 
@@ -127,12 +124,7 @@ public class Criteria implements CriteriaDefinition {
 	}
 
 	/**
-	 * Static factory method to create a {@link Criteria} matching an example object. <br />
-	 * By default the {@link Example} uses typed matching restricting it to probe assignable types. For example, when
-	 * sticking with the default type key ({@code _class}), the query has restrictions such as
-	 * <code>_class : &#123; $in : [com.acme.Person] &#125; </code>. <br />
-	 * To avoid the above mentioned type restriction use an {@link UntypedExampleMatcher} with
-	 * {@link Example#of(Object, org.springframework.data.domain.ExampleMatcher)}.
+	 * Static factory method to create a {@link Criteria} matching an example object.
 	 *
 	 * @param example must not be {@literal null}.
 	 * @return new instance of {@link Criteria}.
@@ -623,15 +615,8 @@ public class Criteria implements CriteriaDefinition {
 	 */
 	public Criteria alike(Example<?> sample) {
 
-		if (StringUtils.hasText(this.getKey())) {
-
-			criteria.put("$example", sample);
-			return this;
-		}
-
-		Criteria exampleCriteria = new Criteria();
-		exampleCriteria.criteria.put("$example", sample);
-		return registerCriteriaChainElement(exampleCriteria);
+		criteria.put("$example", sample);
+		return this;
 	}
 
 	/**
@@ -898,15 +883,15 @@ public class Criteria implements CriteriaDefinition {
 	 * @param right
 	 * @return
 	 */
-	private boolean isEqual(@Nullable Object left, @Nullable Object right) {
+	private boolean isEqual(Object left, Object right) {
 
 		if (left == null) {
 			return right == null;
 		}
 
-		if (left instanceof Pattern) {
+		if (Pattern.class.isInstance(left)) {
 
-			if (!(right instanceof Pattern)) {
+			if (!Pattern.class.isInstance(right)) {
 				return false;
 			}
 
@@ -917,52 +902,6 @@ public class Criteria implements CriteriaDefinition {
 					&& leftPattern.flags() == rightPattern.flags();
 		}
 
-		if (left instanceof Document) {
-
-			if (!(right instanceof Document)) {
-				return false;
-			}
-
-			Document leftDocument = (Document) left;
-			Document rightDocument = (Document) right;
-			Iterator<Entry<String, Object>> leftIterator = leftDocument.entrySet().iterator();
-			Iterator<Entry<String, Object>> rightIterator = rightDocument.entrySet().iterator();
-
-			while (leftIterator.hasNext() && rightIterator.hasNext()) {
-
-				Map.Entry<String, Object> leftEntry = leftIterator.next();
-				Map.Entry<String, Object> rightEntry = rightIterator.next();
-
-				if (!isEqual(leftEntry.getKey(), rightEntry.getKey())
-						|| !isEqual(leftEntry.getValue(), rightEntry.getValue())) {
-					return false;
-				}
-			}
-
-			return !leftIterator.hasNext() && !rightIterator.hasNext();
-		}
-
-		if (Collection.class.isAssignableFrom(left.getClass())) {
-
-			if (!Collection.class.isAssignableFrom(right.getClass())) {
-				return false;
-			}
-
-			Collection<?> leftCollection = (Collection<?>) left;
-			Collection<?> rightCollection = (Collection<?>) right;
-			Iterator<?> leftIterator = leftCollection.iterator();
-			Iterator<?> rightIterator = rightCollection.iterator();
-
-			while (leftIterator.hasNext() && rightIterator.hasNext()) {
-
-				if (!isEqual(leftIterator.next(), rightIterator.next())) {
-					return false;
-				}
-			}
-
-			return !leftIterator.hasNext() && !rightIterator.hasNext();
-		}
-
 		return ObjectUtils.nullSafeEquals(left, right);
 	}
 

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

@@ -15,54 +15,134 @@
  */
 package org.springframework.data.mongodb.core.query;
 
-import lombok.EqualsAndHashCode;
-
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Map.Entry;
 
 import org.bson.Document;
+
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 /**
+ * Field projection.
+ *
  * @author Thomas Risberg
  * @author Oliver Gierke
  * @author Patryk Wasik
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Owen Q
  */
-@EqualsAndHashCode
 public class Field {
 
-	private final Map<String, Integer> criteria = new HashMap<String, Integer>();
-	private final Map<String, Object> slices = new HashMap<String, Object>();
-	private final Map<String, Criteria> elemMatchs = new HashMap<String, Criteria>();
+	private final Map<String, Integer> criteria = new HashMap<>();
+	private final Map<String, Object> slices = new HashMap<>();
+	private final Map<String, Criteria> elemMatchs = new HashMap<>();
 	private @Nullable String positionKey;
 	private int positionValue;
 
-	public Field include(String key) {
-		criteria.put(key, Integer.valueOf(1));
+	/**
+	 * Include a single {@code field} to be returned by the query operation.
+	 *
+	 * @param field the document field name to be included.
+	 * @return {@code this} field projection instance.
+	 */
+	public Field include(String field) {
+
+		Assert.notNull(field, "Key must not be null!");
+
+		criteria.put(field, 1);
+
 		return this;
 	}
 
-	public Field exclude(String key) {
-		criteria.put(key, Integer.valueOf(0));
+	/**
+	 * Include one or more {@code fields} to be returned by the query operation.
+	 *
+	 * @param fields the document field names to be included.
+	 * @return {@code this} field projection instance.
+	 * @since 3.1
+	 */
+	public Field include(String... fields) {
+
+		Assert.notNull(fields, "Keys must not be null!");
+
+		for (String key : fields) {
+			criteria.put(key, 1);
+		}
+
 		return this;
 	}
 
-	public Field slice(String key, int size) {
-		slices.put(key, Integer.valueOf(size));
+	/**
+	 * Exclude a single {@code field} from being returned by the query operation.
+	 *
+	 * @param field the document field name to be included.
+	 * @return {@code this} field projection instance.
+	 */
+	public Field exclude(String field) {
+
+		Assert.notNull(field, "Key must not be null!");
+
+		criteria.put(field, 0);
+
 		return this;
 	}
 
-	public Field slice(String key, int offset, int size) {
-		slices.put(key, new Integer[] { Integer.valueOf(offset), Integer.valueOf(size) });
+	/**
+	 * Exclude one or more {@code fields} from being returned by the query operation.
+	 *
+	 * @param fields the document field names to be included.
+	 * @return {@code this} field projection instance.
+	 * @since 3.1
+	 */
+	public Field exclude(String... fields) {
+
+		Assert.notNull(fields, "Keys must not be null!");
+
+		for (String key : fields) {
+			criteria.put(key, 0);
+		}
+
 		return this;
 	}
 
-	public Field elemMatch(String key, Criteria elemMatchCriteria) {
-		elemMatchs.put(key, elemMatchCriteria);
+	/**
+	 * Project a {@code $slice} of the array {@code field} using the first {@code size} elements.
+	 *
+	 * @param field the document field name to project, must be an array field.
+	 * @param size the number of elements to include.
+	 * @return {@code this} field projection instance.
+	 */
+	public Field slice(String field, int size) {
+
+		Assert.notNull(field, "Key must not be null!");
+
+		slices.put(field, size);
+
+		return this;
+	}
+
+	/**
+	 * Project a {@code $slice} of the array {@code field} using the first {@code size} elements starting at
+	 * {@code offset}.
+	 *
+	 * @param field the document field name to project, must be an array field.
+	 * @param offset the offset to start at.
+	 * @param size the number of elements to include.
+	 * @return {@code this} field projection instance.
+	 */
+	public Field slice(String field, int offset, int size) {
+
+		slices.put(field, new Integer[] { offset, size });
+		return this;
+	}
+
+	public Field elemMatch(String field, Criteria elemMatchCriteria) {
+
+		elemMatchs.put(field, elemMatchCriteria);
 		return this;
 	}
 
@@ -72,7 +152,7 @@ public class Field {
 	 *
 	 * @param field query array field, must not be {@literal null} or empty.
 	 * @param value
-	 * @return
+	 * @return {@code this} field projection instance.
 	 */
 	public Field position(String field, int value) {
 
@@ -103,4 +183,40 @@ public class Field {
 
 		return document;
 	}
+
+	@Override
+	public boolean equals(Object o) {
+
+		if (this == o)
+			return true;
+		if (o == null || getClass() != o.getClass())
+			return false;
+
+		Field field = (Field) o;
+
+		if (positionValue != field.positionValue) {
+			return false;
+		}
+		if (!ObjectUtils.nullSafeEquals(criteria, field.criteria)) {
+			return false;
+		}
+		if (!ObjectUtils.nullSafeEquals(slices, field.slices)) {
+			return false;
+		}
+		if (!ObjectUtils.nullSafeEquals(elemMatchs, field.elemMatchs)) {
+			return false;
+		}
+		return ObjectUtils.nullSafeEquals(positionKey, field.positionKey);
+	}
+
+	@Override
+	public int hashCode() {
+
+		int result = ObjectUtils.nullSafeHashCode(criteria);
+		result = 31 * result + ObjectUtils.nullSafeHashCode(slices);
+		result = 31 * result + ObjectUtils.nullSafeHashCode(elemMatchs);
+		result = 31 * result + ObjectUtils.nullSafeHashCode(positionKey);
+		result = 31 * result + positionValue;
+		return result;
+	}
 }

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

@@ -181,7 +181,11 @@ public class Meta {
 	}
 
 	/**
-	 * Set to {@literal true}, to allow aggregation stages to write data to disk.
+	 * Enables writing to temporary files for aggregation stages and queries. When set to {@literal true}, aggregation
+	 * stages can write data to the {@code _tmp} subdirectory in the {@code dbPath} directory.
+	 * <p>
+	 * Starting in MongoDB 4.2, the profiler log messages and diagnostic log messages includes a {@code usedDisk}
+	 * indicator if any aggregation stage wrote data to temporary files due to memory restrictions.
 	 *
 	 * @param allowDiskUse use {@literal null} for server defaults.
 	 * @since 3.0

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

@@ -17,7 +17,6 @@ package org.springframework.data.mongodb.core.query;
 
 import java.util.regex.Pattern;
 
-import org.bson.BsonRegularExpression;
 import org.springframework.lang.Nullable;
 
 /**
@@ -103,15 +102,6 @@ public enum MongoRegexCreator {
 		}
 	}
 
-	/**
-	 * @param source
-	 * @return
-	 * @since 2.2.14
-	 */
-	public Object toCaseInsensitiveMatch(Object source) {
-		return source instanceof String ? new BsonRegularExpression(Pattern.quote((String) source), "i") : source;
-	}
-
 	private String prepareAndEscapeStringBeforeApplyingLikeRegex(String source, MatchMode matcherType) {
 
 		if (MatchMode.REGEX == matcherType) {

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

@@ -43,7 +43,7 @@ import org.springframework.util.ObjectUtils;
  * <p />
  * In other words: <br />
  * Assume you've got 5 Documents like the ones below <br />
- *
+ * 
  * <pre>
  *     <code>
  * {
@@ -73,10 +73,10 @@ import org.springframework.util.ObjectUtils;
  * }
  *      </code>
  * </pre>
- *
+ * 
  * Fetching all Documents within a 400 Meter radius from {@code [-73.99171, 40.738868] } would look like this using
  * {@literal GeoJSON}:
- *
+ * 
  * <pre>
  *     <code>
  * {
@@ -92,9 +92,9 @@ import org.springframework.util.ObjectUtils;
  *
  *     </code>
  * </pre>
- *
+ * 
  * resulting in the following 3 Documents.
- *
+ * 
  * <pre>
  *     <code>
  * {
@@ -117,11 +117,11 @@ import org.springframework.util.ObjectUtils;
  * }
  *     </code>
  * </pre>
- *
+ * 
  * Using legacy coordinate pairs one operates upon radians as discussed before. Assume we use {@link Metrics#KILOMETERS}
  * when constructing the geoNear command. The {@link Metric} will make sure the distance multiplier is set correctly, so
  * the command is rendered like
- *
+ * 
  * <pre>
  *     <code>
  * {
@@ -137,12 +137,12 @@ import org.springframework.util.ObjectUtils;
  * }
  *     </code>
  * </pre>
- *
+ * 
  * Please note the calculated distance now uses {@literal Kilometers} instead of {@literal Meters} as unit of measure,
  * so we need to take it times 1000 to match up to {@literal Meters} as in the {@literal GeoJSON} variant. <br />
  * Still as we've been requesting the {@link Distance} in {@link Metrics#KILOMETERS} the {@link Distance#getValue()}
  * reflects exactly this.
- *
+ * 
  * <pre>
  *     <code>
  * {
@@ -558,7 +558,7 @@ public final class NearQuery {
 
 	/**
 	 * Get the {@link Collation} to use along with the {@link #query(Query)}.
-	 *
+	 * 
 	 * @return the {@link Collation} if set. {@literal null} otherwise.
 	 * @since 2.2
 	 */

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

@@ -46,6 +46,7 @@ import org.springframework.util.Assert;
  * @author Thomas Darimont
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Anton Barkan
  */
 public class Query {
 
@@ -372,6 +373,24 @@ public class Query {
 		return this;
 	}
 
+	/**
+	 * Enables writing to temporary files for aggregation stages and queries. When set to {@literal true}, aggregation
+	 * stages can write data to the {@code _tmp} subdirectory in the {@code dbPath} directory.
+	 * <p>
+	 * Starting in MongoDB 4.2, the profiler log messages and diagnostic log messages includes a {@code usedDisk}
+	 * indicator if any aggregation stage wrote data to temporary files due to memory restrictions.
+	 *
+	 * @param allowDiskUse
+	 * @return this.
+	 * @see Meta#setAllowDiskUse(Boolean)
+	 * @since 3.2
+	 */
+	public Query allowDiskUse(boolean allowDiskUse) {
+
+		meta.setAllowDiskUse(allowDiskUse);
+		return this;
+	}
+
 	/**
 	 * Set the number of documents to return in each response batch. <br />
 	 * Use {@literal 0 (zero)} for no limit. A <strong>negative limit</strong> closes the cursor after returning a single

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

@@ -15,14 +15,10 @@
  */
 package org.springframework.data.mongodb.core.query;
 
-import lombok.AccessLevel;
-import lombok.EqualsAndHashCode;
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-
 import java.util.Set;
 
 import org.springframework.data.domain.ExampleMatcher;
+import org.springframework.util.ObjectUtils;
 
 /**
  * {@link ExampleMatcher} implementation for query by example (QBE). Unlike plain {@link ExampleMatcher} this untyped
@@ -33,11 +29,13 @@ import org.springframework.data.domain.ExampleMatcher;
  * @author Mark Paluch
  * @since 2.0
  */
-@EqualsAndHashCode
-@RequiredArgsConstructor(access = AccessLevel.PRIVATE)
 public class UntypedExampleMatcher implements ExampleMatcher {
 
-	private final @NonNull ExampleMatcher delegate;
+	private final ExampleMatcher delegate;
+
+	private UntypedExampleMatcher(ExampleMatcher delegate) {
+		this.delegate = delegate;
+	}
 
 	/*
 	 * (non-Javadoc)
@@ -224,4 +222,21 @@ public class UntypedExampleMatcher implements ExampleMatcher {
 		return delegate.getMatchMode();
 	}
 
+	@Override
+	public boolean equals(Object o) {
+
+		if (this == o)
+			return true;
+		if (o == null || getClass() != o.getClass())
+			return false;
+
+		UntypedExampleMatcher that = (UntypedExampleMatcher) o;
+
+		return ObjectUtils.nullSafeEquals(delegate, that.delegate);
+	}
+
+	@Override
+	public int hashCode() {
+		return ObjectUtils.nullSafeHashCode(delegate);
+	}
 }

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

@@ -15,10 +15,8 @@
  */
 package org.springframework.data.mongodb.core.schema;
 
-import lombok.AllArgsConstructor;
-import lombok.NonNull;
-
 import org.bson.Document;
+import org.springframework.util.Assert;
 
 /**
  * Value object representing a MongoDB-specific JSON schema which is the default {@link MongoJsonSchema} implementation.
@@ -27,10 +25,15 @@ import org.bson.Document;
  * @author Mark Paluch
  * @since 2.1
  */
-@AllArgsConstructor
 class DefaultMongoJsonSchema implements MongoJsonSchema {
 
-	private final @NonNull JsonSchemaObject root;
+	private final JsonSchemaObject root;
+
+	DefaultMongoJsonSchema(JsonSchemaObject root) {
+
+		Assert.notNull(root, "Root must not be null!");
+		this.root = root;
+	}
 
 	/*
 	 * (non-Javadoc)

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

@@ -15,10 +15,8 @@
  */
 package org.springframework.data.mongodb.core.schema;
 
-import lombok.AllArgsConstructor;
-import lombok.NonNull;
-
 import org.bson.Document;
+import org.springframework.util.Assert;
 
 /**
  * JSON schema backed by a {@link org.bson.Document} object.
@@ -26,10 +24,15 @@ import org.bson.Document;
  * @author Mark Paluch
  * @since 2.1
  */
-@AllArgsConstructor
 class DocumentJsonSchema implements MongoJsonSchema {
 
-	private final @NonNull Document document;
+	private final Document document;
+
+	DocumentJsonSchema(Document document) {
+
+		Assert.notNull(document, "Document must not be null!");
+		this.document = document;
+	}
 
 	/*
 	 * (non-Javadoc)

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

@@ -15,9 +15,6 @@
  */
 package org.springframework.data.mongodb.core.schema;
 
-import lombok.EqualsAndHashCode;
-import lombok.RequiredArgsConstructor;
-
 import java.math.BigDecimal;
 import java.util.Arrays;
 import java.util.Collection;
@@ -44,6 +41,7 @@ import org.springframework.data.mongodb.core.schema.TypedJsonSchemaObject.String
 import org.springframework.data.mongodb.core.schema.TypedJsonSchemaObject.TimestampJsonSchemaObject;
 import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
+import org.springframework.util.ObjectUtils;
 
 /**
  * Interface that can be implemented by objects that know how to serialize themselves to JSON schema using
@@ -500,12 +498,14 @@ public interface JsonSchemaObject {
 		 * @author Christpoh Strobl
 		 * @since 2.1
 		 */
-		@RequiredArgsConstructor
-		@EqualsAndHashCode
 		class JsonType implements Type {
 
 			private final String name;
 
+			public JsonType(String name) {
+				this.name = name;
+			}
+
 			/*
 			 * (non-Javadoc)
 			 * @see org.springframework.data.mongodb.core.schema.JsonSchemaObject.Type#representation()
@@ -523,18 +523,37 @@ public interface JsonSchemaObject {
 			public String value() {
 				return name;
 			}
+
+			@Override
+			public boolean equals(Object o) {
+				if (this == o)
+					return true;
+				if (o == null || getClass() != o.getClass())
+					return false;
+
+				JsonType jsonType = (JsonType) o;
+
+				return ObjectUtils.nullSafeEquals(name, jsonType.name);
+			}
+
+			@Override
+			public int hashCode() {
+				return ObjectUtils.nullSafeHashCode(name);
+			}
 		}
 
 		/**
 		 * @author Christpoh Strobl
 		 * @since 2.1
 		 */
-		@RequiredArgsConstructor
-		@EqualsAndHashCode
 		class BsonType implements Type {
 
 			private final String name;
 
+			BsonType(String name) {
+				this.name = name;
+			}
+
 			/*
 			 * (non-Javadoc)
 			 * @see org.springframework.data.mongodb.core.schema.JsonSchemaObject.Type#representation()
@@ -552,6 +571,24 @@ public interface JsonSchemaObject {
 			public String value() {
 				return name;
 			}
+
+			@Override
+			public boolean equals(Object o) {
+
+				if (this == o)
+					return true;
+				if (o == null || getClass() != o.getClass())
+					return false;
+
+				BsonType bsonType = (BsonType) o;
+
+				return ObjectUtils.nullSafeEquals(name, bsonType.name);
+			}
+
+			@Override
+			public int hashCode() {
+				return ObjectUtils.nullSafeHashCode(name);
+			}
 		}
 	}
 }

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

@@ -15,9 +15,6 @@
  */
 package org.springframework.data.mongodb.core.schema;
 
-import lombok.AccessLevel;
-import lombok.RequiredArgsConstructor;
-
 import org.springframework.data.mongodb.core.schema.TypedJsonSchemaObject.NumericJsonSchemaObject;
 import org.springframework.data.mongodb.core.schema.TypedJsonSchemaObject.ObjectJsonSchemaObject;
 import org.springframework.data.mongodb.core.schema.IdentifiableJsonSchemaProperty.*;
@@ -239,11 +236,14 @@ public interface JsonSchemaProperty extends JsonSchemaObject {
 	/**
 	 * Builder for {@link IdentifiableJsonSchemaProperty}.
 	 */
-	@RequiredArgsConstructor(access = AccessLevel.PACKAGE)
 	class JsonSchemaPropertyBuilder {
 
 		private final String identifier;
 
+		JsonSchemaPropertyBuilder(String identifier) {
+			this.identifier = identifier;
+		}
+
 		/**
 		 * Configure a {@link Type} for the property.
 		 *

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

@@ -15,9 +15,6 @@
  */
 package org.springframework.data.mongodb.core.schema;
 
-import lombok.AccessLevel;
-import lombok.RequiredArgsConstructor;
-
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
@@ -182,7 +179,6 @@ public class UntypedJsonSchemaObject implements JsonSchemaObject {
 	 * @author Christoph Strobl
 	 * @since 2.1
 	 */
-	@RequiredArgsConstructor(access = AccessLevel.PACKAGE)
 	static class Restrictions {
 
 		private final Collection<? extends Object> possibleValues;
@@ -191,6 +187,16 @@ public class UntypedJsonSchemaObject implements JsonSchemaObject {
 		private final Collection<JsonSchemaObject> oneOf;
 		private final @Nullable JsonSchemaObject notMatch;
 
+		Restrictions(Collection<? extends Object> possibleValues, Collection<JsonSchemaObject> allOf,
+				Collection<JsonSchemaObject> anyOf, Collection<JsonSchemaObject> oneOf, JsonSchemaObject notMatch) {
+
+			this.possibleValues = possibleValues;
+			this.allOf = allOf;
+			this.anyOf = anyOf;
+			this.oneOf = oneOf;
+			this.notMatch = notMatch;
+		}
+
 		/**
 		 * @return new empty {@link Restrictions}.
 		 */

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

@@ -15,15 +15,12 @@
  */
 package org.springframework.data.mongodb.core.validation;
 
-import lombok.AccessLevel;
-import lombok.EqualsAndHashCode;
-import lombok.RequiredArgsConstructor;
-
 import org.bson.Document;
 import org.springframework.data.mongodb.core.query.Criteria;
 import org.springframework.data.mongodb.core.query.CriteriaDefinition;
 import org.springframework.data.mongodb.core.query.SerializationUtils;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 /**
  * {@link Validator} implementation based on {@link CriteriaDefinition query expressions}.
@@ -34,12 +31,14 @@ import org.springframework.util.Assert;
  * @see Criteria
  * @see <a href="https://docs.mongodb.com/manual/core/schema-validation/#query-expressions">Schema Validation</a>
  */
-@RequiredArgsConstructor(access = AccessLevel.PRIVATE)
-@EqualsAndHashCode
 class CriteriaValidator implements Validator {
 
 	private final CriteriaDefinition criteria;
 
+	private CriteriaValidator(CriteriaDefinition criteria) {
+		this.criteria = criteria;
+	}
+
 	/**
 	 * Creates a new {@link Validator} object, which is basically setup of query operators, based on a
 	 * {@link CriteriaDefinition} instance.
@@ -72,4 +71,21 @@ class CriteriaValidator implements Validator {
 	public String toString() {
 		return SerializationUtils.serializeToJsonSafely(toDocument());
 	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o)
+			return true;
+		if (o == null || getClass() != o.getClass())
+			return false;
+
+		CriteriaValidator that = (CriteriaValidator) o;
+
+		return ObjectUtils.nullSafeEquals(criteria, that.criteria);
+	}
+
+	@Override
+	public int hashCode() {
+		return ObjectUtils.nullSafeHashCode(criteria);
+	}
 }

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

@@ -15,13 +15,10 @@
  */
 package org.springframework.data.mongodb.core.validation;
 
-import lombok.AccessLevel;
-import lombok.EqualsAndHashCode;
-import lombok.RequiredArgsConstructor;
-
 import org.bson.Document;
 import org.springframework.data.mongodb.core.query.SerializationUtils;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 /**
  * Most trivial {@link Validator} implementation using plain {@link Document} to describe the desired document structure
@@ -32,12 +29,14 @@ import org.springframework.util.Assert;
  * @since 2.1
  * @see <a href="https://docs.mongodb.com/manual/core/schema-validation/">Schema Validation</a>
  */
-@RequiredArgsConstructor(access = AccessLevel.PRIVATE)
-@EqualsAndHashCode
 class DocumentValidator implements Validator {
 
 	private final Document validatorObject;
 
+	private DocumentValidator(Document validatorObject) {
+		this.validatorObject = validatorObject;
+	}
+
 	/**
 	 * Create new {@link DocumentValidator} defining validation rules via a plain {@link Document}.
 	 *
@@ -68,4 +67,22 @@ class DocumentValidator implements Validator {
 	public String toString() {
 		return SerializationUtils.serializeToJsonSafely(validatorObject);
 	}
+
+	@Override
+	public boolean equals(Object o) {
+
+		if (this == o)
+			return true;
+		if (o == null || getClass() != o.getClass())
+			return false;
+
+		DocumentValidator that = (DocumentValidator) o;
+
+		return ObjectUtils.nullSafeEquals(validatorObject, that.validatorObject);
+	}
+
+	@Override
+	public int hashCode() {
+		return ObjectUtils.nullSafeHashCode(validatorObject);
+	}
 }

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

@@ -15,14 +15,11 @@
  */
 package org.springframework.data.mongodb.core.validation;
 
-import lombok.AccessLevel;
-import lombok.EqualsAndHashCode;
-import lombok.RequiredArgsConstructor;
-
 import org.bson.Document;
 import org.springframework.data.mongodb.core.query.SerializationUtils;
 import org.springframework.data.mongodb.core.schema.MongoJsonSchema;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 /**
  * {@link Validator} implementation based on {@link MongoJsonSchema JSON Schema}.
@@ -32,12 +29,14 @@ import org.springframework.util.Assert;
  * @since 2.1
  * @see <a href="https://docs.mongodb.com/manual/core/schema-validation/#json-schema">Schema Validation</a>
  */
-@RequiredArgsConstructor(access = AccessLevel.PRIVATE)
-@EqualsAndHashCode
 class JsonSchemaValidator implements Validator {
 
 	private final MongoJsonSchema schema;
 
+	private JsonSchemaValidator(MongoJsonSchema schema) {
+		this.schema = schema;
+	}
+
 	/**
 	 * Create new {@link JsonSchemaValidator} defining validation rules via {@link MongoJsonSchema}.
 	 *
@@ -68,4 +67,22 @@ class JsonSchemaValidator implements Validator {
 	public String toString() {
 		return SerializationUtils.serializeToJsonSafely(toDocument());
 	}
+
+	@Override
+	public boolean equals(Object o) {
+
+		if (this == o)
+			return true;
+		if (o == null || getClass() != o.getClass())
+			return false;
+
+		JsonSchemaValidator that = (JsonSchemaValidator) o;
+
+		return ObjectUtils.nullSafeEquals(schema, that.schema);
+	}
+
+	@Override
+	public int hashCode() {
+		return ObjectUtils.nullSafeHashCode(schema);
+	}
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/gridfs/GridFsOperations.java

@@ -129,7 +129,7 @@ public interface GridFsOperations extends ResourcePatternResolver {
 	 *
 	 * @param content must not be {@literal null}.
 	 * @param filename must not be {@literal null} or empty.
-	 * @param contentType can be {@literal null}.
+	 * @param contentType can be {@literal null}. If not empty, may override content type within {@literal metadata}.
 	 * @param metadata can be {@literal null}.
 	 * @return the {@link ObjectId} of the {@link com.mongodb.client.gridfs.model.GridFSFile} just created.
 	 */
@@ -140,12 +140,12 @@ public interface GridFsOperations extends ResourcePatternResolver {
 		if (StringUtils.hasText(filename)) {
 			uploadBuilder.filename(filename);
 		}
-		if (StringUtils.hasText(contentType)) {
-			uploadBuilder.contentType(contentType);
-		}
 		if (!ObjectUtils.isEmpty(metadata)) {
 			uploadBuilder.metadata(metadata);
 		}
+		if (StringUtils.hasText(contentType)) {
+			uploadBuilder.contentType(contentType);
+		}
 
 		return store(uploadBuilder.build());
 	}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/gridfs/ReactiveGridFsOperations.java

@@ -135,7 +135,7 @@ public interface ReactiveGridFsOperations {
 	 *
 	 * @param content must not be {@literal null}.
 	 * @param filename must not be {@literal null} or empty.
-	 * @param contentType can be {@literal null}.
+	 * @param contentType can be {@literal null}. If not empty, may override content type within {@literal metadata}.
 	 * @param metadata can be {@literal null}.
 	 * @return a {@link Mono} emitting the {@link ObjectId} of the {@link com.mongodb.client.gridfs.model.GridFSFile} just
 	 *         created.
@@ -148,12 +148,12 @@ public interface ReactiveGridFsOperations {
 		if (StringUtils.hasText(filename)) {
 			uploadBuilder.filename(filename);
 		}
-		if (StringUtils.hasText(contentType)) {
-			uploadBuilder.contentType(contentType);
-		}
 		if (!ObjectUtils.isEmpty(metadata)) {
 			uploadBuilder.metadata(metadata);
 		}
+		if (StringUtils.hasText(contentType)) {
+			uploadBuilder.contentType(contentType);
+		}
 
 		return store(uploadBuilder.build());
 	}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/MongoRepository.java

@@ -78,31 +78,16 @@ public interface MongoRepository<T, ID> extends PagingAndSortingRepository<T, ID
 	 */
 	<S extends T> List<S> insert(Iterable<S> entities);
 
-	/**
-	 * Returns all entities matching the given {@link Example}. In case no match could be found an empty {@link List} is
-	 * returned. <br />
-	 * By default the {@link Example} uses typed matching restricting it to probe assignable types. For example, when
-	 * sticking with the default type key ({@code _class}), the query has restrictions such as
-	 * <code>_class : &#123; $in : [com.acme.Person] &#125;</code>. <br />
-	 * To avoid the above mentioned type restriction use an {@link org.springframework.data.mongodb.core.query.UntypedExampleMatcher} with
-	 * {@link Example#of(Object, org.springframework.data.domain.ExampleMatcher)}.
-	 *
+	/*
+	 * (non-Javadoc)
 	 * @see org.springframework.data.repository.query.QueryByExampleExecutor#findAll(org.springframework.data.domain.Example)
 	 */
 	@Override
 	<S extends T> List<S> findAll(Example<S> example);
 
-	/**
-	 * Returns all entities matching the given {@link Example} applying the given {@link Sort}. In case no match could be
-	 * found an empty {@link List} is returned. <br />
-	 * By default the {@link Example} uses typed matching restricting it to probe assignable types. For example, when
-	 * sticking with the default type key ({@code _class}), the query has restrictions such as
-	 * <code>_class : &#123; $in : [com.acme.Person] &#125;</code>. <br />
-	 * To avoid the above mentioned type restriction use an {@link org.springframework.data.mongodb.core.query.UntypedExampleMatcher} with
-	 * {@link Example#of(Object, org.springframework.data.domain.ExampleMatcher)}.
-	 *
-	 * @see org.springframework.data.repository.query.QueryByExampleExecutor#findAll(org.springframework.data.domain.Example,
-	 *      org.springframework.data.domain.Sort)
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.repository.query.QueryByExampleExecutor#findAll(org.springframework.data.domain.Example, org.springframework.data.domain.Sort)
 	 */
 	@Override
 	<S extends T> List<S> findAll(Example<S> example, Sort sort);

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/ReactiveMongoRepository.java

@@ -64,33 +64,4 @@ public interface ReactiveMongoRepository<T, ID> extends ReactiveSortingRepositor
 	 */
 	<S extends T> Flux<S> insert(Publisher<S> entities);
 
-	/**
-	 * Returns all entities matching the given {@link Example}. In case no match could be found an empty {@link Flux} is
-	 * returned. <br />
-	 * By default the {@link Example} uses typed matching restricting it to probe assignable types. For example, when
-	 * sticking with the default type key ({@code _class}), the query has restrictions such as
-	 * <code>_class : &#123; $in : [com.acme.Person] &#125;</code>. <br />
-	 * To avoid the above mentioned type restriction use an {@link org.springframework.data.mongodb.core.query.UntypedExampleMatcher} with
-	 * {@link Example#of(Object, org.springframework.data.domain.ExampleMatcher)}.
-	 *
-	 * @see org.springframework.data.repository.query.ReactiveQueryByExampleExecutor#findAll(org.springframework.data.domain.Example)
-	 */
-	@Override
-	<S extends T> Flux<S> findAll(Example<S> example);
-
-	/**
-	 * Returns all entities matching the given {@link Example} applying the given {@link Sort}. In case no match could be
-	 * found an empty {@link Flux} is returned. <br />
-	 * By default the {@link Example} uses typed matching restricting it to probe assignable types. For example, when
-	 * sticking with the default type key ({@code _class}), the query has restrictions such as
-	 * <code>_class : &#123; $in : [com.acme.Person] &#125;</code>. <br />
-	 * To avoid the above mentioned type restriction use an {@link org.springframework.data.mongodb.core.query.UntypedExampleMatcher} with
-	 * {@link Example#of(Object, org.springframework.data.domain.ExampleMatcher)}.
-	 *
-	 * @see org.springframework.data.repository.query.ReactiveQueryByExampleExecutor#findAll(org.springframework.data.domain.Example,
-	 *      org.springframework.data.domain.Sort)
-	 */
-	@Override
-	<S extends T> Flux<S> findAll(Example<S> example, Sort sort);
-
 }

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/AbstractMongoQuery.java

@@ -16,6 +16,8 @@
 package org.springframework.data.mongodb.repository.query;
 
 import org.bson.Document;
+import org.bson.codecs.configuration.CodecRegistry;
+import org.springframework.data.mapping.model.SpELExpressionEvaluator;
 import org.springframework.data.mongodb.core.ExecutableFindOperation.ExecutableFind;
 import org.springframework.data.mongodb.core.ExecutableFindOperation.FindWithQuery;
 import org.springframework.data.mongodb.core.ExecutableFindOperation.TerminatingFind;
@@ -30,10 +32,14 @@ import org.springframework.data.repository.query.ParameterAccessor;
 import org.springframework.data.repository.query.QueryMethodEvaluationContextProvider;
 import org.springframework.data.repository.query.RepositoryQuery;
 import org.springframework.data.repository.query.ResultProcessor;
-import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.data.spel.ExpressionDependencies;
+import org.springframework.expression.EvaluationContext;
+import org.springframework.expression.ExpressionParser;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
+import com.mongodb.client.MongoDatabase;
+
 /**
  * Base class for {@link RepositoryQuery} implementations for Mongo.
  *
@@ -47,7 +53,7 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 	private final MongoQueryMethod method;
 	private final MongoOperations operations;
 	private final ExecutableFind<?> executableFind;
-	private final SpelExpressionParser expressionParser;
+	private final ExpressionParser expressionParser;
 	private final QueryMethodEvaluationContextProvider evaluationContextProvider;
 
 	/**
@@ -58,7 +64,7 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 	 * @param expressionParser must not be {@literal null}.
 	 * @param evaluationContextProvider must not be {@literal null}.
 	 */
-	public AbstractMongoQuery(MongoQueryMethod method, MongoOperations operations, SpelExpressionParser expressionParser,
+	public AbstractMongoQuery(MongoQueryMethod method, MongoOperations operations, ExpressionParser expressionParser,
 			QueryMethodEvaluationContextProvider evaluationContextProvider) {
 
 		Assert.notNull(operations, "MongoOperations must not be null!");
@@ -208,6 +214,29 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 		return applyQueryMetaAttributesWhenPresent(createQuery(accessor));
 	}
 
+	/**
+	 * Obtain a the {@link EvaluationContext} suitable to evaluate expressions backed by the given dependencies.
+	 *
+	 * @param dependencies must not be {@literal null}.
+	 * @param accessor must not be {@literal null}.
+	 * @return the {@link SpELExpressionEvaluator}.
+	 * @since 2.4
+	 */
+	protected SpELExpressionEvaluator getSpELExpressionEvaluatorFor(ExpressionDependencies dependencies,
+			ConvertingParameterAccessor accessor) {
+
+		return new DefaultSpELExpressionEvaluator(expressionParser, evaluationContextProvider
+				.getEvaluationContext(getQueryMethod().getParameters(), accessor.getValues(), dependencies));
+	}
+
+	/**
+	 * @return the {@link CodecRegistry} used.
+	 * @since 2.4
+	 */
+	protected CodecRegistry getCodecRegistry() {
+		return operations.execute(MongoDatabase::getCodecRegistry);
+	}
+
 	/**
 	 * Creates a {@link Query} instance using the given {@link ParameterAccessor}
 	 *

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/AbstractReactiveMongoQuery.java

@@ -15,13 +15,15 @@
  */
 package org.springframework.data.mongodb.repository.query;
 
-import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 import org.bson.Document;
+import org.bson.codecs.configuration.CodecRegistry;
 import org.reactivestreams.Publisher;
+
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.data.mapping.model.EntityInstantiators;
+import org.springframework.data.mapping.model.SpELExpressionEvaluator;
 import org.springframework.data.mongodb.core.MongoOperations;
 import org.springframework.data.mongodb.core.ReactiveFindOperation.FindWithProjection;
 import org.springframework.data.mongodb.core.ReactiveFindOperation.FindWithQuery;
@@ -33,14 +35,17 @@ import org.springframework.data.mongodb.repository.query.ReactiveMongoQueryExecu
 import org.springframework.data.mongodb.repository.query.ReactiveMongoQueryExecution.ResultProcessingConverter;
 import org.springframework.data.mongodb.repository.query.ReactiveMongoQueryExecution.ResultProcessingExecution;
 import org.springframework.data.repository.query.ParameterAccessor;
-import org.springframework.data.repository.query.QueryMethodEvaluationContextProvider;
+import org.springframework.data.repository.query.ReactiveQueryMethodEvaluationContextProvider;
 import org.springframework.data.repository.query.RepositoryQuery;
 import org.springframework.data.repository.query.ResultProcessor;
+import org.springframework.data.spel.ExpressionDependencies;
 import org.springframework.data.util.TypeInformation;
-import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.expression.ExpressionParser;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
+import com.mongodb.MongoClientSettings;
+
 /**
  * Base class for reactive {@link RepositoryQuery} implementations for MongoDB.
  *
@@ -54,8 +59,8 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 	private final ReactiveMongoOperations operations;
 	private final EntityInstantiators instantiators;
 	private final FindWithProjection<?> findOperationWithProjection;
-	private final SpelExpressionParser expressionParser;
-	private final QueryMethodEvaluationContextProvider evaluationContextProvider;
+	private final ExpressionParser expressionParser;
+	private final ReactiveQueryMethodEvaluationContextProvider evaluationContextProvider;
 
 	/**
 	 * Creates a new {@link AbstractReactiveMongoQuery} from the given {@link MongoQueryMethod} and
@@ -67,12 +72,12 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 	 * @param evaluationContextProvider must not be {@literal null}.
 	 */
 	public AbstractReactiveMongoQuery(ReactiveMongoQueryMethod method, ReactiveMongoOperations operations,
-			SpelExpressionParser expressionParser, QueryMethodEvaluationContextProvider evaluationContextProvider) {
+			ExpressionParser expressionParser, ReactiveQueryMethodEvaluationContextProvider evaluationContextProvider) {
 
 		Assert.notNull(method, "MongoQueryMethod must not be null!");
 		Assert.notNull(operations, "ReactiveMongoOperations must not be null!");
 		Assert.notNull(expressionParser, "SpelExpressionParser must not be null!");
-		Assert.notNull(evaluationContextProvider, "QueryMethodEvaluationContextProvider must not be null!");
+		Assert.notNull(evaluationContextProvider, "ReactiveEvaluationContextExtension must not be null!");
 
 		this.method = method;
 		this.operations = operations;
@@ -98,25 +103,21 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 	 * (non-Javadoc)
 	 * @see org.springframework.data.repository.query.RepositoryQuery#execute(java.lang.Object[])
 	 */
-	public Object execute(Object[] parameters) {
+	public Publisher<Object> execute(Object[] parameters) {
 
 		return method.hasReactiveWrapperParameter() ? executeDeferred(parameters)
 				: execute(new MongoParametersParameterAccessor(method, parameters));
 	}
 
 	@SuppressWarnings("unchecked")
-	private Object executeDeferred(Object[] parameters) {
+	private Publisher<Object> executeDeferred(Object[] parameters) {
 
 		ReactiveMongoParameterAccessor parameterAccessor = new ReactiveMongoParameterAccessor(method, parameters);
 
-		if (getQueryMethod().isCollectionQuery()) {
-			return Flux.defer(() -> (Publisher<Object>) execute(parameterAccessor));
-		}
-
-		return Mono.defer(() -> (Mono<Object>) execute(parameterAccessor));
+		return execute(parameterAccessor);
 	}
 
-	private Object execute(MongoParameterAccessor parameterAccessor) {
+	private Publisher<Object> execute(MongoParameterAccessor parameterAccessor) {
 
 		ConvertingParameterAccessor accessor = new ConvertingParameterAccessor(operations.getConverter(),
 				parameterAccessor);
@@ -141,24 +142,26 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 	 * @param accessor for providing invocation arguments. Never {@literal null}.
 	 * @param typeToRead the desired component target type. Can be {@literal null}.
 	 */
-	protected Object doExecute(ReactiveMongoQueryMethod method, ResultProcessor processor,
+	protected Publisher<Object> doExecute(ReactiveMongoQueryMethod method, ResultProcessor processor,
 			ConvertingParameterAccessor accessor, @Nullable Class<?> typeToRead) {
 
-		Query query = createQuery(accessor);
+		return createQuery(accessor).flatMapMany(it -> {
 
-		applyQueryMetaAttributesWhenPresent(query);
-		query = applyAnnotatedDefaultSortIfPresent(query);
-		query = applyAnnotatedCollationIfPresent(query, accessor);
+			Query query = it;
+			applyQueryMetaAttributesWhenPresent(query);
+			query = applyAnnotatedDefaultSortIfPresent(query);
+			query = applyAnnotatedCollationIfPresent(query, accessor);
 
-		FindWithQuery<?> find = typeToRead == null //
-				? findOperationWithProjection //
-				: findOperationWithProjection.as(typeToRead);
+			FindWithQuery<?> find = typeToRead == null //
+					? findOperationWithProjection //
+					: findOperationWithProjection.as(typeToRead);
 
-		String collection = method.getEntityInformation().getCollectionName();
+			String collection = method.getEntityInformation().getCollectionName();
 
-		ReactiveMongoQueryExecution execution = getExecution(accessor,
-				new ResultProcessingConverter(processor, operations, instantiators), find);
-		return execution.execute(query, processor.getReturnedType().getDomainType(), collection);
+			ReactiveMongoQueryExecution execution = getExecution(accessor,
+					new ResultProcessingConverter(processor, operations, instantiators), find);
+			return execution.execute(query, processor.getReturnedType().getDomainType(), collection);
+		});
 	}
 
 	/**
@@ -254,8 +257,37 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 	 * @param accessor must not be {@literal null}.
 	 * @return
 	 */
-	protected Query createCountQuery(ConvertingParameterAccessor accessor) {
-		return applyQueryMetaAttributesWhenPresent(createQuery(accessor));
+	protected Mono<Query> createCountQuery(ConvertingParameterAccessor accessor) {
+		return createQuery(accessor).map(this::applyQueryMetaAttributesWhenPresent);
+	}
+
+	/**
+	 * Obtain a {@link Mono publisher} emitting the {@link SpELExpressionEvaluator} suitable to evaluate expressions
+	 * backed by the given dependencies.
+	 *
+	 * @param dependencies must not be {@literal null}.
+	 * @param accessor must not be {@literal null}.
+	 * @return a {@link Mono} emitting the {@link SpELExpressionEvaluator} when ready.
+	 * @since 2.4
+	 */
+	protected Mono<SpELExpressionEvaluator> getSpelEvaluatorFor(ExpressionDependencies dependencies,
+			ConvertingParameterAccessor accessor) {
+
+		return evaluationContextProvider
+				.getEvaluationContextLater(getQueryMethod().getParameters(), accessor.getValues(), dependencies)
+				.map(evaluationContext -> (SpELExpressionEvaluator) new DefaultSpELExpressionEvaluator(expressionParser,
+						evaluationContext))
+				.defaultIfEmpty(DefaultSpELExpressionEvaluator.unsupported());
+	}
+
+	/**
+	 * @return a {@link Mono} emitting the {@link CodecRegistry} when ready.
+	 * @since 2.4
+	 */
+	protected Mono<CodecRegistry> getCodecRegistry() {
+
+		return Mono.from(operations.execute(db -> Mono.just(db.getCodecRegistry())))
+				.defaultIfEmpty(MongoClientSettings.getDefaultCodecRegistry());
 	}
 
 	/**
@@ -264,7 +296,7 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 	 * @param accessor must not be {@literal null}.
 	 * @return
 	 */
-	protected abstract Query createQuery(ConvertingParameterAccessor accessor);
+	protected abstract Mono<Query> createQuery(ConvertingParameterAccessor accessor);
 
 	/**
 	 * Returns whether the query should get a count projection applied.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/AggregationUtils.java

@@ -15,10 +15,7 @@
  */
 package org.springframework.data.mongodb.repository.query;
 
-import lombok.experimental.UtilityClass;
-
 import java.time.Duration;
-import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 
@@ -27,19 +24,15 @@ import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort.Order;
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
 import org.springframework.data.mongodb.core.aggregation.AggregationOperation;
-import org.springframework.data.mongodb.core.aggregation.AggregationOperationContext;
 import org.springframework.data.mongodb.core.aggregation.AggregationOptions;
 import org.springframework.data.mongodb.core.convert.MongoConverter;
 import org.springframework.data.mongodb.core.query.Collation;
 import org.springframework.data.mongodb.core.query.Meta;
 import org.springframework.data.mongodb.core.query.Query;
-import org.springframework.data.mongodb.util.json.ParameterBindingContext;
-import org.springframework.data.mongodb.util.json.ParameterBindingDocumentCodec;
 import org.springframework.data.repository.query.QueryMethodEvaluationContextProvider;
-import org.springframework.expression.spel.standard.SpelExpressionParser;
+import org.springframework.expression.ExpressionParser;
 import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
-import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
 /**
@@ -50,10 +43,9 @@ import org.springframework.util.StringUtils;
  * @author Mark Paluch
  * @since 2.2
  */
-@UtilityClass
-class AggregationUtils {
+abstract class AggregationUtils {
 
-	private static final ParameterBindingDocumentCodec CODEC = new ParameterBindingDocumentCodec();
+	private AggregationUtils() {}
 
 	/**
 	 * Apply a collation extracted from the given {@literal collationExpression} to the given
@@ -65,12 +57,12 @@ class AggregationUtils {
 	 * @param accessor must not be {@literal null}.
 	 * @return the {@link Query} having proper {@link Collation}.
 	 * @see AggregationOptions#getCollation()
-	 * @see CollationUtils#computeCollation(String, ConvertingParameterAccessor, MongoParameters, SpelExpressionParser,
+	 * @see CollationUtils#computeCollation(String, ConvertingParameterAccessor, MongoParameters, ExpressionParser,
 	 *      QueryMethodEvaluationContextProvider)
 	 */
 	static AggregationOptions.Builder applyCollation(AggregationOptions.Builder builder,
 			@Nullable String collationExpression, ConvertingParameterAccessor accessor, MongoParameters parameters,
-			SpelExpressionParser expressionParser, QueryMethodEvaluationContextProvider evaluationContextProvider) {
+			ExpressionParser expressionParser, QueryMethodEvaluationContextProvider evaluationContextProvider) {
 
 		Collation collation = CollationUtils.computeCollation(collationExpression, accessor, parameters, expressionParser,
 				evaluationContextProvider);
@@ -106,32 +98,6 @@ class AggregationUtils {
 		return builder;
 	}
 
-	/**
-	 * Compute the {@link AggregationOperation aggregation} pipeline for the given {@link MongoQueryMethod}. The raw
-	 * {@link org.springframework.data.mongodb.repository.Aggregation#pipeline()} is parsed with a
-	 * {@link ParameterBindingDocumentCodec} to obtain the MongoDB native {@link Document} representation returned by
-	 * {@link AggregationOperation#toDocument(AggregationOperationContext)} that is mapped against the domain type
-	 * properties.
-	 *
-	 * @param method
-	 * @param accessor
-	 * @param expressionParser
-	 * @param evaluationContextProvider
-	 * @return
-	 */
-	static List<AggregationOperation> computePipeline(MongoQueryMethod method, ConvertingParameterAccessor accessor,
-			SpelExpressionParser expressionParser, QueryMethodEvaluationContextProvider evaluationContextProvider) {
-
-		ParameterBindingContext bindingContext = new ParameterBindingContext((accessor::getBindableValue), expressionParser,
-				() -> evaluationContextProvider.getEvaluationContext(method.getParameters(), accessor.getValues()));
-
-		List<AggregationOperation> target = new ArrayList<>(method.getAnnotatedAggregation().length);
-		for (String source : method.getAnnotatedAggregation()) {
-			target.add(ctx -> ctx.getMappedObject(CODEC.decode(source, bindingContext), method.getDomainClass()));
-		}
-		return target;
-	}
-
 	/**
 	 * Append {@code $sort} aggregation stage if {@link ConvertingParameterAccessor#getSort()} is present.
 	 *
@@ -197,9 +163,9 @@ class AggregationUtils {
 	 * @throws IllegalArgumentException when none of the above rules is met.
 	 */
 	@Nullable
-	static <T> T extractSimpleTypeResult(@Nullable Document source, Class<T> targetType, MongoConverter converter) {
+	static <T> T extractSimpleTypeResult(Document source, Class<T> targetType, MongoConverter converter) {
 
-		if (ObjectUtils.isEmpty(source)) {
+		if (source.isEmpty()) {
 			return null;
 		}
 

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/BooleanUtil.java

@@ -15,16 +15,17 @@
  */
 package org.springframework.data.mongodb.repository.query;
 
-import lombok.experimental.UtilityClass;
-
 /**
  * Utility class containing methods to interact with boolean values.
  *
  * @author Mark Paluch
  * @since 2.0.9
  */
-@UtilityClass
-class BooleanUtil {
+final class BooleanUtil {
+
+	private BooleanUtil() {
+		throw new UnsupportedOperationException("This is a utility class and cannot be instantiated");
+	}
 
 	/**
 	 * Count the number of {@literal true} values.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/query/CollationUtils.java

@@ -15,8 +15,6 @@
  */
 package org.springframework.data.mongodb.repository.query;
 
-import lombok.experimental.UtilityClass;
-
 import java.util.Locale;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -26,6 +24,7 @@ import org.springframework.data.mongodb.core.query.Collation;
 import org.springframework.data.mongodb.util.json.ParameterBindingContext;
 import org.springframework.data.mongodb.util.json.ParameterBindingDocumentCodec;
 import org.springframework.data.repository.query.QueryMethodEvaluationContextProvider;
+import org.springframework.expression.ExpressionParser;
 import org.springframework.expression.spel.standard.SpelExpressionParser;
 import org.springframework.lang.Nullable;
 import org.springframework.util.NumberUtils;
@@ -39,12 +38,14 @@ import org.springframework.util.StringUtils;
  * @author Christoph Strobl
  * @since 2.2
  */
-@UtilityClass
-class CollationUtils {
+abstract class CollationUtils {
 
 	private static final ParameterBindingDocumentCodec CODEC = new ParameterBindingDocumentCodec();
 	private static final Pattern PARAMETER_BINDING_PATTERN = Pattern.compile("\\?(\\d+)");
 
+	private CollationUtils() {
+	}
+
 	/**
 	 * Compute the {@link Collation} by inspecting the {@link ConvertingParameterAccessor#getCollation() parameter
 	 * accessor} or parsing a potentially given {@literal collationExpression}.
@@ -59,7 +60,7 @@ class CollationUtils {
 	 */
 	@Nullable
 	static Collation computeCollation(@Nullable String collationExpression, ConvertingParameterAccessor accessor,
-			MongoParameters parameters, SpelExpressionParser expressionParser,
+			MongoParameters parameters, ExpressionParser expressionParser,
 			QueryMethodEvaluationContextProvider evaluationContextProvider) {
 
 		if (accessor.getCollation() != null) {
@@ -72,8 +73,9 @@ class CollationUtils {
 
 		if (StringUtils.trimLeadingWhitespace(collationExpression).startsWith("{")) {
 
-			ParameterBindingContext bindingContext = new ParameterBindingContext((accessor::getBindableValue),
-					expressionParser, () -> evaluationContextProvider.getEvaluationContext(parameters, accessor.getValues()));
+			ParameterBindingContext bindingContext = ParameterBindingContext.forExpressions(accessor::getBindableValue,
+					expressionParser, dependencies -> evaluationContextProvider.getEvaluationContext(parameters,
+							accessor.getValues(), dependencies));
 
 			return Collation.from(CODEC.decode(collationExpression, bindingContext));
 		}