DATAMONGO-2034 - Release version 2.0.10 (Kay SR10).

We now redeclare the Asciidoctor Maven plugin to register the store specific attributes. Apparently they must not contain dots, so we replaced them with dashes.

.travis.yml

@@ -3,33 +3,33 @@ language: java
 jdk:
   - oraclejdk8
 
-before_script:
-  - mongod --version
-
+before_install:
+  - mkdir -p downloads
+  - mkdir -p var/db var/log
+  - if [[ ! -d downloads/mongodb-linux-x86_64-ubuntu1604-${MONGO_VERSION} ]] ; then cd downloads && wget https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-ubuntu1604-${MONGO_VERSION}.tgz && tar xzf mongodb-linux-x86_64-ubuntu1604-${MONGO_VERSION}.tgz && cd ..; fi
+  - downloads/mongodb-linux-x86_64-ubuntu1604-${MONGO_VERSION}/bin/mongod --version
+  - downloads/mongodb-linux-x86_64-ubuntu1604-${MONGO_VERSION}/bin/mongod --dbpath var/db --replSet rs0 --fork --logpath var/log/mongod.log
+  - sleep 10
+  - |-
+    downloads/mongodb-linux-x86_64-ubuntu1604-${MONGO_VERSION}/bin/mongo --eval "rs.initiate({_id: 'rs0', members:[{_id: 0, host: '127.0.0.1:27017'}]});"
+    sleep 15
+    
 env:
   matrix:
     - PROFILE=ci
-    - PROFILE=mongo35-next
+  global:
+    - MONGO_VERSION=3.7.9
 
-# Current MongoDB version is 2.4.2 as of 2016-04, see https://github.com/travis-ci/travis-ci/issues/3694
-# apt-get starts a MongoDB instance so it's not started using before_script
 addons:
   apt:
-    sources:
-      - mongodb-upstart
-      - sourceline: 'deb [arch=amd64] http://repo.mongodb.org/apt/ubuntu precise/mongodb-org/3.4 multiverse'
-        key_url: 'https://www.mongodb.org/static/pgp/server-3.4.asc'
     packages:
-    - mongodb-org-server
-    - mongodb-org-shell
-    - oracle-java8-installer
+      - oracle-java8-installer
 
 sudo: false
 
 cache:
   directories:
     - $HOME/.m2
-
-install: true
+    - downloads
 
 script: "mvn clean dependency:list test -P${PROFILE} -Dsort"

pom.xml

@@ -5,7 +5,7 @@
 
 	<groupId>org.springframework.data</groupId>
 	<artifactId>spring-data-mongodb-parent</artifactId>
-	<version>2.0.0.RC2</version>
+	<version>2.0.10.RELEASE</version>
 	<packaging>pom</packaging>
 
 	<name>Spring Data MongoDB</name>
@@ -15,7 +15,7 @@
 	<parent>
 		<groupId>org.springframework.data.build</groupId>
 		<artifactId>spring-data-parent</artifactId>
-		<version>2.0.0.RC2</version>
+		<version>2.0.10.RELEASE</version>
 	</parent>
 
 	<modules>
@@ -27,9 +27,9 @@
 	<properties>
 		<project.type>multi</project.type>
 		<dist.id>spring-data-mongodb</dist.id>
-		<springdata.commons>2.0.0.RC2</springdata.commons>
-		<mongo>3.4.2</mongo>
-		<mongo.reactivestreams>1.5.0</mongo.reactivestreams>
+		<springdata.commons>2.0.10.RELEASE</springdata.commons>
+		<mongo>3.5.0</mongo>
+		<mongo.reactivestreams>1.6.0</mongo.reactivestreams>
 		<jmh.version>1.19</jmh.version>
 	</properties>
 
@@ -115,38 +115,6 @@
 
 	<profiles>
 
-		<profile>
-
-			<id>mongo34-next</id>
-			<properties>
-				<mongo>3.4.3-SNAPSHOT</mongo>
-			</properties>
-
-			<repositories>
-				<repository>
-					<id>mongo-snapshots</id>
-					<url>https://oss.sonatype.org/content/repositories/snapshots</url>
-				</repository>
-			</repositories>
-
-		</profile>
-
-		<profile>
-
-			<id>mongo35-next</id>
-			<properties>
-				<mongo>3.5.0-SNAPSHOT</mongo>
-			</properties>
-
-			<repositories>
-				<repository>
-					<id>mongo-snapshots</id>
-					<url>https://oss.sonatype.org/content/repositories/snapshots</url>
-				</repository>
-			</repositories>
-
-		</profile>
-
 		<profile>
 			<id>release</id>
 			<build>
@@ -165,12 +133,29 @@
 			<modules>
 				<module>spring-data-mongodb</module>
 				<module>spring-data-mongodb-cross-store</module>
-				<module>spring-data-mongodb-log4j</module>
 				<module>spring-data-mongodb-distribution</module>
 				<module>spring-data-mongodb-benchmarks</module>
 			</modules>
 		</profile>
 
+		<profile>
+			<id>distribute</id>
+			<build>
+				<plugins>
+					<plugin>
+						<groupId>org.asciidoctor</groupId>
+						<artifactId>asciidoctor-maven-plugin</artifactId>
+						<configuration>
+							<attributes>
+								<mongo-reactivestreams>${mongo.reactivestreams}</mongo-reactivestreams>
+								<reactor>${reactor}</reactor>
+							</attributes>
+						</configuration>
+					</plugin>
+				</plugins>
+			</build>
+		</profile>
+
 	</profiles>
 
 	<dependencies>
@@ -184,8 +169,8 @@
 
 	<repositories>
 		<repository>
-			<id>spring-libs-milestone</id>
-			<url>https://repo.spring.io/libs-milestone</url>
+			<id>spring-libs-release</id>
+			<url>https://repo.spring.io/libs-release</url>
 		</repository>
 	</repositories>
 

spring-data-mongodb-benchmarks/pom.xml

@@ -7,7 +7,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>2.0.0.RC2</version>
+		<version>2.0.10.RELEASE</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

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

@@ -6,7 +6,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>2.0.0.RC2</version>
+		<version>2.0.10.RELEASE</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 
@@ -16,6 +16,8 @@
 	<properties>
 		<jpa>2.1.1</jpa>
 		<hibernate>5.2.1.Final</hibernate>
+		<java-module-name>spring.data.mongodb.cross.store</java-module-name>
+		<project.root>${basedir}/..</project.root>
 	</properties>
 
 	<dependencies>
@@ -48,7 +50,7 @@
 		<dependency>
 			<groupId>org.springframework.data</groupId>
 			<artifactId>spring-data-mongodb</artifactId>
-			<version>2.0.0.RC2</version>
+			<version>2.0.10.RELEASE</version>
 		</dependency>
 
 		<!-- reactive -->

spring-data-mongodb-cross-store/src/main/java/org/springframework/data/mongodb/crossstore/MongoChangeSetPersister.java

@@ -1,214 +1,214 @@
-/*
- * Copyright 2011-2017 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * 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.crossstore;
-
-import javax.persistence.EntityManagerFactory;
-
-import org.bson.Document;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-import org.springframework.dao.DataAccessException;
-import org.springframework.dao.DataAccessResourceFailureException;
-import org.springframework.dao.DataIntegrityViolationException;
-import org.springframework.data.crossstore.ChangeSet;
-import org.springframework.data.crossstore.ChangeSetBacked;
-import org.springframework.data.crossstore.ChangeSetPersister;
-import org.springframework.data.mongodb.core.CollectionCallback;
-import org.springframework.data.mongodb.core.MongoTemplate;
-import org.springframework.util.ClassUtils;
-
-import com.mongodb.MongoException;
-import com.mongodb.client.MongoCollection;
-import com.mongodb.client.model.Filters;
-import com.mongodb.client.result.DeleteResult;
-
-/**
- * @author Thomas Risberg
- * @author Oliver Gierke
- * @author Alex Vengrovsk
- * @author Mark Paluch
- * @deprecated will be removed without replacement.
- */
-@Deprecated
-public class MongoChangeSetPersister implements ChangeSetPersister<Object> {
-
-	private static final String ENTITY_CLASS = "_entity_class";
-	private static final String ENTITY_ID = "_entity_id";
-	private static final String ENTITY_FIELD_NAME = "_entity_field_name";
-	private static final String ENTITY_FIELD_CLASS = "_entity_field_class";
-
-	private final Logger log = LoggerFactory.getLogger(getClass());
-
-	private MongoTemplate mongoTemplate;
-	private EntityManagerFactory entityManagerFactory;
-
-	public void setMongoTemplate(MongoTemplate mongoTemplate) {
-		this.mongoTemplate = mongoTemplate;
-	}
-
-	public void setEntityManagerFactory(EntityManagerFactory entityManagerFactory) {
-		this.entityManagerFactory = entityManagerFactory;
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.crossstore.ChangeSetPersister#getPersistentState(java.lang.Class, java.lang.Object, org.springframework.data.crossstore.ChangeSet)
-	 */
-	public void getPersistentState(Class<? extends ChangeSetBacked> entityClass, Object id, final ChangeSet changeSet)
-			throws DataAccessException, NotFoundException {
-
-		if (id == null) {
-			log.debug("Unable to load MongoDB data for null id");
-			return;
-		}
-
-		String collName = getCollectionNameForEntity(entityClass);
-
-		final Document dbk = new Document();
-		dbk.put(ENTITY_ID, id);
-		dbk.put(ENTITY_CLASS, entityClass.getName());
-		if (log.isDebugEnabled()) {
-			log.debug("Loading MongoDB data for {}", dbk);
-		}
-		mongoTemplate.execute(collName, new CollectionCallback<Object>() {
-			public Object doInCollection(MongoCollection<Document> collection) throws MongoException, DataAccessException {
-				for (Document dbo : collection.find(dbk)) {
-					String key = (String) dbo.get(ENTITY_FIELD_NAME);
-					if (log.isDebugEnabled()) {
-						log.debug("Processing key: {}", key);
-					}
-					if (!changeSet.getValues().containsKey(key)) {
-						String className = (String) dbo.get(ENTITY_FIELD_CLASS);
-						if (className == null) {
-							throw new DataIntegrityViolationException(
-									"Unble to convert property " + key + ": Invalid metadata, " + ENTITY_FIELD_CLASS + " not available");
-						}
-						Class<?> clazz = ClassUtils.resolveClassName(className, ClassUtils.getDefaultClassLoader());
-						Object value = mongoTemplate.getConverter().read(clazz, dbo);
-						if (log.isDebugEnabled()) {
-							log.debug("Adding to ChangeSet: {}", key);
-						}
-						changeSet.set(key, value);
-					}
-				}
-				return null;
-			}
-		});
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.crossstore.ChangeSetPersister#getPersistentId(org.springframework.data.crossstore.ChangeSetBacked, org.springframework.data.crossstore.ChangeSet)
-	 */
-	public Object getPersistentId(ChangeSetBacked entity, ChangeSet cs) throws DataAccessException {
-		if (log.isDebugEnabled()) {
-			log.debug("getPersistentId called on {}", entity);
-		}
-		if (entityManagerFactory == null) {
-			throw new DataAccessResourceFailureException("EntityManagerFactory cannot be null");
-		}
-
-		return entityManagerFactory.getPersistenceUnitUtil().getIdentifier(entity);
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.crossstore.ChangeSetPersister#persistState(org.springframework.data.crossstore.ChangeSetBacked, org.springframework.data.crossstore.ChangeSet)
-	 */
-	public Object persistState(ChangeSetBacked entity, ChangeSet cs) throws DataAccessException {
-		if (cs == null) {
-			log.debug("Flush: changeset was null, nothing to flush.");
-			return 0L;
-		}
-
-		if (log.isDebugEnabled()) {
-			log.debug("Flush: changeset: {}", cs.getValues());
-		}
-
-		String collName = getCollectionNameForEntity(entity.getClass());
-		if (mongoTemplate.getCollection(collName) == null) {
-			mongoTemplate.createCollection(collName);
-		}
-
-		for (String key : cs.getValues().keySet()) {
-			if (key != null && !key.startsWith("_") && !key.equals(ChangeSetPersister.ID_KEY)) {
-				Object value = cs.getValues().get(key);
-				final Document dbQuery = new Document();
-				dbQuery.put(ENTITY_ID, getPersistentId(entity, cs));
-				dbQuery.put(ENTITY_CLASS, entity.getClass().getName());
-				dbQuery.put(ENTITY_FIELD_NAME, key);
-				final Document dbId = mongoTemplate.execute(collName, new CollectionCallback<Document>() {
-					public Document doInCollection(MongoCollection<Document> collection)
-							throws MongoException, DataAccessException {
-						Document id = collection.find(dbQuery).first();
-						return id;
-					}
-				});
-
-				if (value == null) {
-					if (log.isDebugEnabled()) {
-						log.debug("Flush: removing: {}", dbQuery);
-					}
-					mongoTemplate.execute(collName, new CollectionCallback<Object>() {
-						public Object doInCollection(MongoCollection<Document> collection)
-								throws MongoException, DataAccessException {
-							DeleteResult dr = collection.deleteMany(dbQuery);
-							return null;
-						}
-					});
-				} else {
-					final Document dbDoc = new Document();
-					dbDoc.putAll(dbQuery);
-					if (log.isDebugEnabled()) {
-						log.debug("Flush: saving: {}", dbQuery);
-					}
-					mongoTemplate.getConverter().write(value, dbDoc);
-					dbDoc.put(ENTITY_FIELD_CLASS, value.getClass().getName());
-					if (dbId != null) {
-						dbDoc.put("_id", dbId.get("_id"));
-					}
-					mongoTemplate.execute(collName, new CollectionCallback<Object>() {
-						public Object doInCollection(MongoCollection<Document> collection)
-								throws MongoException, DataAccessException {
-
-							if (dbId != null) {
-								collection.replaceOne(Filters.eq("_id", dbId.get("_id")), dbDoc);
-							} else {
-
-								if (dbDoc.containsKey("_id") && dbDoc.get("_id") == null) {
-									dbDoc.remove("_id");
-								}
-								collection.insertOne(dbDoc);
-							}
-							return null;
-						}
-					});
-				}
-			}
-		}
-		return 0L;
-	}
-
-	/**
-	 * Returns the collection the given entity type shall be persisted to.
-	 * 
-	 * @param entityClass must not be {@literal null}.
-	 * @return
-	 */
-	private String getCollectionNameForEntity(Class<? extends ChangeSetBacked> entityClass) {
-		return mongoTemplate.getCollectionName(entityClass);
-	}
-}
+/*
+ * Copyright 2011-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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.crossstore;
+
+import javax.persistence.EntityManagerFactory;
+
+import org.bson.Document;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.dao.DataAccessException;
+import org.springframework.dao.DataAccessResourceFailureException;
+import org.springframework.dao.DataIntegrityViolationException;
+import org.springframework.data.crossstore.ChangeSet;
+import org.springframework.data.crossstore.ChangeSetBacked;
+import org.springframework.data.crossstore.ChangeSetPersister;
+import org.springframework.data.mongodb.core.CollectionCallback;
+import org.springframework.data.mongodb.core.MongoTemplate;
+import org.springframework.util.ClassUtils;
+
+import com.mongodb.MongoException;
+import com.mongodb.client.MongoCollection;
+import com.mongodb.client.model.Filters;
+import com.mongodb.client.result.DeleteResult;
+
+/**
+ * @author Thomas Risberg
+ * @author Oliver Gierke
+ * @author Alex Vengrovsk
+ * @author Mark Paluch
+ * @deprecated will be removed without replacement.
+ */
+@Deprecated
+public class MongoChangeSetPersister implements ChangeSetPersister<Object> {
+
+	private static final String ENTITY_CLASS = "_entity_class";
+	private static final String ENTITY_ID = "_entity_id";
+	private static final String ENTITY_FIELD_NAME = "_entity_field_name";
+	private static final String ENTITY_FIELD_CLASS = "_entity_field_class";
+
+	private final Logger log = LoggerFactory.getLogger(getClass());
+
+	private MongoTemplate mongoTemplate;
+	private EntityManagerFactory entityManagerFactory;
+
+	public void setMongoTemplate(MongoTemplate mongoTemplate) {
+		this.mongoTemplate = mongoTemplate;
+	}
+
+	public void setEntityManagerFactory(EntityManagerFactory entityManagerFactory) {
+		this.entityManagerFactory = entityManagerFactory;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.crossstore.ChangeSetPersister#getPersistentState(java.lang.Class, java.lang.Object, org.springframework.data.crossstore.ChangeSet)
+	 */
+	public void getPersistentState(Class<? extends ChangeSetBacked> entityClass, Object id, final ChangeSet changeSet)
+			throws DataAccessException, NotFoundException {
+
+		if (id == null) {
+			log.debug("Unable to load MongoDB data for null id");
+			return;
+		}
+
+		String collName = getCollectionNameForEntity(entityClass);
+
+		final Document dbk = new Document();
+		dbk.put(ENTITY_ID, id);
+		dbk.put(ENTITY_CLASS, entityClass.getName());
+		if (log.isDebugEnabled()) {
+			log.debug("Loading MongoDB data for {}", dbk);
+		}
+		mongoTemplate.execute(collName, new CollectionCallback<Object>() {
+			public Object doInCollection(MongoCollection<Document> collection) throws MongoException, DataAccessException {
+				for (Document dbo : collection.find(dbk)) {
+					String key = (String) dbo.get(ENTITY_FIELD_NAME);
+					if (log.isDebugEnabled()) {
+						log.debug("Processing key: {}", key);
+					}
+					if (!changeSet.getValues().containsKey(key)) {
+						String className = (String) dbo.get(ENTITY_FIELD_CLASS);
+						if (className == null) {
+							throw new DataIntegrityViolationException(
+									"Unble to convert property " + key + ": Invalid metadata, " + ENTITY_FIELD_CLASS + " not available");
+						}
+						Class<?> clazz = ClassUtils.resolveClassName(className, ClassUtils.getDefaultClassLoader());
+						Object value = mongoTemplate.getConverter().read(clazz, dbo);
+						if (log.isDebugEnabled()) {
+							log.debug("Adding to ChangeSet: {}", key);
+						}
+						changeSet.set(key, value);
+					}
+				}
+				return null;
+			}
+		});
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.crossstore.ChangeSetPersister#getPersistentId(org.springframework.data.crossstore.ChangeSetBacked, org.springframework.data.crossstore.ChangeSet)
+	 */
+	public Object getPersistentId(ChangeSetBacked entity, ChangeSet cs) throws DataAccessException {
+		if (log.isDebugEnabled()) {
+			log.debug("getPersistentId called on {}", entity);
+		}
+		if (entityManagerFactory == null) {
+			throw new DataAccessResourceFailureException("EntityManagerFactory cannot be null");
+		}
+
+		return entityManagerFactory.getPersistenceUnitUtil().getIdentifier(entity);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.crossstore.ChangeSetPersister#persistState(org.springframework.data.crossstore.ChangeSetBacked, org.springframework.data.crossstore.ChangeSet)
+	 */
+	public Object persistState(ChangeSetBacked entity, ChangeSet cs) throws DataAccessException {
+		if (cs == null) {
+			log.debug("Flush: changeset was null, nothing to flush.");
+			return 0L;
+		}
+
+		if (log.isDebugEnabled()) {
+			log.debug("Flush: changeset: {}", cs.getValues());
+		}
+
+		String collName = getCollectionNameForEntity(entity.getClass());
+		if (mongoTemplate.getCollection(collName) == null) {
+			mongoTemplate.createCollection(collName);
+		}
+
+		for (String key : cs.getValues().keySet()) {
+			if (key != null && !key.startsWith("_") && !key.equals(ChangeSetPersister.ID_KEY)) {
+				Object value = cs.getValues().get(key);
+				final Document dbQuery = new Document();
+				dbQuery.put(ENTITY_ID, getPersistentId(entity, cs));
+				dbQuery.put(ENTITY_CLASS, entity.getClass().getName());
+				dbQuery.put(ENTITY_FIELD_NAME, key);
+				final Document dbId = mongoTemplate.execute(collName, new CollectionCallback<Document>() {
+					public Document doInCollection(MongoCollection<Document> collection)
+							throws MongoException, DataAccessException {
+						Document id = collection.find(dbQuery).first();
+						return id;
+					}
+				});
+
+				if (value == null) {
+					if (log.isDebugEnabled()) {
+						log.debug("Flush: removing: {}", dbQuery);
+					}
+					mongoTemplate.execute(collName, new CollectionCallback<Object>() {
+						public Object doInCollection(MongoCollection<Document> collection)
+								throws MongoException, DataAccessException {
+							DeleteResult dr = collection.deleteMany(dbQuery);
+							return null;
+						}
+					});
+				} else {
+					final Document dbDoc = new Document();
+					dbDoc.putAll(dbQuery);
+					if (log.isDebugEnabled()) {
+						log.debug("Flush: saving: {}", dbQuery);
+					}
+					mongoTemplate.getConverter().write(value, dbDoc);
+					dbDoc.put(ENTITY_FIELD_CLASS, value.getClass().getName());
+					if (dbId != null) {
+						dbDoc.put("_id", dbId.get("_id"));
+					}
+					mongoTemplate.execute(collName, new CollectionCallback<Object>() {
+						public Object doInCollection(MongoCollection<Document> collection)
+								throws MongoException, DataAccessException {
+
+							if (dbId != null) {
+								collection.replaceOne(Filters.eq("_id", dbId.get("_id")), dbDoc);
+							} else {
+
+								if (dbDoc.containsKey("_id") && dbDoc.get("_id") == null) {
+									dbDoc.remove("_id");
+								}
+								collection.insertOne(dbDoc);
+							}
+							return null;
+						}
+					});
+				}
+			}
+		}
+		return 0L;
+	}
+
+	/**
+	 * Returns the collection the given entity type shall be persisted to.
+	 * 
+	 * @param entityClass must not be {@literal null}.
+	 * @return
+	 */
+	private String getCollectionNameForEntity(Class<? extends ChangeSetBacked> entityClass) {
+		return mongoTemplate.getCollectionName(entityClass);
+	}
+}

spring-data-mongodb-distribution/pom.xml

@@ -13,7 +13,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>2.0.0.RC2</version>
+		<version>2.0.10.RELEASE</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb/pom.xml

@@ -11,13 +11,15 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>2.0.0.RC2</version>
+		<version>2.0.10.RELEASE</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 
 	<properties>
 		<objenesis>1.3</objenesis>
-		<equalsverifier>1.5</equalsverifier>
+		<equalsverifier>1.7.8</equalsverifier>
+		<java-module-name>spring.data.mongodb</java-module-name>
+		<project.root>${basedir}/..</project.root>
 	</properties>
 
 	<dependencies>
@@ -137,6 +139,21 @@
 		</dependency>
 
 		<!-- CDI -->
+		<!-- Dependency order required to build against CDI 1.0 and test with CDI 2.0 -->
+		<dependency>
+			<groupId>org.apache.geronimo.specs</groupId>
+			<artifactId>geronimo-jcdi_2.0_spec</artifactId>
+			<version>1.0.1</version>
+			<scope>test</scope>
+		</dependency>
+
+		<dependency>
+			<groupId>javax.interceptor</groupId>
+			<artifactId>javax.interceptor-api</artifactId>
+			<version>1.2.1</version>
+			<scope>test</scope>
+		</dependency>
+
 		<dependency>
 			<groupId>javax.enterprise</groupId>
 			<artifactId>cdi-api</artifactId>
@@ -146,26 +163,19 @@
 		</dependency>
 
 		<dependency>
-			<groupId>javax.el</groupId>
-			<artifactId>el-api</artifactId>
-			<version>${cdi}</version>
+			<groupId>javax.annotation</groupId>
+			<artifactId>javax.annotation-api</artifactId>
+			<version>${javax-annotation-api}</version>
 			<scope>test</scope>
 		</dependency>
 
 		<dependency>
-			<groupId>org.apache.openwebbeans.test</groupId>
-			<artifactId>cditest-owb</artifactId>
+			<groupId>org.apache.openwebbeans</groupId>
+			<artifactId>openwebbeans-se</artifactId>
 			<version>${webbeans}</version>
 			<scope>test</scope>
 		</dependency>
 
-		<dependency>
-			<groupId>javax.servlet</groupId>
-			<artifactId>servlet-api</artifactId>
-			<version>2.5</version>
-			<scope>test</scope>
-		</dependency>
-
 		<!-- JSR 303 Validation -->
 		<dependency>
 			<groupId>javax.validation</groupId>
@@ -205,7 +215,6 @@
 		<dependency>
 			<groupId>com.fasterxml.jackson.core</groupId>
 			<artifactId>jackson-databind</artifactId>
-			<version>${jackson}</version>
 			<optional>true</optional>
 		</dependency>
 
@@ -279,74 +288,9 @@
 	</dependencies>
 
 	<build>
+
 		<plugins>
 
-			<plugin>
-				<artifactId>kotlin-maven-plugin</artifactId>
-				<groupId>org.jetbrains.kotlin</groupId>
-				<version>${kotlin}</version>
-				<configuration>
-					<jvmTarget>${source.level}</jvmTarget>
-				</configuration>
-				<executions>
-					<execution>
-						<id>compile</id>
-						<phase>compile</phase>
-						<goals>
-							<goal>compile</goal>
-						</goals>
-						<configuration>
-							<sourceDirs>
-								<sourceDir>${project.basedir}/src/main/kotlin</sourceDir>
-								<sourceDir>${project.basedir}/src/main/java</sourceDir>
-							</sourceDirs>
-						</configuration>
-					</execution>
-					<execution>
-						<id>test-compile</id>
-						<phase>test-compile</phase>
-						<goals>
-							<goal>test-compile</goal>
-						</goals>
-						<configuration>
-							<sourceDirs>
-								<sourceDir>${project.basedir}/src/test/kotlin</sourceDir>
-								<sourceDir>${project.basedir}/src/test/java</sourceDir>
-							</sourceDirs>
-						</configuration>
-					</execution>
-				</executions>
-			</plugin>
-
-			<plugin>
-				<groupId>org.apache.maven.plugins</groupId>
-				<artifactId>maven-compiler-plugin</artifactId>
-				<executions>
-					<execution>
-						<id>default-compile</id>
-						<phase>none</phase>
-					</execution>
-					<execution>
-						<id>default-testCompile</id>
-						<phase>none</phase>
-					</execution>
-					<execution>
-						<id>java-compile</id>
-						<phase>compile</phase>
-						<goals>
-							<goal>compile</goal>
-						</goals>
-					</execution>
-					<execution>
-						<id>java-test-compile</id>
-						<phase>test-compile</phase>
-						<goals>
-							<goal>testCompile</goal>
-						</goals>
-					</execution>
-				</executions>
-			</plugin>
-
 			<plugin>
 				<groupId>com.mysema.maven</groupId>
 				<artifactId>apt-maven-plugin</artifactId>
@@ -375,7 +319,6 @@
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-surefire-plugin</artifactId>
-				<version>2.12</version>
 				<configuration>
 					<useFile>false</useFile>
 					<includes>
@@ -397,6 +340,8 @@
 					</properties>
 				</configuration>
 			</plugin>
+
 		</plugins>
+
 	</build>
 </project>

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/CannotGetMongoDbConnectionException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2012 the original author or authors.
+ * Copyright 2010-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,16 +17,18 @@ package org.springframework.data.mongodb;
 
 import org.springframework.dao.DataAccessResourceFailureException;
 import org.springframework.data.authentication.UserCredentials;
+import org.springframework.lang.Nullable;
 
 /**
  * Exception being thrown in case we cannot connect to a MongoDB instance.
- * 
+ *
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 public class CannotGetMongoDbConnectionException extends DataAccessResourceFailureException {
 
 	private final UserCredentials credentials;
-	private final String database;
+	private final @Nullable String database;
 
 	private static final long serialVersionUID = 1172099106475265589L;
 
@@ -40,7 +42,7 @@ public class CannotGetMongoDbConnectionException extends DataAccessResourceFailu
 		this(msg, null, UserCredentials.NO_CREDENTIALS);
 	}
 
-	public CannotGetMongoDbConnectionException(String msg, String database, UserCredentials credentials) {
+	public CannotGetMongoDbConnectionException(String msg, @Nullable String database, UserCredentials credentials) {
 		super(msg);
 		this.database = database;
 		this.credentials = credentials;
@@ -48,7 +50,7 @@ public class CannotGetMongoDbConnectionException extends DataAccessResourceFailu
 
 	/**
 	 * Returns the {@link UserCredentials} that were used when trying to connect to the MongoDB instance.
-	 * 
+	 *
 	 * @return
 	 */
 	public UserCredentials getCredentials() {
@@ -57,9 +59,10 @@ public class CannotGetMongoDbConnectionException extends DataAccessResourceFailu
 
 	/**
 	 * Returns the name of the database trying to be accessed.
-	 * 
+	 *
 	 * @return
 	 */
+	@Nullable
 	public String getDatabase() {
 		return database;
 	}

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/MongoDbFactory.java

@@ -23,16 +23,16 @@ import com.mongodb.DB;
 import com.mongodb.client.MongoDatabase;
 
 /**
- * Interface for factories creating {@link DB} instances.
- * 
+ * Interface for factories creating {@link MongoDatabase} instances.
+ *
  * @author Mark Pollack
  * @author Thomas Darimont
  */
 public interface MongoDbFactory {
 
 	/**
-	 * Creates a default {@link DB} instance.
-	 * 
+	 * Creates a default {@link MongoDatabase} instance.
+	 *
 	 * @return
 	 * @throws DataAccessException
 	 */
@@ -40,7 +40,7 @@ public interface MongoDbFactory {
 
 	/**
 	 * Creates a {@link DB} instance to access the database with the given name.
-	 * 
+	 *
 	 * @param dbName must not be {@literal null} or empty.
 	 * @return
 	 * @throws DataAccessException
@@ -49,7 +49,7 @@ public interface MongoDbFactory {
 
 	/**
 	 * Exposes a shared {@link MongoExceptionTranslator}.
-	 * 
+	 *
 	 * @return will never be {@literal null}.
 	 */
 	PersistenceExceptionTranslator getExceptionTranslator();

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

@@ -1,112 +1,114 @@
-/*
- * Copyright 2011-2017 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * 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.context.annotation.Bean;
-import org.springframework.context.annotation.Configuration;
-import org.springframework.data.mongodb.MongoDbFactory;
-import org.springframework.data.mongodb.core.MongoTemplate;
-import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
-import org.springframework.data.mongodb.core.convert.DbRefResolver;
-import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver;
-import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
-import org.springframework.data.mongodb.core.mapping.Document;
-
-import com.mongodb.MongoClient;
-
-/**
- * Base class for Spring Data MongoDB configuration using JavaConfig.
- *
- * @author Mark Pollack
- * @author Oliver Gierke
- * @author Thomas Darimont
- * @author Ryan Tenney
- * @author Christoph Strobl
- * @author Mark Paluch
- * @see MongoConfigurationSupport
- */
-@Configuration
-public abstract class
-AbstractMongoConfiguration extends MongoConfigurationSupport {
-
-	/**
-	 * Return the {@link MongoClient} instance to connect to. Annotate with {@link Bean} in case you want to expose a
-	 * {@link MongoClient} instance to the {@link org.springframework.context.ApplicationContext}.
-	 *
-	 * @return
-	 */
-	public abstract MongoClient mongoClient();
-
-	/**
-	 * Creates a {@link MongoTemplate}.
-	 *
-	 * @return
-	 */
-	@Bean
-	public MongoTemplate mongoTemplate() throws Exception {
-		return new MongoTemplate(mongoDbFactory(), mappingMongoConverter());
-	}
-
-	/**
-	 * Creates a {@link SimpleMongoDbFactory} to be used by the {@link MongoTemplate}. Will use the {@link MongoClient}
-	 * instance configured in {@link #mongo()}.
-	 *
-	 * @see #mongoClient()
-	 * @see #mongoTemplate()
-	 * @return
-	 */
-	@Bean
-	public MongoDbFactory mongoDbFactory() {
-		return new SimpleMongoDbFactory(mongoClient(), getDatabaseName());
-	}
-
-	/**
-	 * Return the base package to scan for mapped {@link Document}s. Will return the package name of the configuration
-	 * class' (the concrete class, not this one here) by default. So if you have a {@code com.acme.AppConfig} extending
-	 * {@link AbstractMongoConfiguration} the base package will be considered {@code com.acme} unless the method is
-	 * overridden to implement alternate behavior.
-	 *
-	 * @return the base package to scan for mapped {@link Document} classes or {@literal null} to not enable scanning for
-	 *         entities.
-	 * @deprecated use {@link #getMappingBasePackages()} instead.
-	 */
-	@Deprecated
-	protected String getMappingBasePackage() {
-
-		Package mappingBasePackage = getClass().getPackage();
-		return mappingBasePackage == null ? null : mappingBasePackage.getName();
-	}
-
-	/**
-	 * Creates a {@link MappingMongoConverter} using the configured {@link #mongoDbFactory()} and
-	 * {@link #mongoMappingContext()}. Will get {@link #customConversions()} applied.
-	 *
-	 * @see #customConversions()
-	 * @see #mongoMappingContext()
-	 * @see #mongoDbFactory()
-	 * @return
-	 * @throws Exception
-	 */
-	@Bean
-	public MappingMongoConverter mappingMongoConverter() throws Exception {
-
-		DbRefResolver dbRefResolver = new DefaultDbRefResolver(mongoDbFactory());
-		MappingMongoConverter converter = new MappingMongoConverter(dbRefResolver, mongoMappingContext());
-		converter.setCustomConversions(customConversions());
-
-		return converter;
-	}
-}
+/*
+ * Copyright 2011-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.data.mongodb.MongoDbFactory;
+import org.springframework.data.mongodb.core.MongoTemplate;
+import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
+import org.springframework.data.mongodb.core.convert.DbRefResolver;
+import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver;
+import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
+import org.springframework.data.mongodb.core.mapping.Document;
+import org.springframework.lang.Nullable;
+
+import com.mongodb.MongoClient;
+
+/**
+ * Base class for Spring Data MongoDB configuration using JavaConfig.
+ *
+ * @author Mark Pollack
+ * @author Oliver Gierke
+ * @author Thomas Darimont
+ * @author Ryan Tenney
+ * @author Christoph Strobl
+ * @author Mark Paluch
+ * @see MongoConfigurationSupport
+ */
+@Configuration
+public abstract class
+AbstractMongoConfiguration extends MongoConfigurationSupport {
+
+	/**
+	 * Return the {@link MongoClient} instance to connect to. Annotate with {@link Bean} in case you want to expose a
+	 * {@link MongoClient} instance to the {@link org.springframework.context.ApplicationContext}.
+	 *
+	 * @return
+	 */
+	public abstract MongoClient mongoClient();
+
+	/**
+	 * Creates a {@link MongoTemplate}.
+	 *
+	 * @return
+	 */
+	@Bean
+	public MongoTemplate mongoTemplate() throws Exception {
+		return new MongoTemplate(mongoDbFactory(), mappingMongoConverter());
+	}
+
+	/**
+	 * Creates a {@link SimpleMongoDbFactory} to be used by the {@link MongoTemplate}. Will use the {@link MongoClient}
+	 * instance configured in {@link #mongo()}.
+	 *
+	 * @see #mongoClient()
+	 * @see #mongoTemplate()
+	 * @return
+	 */
+	@Bean
+	public MongoDbFactory mongoDbFactory() {
+		return new SimpleMongoDbFactory(mongoClient(), getDatabaseName());
+	}
+
+	/**
+	 * Return the base package to scan for mapped {@link Document}s. Will return the package name of the configuration
+	 * class' (the concrete class, not this one here) by default. So if you have a {@code com.acme.AppConfig} extending
+	 * {@link AbstractMongoConfiguration} the base package will be considered {@code com.acme} unless the method is
+	 * overridden to implement alternate behavior.
+	 *
+	 * @return the base package to scan for mapped {@link Document} classes or {@literal null} to not enable scanning for
+	 *         entities.
+	 * @deprecated use {@link #getMappingBasePackages()} instead.
+	 */
+	@Deprecated
+	@Nullable
+	protected String getMappingBasePackage() {
+
+		Package mappingBasePackage = getClass().getPackage();
+		return mappingBasePackage == null ? null : mappingBasePackage.getName();
+	}
+
+	/**
+	 * Creates a {@link MappingMongoConverter} using the configured {@link #mongoDbFactory()} and
+	 * {@link #mongoMappingContext()}. Will get {@link #customConversions()} applied.
+	 *
+	 * @see #customConversions()
+	 * @see #mongoMappingContext()
+	 * @see #mongoDbFactory()
+	 * @return
+	 * @throws Exception
+	 */
+	@Bean
+	public MappingMongoConverter mappingMongoConverter() throws Exception {
+
+		DbRefResolver dbRefResolver = new DefaultDbRefResolver(mongoDbFactory());
+		MappingMongoConverter converter = new MappingMongoConverter(dbRefResolver, mongoMappingContext());
+		converter.setCustomConversions(customConversions());
+
+		return converter;
+	}
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -13,17 +13,14 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
 package org.springframework.data.mongodb.config;
 
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.data.mongodb.ReactiveMongoDatabaseFactory;
-import org.springframework.data.mongodb.core.MongoTemplate;
 import org.springframework.data.mongodb.core.ReactiveMongoOperations;
-import org.springframework.data.mongodb.core.SimpleReactiveMongoDatabaseFactory;
 import org.springframework.data.mongodb.core.ReactiveMongoTemplate;
-import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
+import org.springframework.data.mongodb.core.SimpleReactiveMongoDatabaseFactory;
 import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
 
 import com.mongodb.reactivestreams.client.MongoClient;
@@ -32,6 +29,7 @@ import com.mongodb.reactivestreams.client.MongoClient;
  * Base class for reactive Spring Data MongoDB configuration using JavaConfig.
  *
  * @author Mark Paluch
+ * @author Christoph Strobl
  * @since 2.0
  * @see MongoConfigurationSupport
  */
@@ -39,45 +37,44 @@ import com.mongodb.reactivestreams.client.MongoClient;
 public abstract class AbstractReactiveMongoConfiguration extends MongoConfigurationSupport {
 
 	/**
-	 * Return the {@link MongoClient} instance to connect to. Annotate with {@link Bean} in case you want to expose a
-	 * {@link MongoClient} instance to the {@link org.springframework.context.ApplicationContext}.
+	 * Return the Reactive Streams {@link MongoClient} instance to connect to. Annotate with {@link Bean} in case you want
+	 * to expose a {@link MongoClient} instance to the {@link org.springframework.context.ApplicationContext}.
 	 *
-	 * @return
+	 * @return never {@literal null}.
 	 */
-	public abstract MongoClient mongoClient();
+	public abstract MongoClient reactiveMongoClient();
 
 	/**
-	 * Creates a {@link ReactiveMongoTemplate}.
+	 * Creates {@link ReactiveMongoOperations}.
 	 *
-	 * @return
+	 * @return never {@literal null}.
 	 */
 	@Bean
 	public ReactiveMongoOperations reactiveMongoTemplate() throws Exception {
-		return new ReactiveMongoTemplate(mongoDbFactory(), mappingMongoConverter());
+		return new ReactiveMongoTemplate(reactiveMongoDbFactory(), mappingMongoConverter());
 	}
 
 	/**
-	 * Creates a {@link SimpleMongoDbFactory} to be used by the {@link MongoTemplate}. Will use the {@link Mongo} instance
-	 * configured in {@link #mongoClient()}.
+	 * Creates a {@link ReactiveMongoDatabaseFactory} to be used by the {@link ReactiveMongoOperations}. Will use the
+	 * {@link MongoClient} instance configured in {@link #reactiveMongoClient()}.
 	 *
-	 * @see #mongoClient()
+	 * @see #reactiveMongoClient()
 	 * @see #reactiveMongoTemplate()
-	 * @return
-	 * @throws Exception
+	 * @return never {@literal null}.
 	 */
 	@Bean
-	public ReactiveMongoDatabaseFactory mongoDbFactory() {
-		return new SimpleReactiveMongoDatabaseFactory(mongoClient(), getDatabaseName());
+	public ReactiveMongoDatabaseFactory reactiveMongoDbFactory() {
+		return new SimpleReactiveMongoDatabaseFactory(reactiveMongoClient(), getDatabaseName());
 	}
 
 	/**
-	 * Creates a {@link MappingMongoConverter} using the configured {@link #mongoDbFactory()} and
+	 * Creates a {@link MappingMongoConverter} using the configured {@link #reactiveMongoDbFactory()} and
 	 * {@link #mongoMappingContext()}. Will get {@link #customConversions()} applied.
 	 *
 	 * @see #customConversions()
 	 * @see #mongoMappingContext()
-	 * @see #mongoDbFactory()
-	 * @return
+	 * @see #reactiveMongoDbFactory()
+	 * @return never {@literal null}.
 	 * @throws Exception
 	 */
 	@Bean

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

@@ -17,6 +17,7 @@ package org.springframework.data.mongodb.config;
 
 import java.beans.PropertyEditorSupport;
 import java.io.UnsupportedEncodingException;
+import java.lang.reflect.Method;
 import java.net.URLDecoder;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -25,6 +26,8 @@ import java.util.Properties;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
+import org.springframework.lang.Nullable;
+import org.springframework.util.ReflectionUtils;
 import org.springframework.util.StringUtils;
 
 import com.mongodb.MongoCredential;
@@ -34,6 +37,8 @@ import com.mongodb.MongoCredential;
  *
  * @author Christoph Strobl
  * @author Oliver Gierke
+ * @author Stephen Tyler Conrad
+ * @author Mark Paluch
  * @since 1.7
  */
 public class MongoCredentialPropertyEditor extends PropertyEditorSupport {
@@ -51,7 +56,7 @@ public class MongoCredentialPropertyEditor extends PropertyEditorSupport {
 	 * @see java.beans.PropertyEditorSupport#setAsText(java.lang.String)
 	 */
 	@Override
-	public void setAsText(String text) throws IllegalArgumentException {
+	public void setAsText(@Nullable String text) throws IllegalArgumentException {
 
 		if (!StringUtils.hasText(text)) {
 			return;
@@ -97,6 +102,20 @@ public class MongoCredentialPropertyEditor extends PropertyEditorSupport {
 						verifyDatabasePresent(database);
 						credentials.add(MongoCredential.createScramSha1Credential(userNameAndPassword[0], database,
 								userNameAndPassword[1].toCharArray()));
+					} else if ("SCRAM-SHA-256".equals(authMechanism)) {
+
+						Method createScramSha256Credential = ReflectionUtils.findMethod(MongoCredential.class,
+								"createScramSha256Credential", String.class, String.class, char[].class);
+
+						if (createScramSha256Credential == null) {
+							throw new IllegalArgumentException(
+									"SCRAM-SHA-256 auth mechanism is available as of MongoDB 4 and MongoDB Java Driver 3.8! Please make sure to use at least those versions.");
+						}
+
+						verifyUsernameAndPasswordPresent(userNameAndPassword);
+						verifyDatabasePresent(database);
+						credentials.add(MongoCredential.class.cast(ReflectionUtils.invokeMethod(createScramSha256Credential, null,
+								userNameAndPassword[0], database, userNameAndPassword[1].toCharArray())));
 					} else {
 						throw new IllegalArgumentException(
 								String.format("Cannot create MongoCredentials for unknown auth mechanism '%s'!", authMechanism));
@@ -163,7 +182,7 @@ public class MongoCredentialPropertyEditor extends PropertyEditorSupport {
 	private static Properties extractOptions(String text) {
 
 		int optionsSeparationIndex = text.lastIndexOf(OPTIONS_DELIMITER);
-		int dbSeparationIndex = text.lastIndexOf(OPTIONS_DELIMITER);
+		int dbSeparationIndex = text.lastIndexOf(DATABASE_DELIMITER);
 
 		if (optionsSeparationIndex == -1 || dbSeparationIndex > optionsSeparationIndex) {
 			return new Properties();
@@ -172,7 +191,13 @@ public class MongoCredentialPropertyEditor extends PropertyEditorSupport {
 		Properties properties = new Properties();
 
 		for (String option : text.substring(optionsSeparationIndex + 1).split(OPTION_VALUE_DELIMITER)) {
+
 			String[] optionArgs = option.split("=");
+
+			if (optionArgs.length == 1) {
+				throw new IllegalArgumentException(String.format("Query parameter '%s' has no value!", optionArgs[0]));
+			}
+
 			properties.put(optionArgs[0], optionArgs[1]);
 		}
 

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

@@ -1,11 +1,11 @@
 /*
- * Copyright 2011-2017 by the original author(s).
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
- *     http://www.apache.org/licenses/LICENSE-2.0
+ *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
@@ -33,6 +33,7 @@ import org.springframework.beans.factory.xml.ParserContext;
 import org.springframework.data.config.BeanComponentDefinitionBuilder;
 import org.springframework.data.mongodb.core.MongoClientFactoryBean;
 import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
+import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 import org.w3c.dom.Element;
 
@@ -42,12 +43,13 @@ import com.mongodb.MongoURI;
 
 /**
  * {@link BeanDefinitionParser} to parse {@code db-factory} elements into {@link BeanDefinition}s.
- * 
+ *
  * @author Jon Brisbin
  * @author Oliver Gierke
  * @author Thomas Darimont
  * @author Christoph Strobl
  * @author Viktor Khoroshko
+ * @author Mark Paluch
  */
 public class MongoDbFactoryParser extends AbstractBeanDefinitionParser {
 
@@ -62,7 +64,7 @@ public class MongoDbFactoryParser extends AbstractBeanDefinitionParser {
 		MONGO_URI_ALLOWED_ADDITIONAL_ATTRIBUTES = Collections.unmodifiableSet(mongoUriAllowedAdditionalAttributes);
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.beans.factory.xml.AbstractBeanDefinitionParser#resolveId(org.w3c.dom.Element, org.springframework.beans.factory.support.AbstractBeanDefinition, org.springframework.beans.factory.xml.ParserContext)
 	 */
@@ -74,7 +76,7 @@ public class MongoDbFactoryParser extends AbstractBeanDefinitionParser {
 		return StringUtils.hasText(id) ? id : BeanNames.DB_FACTORY_BEAN_NAME;
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.beans.factory.xml.AbstractBeanDefinitionParser#parseInternal(org.w3c.dom.Element, org.springframework.beans.factory.xml.ParserContext)
 	 */
@@ -119,7 +121,7 @@ public class MongoDbFactoryParser extends AbstractBeanDefinitionParser {
 	/**
 	 * Registers a default {@link BeanDefinition} of a {@link Mongo} instance and returns the name under which the
 	 * {@link Mongo} instance was registered under.
-	 * 
+	 *
 	 * @param element must not be {@literal null}.
 	 * @param parserContext must not be {@literal null}.
 	 * @return
@@ -138,11 +140,12 @@ public class MongoDbFactoryParser extends AbstractBeanDefinitionParser {
 	 * attributes. <br />
 	 * Errors when configured element contains {@literal uri} or {@literal client-uri} along with other attributes except
 	 * {@literal write-concern} and/or {@literal id}.
-	 * 
+	 *
 	 * @param element must not be {@literal null}.
 	 * @param parserContext
 	 * @return {@literal null} in case no client-/uri defined.
 	 */
+	@Nullable
 	private BeanDefinition getMongoUri(Element element, ParserContext parserContext) {
 
 		boolean hasClientUri = element.hasAttribute("client-uri");

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

@@ -1,76 +1,76 @@
-/*
- * Copyright 2011-2017 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.config;
-
-import org.springframework.beans.factory.config.BeanDefinition;
-import org.springframework.beans.factory.parsing.BeanComponentDefinition;
-import org.springframework.beans.factory.parsing.CompositeComponentDefinition;
-import org.springframework.beans.factory.support.BeanDefinitionBuilder;
-import org.springframework.beans.factory.xml.BeanDefinitionParser;
-import org.springframework.beans.factory.xml.ParserContext;
-import org.springframework.data.mongodb.core.MongoAdmin;
-import org.springframework.data.mongodb.monitor.*;
-import org.springframework.util.StringUtils;
-import org.w3c.dom.Element;
-
-/**
- * @author Mark Pollack
- * @author Thomas Risberg
- * @author John Brisbin
- * @author Oliver Gierke
- * @author Christoph Strobl
- */
-public class MongoJmxParser implements BeanDefinitionParser {
-
-	public BeanDefinition parse(Element element, ParserContext parserContext) {
-		String name = element.getAttribute("mongo-ref");
-		if (!StringUtils.hasText(name)) {
-			name = BeanNames.MONGO_BEAN_NAME;
-		}
-		registerJmxComponents(name, element, parserContext);
-		return null;
-	}
-
-	protected void registerJmxComponents(String mongoRefName, Element element, ParserContext parserContext) {
-		Object eleSource = parserContext.extractSource(element);
-
-		CompositeComponentDefinition compositeDef = new CompositeComponentDefinition(element.getTagName(), eleSource);
-
-		createBeanDefEntry(AssertMetrics.class, compositeDef, mongoRefName, eleSource, parserContext);
-		createBeanDefEntry(BackgroundFlushingMetrics.class, compositeDef, mongoRefName, eleSource, parserContext);
-		createBeanDefEntry(BtreeIndexCounters.class, compositeDef, mongoRefName, eleSource, parserContext);
-		createBeanDefEntry(ConnectionMetrics.class, compositeDef, mongoRefName, eleSource, parserContext);
-		createBeanDefEntry(GlobalLockMetrics.class, compositeDef, mongoRefName, eleSource, parserContext);
-		createBeanDefEntry(MemoryMetrics.class, compositeDef, mongoRefName, eleSource, parserContext);
-		createBeanDefEntry(OperationCounters.class, compositeDef, mongoRefName, eleSource, parserContext);
-		createBeanDefEntry(ServerInfo.class, compositeDef, mongoRefName, eleSource, parserContext);
-		createBeanDefEntry(MongoAdmin.class, compositeDef, mongoRefName, eleSource, parserContext);
-
-		parserContext.registerComponent(compositeDef);
-
-	}
-
-	protected void createBeanDefEntry(Class<?> clazz, CompositeComponentDefinition compositeDef, String mongoRefName,
-			Object eleSource, ParserContext parserContext) {
-		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(clazz);
-		builder.getRawBeanDefinition().setSource(eleSource);
-		builder.addConstructorArgReference(mongoRefName);
-		BeanDefinition assertDef = builder.getBeanDefinition();
-		String assertName = parserContext.getReaderContext().registerWithGeneratedName(assertDef);
-		compositeDef.addNestedComponent(new BeanComponentDefinition(assertDef, assertName));
-	}
-
-}
+/*
+ * Copyright 2011-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.config;
+
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.parsing.BeanComponentDefinition;
+import org.springframework.beans.factory.parsing.CompositeComponentDefinition;
+import org.springframework.beans.factory.support.BeanDefinitionBuilder;
+import org.springframework.beans.factory.xml.BeanDefinitionParser;
+import org.springframework.beans.factory.xml.ParserContext;
+import org.springframework.data.mongodb.core.MongoAdmin;
+import org.springframework.data.mongodb.monitor.*;
+import org.springframework.util.StringUtils;
+import org.w3c.dom.Element;
+
+/**
+ * @author Mark Pollack
+ * @author Thomas Risberg
+ * @author John Brisbin
+ * @author Oliver Gierke
+ * @author Christoph Strobl
+ */
+public class MongoJmxParser implements BeanDefinitionParser {
+
+	public BeanDefinition parse(Element element, ParserContext parserContext) {
+		String name = element.getAttribute("mongo-ref");
+		if (!StringUtils.hasText(name)) {
+			name = BeanNames.MONGO_BEAN_NAME;
+		}
+		registerJmxComponents(name, element, parserContext);
+		return null;
+	}
+
+	protected void registerJmxComponents(String mongoRefName, Element element, ParserContext parserContext) {
+		Object eleSource = parserContext.extractSource(element);
+
+		CompositeComponentDefinition compositeDef = new CompositeComponentDefinition(element.getTagName(), eleSource);
+
+		createBeanDefEntry(AssertMetrics.class, compositeDef, mongoRefName, eleSource, parserContext);
+		createBeanDefEntry(BackgroundFlushingMetrics.class, compositeDef, mongoRefName, eleSource, parserContext);
+		createBeanDefEntry(BtreeIndexCounters.class, compositeDef, mongoRefName, eleSource, parserContext);
+		createBeanDefEntry(ConnectionMetrics.class, compositeDef, mongoRefName, eleSource, parserContext);
+		createBeanDefEntry(GlobalLockMetrics.class, compositeDef, mongoRefName, eleSource, parserContext);
+		createBeanDefEntry(MemoryMetrics.class, compositeDef, mongoRefName, eleSource, parserContext);
+		createBeanDefEntry(OperationCounters.class, compositeDef, mongoRefName, eleSource, parserContext);
+		createBeanDefEntry(ServerInfo.class, compositeDef, mongoRefName, eleSource, parserContext);
+		createBeanDefEntry(MongoAdmin.class, compositeDef, mongoRefName, eleSource, parserContext);
+
+		parserContext.registerComponent(compositeDef);
+
+	}
+
+	protected void createBeanDefEntry(Class<?> clazz, CompositeComponentDefinition compositeDef, String mongoRefName,
+			Object eleSource, ParserContext parserContext) {
+		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(clazz);
+		builder.getRawBeanDefinition().setSource(eleSource);
+		builder.addConstructorArgReference(mongoRefName);
+		BeanDefinition assertDef = builder.getBeanDefinition();
+		String assertName = parserContext.getReaderContext().registerWithGeneratedName(assertDef);
+		compositeDef.addNestedComponent(new BeanComponentDefinition(assertDef, assertName));
+	}
+
+}

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

@@ -1,170 +1,170 @@
-/*
- * Copyright 2011-2017 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * 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 static org.springframework.data.config.ParsingUtils.*;
-
-import java.util.Map;
-
-import org.springframework.beans.factory.config.BeanDefinition;
-import org.springframework.beans.factory.config.CustomEditorConfigurer;
-import org.springframework.beans.factory.support.BeanDefinitionBuilder;
-import org.springframework.beans.factory.support.ManagedMap;
-import org.springframework.beans.factory.xml.BeanDefinitionParser;
-import org.springframework.data.mongodb.core.MongoClientOptionsFactoryBean;
-import org.springframework.util.xml.DomUtils;
-import org.w3c.dom.Element;
-
-/**
- * Utility methods for {@link BeanDefinitionParser} implementations for MongoDB.
- * 
- * @author Mark Pollack
- * @author Oliver Gierke
- * @author Thomas Darimont
- * @author Christoph Strobl
- */
-@SuppressWarnings("deprecation")
-abstract class MongoParsingUtils {
-
-	private MongoParsingUtils() {}
-
-	/**
-	 * Parses the mongo replica-set element.
-	 * 
-	 * @param parserContext the parser context
-	 * @param element the mongo element
-	 * @param mongoBuilder the bean definition builder to populate
-	 * @return
-	 */
-	static void parseReplicaSet(Element element, BeanDefinitionBuilder mongoBuilder) {
-		setPropertyValue(mongoBuilder, element, "replica-set", "replicaSetSeeds");
-	}
-
-	/**
-	 * Parses the {@code mongo:client-options} sub-element. Populates the given attribute factory with the proper
-	 * attributes.
-	 * 
-	 * @param element must not be {@literal null}.
-	 * @param mongoClientBuilder must not be {@literal null}.
-	 * @return
-	 * @since 1.7
-	 */
-	public static boolean parseMongoClientOptions(Element element, BeanDefinitionBuilder mongoClientBuilder) {
-
-		Element optionsElement = DomUtils.getChildElementByTagName(element, "client-options");
-
-		if (optionsElement == null) {
-			return false;
-		}
-
-		BeanDefinitionBuilder clientOptionsDefBuilder = BeanDefinitionBuilder
-				.genericBeanDefinition(MongoClientOptionsFactoryBean.class);
-
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "description", "description");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "min-connections-per-host", "minConnectionsPerHost");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "connections-per-host", "connectionsPerHost");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "threads-allowed-to-block-for-connection-multiplier",
-				"threadsAllowedToBlockForConnectionMultiplier");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "max-wait-time", "maxWaitTime");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "max-connection-idle-time", "maxConnectionIdleTime");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "max-connection-life-time", "maxConnectionLifeTime");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "connect-timeout", "connectTimeout");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "socket-timeout", "socketTimeout");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "socket-keep-alive", "socketKeepAlive");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "read-preference", "readPreference");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "write-concern", "writeConcern");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "heartbeat-frequency", "heartbeatFrequency");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "min-heartbeat-frequency", "minHeartbeatFrequency");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "heartbeat-connect-timeout", "heartbeatConnectTimeout");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "heartbeat-socket-timeout", "heartbeatSocketTimeout");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "ssl", "ssl");
-		setPropertyReference(clientOptionsDefBuilder, optionsElement, "ssl-socket-factory-ref", "sslSocketFactory");
-		setPropertyValue(clientOptionsDefBuilder, optionsElement, "server-selection-timeout", "serverSelectionTimeout");
-
-		mongoClientBuilder.addPropertyValue("mongoClientOptions", clientOptionsDefBuilder.getBeanDefinition());
-
-		return true;
-	}
-
-	/**
-	 * Returns the {@link BeanDefinitionBuilder} to build a {@link BeanDefinition} for a
-	 * {@link WriteConcernPropertyEditor}.
-	 * 
-	 * @return
-	 */
-	static BeanDefinitionBuilder getWriteConcernPropertyEditorBuilder() {
-
-		Map<String, Class<?>> customEditors = new ManagedMap<String, Class<?>>();
-		customEditors.put("com.mongodb.WriteConcern", WriteConcernPropertyEditor.class);
-
-		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(CustomEditorConfigurer.class);
-		builder.addPropertyValue("customEditors", customEditors);
-
-		return builder;
-	}
-
-	/**
-	 * One should only register one bean definition but want to have the convenience of using
-	 * AbstractSingleBeanDefinitionParser but have the side effect of registering a 'default' property editor with the
-	 * container.
-	 */
-	static BeanDefinitionBuilder getServerAddressPropertyEditorBuilder() {
-
-		Map<String, String> customEditors = new ManagedMap<String, String>();
-		customEditors.put("com.mongodb.ServerAddress[]",
-				"org.springframework.data.mongodb.config.ServerAddressPropertyEditor");
-
-		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(CustomEditorConfigurer.class);
-		builder.addPropertyValue("customEditors", customEditors);
-		return builder;
-	}
-
-	/**
-	 * Returns the {@link BeanDefinitionBuilder} to build a {@link BeanDefinition} for a
-	 * {@link ReadPreferencePropertyEditor}.
-	 * 
-	 * @return
-	 * @since 1.7
-	 */
-	static BeanDefinitionBuilder getReadPreferencePropertyEditorBuilder() {
-
-		Map<String, Class<?>> customEditors = new ManagedMap<String, Class<?>>();
-		customEditors.put("com.mongodb.ReadPreference", ReadPreferencePropertyEditor.class);
-
-		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(CustomEditorConfigurer.class);
-		builder.addPropertyValue("customEditors", customEditors);
-
-		return builder;
-	}
-
-	/**
-	 * Returns the {@link BeanDefinitionBuilder} to build a {@link BeanDefinition} for a
-	 * {@link MongoCredentialPropertyEditor}.
-	 * 
-	 * @return
-	 * @since 1.7
-	 */
-	static BeanDefinitionBuilder getMongoCredentialPropertyEditor() {
-
-		Map<String, Class<?>> customEditors = new ManagedMap<String, Class<?>>();
-		customEditors.put("com.mongodb.MongoCredential[]", MongoCredentialPropertyEditor.class);
-
-		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(CustomEditorConfigurer.class);
-		builder.addPropertyValue("customEditors", customEditors);
-
-		return builder;
-	}
-}
+/*
+ * Copyright 2011-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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 static org.springframework.data.config.ParsingUtils.*;
+
+import java.util.Map;
+
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.config.CustomEditorConfigurer;
+import org.springframework.beans.factory.support.BeanDefinitionBuilder;
+import org.springframework.beans.factory.support.ManagedMap;
+import org.springframework.beans.factory.xml.BeanDefinitionParser;
+import org.springframework.data.mongodb.core.MongoClientOptionsFactoryBean;
+import org.springframework.util.xml.DomUtils;
+import org.w3c.dom.Element;
+
+/**
+ * Utility methods for {@link BeanDefinitionParser} implementations for MongoDB.
+ * 
+ * @author Mark Pollack
+ * @author Oliver Gierke
+ * @author Thomas Darimont
+ * @author Christoph Strobl
+ */
+@SuppressWarnings("deprecation")
+abstract class MongoParsingUtils {
+
+	private MongoParsingUtils() {}
+
+	/**
+	 * Parses the mongo replica-set element.
+	 * 
+	 * @param parserContext the parser context
+	 * @param element the mongo element
+	 * @param mongoBuilder the bean definition builder to populate
+	 * @return
+	 */
+	static void parseReplicaSet(Element element, BeanDefinitionBuilder mongoBuilder) {
+		setPropertyValue(mongoBuilder, element, "replica-set", "replicaSetSeeds");
+	}
+
+	/**
+	 * Parses the {@code mongo:client-options} sub-element. Populates the given attribute factory with the proper
+	 * attributes.
+	 * 
+	 * @param element must not be {@literal null}.
+	 * @param mongoClientBuilder must not be {@literal null}.
+	 * @return
+	 * @since 1.7
+	 */
+	public static boolean parseMongoClientOptions(Element element, BeanDefinitionBuilder mongoClientBuilder) {
+
+		Element optionsElement = DomUtils.getChildElementByTagName(element, "client-options");
+
+		if (optionsElement == null) {
+			return false;
+		}
+
+		BeanDefinitionBuilder clientOptionsDefBuilder = BeanDefinitionBuilder
+				.genericBeanDefinition(MongoClientOptionsFactoryBean.class);
+
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "description", "description");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "min-connections-per-host", "minConnectionsPerHost");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "connections-per-host", "connectionsPerHost");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "threads-allowed-to-block-for-connection-multiplier",
+				"threadsAllowedToBlockForConnectionMultiplier");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "max-wait-time", "maxWaitTime");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "max-connection-idle-time", "maxConnectionIdleTime");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "max-connection-life-time", "maxConnectionLifeTime");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "connect-timeout", "connectTimeout");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "socket-timeout", "socketTimeout");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "socket-keep-alive", "socketKeepAlive");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "read-preference", "readPreference");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "write-concern", "writeConcern");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "heartbeat-frequency", "heartbeatFrequency");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "min-heartbeat-frequency", "minHeartbeatFrequency");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "heartbeat-connect-timeout", "heartbeatConnectTimeout");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "heartbeat-socket-timeout", "heartbeatSocketTimeout");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "ssl", "ssl");
+		setPropertyReference(clientOptionsDefBuilder, optionsElement, "ssl-socket-factory-ref", "sslSocketFactory");
+		setPropertyValue(clientOptionsDefBuilder, optionsElement, "server-selection-timeout", "serverSelectionTimeout");
+
+		mongoClientBuilder.addPropertyValue("mongoClientOptions", clientOptionsDefBuilder.getBeanDefinition());
+
+		return true;
+	}
+
+	/**
+	 * Returns the {@link BeanDefinitionBuilder} to build a {@link BeanDefinition} for a
+	 * {@link WriteConcernPropertyEditor}.
+	 * 
+	 * @return
+	 */
+	static BeanDefinitionBuilder getWriteConcernPropertyEditorBuilder() {
+
+		Map<String, Class<?>> customEditors = new ManagedMap<String, Class<?>>();
+		customEditors.put("com.mongodb.WriteConcern", WriteConcernPropertyEditor.class);
+
+		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(CustomEditorConfigurer.class);
+		builder.addPropertyValue("customEditors", customEditors);
+
+		return builder;
+	}
+
+	/**
+	 * One should only register one bean definition but want to have the convenience of using
+	 * AbstractSingleBeanDefinitionParser but have the side effect of registering a 'default' property editor with the
+	 * container.
+	 */
+	static BeanDefinitionBuilder getServerAddressPropertyEditorBuilder() {
+
+		Map<String, String> customEditors = new ManagedMap<String, String>();
+		customEditors.put("com.mongodb.ServerAddress[]",
+				"org.springframework.data.mongodb.config.ServerAddressPropertyEditor");
+
+		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(CustomEditorConfigurer.class);
+		builder.addPropertyValue("customEditors", customEditors);
+		return builder;
+	}
+
+	/**
+	 * Returns the {@link BeanDefinitionBuilder} to build a {@link BeanDefinition} for a
+	 * {@link ReadPreferencePropertyEditor}.
+	 * 
+	 * @return
+	 * @since 1.7
+	 */
+	static BeanDefinitionBuilder getReadPreferencePropertyEditorBuilder() {
+
+		Map<String, Class<?>> customEditors = new ManagedMap<String, Class<?>>();
+		customEditors.put("com.mongodb.ReadPreference", ReadPreferencePropertyEditor.class);
+
+		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(CustomEditorConfigurer.class);
+		builder.addPropertyValue("customEditors", customEditors);
+
+		return builder;
+	}
+
+	/**
+	 * Returns the {@link BeanDefinitionBuilder} to build a {@link BeanDefinition} for a
+	 * {@link MongoCredentialPropertyEditor}.
+	 * 
+	 * @return
+	 * @since 1.7
+	 */
+	static BeanDefinitionBuilder getMongoCredentialPropertyEditor() {
+
+		Map<String, Class<?>> customEditors = new ManagedMap<String, Class<?>>();
+		customEditors.put("com.mongodb.MongoCredential[]", MongoCredentialPropertyEditor.class);
+
+		BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(CustomEditorConfigurer.class);
+		builder.addPropertyValue("customEditors", customEditors);
+
+		return builder;
+	}
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015 the original author or authors.
+ * Copyright 2015-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,8 @@ package org.springframework.data.mongodb.config;
 
 import java.beans.PropertyEditorSupport;
 
+import org.springframework.lang.Nullable;
+
 import com.mongodb.ReadPreference;
 
 /**
@@ -32,7 +34,7 @@ public class ReadPreferencePropertyEditor extends PropertyEditorSupport {
 	 * @see java.beans.PropertyEditorSupport#setAsText(java.lang.String)
 	 */
 	@Override
-	public void setAsText(String readPreferenceString) throws IllegalArgumentException {
+	public void setAsText(@Nullable String readPreferenceString) throws IllegalArgumentException {
 
 		if (readPreferenceString == null) {
 			return;
@@ -59,8 +61,8 @@ public class ReadPreferencePropertyEditor extends PropertyEditorSupport {
 		} else if ("NEAREST".equalsIgnoreCase(readPreferenceString)) {
 			setValue(ReadPreference.nearest());
 		} else {
-			throw new IllegalArgumentException(String.format("Cannot find matching ReadPreference for %s",
-					readPreferenceString));
+			throw new IllegalArgumentException(
+					String.format("Cannot find matching ReadPreference for %s", readPreferenceString));
 		}
 	}
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2013 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,6 +23,7 @@ import java.util.Set;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -30,10 +31,11 @@ import com.mongodb.ServerAddress;
 
 /**
  * Parse a {@link String} to a {@link ServerAddress} array. The format is host1:port1,host2:port2,host3:port3.
- * 
+ *
  * @author Mark Pollack
  * @author Oliver Gierke
  * @author Thomas Darimont
+ * @author Christoph Strobl
  */
 public class ServerAddressPropertyEditor extends PropertyEditorSupport {
 
@@ -49,7 +51,7 @@ public class ServerAddressPropertyEditor extends PropertyEditorSupport {
 	 * @see java.beans.PropertyEditorSupport#setAsText(java.lang.String)
 	 */
 	@Override
-	public void setAsText(String replicaSetString) {
+	public void setAsText(@Nullable String replicaSetString) {
 
 		if (!StringUtils.hasText(replicaSetString)) {
 			setValue(null);
@@ -78,10 +80,11 @@ public class ServerAddressPropertyEditor extends PropertyEditorSupport {
 
 	/**
 	 * Parses the given source into a {@link ServerAddress}.
-	 * 
+	 *
 	 * @param source
 	 * @return the
 	 */
+	@Nullable
 	private ServerAddress parseServerAddress(String source) {
 
 		if (!StringUtils.hasText(source)) {
@@ -112,7 +115,7 @@ public class ServerAddressPropertyEditor extends PropertyEditorSupport {
 
 	/**
 	 * Extract the host and port from the given {@link String}.
-	 * 
+	 *
 	 * @param addressAndPortSource must not be {@literal null}.
 	 * @return
 	 */

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,9 @@ package org.springframework.data.mongodb.config;
 
 import java.beans.PropertyEditorSupport;
 
+import org.springframework.lang.Nullable;
+import org.springframework.util.StringUtils;
+
 import com.mongodb.WriteConcern;
 
 /**
@@ -26,6 +29,7 @@ import com.mongodb.WriteConcern;
  * string value.
  * 
  * @author Mark Pollack
+ * @author Christoph Strobl
  */
 public class WriteConcernPropertyEditor extends PropertyEditorSupport {
 
@@ -33,7 +37,11 @@ public class WriteConcernPropertyEditor extends PropertyEditorSupport {
 	 * Parse a string to a List<ServerAddress>
 	 */
 	@Override
-	public void setAsText(String writeConcernString) {
+	public void setAsText(@Nullable String writeConcernString) {
+
+		if (!StringUtils.hasText(writeConcernString)) {
+			return;
+		}
 
 		WriteConcern writeConcern = WriteConcern.valueOf(writeConcernString);
 		if (writeConcern != null) {

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

@@ -1,5 +1,6 @@
 /**
  * Spring XML namespace configuration for MongoDB specific repositories.
  */
+@org.springframework.lang.NonNullApi
 package org.springframework.data.mongodb.config;
 

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

@@ -0,0 +1,118 @@
+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core;
+
+import lombok.AllArgsConstructor;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Collectors;
+
+import org.bson.Document;
+import org.springframework.data.mapping.context.MappingContext;
+import org.springframework.data.mongodb.core.aggregation.Aggregation;
+import org.springframework.data.mongodb.core.aggregation.AggregationOperationContext;
+import org.springframework.data.mongodb.core.aggregation.TypeBasedAggregationOperationContext;
+import org.springframework.data.mongodb.core.aggregation.TypedAggregation;
+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.lang.Nullable;
+import org.springframework.util.ObjectUtils;
+
+/**
+ * Utility methods to map {@link org.springframework.data.mongodb.core.aggregation.Aggregation} pipeline definitions and
+ * create type-bound {@link AggregationOperationContext}.
+ *
+ * @author Christoph Strobl
+ * @author Mark Paluch
+ * @since 2.0.8
+ */
+@AllArgsConstructor
+class AggregationUtil {
+
+	QueryMapper queryMapper;
+	MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> 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
+	 * information (is a {@link TypedAggregation}) or use the {@link Aggregation#DEFAULT_CONTEXT}.
+	 *
+	 * @param aggregation must not be {@literal null}.
+	 * @param context can be {@literal null}.
+	 * @return the root {@link AggregationOperationContext} to use.
+	 */
+	AggregationOperationContext prepareAggregationContext(Aggregation aggregation,
+			@Nullable AggregationOperationContext context) {
+
+		if (context != null) {
+			return context;
+		}
+
+		if (aggregation instanceof TypedAggregation) {
+			return new TypeBasedAggregationOperationContext(((TypedAggregation) aggregation).getInputType(), mappingContext,
+					queryMapper);
+		}
+
+		return Aggregation.DEFAULT_CONTEXT;
+	}
+
+	/**
+	 * Extract and map the aggregation pipeline into a {@link List} of {@link Document}.
+	 *
+	 * @param aggregation
+	 * @param context
+	 * @return
+	 */
+	Document createPipeline(String collectionName, Aggregation aggregation, AggregationOperationContext context) {
+
+		if (!ObjectUtils.nullSafeEquals(context, Aggregation.DEFAULT_CONTEXT)) {
+			return aggregation.toDocument(collectionName, context);
+		}
+
+		Document command = aggregation.toDocument(collectionName, context);
+		command.put("pipeline", mapAggregationPipeline(command.get("pipeline", List.class)));
+
+		return command;
+	}
+
+	/**
+	 * Extract the command and map the aggregation pipeline.
+	 *
+	 * @param aggregation
+	 * @param context
+	 * @return
+	 */
+	Document createCommand(String collection, Aggregation aggregation, AggregationOperationContext context) {
+
+		Document command = aggregation.toDocument(collection, context);
+
+		if (!ObjectUtils.nullSafeEquals(context, Aggregation.DEFAULT_CONTEXT)) {
+			return command;
+		}
+
+		command.put("pipeline", mapAggregationPipeline(command.get("pipeline", List.class)));
+
+		return command;
+	}
+
+	private List<Document> mapAggregationPipeline(List<Document> pipeline) {
+
+		return pipeline.stream().map(val -> queryMapper.getMappedObject(val, Optional.empty()))
+				.collect(Collectors.toList());
+	}
+}

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

@@ -1,44 +1,46 @@
-/*
- * Copyright 2010-2016 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import org.bson.Document;
-import org.springframework.dao.DataAccessException;
-
-import com.mongodb.MongoException;
-import com.mongodb.client.MongoCollection;
-
-/**
- * Callback interface for executing actions against a {@link MongoCollection}
- *
- * @author Mark Pollak
- * @author Grame Rocher
- * @author Oliver Gierke
- * @author John Brisbin
- * @auhtor Christoph Strobl
- * @since 1.0
- */
-public interface CollectionCallback<T> {
-
-	/**
-	 * @param collection never {@literal null}.
-	 * @return
-	 * @throws MongoException
-	 * @throws DataAccessException
-	 */
-	T doInCollection(MongoCollection<Document> collection) throws MongoException, DataAccessException;
-
-}
+/*
+ * Copyright 2010-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core;
+
+import org.bson.Document;
+import org.springframework.dao.DataAccessException;
+import org.springframework.lang.Nullable;
+
+import com.mongodb.MongoException;
+import com.mongodb.client.MongoCollection;
+
+/**
+ * Callback interface for executing actions against a {@link MongoCollection}.
+ *
+ * @author Mark Pollak
+ * @author Grame Rocher
+ * @author Oliver Gierke
+ * @author John Brisbin
+ * @auhtor Christoph Strobl
+ * @since 1.0
+ */
+public interface CollectionCallback<T> {
+
+	/**
+	 * @param collection never {@literal null}.
+	 * @return can be {@literal null}.
+	 * @throws MongoException
+	 * @throws DataAccessException
+	 */
+	@Nullable
+	T doInCollection(MongoCollection<Document> collection) throws MongoException, DataAccessException;
+
+}

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

@@ -1,164 +1,166 @@
-/*
- * Copyright 2010-2017 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import java.util.Optional;
-
-import org.springframework.data.mongodb.core.query.Collation;
-import org.springframework.util.Assert;
-
-/**
- * Provides a simple wrapper to encapsulate the variety of settings you can use when creating a collection.
- *
- * @author Thomas Risberg
- * @author Christoph Strobl
- * @author Mark Paluch
- */
-public class CollectionOptions {
-
-	private Long maxDocuments;
-	private Long size;
-	private Boolean capped;
-	private Collation collation;
-
-	/**
-	 * Constructs a new <code>CollectionOptions</code> instance.
-	 *
-	 * @param size the collection size in bytes, this data space is preallocated.
-	 * @param maxDocuments the maximum number of documents in the collection.
-	 * @param capped true to created a "capped" collection (fixed size with auto-FIFO behavior based on insertion order),
-	 *          false otherwise.
-	 * @deprecated since 2.0 please use {@link CollectionOptions#empty()} as entry point.
-	 */
-	@Deprecated
-	public CollectionOptions(Long size, Long maxDocuments, Boolean capped) {
-		this(size, maxDocuments, capped, null);
-	}
-
-	private CollectionOptions(Long size, Long maxDocuments, Boolean capped, Collation collation) {
-
-		this.maxDocuments = maxDocuments;
-		this.size = size;
-		this.capped = capped;
-		this.collation = collation;
-	}
-
-	/**
-	 * Create new {@link CollectionOptions} by just providing the {@link Collation} to use.
-	 *
-	 * @param collation must not be {@literal null}.
-	 * @return new {@link CollectionOptions}.
-	 * @since 2.0
-	 */
-	public static CollectionOptions just(Collation collation) {
-
-		Assert.notNull(collation, "Collation must not be null!");
-
-		return new CollectionOptions(null, null, null, collation);
-	}
-
-	/**
-	 * Create new empty {@link CollectionOptions}.
-	 *
-	 * @return new {@link CollectionOptions}.
-	 * @since 2.0
-	 */
-	public static CollectionOptions empty() {
-		return new CollectionOptions(null, null, null, null);
-	}
-
-	/**
-	 * Create new {@link CollectionOptions} with already given settings and capped set to {@literal true}. <br />
-	 * <strong>NOTE</strong> Using capped collections requires defining {@link #size(int)}.
-	 *
-	 * @return new {@link CollectionOptions}.
-	 * @since 2.0
-	 */
-	public CollectionOptions capped() {
-		return new CollectionOptions(size, maxDocuments, true, collation);
-	}
-
-	/**
-	 * Create new {@link CollectionOptions} with already given settings and {@code maxDocuments} set to given value.
-	 *
-	 * @param maxDocuments can be {@literal null}.
-	 * @return new {@link CollectionOptions}.
-	 * @since 2.0
-	 */
-	public CollectionOptions maxDocuments(long maxDocuments) {
-		return new CollectionOptions(size, maxDocuments, capped, collation);
-	}
-
-	/**
-	 * Create new {@link CollectionOptions} with already given settings and {@code size} set to given value.
-	 *
-	 * @param size can be {@literal null}.
-	 * @return new {@link CollectionOptions}.
-	 * @since 2.0
-	 */
-	public CollectionOptions size(long size) {
-		return new CollectionOptions(size, maxDocuments, capped, collation);
-	}
-
-	/**
-	 * Create new {@link CollectionOptions} with already given settings and {@code collation} set to given value.
-	 *
-	 * @param collation can be {@literal null}.
-	 * @return new {@link CollectionOptions}.
-	 * @since 2.0
-	 */
-	public CollectionOptions collation(Collation collation) {
-		return new CollectionOptions(size, maxDocuments, capped, collation);
-	}
-
-	/**
-	 * Get the max number of documents the collection should be limited to.
-	 *
-	 * @return {@link Optional#empty()} if not set.
-	 */
-	public Optional<Long> getMaxDocuments() {
-		return Optional.ofNullable(maxDocuments);
-	}
-
-	/**
-	 * Get the {@literal size} in bytes the collection should be limited to.
-	 *
-	 * @return {@link Optional#empty()} if not set.
-	 */
-	public Optional<Long> getSize() {
-		return Optional.ofNullable(size);
-	}
-
-	/**
-	 * Get if the collection should be capped.
-	 *
-	 * @return {@link Optional#empty()} if not set.
-	 * @since 2.0
-	 */
-	public Optional<Boolean> getCapped() {
-		return Optional.ofNullable(capped);
-	}
-
-	/**
-	 * Get the {@link Collation} settings.
-	 *
-	 * @return {@link Optional#empty()} if not set.
-	 * @since 2.0
-	 */
-	public Optional<Collation> getCollation() {
-		return Optional.ofNullable(collation);
-	}
-}
+/*
+ * Copyright 2010-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core;
+
+import java.util.Optional;
+
+import org.springframework.data.mongodb.core.query.Collation;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+
+/**
+ * Provides a simple wrapper to encapsulate the variety of settings you can use when creating a collection.
+ *
+ * @author Thomas Risberg
+ * @author Christoph Strobl
+ * @author Mark Paluch
+ */
+public class CollectionOptions {
+
+	private @Nullable Long maxDocuments;
+	private @Nullable Long size;
+	private @Nullable Boolean capped;
+	private @Nullable Collation collation;
+
+	/**
+	 * Constructs a new <code>CollectionOptions</code> instance.
+	 *
+	 * @param size the collection size in bytes, this data space is preallocated. Can be {@literal null}.
+	 * @param maxDocuments the maximum number of documents in the collection. Can be {@literal null}.
+	 * @param capped true to created a "capped" collection (fixed size with auto-FIFO behavior based on insertion order),
+	 *          false otherwise. Can be {@literal null}.
+	 * @deprecated since 2.0 please use {@link CollectionOptions#empty()} as entry point.
+	 */
+	@Deprecated
+	public CollectionOptions(@Nullable Long size, @Nullable Long maxDocuments, @Nullable Boolean capped) {
+		this(size, maxDocuments, capped, null);
+	}
+
+	private CollectionOptions(@Nullable Long size, @Nullable Long maxDocuments, @Nullable Boolean capped,
+			@Nullable Collation collation) {
+
+		this.maxDocuments = maxDocuments;
+		this.size = size;
+		this.capped = capped;
+		this.collation = collation;
+	}
+
+	/**
+	 * Create new {@link CollectionOptions} by just providing the {@link Collation} to use.
+	 *
+	 * @param collation must not be {@literal null}.
+	 * @return new {@link CollectionOptions}.
+	 * @since 2.0
+	 */
+	public static CollectionOptions just(Collation collation) {
+
+		Assert.notNull(collation, "Collation must not be null!");
+
+		return new CollectionOptions(null, null, null, collation);
+	}
+
+	/**
+	 * Create new empty {@link CollectionOptions}.
+	 *
+	 * @return new {@link CollectionOptions}.
+	 * @since 2.0
+	 */
+	public static CollectionOptions empty() {
+		return new CollectionOptions(null, null, null, null);
+	}
+
+	/**
+	 * Create new {@link CollectionOptions} with already given settings and capped set to {@literal true}. <br />
+	 * <strong>NOTE</strong> Using capped collections requires defining {@link #size(int)}.
+	 *
+	 * @return new {@link CollectionOptions}.
+	 * @since 2.0
+	 */
+	public CollectionOptions capped() {
+		return new CollectionOptions(size, maxDocuments, true, collation);
+	}
+
+	/**
+	 * Create new {@link CollectionOptions} with already given settings and {@code maxDocuments} set to given value.
+	 *
+	 * @param maxDocuments can be {@literal null}.
+	 * @return new {@link CollectionOptions}.
+	 * @since 2.0
+	 */
+	public CollectionOptions maxDocuments(long maxDocuments) {
+		return new CollectionOptions(size, maxDocuments, capped, collation);
+	}
+
+	/**
+	 * Create new {@link CollectionOptions} with already given settings and {@code size} set to given value.
+	 *
+	 * @param size can be {@literal null}.
+	 * @return new {@link CollectionOptions}.
+	 * @since 2.0
+	 */
+	public CollectionOptions size(long size) {
+		return new CollectionOptions(size, maxDocuments, capped, collation);
+	}
+
+	/**
+	 * Create new {@link CollectionOptions} with already given settings and {@code collation} set to given value.
+	 *
+	 * @param collation can be {@literal null}.
+	 * @return new {@link CollectionOptions}.
+	 * @since 2.0
+	 */
+	public CollectionOptions collation(@Nullable Collation collation) {
+		return new CollectionOptions(size, maxDocuments, capped, collation);
+	}
+
+	/**
+	 * Get the max number of documents the collection should be limited to.
+	 *
+	 * @return {@link Optional#empty()} if not set.
+	 */
+	public Optional<Long> getMaxDocuments() {
+		return Optional.ofNullable(maxDocuments);
+	}
+
+	/**
+	 * Get the {@literal size} in bytes the collection should be limited to.
+	 *
+	 * @return {@link Optional#empty()} if not set.
+	 */
+	public Optional<Long> getSize() {
+		return Optional.ofNullable(size);
+	}
+
+	/**
+	 * Get if the collection should be capped.
+	 *
+	 * @return {@link Optional#empty()} if not set.
+	 * @since 2.0
+	 */
+	public Optional<Boolean> getCapped() {
+		return Optional.ofNullable(capped);
+	}
+
+	/**
+	 * Get the {@link Collation} settings.
+	 *
+	 * @return {@link Optional#empty()} if not set.
+	 * @since 2.0
+	 */
+	public Optional<Collation> getCollation() {
+		return Optional.ofNullable(collation);
+	}
+}

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

@@ -1,30 +1,44 @@
-/*
- * Copyright 2010-2016 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import org.springframework.dao.DataAccessException;
-
-import com.mongodb.MongoException;
-import com.mongodb.client.MongoDatabase;
-
-/**
- *
- * @param <T>
- */
-public interface DbCallback<T> {
-
-	T doInDB(MongoDatabase db) throws MongoException, DataAccessException;
-}
+/*
+ * Copyright 2010-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core;
+
+import org.springframework.dao.DataAccessException;
+import org.springframework.lang.Nullable;
+
+import com.mongodb.MongoException;
+import com.mongodb.client.MongoDatabase;
+
+/**
+ * Callback interface for executing actions against a {@link MongoDatabase}.
+ *
+ * @author Mark Pollak
+ * @author Graeme Rocher
+ * @author Thomas Risberg
+ * @author Oliver Gierke
+ * @author John Brisbin
+ * @author Christoph Strobl
+ */
+public interface DbCallback<T> {
+
+	/**
+	 * @param db must not be {@literal null}.
+	 * @return can be {@literal null}.
+	 * @throws MongoException
+	 * @throws DataAccessException
+	 */
+	@Nullable
+	T doInDB(MongoDatabase db) throws MongoException, DataAccessException;
+}

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

@@ -1,66 +0,0 @@
-package org.springframework.data.mongodb.core;
-
-import java.util.Map;
-import java.util.concurrent.ConcurrentHashMap;
-
-import com.mongodb.DB;
-import org.springframework.transaction.support.ResourceHolderSupport;
-import org.springframework.util.Assert;
-
-class DbHolder extends ResourceHolderSupport {
-	private static final Object DEFAULT_KEY = new Object();
-
-	private final Map<Object, DB> dbMap = new ConcurrentHashMap<Object, DB>();
-
-	public DbHolder(DB db) {
-		addDB(db);
-	}
-
-	public DbHolder(Object key, DB db) {
-		addDB(key, db);
-	}
-
-	public DB getDB() {
-		return getDB(DEFAULT_KEY);
-	}
-
-	public DB getDB(Object key) {
-		return this.dbMap.get(key);
-	}
-
-	public DB getAnyDB() {
-		if (!this.dbMap.isEmpty()) {
-			return this.dbMap.values().iterator().next();
-		}
-		return null;
-	}
-
-	public void addDB(DB session) {
-		addDB(DEFAULT_KEY, session);
-	}
-
-	public void addDB(Object key, DB session) {
-		Assert.notNull(key, "Key must not be null");
-		Assert.notNull(session, "DB must not be null");
-		this.dbMap.put(key, session);
-	}
-
-	public DB removeDB(Object key) {
-		return this.dbMap.remove(key);
-	}
-
-	public boolean containsDB(DB session) {
-		return this.dbMap.containsValue(session);
-	}
-
-	public boolean isEmpty() {
-		return this.dbMap.isEmpty();
-	}
-
-	public boolean doesNotHoldNonDefaultDB() {
-		synchronized (this.dbMap) {
-			return this.dbMap.isEmpty() || (this.dbMap.size() == 1 && this.dbMap.containsKey(DEFAULT_KEY));
-		}
-	}
-
-}

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

@@ -35,6 +35,7 @@ import org.springframework.data.mongodb.core.query.Collation;
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.data.mongodb.core.query.Update;
 import org.springframework.data.util.Pair;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 import com.mongodb.BulkWriteException;
@@ -67,7 +68,7 @@ class DefaultBulkOperations implements BulkOperations {
 	private final List<WriteModel<Document>> models = new ArrayList<>();
 
 	private PersistenceExceptionTranslator exceptionTranslator;
-	private WriteConcern defaultWriteConcern;
+	private @Nullable WriteConcern defaultWriteConcern;
 
 	private BulkWriteOptions bulkOptions;
 
@@ -99,7 +100,7 @@ class DefaultBulkOperations implements BulkOperations {
 	 *
 	 * @param exceptionTranslator can be {@literal null}.
 	 */
-	public void setExceptionTranslator(PersistenceExceptionTranslator exceptionTranslator) {
+	public void setExceptionTranslator(@Nullable PersistenceExceptionTranslator exceptionTranslator) {
 		this.exceptionTranslator = exceptionTranslator == null ? new MongoExceptionTranslator() : exceptionTranslator;
 	}
 
@@ -108,7 +109,7 @@ class DefaultBulkOperations implements BulkOperations {
 	 *
 	 * @param defaultWriteConcern can be {@literal null}.
 	 */
-	void setDefaultWriteConcern(WriteConcern defaultWriteConcern) {
+	void setDefaultWriteConcern(@Nullable WriteConcern defaultWriteConcern) {
 		this.defaultWriteConcern = defaultWriteConcern;
 	}
 

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

@@ -29,6 +29,7 @@ import org.springframework.data.mongodb.core.index.IndexDefinition;
 import org.springframework.data.mongodb.core.index.IndexInfo;
 import org.springframework.data.mongodb.core.index.IndexOperations;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 import com.mongodb.MongoException;
@@ -52,7 +53,7 @@ public class DefaultIndexOperations implements IndexOperations {
 	private final MongoDbFactory mongoDbFactory;
 	private final String collectionName;
 	private final QueryMapper mapper;
-	private final Class<?> type;
+	private final @Nullable Class<?> type;
 
 	/**
 	 * Creates a new {@link DefaultIndexOperations}.
@@ -62,7 +63,6 @@ public class DefaultIndexOperations implements IndexOperations {
 	 * @param queryMapper must not be {@literal null}.
 	 */
 	public DefaultIndexOperations(MongoDbFactory mongoDbFactory, String collectionName, QueryMapper queryMapper) {
-
 		this(mongoDbFactory, collectionName, queryMapper, null);
 	}
 
@@ -76,7 +76,7 @@ public class DefaultIndexOperations implements IndexOperations {
 	 * @since 1.10
 	 */
 	public DefaultIndexOperations(MongoDbFactory mongoDbFactory, String collectionName, QueryMapper queryMapper,
-			Class<?> type) {
+			@Nullable Class<?> type) {
 
 		Assert.notNull(mongoDbFactory, "MongoDbFactory must not be null!");
 		Assert.notNull(collectionName, "Collection name can not be null!");
@@ -98,10 +98,6 @@ public class DefaultIndexOperations implements IndexOperations {
 
 			Document indexOptions = indexDefinition.getIndexOptions();
 
-			if (indexOptions == null) {
-				return collection.createIndex(indexDefinition.getIndexKeys());
-			}
-
 			IndexOptions ops = IndexConverters.indexDefinitionToIndexOptionsConverter().convert(indexDefinition);
 
 			if (indexOptions.containsKey(PARTIAL_FILTER_EXPRESSION_KEY)) {
@@ -116,7 +112,8 @@ public class DefaultIndexOperations implements IndexOperations {
 		});
 	}
 
-	private MongoPersistentEntity<?> lookupPersistentEntity(Class<?> entityType, String collection) {
+	@Nullable
+	private MongoPersistentEntity<?> lookupPersistentEntity(@Nullable Class<?> entityType, String collection) {
 
 		if (entityType != null) {
 			return mapper.getMappingContext().getRequiredPersistentEntity(entityType);
@@ -185,6 +182,7 @@ public class DefaultIndexOperations implements IndexOperations {
 		});
 	}
 
+	@Nullable
 	public <T> T execute(CollectionCallback<T> callback) {
 
 		Assert.notNull(callback, "CollectionCallback must not be null!");

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,10 +21,10 @@ import org.springframework.data.mongodb.core.index.IndexOperations;
 import org.springframework.data.mongodb.core.index.IndexOperationsProvider;
 
 /**
- * {@link IndexOperationsProvider} to obtain {@link IndexOperations} from a given {@link MongoDbFactory}. TODO: Review
- * me
+ * {@link IndexOperationsProvider} to obtain {@link IndexOperations} from a given {@link MongoDbFactory}.
  *
  * @author Mark Paluch
+ * @author Christoph Strobl
  * @since 2.0
  */
 class DefaultIndexOperationsProvider implements IndexOperationsProvider {
@@ -34,12 +34,16 @@ class DefaultIndexOperationsProvider implements IndexOperationsProvider {
 
 	/**
 	 * @param mongoDbFactory must not be {@literal null}.
+	 * @param mapper must not be {@literal null}.
 	 */
 	DefaultIndexOperationsProvider(MongoDbFactory mongoDbFactory, QueryMapper mapper) {
-		this.mongoDbFactory = mongoDbFactory; this.mapper = mapper;
+
+		this.mongoDbFactory = mongoDbFactory;
+		this.mapper = mapper;
 	}
 
-	/* (non-Javadoc)
+	/*
+	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.index.IndexOperationsProvider#reactiveIndexOps(java.lang.String)
 	 */
 	@Override

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

@@ -15,7 +15,6 @@
  */
 package org.springframework.data.mongodb.core;
 
-import org.springframework.data.mongodb.core.index.ReactiveIndexOperations;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
@@ -26,7 +25,9 @@ import org.bson.Document;
 import org.springframework.data.mongodb.core.convert.QueryMapper;
 import org.springframework.data.mongodb.core.index.IndexDefinition;
 import org.springframework.data.mongodb.core.index.IndexInfo;
+import org.springframework.data.mongodb.core.index.ReactiveIndexOperations;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 import com.mongodb.client.model.IndexOptions;
@@ -85,7 +86,8 @@ public class DefaultReactiveIndexOperations implements ReactiveIndexOperations {
 		this.type = type;
 	}
 
-	/* (non-Javadoc)
+	/*
+	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.index.ReactiveIndexOperations#ensureIndex(org.springframework.data.mongodb.core.index.IndexDefinition)
 	 */
 	public Mono<String> ensureIndex(final IndexDefinition indexDefinition) {
@@ -94,10 +96,6 @@ public class DefaultReactiveIndexOperations implements ReactiveIndexOperations {
 
 			Document indexOptions = indexDefinition.getIndexOptions();
 
-			if (indexOptions == null) {
-				return collection.createIndex(indexDefinition.getIndexKeys());
-			}
-
 			IndexOptions ops = IndexConverters.indexDefinitionToIndexOptionsConverter().convert(indexDefinition);
 
 			if (indexOptions.containsKey(PARTIAL_FILTER_EXPRESSION_KEY)) {
@@ -117,6 +115,7 @@ public class DefaultReactiveIndexOperations implements ReactiveIndexOperations {
 		}).next();
 	}
 
+	@Nullable
 	private MongoPersistentEntity<?> lookupPersistentEntity(String collection) {
 
 		Collection<? extends MongoPersistentEntity<?>> entities = queryMapper.getMappingContext().getPersistentEntities();

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2016 the original author or authors.
+ * Copyright 2014-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -31,6 +31,7 @@ import org.bson.types.ObjectId;
 import org.springframework.dao.DataAccessException;
 import org.springframework.data.mongodb.core.script.ExecutableMongoScript;
 import org.springframework.data.mongodb.core.script.NamedMongoScript;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.ObjectUtils;
@@ -42,9 +43,10 @@ import com.mongodb.client.MongoDatabase;
 
 /**
  * Default implementation of {@link ScriptOperations} capable of saving and executing {@link ServerSideJavaScript}.
- * 
+ *
  * @author Christoph Strobl
  * @author Oliver Gierke
+ * @author Mark Paluch
  * @since 1.7
  */
 class DefaultScriptOperations implements ScriptOperations {
@@ -56,7 +58,7 @@ class DefaultScriptOperations implements ScriptOperations {
 
 	/**
 	 * Creates new {@link DefaultScriptOperations} using given {@link MongoOperations}.
-	 * 
+	 *
 	 * @param mongoOperations must not be {@literal null}.
 	 */
 	public DefaultScriptOperations(MongoOperations mongoOperations) {
@@ -140,7 +142,7 @@ class DefaultScriptOperations implements ScriptOperations {
 
 		Assert.hasText(scriptName, "ScriptName must not be null or empty!");
 
-		return mongoOperations.exists(query(where("name").is(scriptName)), NamedMongoScript.class, SCRIPT_COLLECTION_NAME);
+		return mongoOperations.exists(query(where("_id").is(scriptName)), NamedMongoScript.class, SCRIPT_COLLECTION_NAME);
 	}
 
 	/*
@@ -189,7 +191,7 @@ class DefaultScriptOperations implements ScriptOperations {
 	 * Generate a valid name for the {@literal JavaScript}. MongoDB requires an id of type String for scripts. Calling
 	 * scripts having {@link ObjectId} as id fails. Therefore we create a random UUID without {@code -} (as this won't
 	 * work) an prefix the result with {@link #SCRIPT_NAME_PREFIX}.
-	 * 
+	 *
 	 * @return
 	 */
 	private static String generateScriptName() {

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

@@ -24,6 +24,7 @@ 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;
 
@@ -74,8 +75,8 @@ class ExecutableAggregationOperationSupport implements ExecutableAggregationOper
 
 		@NonNull MongoTemplate template;
 		@NonNull Class<T> domainType;
-		Aggregation aggregation;
-		String collection;
+		@Nullable Aggregation aggregation;
+		@Nullable String collection;
 
 		/*
 		 * (non-Javadoc)

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

@@ -22,6 +22,7 @@ import java.util.stream.Stream;
 import org.springframework.data.geo.GeoResults;
 import org.springframework.data.mongodb.core.query.NearQuery;
 import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.lang.Nullable;
 
 /**
  * {@link ExecutableFindOperation} allows creation and execution of MongoDB find operations in a fluent API style.
@@ -83,6 +84,7 @@ public interface ExecutableFindOperation {
 		 * @return {@literal null} if no match found.
 		 * @throws org.springframework.dao.IncorrectResultSizeDataAccessException if more than one match found.
 		 */
+		@Nullable
 		T oneValue();
 
 		/**
@@ -99,6 +101,7 @@ public interface ExecutableFindOperation {
 		 *
 		 * @return {@literal null} if no match found.
 		 */
+		@Nullable
 		T firstValue();
 
 		/**

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

@@ -31,6 +31,7 @@ import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.data.mongodb.core.query.SerializationUtils;
 import org.springframework.data.util.CloseableIterator;
 import org.springframework.data.util.StreamUtils;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
@@ -88,7 +89,7 @@ class ExecutableFindOperationSupport implements ExecutableFindOperation {
 		@NonNull MongoTemplate template;
 		@NonNull Class<?> domainType;
 		Class<T> returnType;
-		String collection;
+		@Nullable String collection;
 		Query query;
 
 		/*
@@ -204,7 +205,7 @@ class ExecutableFindOperationSupport implements ExecutableFindOperation {
 			return template.exists(query, domainType, getCollectionName());
 		}
 
-		private List<T> doFind(CursorPreparer preparer) {
+		private List<T> doFind(@Nullable CursorPreparer preparer) {
 
 			Document queryObject = query.getQueryObject();
 			Document fieldsObject = query.getFieldsObject();
@@ -217,8 +218,8 @@ class ExecutableFindOperationSupport implements ExecutableFindOperation {
 			return template.doStream(query, domainType, getCollectionName(), returnType);
 		}
 
-		private CursorPreparer getCursorPreparer(Query query, CursorPreparer preparer) {
-			return query == null || preparer != null ? preparer : template.new QueryCursorPreparer(query, domainType);
+		private CursorPreparer getCursorPreparer(Query query, @Nullable CursorPreparer preparer) {
+			return preparer != null ? preparer : template.new QueryCursorPreparer(query, domainType);
 		}
 
 		private String getCollectionName() {
@@ -236,10 +237,10 @@ class ExecutableFindOperationSupport implements ExecutableFindOperation {
 	 */
 	static class DelegatingQueryCursorPreparer implements CursorPreparer {
 
-		private final CursorPreparer delegate;
+		private final @Nullable CursorPreparer delegate;
 		private Optional<Integer> limit = Optional.empty();
 
-		DelegatingQueryCursorPreparer(CursorPreparer delegate) {
+		DelegatingQueryCursorPreparer(@Nullable CursorPreparer delegate) {
 			this.delegate = delegate;
 		}
 

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

@@ -24,6 +24,7 @@ import java.util.ArrayList;
 import java.util.Collection;
 
 import org.springframework.data.mongodb.core.BulkOperations.BulkMode;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -75,8 +76,8 @@ class ExecutableInsertOperationSupport implements ExecutableInsertOperation {
 
 		@NonNull MongoTemplate template;
 		@NonNull Class<T> domainType;
-		String collection;
-		BulkMode bulkMode;
+		@Nullable String collection;
+		@Nullable BulkMode bulkMode;
 
 		/*
 		 * (non-Javadoc)

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

@@ -23,6 +23,7 @@ import lombok.experimental.FieldDefaults;
 import java.util.List;
 
 import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -77,7 +78,7 @@ class ExecutableRemoveOperationSupport implements ExecutableRemoveOperation {
 		@NonNull MongoTemplate template;
 		@NonNull Class<T> domainType;
 		Query query;
-		String collection;
+		@Nullable String collection;
 
 		/*
 		 * (non-Javadoc)

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

@@ -21,6 +21,7 @@ import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.data.mongodb.core.query.Update;
 
 import com.mongodb.client.result.UpdateResult;
+import org.springframework.lang.Nullable;
 
 /**
  * {@link ExecutableUpdateOperation} allows creation and execution of MongoDB update / findAndModify operations in a
@@ -148,6 +149,7 @@ public interface ExecutableUpdateOperation {
 		 *
 		 * @return {@literal null} if nothing found.
 		 */
+		@Nullable
 		T findAndModifyValue();
 	}
 

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

@@ -22,6 +22,7 @@ import lombok.experimental.FieldDefaults;
 
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.data.mongodb.core.query.Update;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -76,9 +77,9 @@ class ExecutableUpdateOperationSupport implements ExecutableUpdateOperation {
 		@NonNull MongoTemplate template;
 		@NonNull Class<T> domainType;
 		Query query;
-		Update update;
-		String collection;
-		FindAndModifyOptions options;
+		@Nullable Update update;
+		@Nullable String collection;
+		@Nullable FindAndModifyOptions options;
 
 		/*
 		 * (non-Javadoc)
@@ -160,8 +161,8 @@ class ExecutableUpdateOperationSupport implements ExecutableUpdateOperation {
 		 * @see org.springframework.data.mongodb.core.ExecutableUpdateOperation.TerminatingFindAndModify#findAndModifyValue()
 		 */
 		@Override
-		public T findAndModifyValue() {
-			return template.findAndModify(query, update, options, domainType, getCollectionName());
+		public @Nullable T findAndModifyValue() {
+			return template.findAndModify(query, update, options != null ? options : new FindAndModifyOptions(), domainType, getCollectionName());
 		}
 
 		private UpdateResult doUpdate(boolean multi, boolean upsert) {

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

@@ -18,6 +18,7 @@ package org.springframework.data.mongodb.core;
 import java.util.Optional;
 
 import org.springframework.data.mongodb.core.query.Collation;
+import org.springframework.lang.Nullable;
 
 /**
  * @author Mark Pollak
@@ -30,7 +31,7 @@ public class FindAndModifyOptions {
 	private boolean upsert;
 	private boolean remove;
 
-	private Collation collation;
+	private @Nullable Collation collation;
 
 	/**
 	 * Static factory method to create a FindAndModifyOptions instance
@@ -46,7 +47,7 @@ public class FindAndModifyOptions {
 	 * @return
 	 * @since 2.0
 	 */
-	public static FindAndModifyOptions of(FindAndModifyOptions source) {
+	public static FindAndModifyOptions of(@Nullable FindAndModifyOptions source) {
 
 		FindAndModifyOptions options = new FindAndModifyOptions();
 		if (source == null) {
@@ -83,7 +84,7 @@ public class FindAndModifyOptions {
 	 * @return
 	 * @since 2.0
 	 */
-	public FindAndModifyOptions collation(Collation collation) {
+	public FindAndModifyOptions collation(@Nullable Collation collation) {
 
 		this.collation = collation;
 		return this;

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -13,7 +13,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
 package org.springframework.data.mongodb.core;
 
 import java.util.concurrent.TimeUnit;
@@ -22,6 +21,7 @@ import org.bson.Document;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.data.mongodb.core.index.IndexDefinition;
 import org.springframework.data.mongodb.core.index.IndexInfo;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
 import com.mongodb.client.model.Collation;
@@ -119,7 +119,8 @@ abstract class IndexConverters {
 		};
 	}
 
-	public static Collation fromDocument(Document source) {
+	@Nullable
+	public static Collation fromDocument(@Nullable Document source) {
 
 		if (source == null) {
 			return null;

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2016 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 package org.springframework.data.mongodb.core;
 
 import org.bson.Document;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 import com.mongodb.WriteConcern;
@@ -36,26 +37,28 @@ import com.mongodb.WriteConcern;
 public class MongoAction {
 
 	private final String collectionName;
-	private final WriteConcern defaultWriteConcern;
-	private final Class<?> entityType;
 	private final MongoActionOperation mongoActionOperation;
-	private final Document query;
-	private final Document document;
+
+	private final @Nullable WriteConcern defaultWriteConcern;
+	private final @Nullable Class<?> entityType;
+	private final @Nullable Document query;
+	private final @Nullable Document document;
 
 	/**
 	 * Create an instance of a {@link MongoAction}.
 	 * 
-	 * @param defaultWriteConcern the default write concern.
-	 * @param mongoActionOperation action being taken against the collection
+	 * @param defaultWriteConcern the default write concern. Can be {@literal null}.
+	 * @param mongoActionOperation action being taken against the collection. Must not be {@literal null}.
 	 * @param collectionName the collection name, must not be {@literal null} or empty.
-	 * @param entityType the POJO that is being operated against
-	 * @param document the converted Document from the POJO or Spring Update object
-	 * @param query the converted Document from the Spring Query object
+	 * @param entityType the POJO that is being operated against. Can be {@literal null}.
+	 * @param document the converted Document from the POJO or Spring Update object. Can be {@literal null}.
+	 * @param query the converted Document from the Spring Query object. Can be {@literal null}.
 	 */
-	public MongoAction(WriteConcern defaultWriteConcern, MongoActionOperation mongoActionOperation, String collectionName,
-			Class<?> entityType, Document document, Document query) {
+	public MongoAction(@Nullable WriteConcern defaultWriteConcern, MongoActionOperation mongoActionOperation,
+			String collectionName, @Nullable Class<?> entityType, @Nullable Document document, @Nullable Document query) {
 
 		Assert.hasText(collectionName, "Collection name must not be null or empty!");
+		Assert.notNull(mongoActionOperation, "MongoActionOperation must not be null!");
 
 		this.defaultWriteConcern = defaultWriteConcern;
 		this.mongoActionOperation = mongoActionOperation;
@@ -69,22 +72,27 @@ public class MongoAction {
 		return collectionName;
 	}
 
+	@Nullable
 	public WriteConcern getDefaultWriteConcern() {
 		return defaultWriteConcern;
 	}
 
+	@Nullable
 	public Class<?> getEntityType() {
 		return entityType;
 	}
 
+	@Nullable
 	public MongoActionOperation getMongoActionOperation() {
 		return mongoActionOperation;
 	}
 
+	@Nullable
 	public Document getQuery() {
 		return query;
 	}
 
+	@Nullable
 	public Document getDocument() {
 		return document;
 	}

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

@@ -1,77 +1,78 @@
-/*
- * Copyright 2011-2017 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import com.mongodb.MongoClient;
-import com.mongodb.client.MongoDatabase;
-import org.bson.Document;
-import org.springframework.jmx.export.annotation.ManagedOperation;
-import org.springframework.jmx.export.annotation.ManagedResource;
-import org.springframework.util.Assert;
-
-/**
- * Mongo server administration exposed via JMX annotations
- * 
- * @author Mark Pollack
- * @author Thomas Darimont
- * @author Mark Paluch
- * @author Christoph Strobl
- */
-@ManagedResource(description = "Mongo Admin Operations")
-public class MongoAdmin implements MongoAdminOperations {
-
-	private final MongoClient mongoClient;
-
-	public MongoAdmin(MongoClient mongoClient) {
-
-		Assert.notNull(mongoClient, "MongoClient must not be null!");
-		this.mongoClient = mongoClient;
-	}
-
-	/* (non-Javadoc)
-	  * @see org.springframework.data.mongodb.core.core.MongoAdminOperations#dropDatabase(java.lang.String)
-	  */
-	@ManagedOperation
-	public void dropDatabase(String databaseName) {
-		getDB(databaseName).drop();
-	}
-
-	/* (non-Javadoc)
-	  * @see org.springframework.data.mongodb.core.core.MongoAdminOperations#createDatabase(java.lang.String)
-	  */
-	@ManagedOperation
-	public void createDatabase(String databaseName) {
-		getDB(databaseName);
-	}
-
-	/* (non-Javadoc)
-	  * @see org.springframework.data.mongodb.core.core.MongoAdminOperations#getDatabaseStats(java.lang.String)
-	  */
-	@ManagedOperation
-	public String getDatabaseStats(String databaseName) {
-		return getDB(databaseName).runCommand(new Document("dbStats", 1).append("scale" , 1024)).toJson();
-	}
-
-	@ManagedOperation
-	public String getServerStatus() {
-		return getDB("admin").runCommand(new Document("serverStatus", 1).append("rangeDeleter", 1).append("repl", 1)).toJson();
-	}
-
-
-	MongoDatabase getDB(String databaseName) {
-		return mongoClient.getDatabase(databaseName);
-	}
-}
+/*
+ * Copyright 2011-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core;
+
+import org.bson.Document;
+import org.springframework.jmx.export.annotation.ManagedOperation;
+import org.springframework.jmx.export.annotation.ManagedResource;
+import org.springframework.util.Assert;
+
+import com.mongodb.MongoClient;
+import com.mongodb.client.MongoDatabase;
+
+/**
+ * Mongo server administration exposed via JMX annotations
+ * 
+ * @author Mark Pollack
+ * @author Thomas Darimont
+ * @author Mark Paluch
+ * @author Christoph Strobl
+ */
+@ManagedResource(description = "Mongo Admin Operations")
+public class MongoAdmin implements MongoAdminOperations {
+
+	private final MongoClient mongoClient;
+
+	public MongoAdmin(MongoClient mongoClient) {
+
+		Assert.notNull(mongoClient, "MongoClient must not be null!");
+		this.mongoClient = mongoClient;
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.core.MongoAdminOperations#dropDatabase(java.lang.String)
+	 */
+	@ManagedOperation
+	public void dropDatabase(String databaseName) {
+		getDB(databaseName).drop();
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.core.MongoAdminOperations#createDatabase(java.lang.String)
+	 */
+	@ManagedOperation
+	public void createDatabase(String databaseName) {
+		getDB(databaseName);
+	}
+
+	/* (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.core.MongoAdminOperations#getDatabaseStats(java.lang.String)
+	 */
+	@ManagedOperation
+	public String getDatabaseStats(String databaseName) {
+		return getDB(databaseName).runCommand(new Document("dbStats", 1).append("scale", 1024)).toJson();
+	}
+
+	@ManagedOperation
+	public String getServerStatus() {
+		return getDB("admin").runCommand(new Document("serverStatus", 1).append("rangeDeleter", 1).append("repl", 1))
+				.toJson();
+	}
+
+	MongoDatabase getDB(String databaseName) {
+		return mongoClient.getDatabase(databaseName);
+	}
+}

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

@@ -1,34 +1,34 @@
-/*
- * Copyright 2011-2014 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import org.springframework.jmx.export.annotation.ManagedOperation;
-
-/**
- * @author Mark Pollack
- * @author Oliver Gierke
- */
-public interface MongoAdminOperations {
-
-	@ManagedOperation
-	void dropDatabase(String databaseName);
-
-	@ManagedOperation
-	void createDatabase(String databaseName);
-
-	@ManagedOperation
-	String getDatabaseStats(String databaseName);
-}
+/*
+ * Copyright 2011-2014 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core;
+
+import org.springframework.jmx.export.annotation.ManagedOperation;
+
+/**
+ * @author Mark Pollack
+ * @author Oliver Gierke
+ */
+public interface MongoAdminOperations {
+
+	@ManagedOperation
+	void dropDatabase(String databaseName);
+
+	@ManagedOperation
+	void createDatabase(String databaseName);
+
+	@ManagedOperation
+	String getDatabaseStats(String databaseName);
+}

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

@@ -23,6 +23,7 @@ import java.util.List;
 import org.springframework.beans.factory.config.AbstractFactoryBean;
 import org.springframework.dao.DataAccessException;
 import org.springframework.dao.support.PersistenceExceptionTranslator;
+import org.springframework.lang.Nullable;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.StringUtils;
 
@@ -33,61 +34,62 @@ import com.mongodb.ServerAddress;
 
 /**
  * Convenient factory for configuring MongoDB.
- * 
+ *
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @since 1.7
  */
 public class MongoClientFactoryBean extends AbstractFactoryBean<MongoClient> implements PersistenceExceptionTranslator {
 
 	private static final PersistenceExceptionTranslator DEFAULT_EXCEPTION_TRANSLATOR = new MongoExceptionTranslator();
 
-	private MongoClientOptions mongoClientOptions;
-	private String host;
-	private Integer port;
-	private List<ServerAddress> replicaSetSeeds;
-	private List<MongoCredential> credentials;
+	private @Nullable MongoClientOptions mongoClientOptions;
+	private @Nullable String host;
+	private @Nullable Integer port;
+	private List<ServerAddress> replicaSetSeeds = Collections.emptyList();
+	private List<MongoCredential> credentials = Collections.emptyList();
 
 	private PersistenceExceptionTranslator exceptionTranslator = DEFAULT_EXCEPTION_TRANSLATOR;
 
 	/**
 	 * Set the {@link MongoClientOptions} to be used when creating {@link MongoClient}.
-	 * 
+	 *
 	 * @param mongoClientOptions
 	 */
-	public void setMongoClientOptions(MongoClientOptions mongoClientOptions) {
+	public void setMongoClientOptions(@Nullable MongoClientOptions mongoClientOptions) {
 		this.mongoClientOptions = mongoClientOptions;
 	}
 
 	/**
 	 * Set the list of credentials to be used when creating {@link MongoClient}.
-	 * 
+	 *
 	 * @param credentials can be {@literal null}.
 	 */
-	public void setCredentials(MongoCredential[] credentials) {
+	public void setCredentials(@Nullable MongoCredential[] credentials) {
 		this.credentials = filterNonNullElementsAsList(credentials);
 	}
 
 	/**
 	 * Set the list of {@link ServerAddress} to build up a replica set for.
-	 * 
+	 *
 	 * @param replicaSetSeeds can be {@literal null}.
 	 */
-	public void setReplicaSetSeeds(ServerAddress[] replicaSetSeeds) {
+	public void setReplicaSetSeeds(@Nullable ServerAddress[] replicaSetSeeds) {
 		this.replicaSetSeeds = filterNonNullElementsAsList(replicaSetSeeds);
 	}
 
 	/**
 	 * Configures the host to connect to.
-	 * 
+	 *
 	 * @param host
 	 */
-	public void setHost(String host) {
+	public void setHost(@Nullable String host) {
 		this.host = host;
 	}
 
 	/**
 	 * Configures the port to connect to.
-	 * 
+	 *
 	 * @param port
 	 */
 	public void setPort(int port) {
@@ -96,10 +98,10 @@ public class MongoClientFactoryBean extends AbstractFactoryBean<MongoClient> imp
 
 	/**
 	 * Configures the {@link PersistenceExceptionTranslator} to use.
-	 * 
+	 *
 	 * @param exceptionTranslator
 	 */
-	public void setExceptionTranslator(PersistenceExceptionTranslator exceptionTranslator) {
+	public void setExceptionTranslator(@Nullable PersistenceExceptionTranslator exceptionTranslator) {
 		this.exceptionTranslator = exceptionTranslator == null ? DEFAULT_EXCEPTION_TRANSLATOR : exceptionTranslator;
 	}
 
@@ -115,11 +117,12 @@ public class MongoClientFactoryBean extends AbstractFactoryBean<MongoClient> imp
 	 * (non-Javadoc)
 	 * @see org.springframework.dao.support.PersistenceExceptionTranslator#translateExceptionIfPossible(java.lang.RuntimeException)
 	 */
+	@Nullable
 	public DataAccessException translateExceptionIfPossible(RuntimeException ex) {
 		return exceptionTranslator.translateExceptionIfPossible(ex);
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.beans.factory.config.AbstractFactoryBean#createInstance()
 	 */
@@ -130,20 +133,19 @@ public class MongoClientFactoryBean extends AbstractFactoryBean<MongoClient> imp
 			mongoClientOptions = MongoClientOptions.builder().build();
 		}
 
-		if (credentials == null) {
-			credentials = Collections.emptyList();
-		}
-
 		return createMongoClient();
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.beans.factory.config.AbstractFactoryBean#destroyInstance(java.lang.Object)
 	 */
 	@Override
-	protected void destroyInstance(MongoClient instance) throws Exception {
-		instance.close();
+	protected void destroyInstance(@Nullable MongoClient instance) throws Exception {
+
+		if (instance != null) {
+			instance.close();
+		}
 	}
 
 	private MongoClient createMongoClient() throws UnknownHostException {
@@ -165,11 +167,11 @@ public class MongoClientFactoryBean extends AbstractFactoryBean<MongoClient> imp
 
 	/**
 	 * Returns the given array as {@link List} with all {@literal null} elements removed.
-	 * 
+	 *
 	 * @param elements the elements to filter <T>, can be {@literal null}.
 	 * @return a new unmodifiable {@link List#} from the given elements without {@literal null}s.
 	 */
-	private static <T> List<T> filterNonNullElementsAsList(T[] elements) {
+	private static <T> List<T> filterNonNullElementsAsList(@Nullable T[] elements) {
 
 		if (elements == null) {
 			return Collections.emptyList();

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

@@ -20,6 +20,7 @@ import javax.net.ssl.SSLSocketFactory;
 
 import org.springframework.beans.factory.config.AbstractFactoryBean;
 import org.springframework.data.mongodb.MongoDbFactory;
+import org.springframework.lang.Nullable;
 
 import com.mongodb.DBDecoderFactory;
 import com.mongodb.DBEncoderFactory;
@@ -40,7 +41,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 
 	private static final MongoClientOptions DEFAULT_MONGO_OPTIONS = MongoClientOptions.builder().build();
 
-	private String description = DEFAULT_MONGO_OPTIONS.getDescription();
+	private @Nullable String description = DEFAULT_MONGO_OPTIONS.getDescription();
 	private int minConnectionsPerHost = DEFAULT_MONGO_OPTIONS.getMinConnectionsPerHost();
 	private int connectionsPerHost = DEFAULT_MONGO_OPTIONS.getConnectionsPerHost();
 	private int threadsAllowedToBlockForConnectionMultiplier = DEFAULT_MONGO_OPTIONS
@@ -51,11 +52,11 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 	private int connectTimeout = DEFAULT_MONGO_OPTIONS.getConnectTimeout();
 	private int socketTimeout = DEFAULT_MONGO_OPTIONS.getSocketTimeout();
 	private boolean socketKeepAlive = DEFAULT_MONGO_OPTIONS.isSocketKeepAlive();
-	private ReadPreference readPreference = DEFAULT_MONGO_OPTIONS.getReadPreference();
+	private @Nullable ReadPreference readPreference = DEFAULT_MONGO_OPTIONS.getReadPreference();
 	private DBDecoderFactory dbDecoderFactory = DEFAULT_MONGO_OPTIONS.getDbDecoderFactory();
 	private DBEncoderFactory dbEncoderFactory = DEFAULT_MONGO_OPTIONS.getDbEncoderFactory();
-	private WriteConcern writeConcern = DEFAULT_MONGO_OPTIONS.getWriteConcern();
-	private SocketFactory socketFactory = DEFAULT_MONGO_OPTIONS.getSocketFactory();
+	private @Nullable WriteConcern writeConcern = DEFAULT_MONGO_OPTIONS.getWriteConcern();
+	private @Nullable SocketFactory socketFactory = DEFAULT_MONGO_OPTIONS.getSocketFactory();
 	private boolean cursorFinalizerEnabled = DEFAULT_MONGO_OPTIONS.isCursorFinalizerEnabled();
 	private boolean alwaysUseMBeans = DEFAULT_MONGO_OPTIONS.isAlwaysUseMBeans();
 	private int heartbeatFrequency = DEFAULT_MONGO_OPTIONS.getHeartbeatFrequency();
@@ -66,14 +67,14 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 	private int serverSelectionTimeout = DEFAULT_MONGO_OPTIONS.getServerSelectionTimeout();
 
 	private boolean ssl;
-	private SSLSocketFactory sslSocketFactory;
+	private @Nullable SSLSocketFactory sslSocketFactory;
 
 	/**
 	 * Set the {@link MongoClient} description.
 	 *
 	 * @param description
 	 */
-	public void setDescription(String description) {
+	public void setDescription(@Nullable String description) {
 		this.description = description;
 	}
 
@@ -166,7 +167,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 	 *
 	 * @param readPreference
 	 */
-	public void setReadPreference(ReadPreference readPreference) {
+	public void setReadPreference(@Nullable ReadPreference readPreference) {
 		this.readPreference = readPreference;
 	}
 
@@ -176,14 +177,14 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 	 *
 	 * @param writeConcern
 	 */
-	public void setWriteConcern(WriteConcern writeConcern) {
+	public void setWriteConcern(@Nullable WriteConcern writeConcern) {
 		this.writeConcern = writeConcern;
 	}
 
 	/**
 	 * @param socketFactory
 	 */
-	public void setSocketFactory(SocketFactory socketFactory) {
+	public void setSocketFactory(@Nullable SocketFactory socketFactory) {
 		this.socketFactory = socketFactory;
 	}
 
@@ -248,7 +249,7 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 	 *
 	 * @param sslSocketFactory
 	 */
-	public void setSslSocketFactory(SSLSocketFactory sslSocketFactory) {
+	public void setSslSocketFactory(@Nullable SSLSocketFactory sslSocketFactory) {
 
 		this.sslSocketFactory = sslSocketFactory;
 		this.ssl = sslSocketFactory != null;
@@ -269,11 +270,13 @@ public class MongoClientOptionsFactoryBean extends AbstractFactoryBean<MongoClie
 	 * (non-Javadoc)
 	 * @see org.springframework.beans.factory.config.AbstractFactoryBean#createInstance()
 	 */
+	@SuppressWarnings("ConstantConditions")
 	@Override
 	protected MongoClientOptions createInstance() throws Exception {
 
 		SocketFactory socketFactoryToUse = ssl
-				? (sslSocketFactory != null ? sslSocketFactory : SSLSocketFactory.getDefault()) : this.socketFactory;
+				? (sslSocketFactory != null ? sslSocketFactory : SSLSocketFactory.getDefault())
+				: this.socketFactory;
 
 		return MongoClientOptions.builder() //
 				.alwaysUseMBeans(this.alwaysUseMBeans) //

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 package org.springframework.data.mongodb.core;
 
 import org.springframework.dao.DataIntegrityViolationException;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 import com.mongodb.WriteResult;
@@ -40,7 +41,7 @@ public class MongoDataIntegrityViolationException extends DataIntegrityViolation
 	 * @param actionOperation the {@link MongoActionOperation} that caused the exception, must not be {@literal null}.
 	 */
 	public MongoDataIntegrityViolationException(String message, WriteResult writeResult,
-			MongoActionOperation actionOperation) {
+												MongoActionOperation actionOperation) {
 
 		super(message);
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2010-2016 the original author or authors.
+ * Copyright 2010-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@
 package org.springframework.data.mongodb.core;
 
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.Set;
 
@@ -31,6 +32,7 @@ import org.springframework.dao.support.PersistenceExceptionTranslator;
 import org.springframework.data.mongodb.BulkOperationException;
 import org.springframework.data.mongodb.UncategorizedMongoDbException;
 import org.springframework.data.mongodb.util.MongoDbErrorCodes;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 
 import com.mongodb.BulkWriteException;
@@ -50,23 +52,24 @@ import com.mongodb.bulk.BulkWriteError;
  */
 public class MongoExceptionTranslator implements PersistenceExceptionTranslator {
 
-	private static final Set<String> DULICATE_KEY_EXCEPTIONS = new HashSet<String>(
+	private static final Set<String> DUPLICATE_KEY_EXCEPTIONS = new HashSet<>(
 			Arrays.asList("MongoException.DuplicateKey", "DuplicateKeyException"));
 
-	private static final Set<String> RESOURCE_FAILURE_EXCEPTIONS = new HashSet<String>(
+	private static final Set<String> RESOURCE_FAILURE_EXCEPTIONS = new HashSet<>(
 			Arrays.asList("MongoException.Network", "MongoSocketException", "MongoException.CursorNotFound",
 					"MongoCursorNotFoundException", "MongoServerSelectionException", "MongoTimeoutException"));
 
-	private static final Set<String> RESOURCE_USAGE_EXCEPTIONS = new HashSet<String>(
-			Arrays.asList("MongoInternalException"));
+	private static final Set<String> RESOURCE_USAGE_EXCEPTIONS = new HashSet<>(
+			Collections.singletonList("MongoInternalException"));
 
-	private static final Set<String> DATA_INTEGRETY_EXCEPTIONS = new HashSet<String>(
+	private static final Set<String> DATA_INTEGRITY_EXCEPTIONS = new HashSet<>(
 			Arrays.asList("WriteConcernException", "MongoWriteException", "MongoBulkWriteException"));
 
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.dao.support.PersistenceExceptionTranslator#translateExceptionIfPossible(java.lang.RuntimeException)
 	 */
+	@Nullable
 	public DataAccessException translateExceptionIfPossible(RuntimeException ex) {
 
 		// Check for well-known MongoException subclasses.
@@ -77,7 +80,7 @@ public class MongoExceptionTranslator implements PersistenceExceptionTranslator
 
 		String exception = ClassUtils.getShortName(ClassUtils.getUserClass(ex.getClass()));
 
-		if (DULICATE_KEY_EXCEPTIONS.contains(exception)) {
+		if (DUPLICATE_KEY_EXCEPTIONS.contains(exception)) {
 			return new DuplicateKeyException(ex.getMessage(), ex);
 		}
 
@@ -89,7 +92,7 @@ public class MongoExceptionTranslator implements PersistenceExceptionTranslator
 			return new InvalidDataAccessResourceUsageException(ex.getMessage(), ex);
 		}
 
-		if (DATA_INTEGRETY_EXCEPTIONS.contains(exception)) {
+		if (DATA_INTEGRITY_EXCEPTIONS.contains(exception)) {
 
 			if (ex instanceof MongoServerException) {
 				if (((MongoServerException) ex).getCode() == 11000) {

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

@@ -1,29 +0,0 @@
-/*
- * Copyright 2012-2014 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import org.springframework.transaction.support.ResourceHolder;
-import org.springframework.transaction.support.ResourceHolderSynchronization;
-
-/**
- * @author Oliver Gierke
- */
-class MongoSynchronization extends ResourceHolderSynchronization<ResourceHolder, Object> {
-
-	public MongoSynchronization(ResourceHolder resourceHolder, Object resourceKey) {
-		super(resourceHolder, resourceKey);
-	}
-}

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

@@ -1,34 +1,34 @@
-/*
- * Copyright 2016 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import org.springframework.dao.DataAccessException;
-
-import com.mongodb.MongoException;
-import com.mongodb.reactivestreams.client.MongoCollection;
-import org.bson.Document;
-import org.reactivestreams.Publisher;
-
-/**
- * @author Mark Paluch
- * @param <T>
- * @since 2.0
- */
-public interface ReactiveCollectionCallback<T> {
-
-	Publisher<T> doInCollection(MongoCollection<Document> collection) throws MongoException, DataAccessException;
-
-}
+/*
+ * Copyright 2016-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core;
+
+import org.bson.Document;
+import org.reactivestreams.Publisher;
+import org.springframework.dao.DataAccessException;
+
+import com.mongodb.MongoException;
+import com.mongodb.reactivestreams.client.MongoCollection;
+
+/**
+ * @author Mark Paluch
+ * @param <T>
+ * @since 2.0
+ */
+public interface ReactiveCollectionCallback<T> {
+
+	Publisher<T> doInCollection(MongoCollection<Document> collection) throws MongoException, DataAccessException;
+
+}

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

@@ -19,6 +19,7 @@ import lombok.AccessLevel;
 import lombok.NonNull;
 import lombok.RequiredArgsConstructor;
 import lombok.experimental.FieldDefaults;
+import org.springframework.lang.Nullable;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
@@ -195,7 +196,7 @@ class ReactiveFindOperationSupport implements ReactiveFindOperation {
 			return template.exists(query, domainType, getCollectionName());
 		}
 
-		private Flux<T> doFind(FindPublisherPreparer preparer) {
+		private Flux<T> doFind(@Nullable FindPublisherPreparer preparer) {
 
 			Document queryObject = query.getQueryObject();
 			Document fieldsObject = query.getFieldsObject();

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@ package org.springframework.data.mongodb.core;
 import org.springframework.beans.factory.config.AbstractFactoryBean;
 import org.springframework.dao.DataAccessException;
 import org.springframework.dao.support.PersistenceExceptionTranslator;
+import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 
 import com.mongodb.async.client.MongoClientSettings;
@@ -37,10 +38,10 @@ public class ReactiveMongoClientFactoryBean extends AbstractFactoryBean<MongoCli
 
 	private static final PersistenceExceptionTranslator DEFAULT_EXCEPTION_TRANSLATOR = new MongoExceptionTranslator();
 
-	private String connectionString;
-	private String host;
-	private Integer port;
-	private MongoClientSettings mongoClientSettings;
+	private @Nullable String connectionString;
+	private @Nullable String host;
+	private @Nullable Integer port;
+	private @Nullable MongoClientSettings mongoClientSettings;
 	private PersistenceExceptionTranslator exceptionTranslator = DEFAULT_EXCEPTION_TRANSLATOR;
 
 	/**
@@ -48,7 +49,7 @@ public class ReactiveMongoClientFactoryBean extends AbstractFactoryBean<MongoCli
 	 *
 	 * @param host
 	 */
-	public void setHost(String host) {
+	public void setHost(@Nullable String host) {
 		this.host = host;
 	}
 
@@ -66,7 +67,7 @@ public class ReactiveMongoClientFactoryBean extends AbstractFactoryBean<MongoCli
 	 *
 	 * @param connectionString
 	 */
-	public void setConnectionString(String connectionString) {
+	public void setConnectionString(@Nullable String connectionString) {
 		this.connectionString = connectionString;
 	}
 
@@ -75,7 +76,7 @@ public class ReactiveMongoClientFactoryBean extends AbstractFactoryBean<MongoCli
 	 *
 	 * @param mongoClientSettings
 	 */
-	public void setMongoClientSettings(MongoClientSettings mongoClientSettings) {
+	public void setMongoClientSettings(@Nullable MongoClientSettings mongoClientSettings) {
 		this.mongoClientSettings = mongoClientSettings;
 	}
 
@@ -84,7 +85,7 @@ public class ReactiveMongoClientFactoryBean extends AbstractFactoryBean<MongoCli
 	 *
 	 * @param exceptionTranslator
 	 */
-	public void setExceptionTranslator(PersistenceExceptionTranslator exceptionTranslator) {
+	public void setExceptionTranslator(@Nullable PersistenceExceptionTranslator exceptionTranslator) {
 		this.exceptionTranslator = exceptionTranslator == null ? DEFAULT_EXCEPTION_TRANSLATOR : exceptionTranslator;
 	}
 
@@ -118,7 +119,7 @@ public class ReactiveMongoClientFactoryBean extends AbstractFactoryBean<MongoCli
 	}
 
 	@Override
-	protected void destroyInstance(MongoClient instance) throws Exception {
+	protected void destroyInstance(@Nullable MongoClient instance) throws Exception {
 		instance.close();
 	}
 

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

@@ -35,6 +35,7 @@ import org.springframework.data.mongodb.core.query.Criteria;
 import org.springframework.data.mongodb.core.query.NearQuery;
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.data.mongodb.core.query.Update;
+import org.springframework.lang.Nullable;
 
 import com.mongodb.ReadPreference;
 import com.mongodb.client.result.DeleteResult;
@@ -60,6 +61,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	/**
 	 * Returns the reactive operations that can be performed on indexes
 	 *
+	 * @param collectionName must not be {@literal null}.
 	 * @return index operations on the named collection
 	 */
 	ReactiveIndexOperations indexOps(String collectionName);
@@ -67,13 +69,14 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	/**
 	 * Returns the reactive operations that can be performed on indexes
 	 *
+	 * @param entityClass must not be {@literal null}.
 	 * @return index operations on the named collection associated with the given entity class
 	 */
 	ReactiveIndexOperations indexOps(Class<?> entityClass);
 
 	/**
 	 * Execute the a MongoDB command expressed as a JSON string. This will call the method JSON.parse that is part of the
-	 * MongoDB driver to convert the JSON string to a DBObject. Any errors that result from executing this command will be
+	 * MongoDB driver to convert the JSON string to a Document. Any errors that result from executing this command will be
 	 * converted into Spring's DAO exception hierarchy.
 	 *
 	 * @param jsonCommand a MongoDB command expressed as a JSON string.
@@ -85,7 +88,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * Execute a MongoDB command. Any errors that result from executing this command will be converted into Spring's DAO
 	 * exception hierarchy.
 	 *
-	 * @param command a MongoDB command
+	 * @param command a MongoDB command.
 	 * @return a result object returned by the action
 	 */
 	Mono<Document> executeCommand(Document command);
@@ -96,17 +99,18 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 *
 	 * @param command a MongoDB command, must not be {@literal null}.
 	 * @param readPreference read preferences to use, can be {@literal null}.
-	 * @return a result object returned by the action
+	 * @return a result object returned by the action.
 	 */
-	Mono<Document> executeCommand(Document command, ReadPreference readPreference);
+	Mono<Document> executeCommand(Document command, @Nullable ReadPreference readPreference);
 
 	/**
 	 * Executes a {@link ReactiveDatabaseCallback} translating any exceptions as necessary.
 	 * <p/>
 	 * Allows for returning a result object, that is a domain object or a collection of domain objects.
 	 *
-	 * @param <T> return type
-	 * @param action callback object that specifies the MongoDB actions to perform on the passed in DB instance.
+	 * @param action callback object that specifies the MongoDB actions to perform on the passed in DB instance. Must not
+	 *          be {@literal null}.
+	 * @param <T> return type.
 	 * @return a result object returned by the action
 	 */
 	<T> Flux<T> execute(ReactiveDatabaseCallback<T> action);
@@ -116,10 +120,10 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * <p/>
 	 * Allows for returning a result object, that is a domain object or a collection of domain objects.
 	 *
-	 * @param entityClass class that determines the collection to use
-	 * @param <T> return type
-	 * @param action callback object that specifies the MongoDB action
-	 * @return a result object returned by the action or <tt>null</tt>
+	 * @param entityClass class that determines the collection to use. Must not be {@literal null}.
+	 * @param action callback object that specifies the MongoDB action. Must not be {@literal null}.
+	 * @param <T> return type.
+	 * @return a result object returned by the action or {@literal null}.
 	 */
 	<T> Flux<T> execute(Class<?> entityClass, ReactiveCollectionCallback<T> action);
 
@@ -128,51 +132,53 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * <p/>
 	 * Allows for returning a result object, that is a domain object or a collection of domain objects.
 	 *
-	 * @param <T> return type
-	 * @param collectionName the name of the collection that specifies which DBCollection instance will be passed into
-	 * @param action callback object that specifies the MongoDB action the callback action.
-	 * @return a result object returned by the action or <tt>null</tt>
+	 * @param collectionName the name of the collection that specifies which {@link MongoCollection} instance will be
+	 *          passed into. Must not be {@literal null} or empty.
+	 * @param action callback object that specifies the MongoDB action the callback action. Must not be {@literal null}.
+	 * @param <T> return type.
+	 * @return a result object returned by the action or {@literal null}.
 	 */
 	<T> Flux<T> execute(String collectionName, ReactiveCollectionCallback<T> action);
 
 	/**
 	 * Create an uncapped collection with a name based on the provided entity class.
 	 *
-	 * @param entityClass class that determines the collection to create
-	 * @return the created collection
+	 * @param entityClass class that determines the collection to create.
+	 * @return the created collection.
 	 */
 	<T> Mono<MongoCollection<Document>> createCollection(Class<T> entityClass);
 
 	/**
 	 * Create a collection with a name based on the provided entity class using the options.
 	 *
-	 * @param entityClass class that determines the collection to create
+	 * @param entityClass class that determines the collection to create. Must not be {@literal null}.
 	 * @param collectionOptions options to use when creating the collection.
-	 * @return the created collection
+	 * @return the created collection.
 	 */
-	<T> Mono<MongoCollection<Document>> createCollection(Class<T> entityClass, CollectionOptions collectionOptions);
+	<T> Mono<MongoCollection<Document>> createCollection(Class<T> entityClass,
+			@Nullable CollectionOptions collectionOptions);
 
 	/**
 	 * Create an uncapped collection with the provided name.
 	 *
-	 * @param collectionName name of the collection
-	 * @return the created collection
+	 * @param collectionName name of the collection.
+	 * @return the created collection.
 	 */
 	Mono<MongoCollection<Document>> createCollection(String collectionName);
 
 	/**
 	 * Create a collection with the provided name and options.
 	 *
-	 * @param collectionName name of the collection
+	 * @param collectionName name of the collection. Must not be {@literal null} nor empty.
 	 * @param collectionOptions options to use when creating the collection.
-	 * @return the created collection
+	 * @return the created collection.
 	 */
 	Mono<MongoCollection<Document>> createCollection(String collectionName, CollectionOptions collectionOptions);
 
 	/**
 	 * A set of collection names.
 	 *
-	 * @return Flux of collection names
+	 * @return Flux of collection names.
 	 */
 	Flux<String> getCollectionNames();
 
@@ -181,7 +187,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * <p/>
 	 * Translate any exceptions as necessary.
 	 *
-	 * @param collectionName name of the collection
+	 * @param collectionName name of the collection.
 	 * @return an existing collection or a newly created one.
 	 */
 	MongoCollection<Document> getCollection(String collectionName);
@@ -191,7 +197,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * <p/>
 	 * Translate any exceptions as necessary.
 	 *
-	 * @param entityClass class that determines the name of the collection
+	 * @param entityClass class that determines the name of the collection. Must not be {@literal null}.
 	 * @return true if a collection with the given name is found, false otherwise.
 	 */
 	<T> Mono<Boolean> collectionExists(Class<T> entityClass);
@@ -201,7 +207,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * <p/>
 	 * Translate any exceptions as necessary.
 	 *
-	 * @param collectionName name of the collection
+	 * @param collectionName name of the collection. Must not be {@literal null}.
 	 * @return true if a collection with the given name is found, false otherwise.
 	 */
 	Mono<Boolean> collectionExists(String collectionName);
@@ -211,7 +217,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * <p/>
 	 * Translate any exceptions as necessary.
 	 *
-	 * @param entityClass class that determines the collection to drop/delete.
+	 * @param entityClass class that determines the collection to drop/delete. Must not be {@literal null}.
 	 */
 	<T> Mono<Void> dropCollection(Class<T> entityClass);
 
@@ -234,7 +240,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * to map objects since the test for class type is done in the client and not on the server.
 	 *
 	 * @param entityClass the parametrized type of the returned {@link Flux}.
-	 * @return the converted collection
+	 * @return the converted collection.
 	 */
 	<T> Flux<T> findAll(Class<T> entityClass);
 
@@ -248,8 +254,8 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * to map objects since the test for class type is done in the client and not on the server.
 	 *
 	 * @param entityClass the parametrized type of the returned {@link Flux}.
-	 * @param collectionName name of the collection to retrieve the objects from
-	 * @return the converted collection
+	 * @param collectionName name of the collection to retrieve the objects from.
+	 * @return the converted collection.
 	 */
 	<T> Flux<T> findAll(Class<T> entityClass, String collectionName);
 
@@ -264,9 +270,9 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * feature rich {@link Query}.
 	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
-	 *          specification
+	 *          specification.
 	 * @param entityClass the parametrized type of the returned {@link Mono}.
-	 * @return the converted object
+	 * @return the converted object.
 	 */
 	<T> Mono<T> findOne(Query query, Class<T> entityClass);
 
@@ -281,10 +287,10 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * feature rich {@link Query}.
 	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
-	 *          specification
+	 *          specification.
 	 * @param entityClass the parametrized type of the returned {@link Mono}.
-	 * @param collectionName name of the collection to retrieve the objects from
-	 * @return the converted object
+	 * @param collectionName name of the collection to retrieve the objects from.
+	 * @return the converted object.
 	 */
 	<T> Mono<T> findOne(Query query, Class<T> entityClass, String collectionName);
 
@@ -295,7 +301,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 *
 	 * @param query the {@link Query} class that specifies the criteria used to find a record.
 	 * @param collectionName name of the collection to check for objects.
-	 * @return
+	 * @return {@literal true} if the query yields a result.
 	 */
 	Mono<Boolean> exists(Query query, String collectionName);
 
@@ -304,7 +310,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 *
 	 * @param query the {@link Query} class that specifies the criteria used to find a record.
 	 * @param entityClass the parametrized type.
-	 * @return
+	 * @return {@literal true} if the query yields a result.
 	 */
 	Mono<Boolean> exists(Query query, Class<?> entityClass);
 
@@ -312,11 +318,11 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * Determine result of given {@link Query} contains at least one element.
 	 *
 	 * @param query the {@link Query} class that specifies the criteria used to find a record.
-	 * @param entityClass the parametrized type.
+	 * @param entityClass the parametrized type. Can be {@literal null}.
 	 * @param collectionName name of the collection to check for objects.
-	 * @return
+	 * @return {@literal true} if the query yields a result.
 	 */
-	Mono<Boolean> exists(Query query, Class<?> entityClass, String collectionName);
+	Mono<Boolean> exists(Query query, @Nullable Class<?> entityClass, String collectionName);
 
 	/**
 	 * Map the results of an ad-hoc query on the collection for the entity class to a {@link Flux} of the specified type.
@@ -328,9 +334,9 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * feature rich {@link Query}.
 	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
-	 *          specification
-	 * @param entityClass the parametrized type of the returned {@link Flux}.
-	 * @return the {@link Flux} of converted objects
+	 *          specification. Must not be {@literal null}.
+	 * @param entityClass the parametrized type of the returned {@link Flux}. Must not be {@literal null}.
+	 * @return the {@link Flux} of converted objects.
 	 */
 	<T> Flux<T> find(Query query, Class<T> entityClass);
 
@@ -344,10 +350,10 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * feature rich {@link Query}.
 	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
-	 *          specification
+	 *          specification. Must not be {@literal null}.
 	 * @param entityClass the parametrized type of the returned {@link Flux}.
-	 * @param collectionName name of the collection to retrieve the objects from
-	 * @return the {@link Flux} of converted objects
+	 * @param collectionName name of the collection to retrieve the objects from. Must not be {@literal null}.
+	 * @return the {@link Flux} of converted objects.
 	 */
 	<T> Flux<T> find(Query query, Class<T> entityClass, String collectionName);
 
@@ -355,9 +361,8 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * Returns a document with the given id mapped onto the given class. The collection the query is ran against will be
 	 * derived from the given target class as well.
 	 *
-	 * @param <T>
-	 * @param id the id of the document to return.
-	 * @param entityClass the type the document shall be converted into.
+	 * @param id the id of the document to return. Must not be {@literal null}.
+	 * @param entityClass the type the document shall be converted into. Must not be {@literal null}.
 	 * @return the document with the given id mapped onto the given target class.
 	 */
 	<T> Mono<T> findById(Object id, Class<T> entityClass);
@@ -365,11 +370,10 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	/**
 	 * Returns the document with the given id from the given collection mapped onto the given target class.
 	 *
-	 * @param id the id of the document to return
-	 * @param entityClass the type to convert the document to
-	 * @param collectionName the collection to query for the document
-	 * @param <T>
-	 * @return
+	 * @param id the id of the document to return.
+	 * @param entityClass the type to convert the document to.
+	 * @param collectionName the collection to query for the document.
+	 * @return the converted object.
 	 */
 	<T> Mono<T> findById(Object id, Class<T> entityClass, String collectionName);
 
@@ -458,7 +462,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 *
 	 * @param near must not be {@literal null}.
 	 * @param entityClass must not be {@literal null}.
-	 * @return
+	 * @return the converted {@link GeoResult}s.
 	 */
 	<T> Flux<GeoResult<T>> geoNear(NearQuery near, Class<T> entityClass);
 
@@ -471,37 +475,37 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * @param entityClass must not be {@literal null}.
 	 * @param collectionName the collection to trigger the query against. If no collection name is given the entity class
 	 *          will be inspected.
-	 * @return
+	 * @return the converted {@link GeoResult}s.
 	 */
 	<T> Flux<GeoResult<T>> geoNear(NearQuery near, Class<T> entityClass, String collectionName);
 
 	/**
-	 * Triggers <a href="https://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
+	 * Triggers <a href="https://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify<a/>
 	 * to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query}.
 	 *
 	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
-	 *          fields specification.
-	 * @param update the {@link Update} to apply on matching documents.
-	 * @param entityClass the parametrized type.
-	 * @return
+	 *          fields specification. Must not be {@literal null}.
+	 * @param update the {@link Update} to apply on matching documents. Must not be {@literal null}.
+	 * @param entityClass the parametrized type. Must not be {@literal null}.
+	 * @return the converted object that was updated before it was updated.
 	 */
 	<T> Mono<T> findAndModify(Query query, Update update, Class<T> entityClass);
 
 	/**
-	 * Triggers <a href="https://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
+	 * Triggers <a href="https://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify<a/>
 	 * to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query}.
 	 *
 	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
-	 *          fields specification.
-	 * @param update the {@link Update} to apply on matching documents.
-	 * @param entityClass the parametrized type.
-	 * @param collectionName the collection to query.
-	 * @return
+	 *          fields specification. Must not be {@literal null}.
+	 * @param update the {@link Update} to apply on matching documents. Must not be {@literal null}.
+	 * @param entityClass the parametrized type. Must not be {@literal null}.
+	 * @param collectionName the collection to query. Must not be {@literal null}.
+	 * @return the converted object that was updated before it was updated.
 	 */
 	<T> Mono<T> findAndModify(Query query, Update update, Class<T> entityClass, String collectionName);
 
 	/**
-	 * Triggers <a href="https://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
+	 * Triggers <a href="https://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify<a/>
 	 * to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query} taking
 	 * {@link FindAndModifyOptions} into account.
 	 *
@@ -510,22 +514,24 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * @param update the {@link Update} to apply on matching documents.
 	 * @param options the {@link FindAndModifyOptions} holding additional information.
 	 * @param entityClass the parametrized type.
-	 * @return
+	 * @return the converted object that was updated. Depending on the value of {@link FindAndModifyOptions#isReturnNew()}
+	 *         this will either be the object as it was before the update or as it is after the update.
 	 */
 	<T> Mono<T> findAndModify(Query query, Update update, FindAndModifyOptions options, Class<T> entityClass);
 
 	/**
-	 * Triggers <a href="https://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify <a/>
+	 * Triggers <a href="https://docs.mongodb.org/manual/reference/method/db.collection.findAndModify/">findAndModify<a/>
 	 * to apply provided {@link Update} on documents matching {@link Criteria} of given {@link Query} taking
 	 * {@link FindAndModifyOptions} into account.
 	 *
 	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
-	 *          fields specification.
-	 * @param update the {@link Update} to apply on matching documents.
-	 * @param options the {@link FindAndModifyOptions} holding additional information.
-	 * @param entityClass the parametrized type.
-	 * @param collectionName the collection to query.
-	 * @return
+	 *          fields specification. Must not be {@literal null}.
+	 * @param update the {@link Update} to apply on matching documents. Must not be {@literal null}.
+	 * @param options the {@link FindAndModifyOptions} holding additional information. Must not be {@literal null}.
+	 * @param entityClass the parametrized type. Must not be {@literal null}.
+	 * @param collectionName the collection to query. Must not be {@literal null}.
+	 * @return the converted object that was updated. Depending on the value of {@link FindAndModifyOptions#isReturnNew()}
+	 *         this will either be the object as it was before the update or as it is after the update.
 	 */
 	<T> Mono<T> findAndModify(Query query, Update update, FindAndModifyOptions options, Class<T> entityClass,
 			String collectionName);
@@ -541,7 +547,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * feature rich {@link Query}.
 	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
-	 *          specification
+	 *          specification.
 	 * @param entityClass the parametrized type of the returned {@link Mono}.
 	 * @return the converted object
 	 */
@@ -558,19 +564,20 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * feature rich {@link Query}.
 	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
-	 *          specification
+	 *          specification.
 	 * @param entityClass the parametrized type of the returned {@link Mono}.
 	 * @param collectionName name of the collection to retrieve the objects from.
-	 * @return the converted object
+	 * @return the converted object.
 	 */
 	<T> Mono<T> findAndRemove(Query query, Class<T> entityClass, String collectionName);
 
 	/**
 	 * Returns the number of documents for the given {@link Query} by querying the collection of the given entity class.
 	 *
-	 * @param query
-	 * @param entityClass must not be {@literal null}.
-	 * @return
+	 * @param query the {@link Query} class that specifies the criteria used to find documents. Must not be
+	 *          {@literal null}.
+	 * @param entityClass class that determines the collection to use. Must not be {@literal null}.
+	 * @return the count of matching documents.
 	 */
 	Mono<Long> count(Query query, Class<?> entityClass);
 
@@ -579,9 +586,9 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * must solely consist of document field references as we lack type information to map potential property references
 	 * onto document fields. Use {@link #count(Query, Class, String)} to get full type specific support.
 	 *
-	 * @param query
+	 * @param query the {@link Query} class that specifies the criteria used to find documents.
 	 * @param collectionName must not be {@literal null} or empty.
-	 * @return
+	 * @return the count of matching documents.
 	 * @see #count(Query, Class, String)
 	 */
 	Mono<Long> count(Query query, String collectionName);
@@ -590,12 +597,13 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * Returns the number of documents for the given {@link Query} by querying the given collection using the given entity
 	 * class to map the given {@link Query}.
 	 *
-	 * @param query
-	 * @param entityClass must not be {@literal null}.
+	 * @param query the {@link Query} class that specifies the criteria used to find documents. Must not be
+	 *          {@literal null}.
+	 * @param entityClass the parametrized type. Can be {@literal null}.
 	 * @param collectionName must not be {@literal null} or empty.
-	 * @return
+	 * @return the count of matching documents.
 	 */
-	Mono<Long> count(Query query, Class<?> entityClass, String collectionName);
+	Mono<Long> count(Query query, @Nullable Class<?> entityClass, String collectionName);
 
 	/**
 	 * Insert the object into the collection for the entity type of the object to save.
@@ -605,14 +613,14 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * If you object has an "Id' property, it will be set with the generated Id from MongoDB. If your Id property is a
 	 * String then MongoDB ObjectId will be used to populate that string. Otherwise, the conversion from ObjectId to your
 	 * property type will be handled by Spring's BeanWrapper class that leverages Type Conversion API. See
-	 * <a href="http://docs.spring.io/spring/docs/current/spring-framework-reference/html/validation.html#core-convert" >
+	 * <a href="http://docs.spring.io/spring/docs/current/spring-framework-reference/core.html#validation" >
 	 * Spring's Type Conversion"</a> for more details.
 	 * <p/>
 	 * <p/>
 	 * Insert is used to initially store the object into the database. To update an existing object use the save method.
 	 *
-	 * @param objectToSave the object to store in the collection.
-	 * @return
+	 * @param objectToSave the object to store in the collection. Must not be {@literal null}.
+	 * @return the saved object.
 	 */
 	<T> Mono<T> insert(T objectToSave);
 
@@ -624,27 +632,27 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * <p/>
 	 * Insert is used to initially store the object into the database. To update an existing object use the save method.
 	 *
-	 * @param objectToSave the object to store in the collection
-	 * @param collectionName name of the collection to store the object in
-	 * @return
+	 * @param objectToSave the object to store in the collection. Must not be {@literal null}.
+	 * @param collectionName name of the collection to store the object in. Must not be {@literal null}.
+	 * @return the saved object.
 	 */
 	<T> Mono<T> insert(T objectToSave, String collectionName);
 
 	/**
 	 * Insert a Collection of objects into a collection in a single batch write to the database.
 	 *
-	 * @param batchToSave the batch of objects to save.
-	 * @param entityClass class that determines the collection to use
-	 * @return
+	 * @param batchToSave the batch of objects to save. Must not be {@literal null}.
+	 * @param entityClass class that determines the collection to use. Must not be {@literal null}.
+	 * @return the saved objects.
 	 */
 	<T> Flux<T> insert(Collection<? extends T> batchToSave, Class<?> entityClass);
 
 	/**
 	 * Insert a batch of objects into the specified collection in a single batch write to the database.
 	 *
-	 * @param batchToSave the list of objects to save.
-	 * @param collectionName name of the collection to store the object in
-	 * @return
+	 * @param batchToSave the list of objects to save. Must not be {@literal null}.
+	 * @param collectionName name of the collection to store the object in. Must not be {@literal null}.
+	 * @return the saved objects.
 	 */
 	<T> Flux<T> insert(Collection<? extends T> batchToSave, String collectionName);
 
@@ -652,8 +660,8 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * Insert a mixed Collection of objects into a database collection determining the collection name to use based on the
 	 * class.
 	 *
-	 * @param objectsToSave the list of objects to save.
-	 * @return
+	 * @param objectsToSave the list of objects to save. Must not be {@literal null}.
+	 * @return the saved objects.
 	 */
 	<T> Flux<T> insertAll(Collection<? extends T> objectsToSave);
 
@@ -665,32 +673,32 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * If you object has an "Id' property, it will be set with the generated Id from MongoDB. If your Id property is a
 	 * String then MongoDB ObjectId will be used to populate that string. Otherwise, the conversion from ObjectId to your
 	 * property type will be handled by Spring's BeanWrapper class that leverages Type Conversion API. See
-	 * <a href="http://docs.spring.io/spring/docs/current/spring-framework-reference/html/validation.html#core-convert" >
+	 * <a href="http://docs.spring.io/spring/docs/current/spring-framework-reference/core.html#validation" >
 	 * Spring's Type Conversion"</a> for more details.
 	 * <p/>
 	 * <p/>
 	 * Insert is used to initially store the object into the database. To update an existing object use the save method.
 	 *
-	 * @param objectToSave the object to store in the collection.
-	 * @return
+	 * @param objectToSave the object to store in the collection. Must not be {@literal null}.
+	 * @return the saved object.
 	 */
 	<T> Mono<T> insert(Mono<? extends T> objectToSave);
 
 	/**
 	 * Insert a Collection of objects into a collection in a single batch write to the database.
 	 *
-	 * @param batchToSave the publisher which provides objects to save.
-	 * @param entityClass class that determines the collection to use
-	 * @return
+	 * @param batchToSave the publisher which provides objects to save. Must not be {@literal null}.
+	 * @param entityClass class that determines the collection to use. Must not be {@literal null}.
+	 * @return the saved objects.
 	 */
 	<T> Flux<T> insertAll(Mono<? extends Collection<? extends T>> batchToSave, Class<?> entityClass);
 
 	/**
 	 * Insert objects into the specified collection in a single batch write to the database.
 	 *
-	 * @param batchToSave the publisher which provides objects to save.
-	 * @param collectionName name of the collection to store the object in
-	 * @return
+	 * @param batchToSave the publisher which provides objects to save. Must not be {@literal null}.
+	 * @param collectionName name of the collection to store the object in. Must not be {@literal null}.
+	 * @return the saved objects.
 	 */
 	<T> Flux<T> insertAll(Mono<? extends Collection<? extends T>> batchToSave, String collectionName);
 
@@ -698,8 +706,8 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * Insert a mixed Collection of objects into a database collection determining the collection name to use based on the
 	 * class.
 	 *
-	 * @param objectsToSave the publisher which provides objects to save.
-	 * @return
+	 * @param objectsToSave the publisher which provides objects to save. Must not be {@literal null}.
+	 * @return the saved objects.
 	 */
 	<T> Flux<T> insertAll(Mono<? extends Collection<? extends T>> objectsToSave);
 
@@ -713,11 +721,11 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * If you object has an "Id' property, it will be set with the generated Id from MongoDB. If your Id property is a
 	 * String then MongoDB ObjectId will be used to populate that string. Otherwise, the conversion from ObjectId to your
 	 * property type will be handled by Spring's BeanWrapper class that leverages Type Conversion API. See
-	 * <a href="http://docs.spring.io/spring/docs/current/spring-framework-reference/html/validation.html#core-convert" >
+	 * <a href="http://docs.spring.io/spring/docs/current/spring-framework-reference/core.html#validation" >
 	 * Spring's Type Conversion"</a> for more details.
 	 *
-	 * @param objectToSave the object to store in the collection
-	 * @return
+	 * @param objectToSave the object to store in the collection. Must not be {@literal null}.
+	 * @return the saved object.
 	 */
 	<T> Mono<T> save(T objectToSave);
 
@@ -731,12 +739,12 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * If you object has an "Id' property, it will be set with the generated Id from MongoDB. If your Id property is a
 	 * String then MongoDB ObjectId will be used to populate that string. Otherwise, the conversion from ObjectId to your
 	 * property type will be handled by Spring's BeanWrapper class that leverages Type Conversion API. See <a
-	 * http://docs.spring.io/spring/docs/current/spring-framework-reference/html/validation.html#core-convert">Spring's
+	 * http://docs.spring.io/spring/docs/current/spring-framework-reference/core.html#validation">Spring's
 	 * Type Conversion"</a> for more details.
 	 *
-	 * @param objectToSave the object to store in the collection
-	 * @param collectionName name of the collection to store the object in
-	 * @return
+	 * @param objectToSave the object to store in the collection. Must not be {@literal null}.
+	 * @param collectionName name of the collection to store the object in. Must not be {@literal null}.
+	 * @return the saved object.
 	 */
 	<T> Mono<T> save(T objectToSave, String collectionName);
 
@@ -750,11 +758,11 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * If you object has an "Id' property, it will be set with the generated Id from MongoDB. If your Id property is a
 	 * String then MongoDB ObjectId will be used to populate that string. Otherwise, the conversion from ObjectId to your
 	 * property type will be handled by Spring's BeanWrapper class that leverages Type Conversion API. See
-	 * <a href="http://docs.spring.io/spring/docs/current/spring-framework-reference/html/validation.html#core-convert" >
+	 * <a href="http://docs.spring.io/spring/docs/current/spring-framework-reference/core.html#validation" >
 	 * Spring's Type Conversion"</a> for more details.
 	 *
-	 * @param objectToSave the object to store in the collection
-	 * @return
+	 * @param objectToSave the object to store in the collection. Must not be {@literal null}.
+	 * @return the saved object.
 	 */
 	<T> Mono<T> save(Mono<? extends T> objectToSave);
 
@@ -768,12 +776,12 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * If you object has an "Id' property, it will be set with the generated Id from MongoDB. If your Id property is a
 	 * String then MongoDB ObjectId will be used to populate that string. Otherwise, the conversion from ObjectId to your
 	 * property type will be handled by Spring's BeanWrapper class that leverages Type Conversion API. See <a
-	 * http://docs.spring.io/spring/docs/current/spring-framework-reference/html/validation.html#core-convert">Spring's
+	 * http://docs.spring.io/spring/docs/current/spring-framework-reference/core.html#validation">Spring's
 	 * Type Conversion"</a> for more details.
 	 *
-	 * @param objectToSave the object to store in the collection
-	 * @param collectionName name of the collection to store the object in
-	 * @return
+	 * @param objectToSave the object to store in the collection. Must not be {@literal null}.
+	 * @param collectionName name of the collection to store the object in. Must not be {@literal null}.
+	 * @return the saved object.
 	 */
 	<T> Mono<T> save(Mono<? extends T> objectToSave, String collectionName);
 
@@ -781,10 +789,12 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * Performs an upsert. If no document is found that matches the query, a new document is created and inserted by
 	 * combining the query document and the update document.
 	 *
-	 * @param query the query document that specifies the criteria used to select a record to be upserted
-	 * @param update the update document that contains the updated object or $ operators to manipulate the existing object
-	 * @param entityClass class that determines the collection to use
-	 * @return the WriteResult which lets you access the results of the previous write.
+	 * @param query the query document that specifies the criteria used to select a record to be upserted. Must not be
+	 *          {@literal null}.
+	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
+	 *          object. Must not be {@literal null}.
+	 * @param entityClass class that determines the collection to use. Must not be {@literal null}.
+	 * @return the {@link UpdateResult} which lets you access the results of the previous write.
 	 */
 	Mono<UpdateResult> upsert(Query query, Update update, Class<?> entityClass);
 
@@ -794,11 +804,12 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * <strong>NOTE:</strong> Any additional support for field mapping, versions, etc. is not available due to the lack of
 	 * domain type information. Use {@link #upsert(Query, Update, Class, String)} to get full type specific support.
 	 *
-	 * @param query the query document that specifies the criteria used to select a record to be updated
+	 * @param query the query document that specifies the criteria used to select a record to be upserted. Must not be
+	 *          {@literal null}.
 	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
-	 *          object.
-	 * @param collectionName name of the collection to update the object in
-	 * @return the WriteResult which lets you access the results of the previous write.
+	 *          object. Must not be {@literal null}.
+	 * @param collectionName name of the collection to update the object in.
+	 * @return the {@link UpdateResult} which lets you access the results of the previous write.
 	 */
 	Mono<UpdateResult> upsert(Query query, Update update, String collectionName);
 
@@ -806,11 +817,13 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * Performs an upsert. If no document is found that matches the query, a new document is created and inserted by
 	 * combining the query document and the update document.
 	 *
-	 * @param query the query document that specifies the criteria used to select a record to be upserted
-	 * @param update the update document that contains the updated object or $ operators to manipulate the existing object
-	 * @param entityClass class of the pojo to be operated on
-	 * @param collectionName name of the collection to update the object in
-	 * @return the WriteResult which lets you access the results of the previous write.
+	 * @param query the query document that specifies the criteria used to select a record to be upserted. Must not be
+	 *          {@literal null}.
+	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
+	 *          object. Must not be {@literal null}.
+	 * @param entityClass class of the pojo to be operated on. Must not be {@literal null}.
+	 * @param collectionName name of the collection to update the object in. Must not be {@literal null}.
+	 * @return the {@link UpdateResult} which lets you access the results of the previous write.
 	 */
 	Mono<UpdateResult> upsert(Query query, Update update, Class<?> entityClass, String collectionName);
 
@@ -818,11 +831,12 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * Updates the first object that is found in the collection of the entity class that matches the query document with
 	 * the provided update document.
 	 *
-	 * @param query the query document that specifies the criteria used to select a record to be updated
-	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
-	 *          object.
-	 * @param entityClass class that determines the collection to use
-	 * @return the WriteResult which lets you access the results of the previous write.
+	 * @param query the query document that specifies the criteria used to select a record to be updated. Must not be
+	 *          {@literal null}.
+	 * @param update the update document that contains the updated object or $ operators to manipulate the existing. Must
+	 *          not be {@literal null}.
+	 * @param entityClass class that determines the collection to use.
+	 * @return the {@link UpdateResult} which lets you access the results of the previous write.
 	 */
 	Mono<UpdateResult> updateFirst(Query query, Update update, Class<?> entityClass);
 
@@ -832,26 +846,26 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * <strong>NOTE:</strong> Any additional support for field mapping, versions, etc. is not available due to the lack of
 	 * domain type information. Use {@link #updateFirst(Query, Update, Class, String)} to get full type specific support.
 	 *
-	 * @param query the query document that specifies the criteria used to select a record to be updated
-	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
-	 *          object.
-	 * @param collectionName name of the collection to update the object in
-	 * @return the WriteResult which lets you access the results of the previous write.
+	 * @param query the query document that specifies the criteria used to select a record to be updated. Must not be
+	 *          {@literal null}.
+	 * @param update the update document that contains the updated object or $ operators to manipulate the existing. Must
+	 *          not be {@literal null}.
+	 * @param collectionName name of the collection to update the object in. Must not be {@literal null}.
+	 * @return the {@link UpdateResult} which lets you access the results of the previous write.
 	 */
 	Mono<UpdateResult> updateFirst(Query query, Update update, String collectionName);
 
 	/**
 	 * Updates the first object that is found in the specified collection that matches the query document criteria with
 	 * the provided updated document. <br />
-	 * <strong>NOTE:</strong> Any additional support for field mapping, versions, etc. is not available due to the lack of
-	 * domain type information. Use {@link #updateFirst(Query, Update, Class, String)} to get full type specific support.
 	 *
-	 * @param query the query document that specifies the criteria used to select a record to be updated
-	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
-	 *          object.
-	 * @param entityClass class of the pojo to be operated on
-	 * @param collectionName name of the collection to update the object in
-	 * @return the WriteResult which lets you access the results of the previous write.
+	 * @param query the query document that specifies the criteria used to select a record to be updated. Must not be
+	 *          {@literal null}.
+	 * @param update the update document that contains the updated object or $ operators to manipulate the existing. Must
+	 *          not be {@literal null}.
+	 * @param entityClass class of the pojo to be operated on. Must not be {@literal null}.
+	 * @param collectionName name of the collection to update the object in. Must not be {@literal null}.
+	 * @return the {@link UpdateResult} which lets you access the results of the previous write.
 	 */
 	Mono<UpdateResult> updateFirst(Query query, Update update, Class<?> entityClass, String collectionName);
 
@@ -859,11 +873,12 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * Updates all objects that are found in the collection for the entity class that matches the query document criteria
 	 * with the provided updated document.
 	 *
-	 * @param query the query document that specifies the criteria used to select a record to be updated
-	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
-	 *          object.
-	 * @param entityClass class that determines the collection to use
-	 * @return the WriteResult which lets you access the results of the previous write.
+	 * @param query the query document that specifies the criteria used to select a record to be updated. Must not be
+	 *          {@literal null}.
+	 * @param update the update document that contains the updated object or $ operators to manipulate the existing. Must
+	 *          not be {@literal null}.
+	 * @param entityClass class of the pojo to be operated on. Must not be {@literal null}.
+	 * @return the {@link UpdateResult} which lets you access the results of the previous write.
 	 */
 	Mono<UpdateResult> updateMulti(Query query, Update update, Class<?> entityClass);
 
@@ -873,11 +888,12 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * <strong>NOTE:</strong> Any additional support for field mapping, versions, etc. is not available due to the lack of
 	 * domain type information. Use {@link #updateMulti(Query, Update, Class, String)} to get full type specific support.
 	 *
-	 * @param query the query document that specifies the criteria used to select a record to be updated
-	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
-	 *          object.
-	 * @param collectionName name of the collection to update the object in
-	 * @return the WriteResult which lets you access the results of the previous write.
+	 * @param query the query document that specifies the criteria used to select a record to be updated. Must not be
+	 *          {@literal null}.
+	 * @param update the update document that contains the updated object or $ operators to manipulate the existing. Must
+	 *          not be {@literal null}.
+	 * @param collectionName name of the collection to update the object in. Must not be {@literal null}.
+	 * @return the {@link UpdateResult} which lets you access the results of the previous write.
 	 */
 	Mono<UpdateResult> updateMulti(Query query, Update update, String collectionName);
 
@@ -885,55 +901,57 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * Updates all objects that are found in the collection for the entity class that matches the query document criteria
 	 * with the provided updated document.
 	 *
-	 * @param query the query document that specifies the criteria used to select a record to be updated
-	 * @param update the update document that contains the updated object or $ operators to manipulate the existing
-	 *          object.
-	 * @param entityClass class of the pojo to be operated on
-	 * @param collectionName name of the collection to update the object in
-	 * @return the WriteResult which lets you access the results of the previous write.
+	 * @param query the query document that specifies the criteria used to select a record to be updated. Must not be
+	 *          {@literal null}.
+	 * @param update the update document that contains the updated object or $ operators to manipulate the existing. Must
+	 *          not be {@literal null}.
+	 * @param entityClass class of the pojo to be operated on. Must not be {@literal null}.
+	 * @param collectionName name of the collection to update the object in. Must not be {@literal null}.
+	 * @return the {@link UpdateResult} which lets you access the results of the previous write.
 	 */
-	Mono<UpdateResult> updateMulti(final Query query, final Update update, Class<?> entityClass, String collectionName);
+	Mono<UpdateResult> updateMulti(Query query, Update update, Class<?> entityClass, String collectionName);
 
 	/**
 	 * Remove the given object from the collection by id.
 	 *
-	 * @param object
-	 * @return
+	 * @param object must not be {@literal null}.
+	 * @return the {@link DeleteResult} which lets you access the results of the previous delete.
 	 */
 	Mono<DeleteResult> remove(Object object);
 
 	/**
 	 * Removes the given object from the given collection.
 	 *
-	 * @param object
-	 * @param collection must not be {@literal null} or empty.
+	 * @param object must not be {@literal null}.
+	 * @param collectionName name of the collection where the objects will removed, must not be {@literal null} or empty.
+	 * @return the {@link DeleteResult} which lets you access the results of the previous delete.
 	 */
-	Mono<DeleteResult> remove(Object object, String collection);
+	Mono<DeleteResult> remove(Object object, String collectionName);
 
 	/**
 	 * Remove the given object from the collection by id.
 	 *
-	 * @param objectToRemove
-	 * @return
+	 * @param objectToRemove must not be {@literal null}.
+	 * @return the {@link DeleteResult} which lets you access the results of the previous delete.
 	 */
 	Mono<DeleteResult> remove(Mono<? extends Object> objectToRemove);
 
 	/**
 	 * Removes the given object from the given collection.
 	 *
-	 * @param objectToRemove
-	 * @param collection must not be {@literal null} or empty.
-	 * @return
+	 * @param objectToRemove must not be {@literal null}.
+	 * @param collectionName name of the collection where the objects will removed, must not be {@literal null} or empty.
+	 * @return the {@link DeleteResult} which lets you access the results of the previous delete.
 	 */
-	Mono<DeleteResult> remove(Mono<? extends Object> objectToRemove, String collection);
+	Mono<DeleteResult> remove(Mono<? extends Object> objectToRemove, String collectionName);
 
 	/**
 	 * Remove all documents that match the provided query document criteria from the the collection used to store the
 	 * entityClass. The Class parameter is also used to help convert the Id of the object if it is present in the query.
 	 *
-	 * @param query
-	 * @param entityClass
-	 * @return
+	 * @param query the query document that specifies the criteria used to remove a record.
+	 * @param entityClass class that determines the collection to use.
+	 * @return the {@link DeleteResult} which lets you access the results of the previous delete.
 	 */
 	Mono<DeleteResult> remove(Query query, Class<?> entityClass);
 
@@ -941,12 +959,12 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * Remove all documents that match the provided query document criteria from the the collection used to store the
 	 * entityClass. The Class parameter is also used to help convert the Id of the object if it is present in the query.
 	 *
-	 * @param query
-	 * @param entityClass
-	 * @param collectionName
-	 * @return
+	 * @param query the query document that specifies the criteria used to remove a record.
+	 * @param entityClass class of the pojo to be operated on. Can be {@literal null}.
+	 * @param collectionName name of the collection where the objects will removed, must not be {@literal null} or empty.
+	 * @return the {@link DeleteResult} which lets you access the results of the previous delete.
 	 */
-	Mono<DeleteResult> remove(Query query, Class<?> entityClass, String collectionName);
+	Mono<DeleteResult> remove(Query query, @Nullable Class<?> entityClass, String collectionName);
 
 	/**
 	 * Remove all documents from the specified collection that match the provided query document criteria. There is no
@@ -954,8 +972,9 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * <strong>NOTE:</strong> Any additional support for field mapping is not available due to the lack of domain type
 	 * information. Use {@link #remove(Query, Class, String)} to get full type specific support.
 	 *
-	 * @param query the query document that specifies the criteria used to remove a record
-	 * @param collectionName name of the collection where the objects will removed
+	 * @param query the query document that specifies the criteria used to remove a record.
+	 * @param collectionName name of the collection where the objects will removed, must not be {@literal null} or empty.
+	 * @return the {@link DeleteResult} which lets you access the results of the previous delete.
 	 */
 	Mono<DeleteResult> remove(Query query, String collectionName);
 
@@ -964,18 +983,18 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * <strong>NOTE:</strong> Any additional support for field mapping is not available due to the lack of domain type
 	 * information. Use {@link #findAllAndRemove(Query, Class, String)} to get full type specific support.
 	 *
-	 * @param query
-	 * @param collectionName
-	 * @return
+	 * @param query the query document that specifies the criteria used to find and remove documents.
+	 * @param collectionName name of the collection where the objects will removed, must not be {@literal null} or empty.
+	 * @return the {@link Flux} converted objects deleted by this operation.
 	 */
 	<T> Flux<T> findAllAndRemove(Query query, String collectionName);
 
 	/**
 	 * Returns and removes all documents matching the given query form the collection used to store the entityClass.
 	 *
-	 * @param query
-	 * @param entityClass
-	 * @return
+	 * @param query the query document that specifies the criteria used to find and remove documents.
+	 * @param entityClass class of the pojo to be operated on.
+	 * @return the {@link Flux} converted objects deleted by this operation.
 	 */
 	<T> Flux<T> findAllAndRemove(Query query, Class<T> entityClass);
 
@@ -984,10 +1003,10 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * store the entityClass. The Class parameter is also used to help convert the Id of the object if it is present in
 	 * the query.
 	 *
-	 * @param query
-	 * @param entityClass
-	 * @param collectionName
-	 * @return
+	 * @param query the query document that specifies the criteria used to find and remove documents.
+	 * @param entityClass class of the pojo to be operated on.
+	 * @param collectionName name of the collection where the objects will removed, must not be {@literal null} or empty.
+	 * @return the {@link Flux} converted objects deleted by this operation.
 	 */
 	<T> Flux<T> findAllAndRemove(Query query, Class<T> entityClass, String collectionName);
 
@@ -1004,9 +1023,9 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * feature rich {@link Query}.
 	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
-	 *          specification
+	 *          specification.
 	 * @param entityClass the parametrized type of the returned {@link Flux}.
-	 * @return the {@link Flux} of converted objects
+	 * @return the {@link Flux} of converted objects.
 	 */
 	<T> Flux<T> tail(Query query, Class<T> entityClass);
 
@@ -1023,10 +1042,10 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * feature rich {@link Query}.
 	 *
 	 * @param query the query class that specifies the criteria used to find a record and also an optional fields
-	 *          specification
+	 *          specification.
 	 * @param entityClass the parametrized type of the returned {@link Flux}.
-	 * @param collectionName name of the collection to retrieve the objects from
-	 * @return the {@link Flux} of converted objects
+	 * @param collectionName name of the collection to retrieve the objects from.
+	 * @return the {@link Flux} of converted objects.
 	 */
 	<T> Flux<T> tail(Query query, Class<T> entityClass, String collectionName);
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2017 the original author or authors.
+ * Copyright 2016-2018 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.
@@ -20,8 +20,6 @@ import static org.springframework.data.mongodb.core.query.SerializationUtils.*;
 
 import lombok.NonNull;
 import lombok.RequiredArgsConstructor;
-import org.springframework.data.projection.ProjectionInformation;
-import org.springframework.util.ClassUtils;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 import reactor.util.function.Tuple2;
@@ -40,6 +38,8 @@ import java.util.Set;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 
+import javax.annotation.Nonnull;
+
 import org.bson.Document;
 import org.bson.conversions.Bson;
 import org.bson.types.ObjectId;
@@ -105,10 +105,13 @@ import org.springframework.data.mongodb.core.query.NearQuery;
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.data.mongodb.core.query.Update;
 import org.springframework.data.mongodb.util.MongoClientVersion;
+import org.springframework.data.projection.ProjectionInformation;
 import org.springframework.data.projection.SpelAwareProxyProjectionFactory;
 import org.springframework.data.util.Optionals;
 import org.springframework.data.util.Pair;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
@@ -122,6 +125,7 @@ import com.mongodb.MongoException;
 import com.mongodb.ReadPreference;
 import com.mongodb.WriteConcern;
 import com.mongodb.client.model.CreateCollectionOptions;
+import com.mongodb.client.model.DeleteOptions;
 import com.mongodb.client.model.Filters;
 import com.mongodb.client.model.FindOneAndDeleteOptions;
 import com.mongodb.client.model.FindOneAndUpdateOptions;
@@ -179,12 +183,12 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	private final UpdateMapper updateMapper;
 	private final SpelAwareProxyProjectionFactory projectionFactory;
 
-	private WriteConcern writeConcern;
+	private @Nullable WriteConcern writeConcern;
 	private WriteConcernResolver writeConcernResolver = DefaultWriteConcernResolver.INSTANCE;
 	private WriteResultChecking writeResultChecking = WriteResultChecking.NONE;
-	private ReadPreference readPreference;
-	private ApplicationEventPublisher eventPublisher;
-	private MongoPersistentEntityIndexCreator indexCreator;
+	private @Nullable ReadPreference readPreference;
+	private @Nullable ApplicationEventPublisher eventPublisher;
+	private @Nullable MongoPersistentEntityIndexCreator indexCreator;
 
 	/**
 	 * Constructor used for a basic template configuration.
@@ -209,9 +213,10 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * Constructor used for a basic template configuration.
 	 *
 	 * @param mongoDatabaseFactory must not be {@literal null}.
-	 * @param mongoConverter
+	 * @param mongoConverter can be {@literal null}.
 	 */
-	public ReactiveMongoTemplate(ReactiveMongoDatabaseFactory mongoDatabaseFactory, MongoConverter mongoConverter) {
+	public ReactiveMongoTemplate(ReactiveMongoDatabaseFactory mongoDatabaseFactory,
+			@Nullable MongoConverter mongoConverter) {
 
 		Assert.notNull(mongoDatabaseFactory, "ReactiveMongoDatabaseFactory must not be null!");
 
@@ -226,7 +231,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		mappingContext = this.mongoConverter.getMappingContext();
 		// We create indexes based on mapping events
 
-		if (null != mappingContext && mappingContext instanceof MongoMappingContext) {
+		if (mappingContext instanceof MongoMappingContext) {
 			indexCreator = new MongoPersistentEntityIndexCreator((MongoMappingContext) mappingContext,
 					(collectionName) -> IndexOperationsAdapter.blocking(indexOps(collectionName)));
 			eventPublisher = new MongoMappingEventPublisher(indexCreator);
@@ -242,7 +247,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 *
 	 * @param resultChecking
 	 */
-	public void setWriteResultChecking(WriteResultChecking resultChecking) {
+	public void setWriteResultChecking(@Nullable WriteResultChecking resultChecking) {
 		this.writeResultChecking = resultChecking == null ? DEFAULT_WRITE_RESULT_CHECKING : resultChecking;
 	}
 
@@ -251,18 +256,18 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * configured on the {@link MongoDbFactory} will apply. If you configured a {@link Mongo} instance no
 	 * {@link WriteConcern} will be used.
 	 *
-	 * @param writeConcern
+	 * @param writeConcern can be {@literal null}.
 	 */
-	public void setWriteConcern(WriteConcern writeConcern) {
+	public void setWriteConcern(@Nullable WriteConcern writeConcern) {
 		this.writeConcern = writeConcern;
 	}
 
 	/**
 	 * Configures the {@link WriteConcernResolver} to be used with the template.
 	 *
-	 * @param writeConcernResolver
+	 * @param writeConcernResolver can be {@literal null}.
 	 */
-	public void setWriteConcernResolver(WriteConcernResolver writeConcernResolver) {
+	public void setWriteConcernResolver(@Nullable WriteConcernResolver writeConcernResolver) {
 		this.writeConcernResolver = writeConcernResolver;
 	}
 
@@ -370,7 +375,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#executeCommand(org.bson.Document, com.mongodb.ReadPreference)
 	 */
-	public Mono<Document> executeCommand(final Document command, final ReadPreference readPreference) {
+	public Mono<Document> executeCommand(final Document command, @Nullable ReadPreference readPreference) {
 
 		Assert.notNull(command, "Command must not be null!");
 
@@ -485,7 +490,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#createCollection(java.lang.Class, org.springframework.data.mongodb.core.CollectionOptions)
 	 */
 	public <T> Mono<MongoCollection<Document>> createCollection(Class<T> entityClass,
-			CollectionOptions collectionOptions) {
+			@Nullable CollectionOptions collectionOptions) {
 		return createCollection(determineCollectionName(entityClass), collectionOptions);
 	}
 
@@ -609,7 +614,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#exists(org.springframework.data.mongodb.core.query.Query, java.lang.Class, java.lang.String)
 	 */
-	public Mono<Boolean> exists(final Query query, final Class<?> entityClass, String collectionName) {
+	public Mono<Boolean> exists(final Query query, @Nullable Class<?> entityClass, String collectionName) {
 
 		if (query == null) {
 			throw new InvalidDataAccessApiUsageException("Query passed in to exist can't be null");
@@ -639,7 +644,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#find(org.springframework.data.mongodb.core.query.Query, java.lang.Class, java.lang.String)
 	 */
-	public <T> Flux<T> find(final Query query, Class<T> entityClass, String collectionName) {
+	public <T> Flux<T> find(@Nullable Query query, Class<T> entityClass, String collectionName) {
 
 		if (query == null) {
 			return findAll(entityClass, collectionName);
@@ -722,14 +727,15 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * @return never {@literal null}.
 	 */
 	protected <O> Flux<O> aggregate(Aggregation aggregation, String collectionName, Class<O> outputType,
-			AggregationOperationContext context) {
+			@Nullable AggregationOperationContext context) {
 
 		Assert.notNull(aggregation, "Aggregation pipeline must not be null!");
 		Assert.hasText(collectionName, "Collection name must not be null or empty!");
 		Assert.notNull(outputType, "Output type must not be null!");
 
-		AggregationOperationContext rootContext = context == null ? Aggregation.DEFAULT_CONTEXT : context;
-		Document command = aggregation.toDocument(collectionName, rootContext);
+		AggregationUtil aggregationUtil = new AggregationUtil(queryMapper, mappingContext);
+		AggregationOperationContext rootContext = aggregationUtil.prepareAggregationContext(aggregation, context);
+		Document command = aggregationUtil.createPipeline(collectionName, aggregation, rootContext);
 		AggregationOptions options = AggregationOptions.fromDocument(command);
 
 		Assert.isTrue(!options.isExplain(), "Cannot use explain option with streaming!");
@@ -747,8 +753,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	private <O> Flux<O> aggregateAndMap(MongoCollection<Document> collection, List<Document> pipeline,
 			AggregationOptions options, ReadDocumentCallback<O> readCallback) {
 
-		AggregatePublisher<Document> cursor = collection.aggregate(pipeline).allowDiskUse(options.isAllowDiskUse())
-				.useCursor(true);
+		AggregatePublisher<Document> cursor = collection.aggregate(pipeline)
+				.allowDiskUse(options.isAllowDiskUse());
 
 		if (options.getCollation().isPresent()) {
 			cursor = cursor.collation(options.getCollation().map(Collation::toMongoCollation).get());
@@ -904,7 +910,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#count(org.springframework.data.mongodb.core.query.Query, java.lang.Class, java.lang.String)
 	 */
-	public Mono<Long> count(final Query query, final Class<?> entityClass, String collectionName) {
+	public Mono<Long> count(@Nullable Query query, @Nullable Class<?> entityClass, String collectionName) {
 
 		Assert.hasText(collectionName, "Collection name must not be null or empty!");
 
@@ -924,12 +930,15 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	@Override
 	public <T> Mono<T> insert(Mono<? extends T> objectToSave) {
+
+		Assert.notNull(objectToSave, "Mono to insert must not be null!");
+
 		return objectToSave.flatMap(this::insert);
 	}
 
 	/*
 	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#insert(org.reactivestreams.Publisher, java.lang.Class)
+	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#insert(reactor.core.publisher.Mono, java.lang.Class)
 	 */
 	@Override
 	public <T> Flux<T> insertAll(Mono<? extends Collection<? extends T>> batchToSave, Class<?> entityClass) {
@@ -938,10 +947,13 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 
 	/*
 	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#insert(org.reactivestreams.Publisher, java.lang.String)
+	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#insert(reactor.core.publisher.Mono, java.lang.String)
 	 */
 	@Override
 	public <T> Flux<T> insertAll(Mono<? extends Collection<? extends T>> batchToSave, String collectionName) {
+
+		Assert.notNull(batchToSave, "Batch to insert must not be null!");
+
 		return Flux.from(batchToSave).flatMap(collection -> insert(collection, collectionName));
 	}
 
@@ -951,6 +963,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	public <T> Mono<T> insert(T objectToSave) {
 
+		Assert.notNull(objectToSave, "Object to insert must not be null!");
+
 		ensureNotIterable(objectToSave);
 		return insert(objectToSave, determineEntityCollectionName(objectToSave));
 	}
@@ -961,6 +975,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	public <T> Mono<T> insert(T objectToSave, String collectionName) {
 
+		Assert.notNull(objectToSave, "Object to insert must not be null!");
+
 		ensureNotIterable(objectToSave);
 		return doInsert(collectionName, objectToSave, this.mongoConverter);
 	}
@@ -1014,7 +1030,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 
 	/*
 	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#insertAll(org.reactivestreams.Publisher)
+	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#insertAll(reactor.core.publisher.Mono)
 	 */
 	@Override
 	public <T> Flux<T> insertAll(Mono<? extends Collection<? extends T>> objectsToSave) {
@@ -1084,6 +1100,9 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	@Override
 	public <T> Mono<T> save(Mono<? extends T> objectToSave) {
+
+		Assert.notNull(objectToSave, "Mono to save must not be null!");
+
 		return objectToSave.flatMap(this::save);
 	}
 
@@ -1093,6 +1112,9 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	@Override
 	public <T> Mono<T> save(Mono<? extends T> objectToSave, String collectionName) {
+
+		Assert.notNull(objectToSave, "Mono to save must not be null!");
+
 		return objectToSave.flatMap(o -> save(o, collectionName));
 	}
 
@@ -1241,7 +1263,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	}
 
 	private MongoCollection<Document> prepareCollection(MongoCollection<Document> collection,
-			WriteConcern writeConcernToUse) {
+			@Nullable WriteConcern writeConcernToUse) {
 		MongoCollection<Document> collectionToUse = collection;
 
 		if (writeConcernToUse != null) {
@@ -1355,8 +1377,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		return doUpdate(collectionName, query, update, entityClass, false, true);
 	}
 
-	protected Mono<UpdateResult> doUpdate(final String collectionName, final Query query, final Update update,
-			final Class<?> entityClass, final boolean upsert, final boolean multi) {
+	protected Mono<UpdateResult> doUpdate(final String collectionName, @Nullable Query query, @Nullable Update update,
+			@Nullable Class<?> entityClass, final boolean upsert, final boolean multi) {
 
 		MongoPersistentEntity<?> entity = entityClass == null ? null : getPersistentEntity(entityClass);
 
@@ -1407,7 +1429,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		return result.next();
 	}
 
-	private void increaseVersionForUpdateIfNecessary(MongoPersistentEntity<?> persistentEntity, Update update) {
+	private void increaseVersionForUpdateIfNecessary(@Nullable MongoPersistentEntity<?> persistentEntity, Update update) {
 
 		if (persistentEntity != null && persistentEntity.hasVersionProperty()) {
 			String versionFieldName = persistentEntity.getRequiredVersionProperty().getFieldName();
@@ -1417,7 +1439,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		}
 	}
 
-	private boolean dbObjectContainsVersionProperty(Document document, MongoPersistentEntity<?> persistentEntity) {
+	private boolean dbObjectContainsVersionProperty(Document document,
+			@Nullable MongoPersistentEntity<?> persistentEntity) {
 
 		if (persistentEntity == null || !persistentEntity.hasVersionProperty()) {
 			return false;
@@ -1440,8 +1463,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#remove(reactor.core.publisher.Mono, java.lang.String)
 	 */
 	@Override
-	public Mono<DeleteResult> remove(Mono<? extends Object> objectToRemove, String collection) {
-		return objectToRemove.flatMap(o -> remove(objectToRemove, collection));
+	public Mono<DeleteResult> remove(Mono<? extends Object> objectToRemove, String collectionName) {
+		return objectToRemove.flatMap(it -> remove(it, collectionName));
 	}
 
 	/*
@@ -1450,9 +1473,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	public Mono<DeleteResult> remove(Object object) {
 
-		if (object == null) {
-			return null;
-		}
+		Assert.notNull(object, "Object must not be null!");
 
 		return remove(getIdQueryFor(object), object.getClass());
 	}
@@ -1461,15 +1482,12 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#remove(java.lang.Object, java.lang.String)
 	 */
-	public Mono<DeleteResult> remove(Object object, String collection) {
+	public Mono<DeleteResult> remove(Object object, String collectionName) {
 
-		Assert.hasText(collection, "Collection name must not be null or empty!");
+		Assert.notNull(object, "Object must not be null!");
+		Assert.hasText(collectionName, "Collection name must not be null or empty!");
 
-		if (object == null) {
-			return null;
-		}
-
-		return doRemove(collection, getIdQueryFor(object), object.getClass());
+		return doRemove(collectionName, getIdQueryFor(object), object.getClass());
 	}
 
 	/**
@@ -1578,12 +1596,11 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#remove(org.springframework.data.mongodb.core.query.Query, java.lang.Class, java.lang.String)
 	 */
-	public Mono<DeleteResult> remove(Query query, Class<?> entityClass, String collectionName) {
+	public Mono<DeleteResult> remove(Query query, @Nullable Class<?> entityClass, String collectionName) {
 		return doRemove(collectionName, query, entityClass);
 	}
 
-	protected <T> Mono<DeleteResult> doRemove(final String collectionName, final Query query,
-			final Class<T> entityClass) {
+	protected <T> Mono<DeleteResult> doRemove(String collectionName, Query query, @Nullable Class<T> entityClass) {
 
 		if (query == null) {
 			throw new InvalidDataAccessApiUsageException("Query passed in to remove can't be null!");
@@ -1596,27 +1613,39 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 
 		return execute(collectionName, collection -> {
 
-			maybeEmitEvent(new BeforeDeleteEvent<T>(queryObject, entityClass, collectionName));
+			Document removeQuey = queryMapper.getMappedObject(queryObject, entity);
 
-			Document dboq = queryMapper.getMappedObject(queryObject, entity);
+			maybeEmitEvent(new BeforeDeleteEvent<T>(removeQuey, entityClass, collectionName));
 
 			MongoAction mongoAction = new MongoAction(writeConcern, MongoActionOperation.REMOVE, collectionName, entityClass,
-					null, queryObject);
+					null, removeQuey);
+
+			final DeleteOptions deleteOptions = new DeleteOptions();
+			query.getCollation().map(Collation::toMongoCollation).ifPresent(deleteOptions::collation);
+
 			WriteConcern writeConcernToUse = prepareWriteConcern(mongoAction);
 			MongoCollection<Document> collectionToUse = prepareCollection(collection, writeConcernToUse);
 
 			if (LOGGER.isDebugEnabled()) {
 				LOGGER.debug("Remove using query: {} in collection: {}.",
-						new Object[] { serializeToJsonSafely(dboq), collectionName });
+						new Object[] { serializeToJsonSafely(removeQuey), collectionName });
 			}
 
-			query.getCollation().ifPresent(val -> {
+			if (query.getLimit() > 0 || query.getSkip() > 0) {
 
-				// TODO: add collation support as soon as it's there! See https://jira.mongodb.org/browse/JAVARS-27
-				throw new IllegalArgumentException("DeleteMany does currently not accept collation settings.");
-			});
+				FindPublisher<Document> cursor = new QueryFindPublisherPreparer(query, entityClass)
+						.prepare(collection.find(removeQuey)) //
+						.projection(new Document(ID_FIELD, 1));
 
-			return collectionToUse.deleteMany(dboq);
+				return Flux.from(cursor) //
+						.map(doc -> doc.get(ID_FIELD)) //
+						.collectList() //
+						.flatMapMany(val -> {
+							return collectionToUse.deleteMany(new Document(ID_FIELD, new Document("$in", val)), deleteOptions);
+						});
+			} else {
+				return collectionToUse.deleteMany(removeQuey, deleteOptions);
+			}
 
 		}).doOnNext(deleteResult -> maybeEmitEvent(new AfterDeleteEvent<T>(queryObject, entityClass, collectionName)))
 				.next();
@@ -1645,8 +1674,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	@Override
 	public <T> Flux<T> findAllAndRemove(Query query, String collectionName) {
-
-		return findAllAndRemove(query, null, collectionName);
+		return (Flux<T>) findAllAndRemove(query, Object.class, collectionName);
 	}
 
 	/*
@@ -1681,7 +1709,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * @see org.springframework.data.mongodb.core.ReactiveMongoOperations#tail(org.springframework.data.mongodb.core.query.Query, java.lang.Class, java.lang.String)
 	 */
 	@Override
-	public <T> Flux<T> tail(Query query, Class<T> entityClass, String collectionName) {
+	public <T> Flux<T> tail(@Nullable Query query, Class<T> entityClass, String collectionName) {
 
 		if (query == null) {
 
@@ -1789,10 +1817,11 @@ 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 collation can be {@literal null}.
 	 * @return the {@link List} of converted objects.
 	 */
-	protected <T> Mono<T> doFindOne(String collectionName, Document query, Document fields, Class<T> entityClass,
-			Collation collation) {
+	protected <T> Mono<T> doFindOne(String collectionName, Document query, @Nullable Document fields,
+			Class<T> entityClass, @Nullable Collation collation) {
 
 		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
 		Document mappedQuery = queryMapper.getMappedObject(query, entity);
@@ -1842,7 +1871,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	}
 
 	protected <S, T> Flux<T> doFind(String collectionName, Document query, Document fields, Class<S> entityClass,
-			FindPublisherPreparer preparer, DocumentCallback<T> objectCallback) {
+			@Nullable FindPublisherPreparer preparer, DocumentCallback<T> objectCallback) {
 
 		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
 
@@ -1889,15 +1918,14 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * For cases where {@code fields} is {@literal null} or {@literal empty} add fields required for creating the
 	 * projection (target) type if the {@code targetType} is a {@literal closed interface projection}.
 	 *
-	 * @param fields can be {@literal null}.
+	 * @param fields must not be {@literal null}.
 	 * @param domainType must not be {@literal null}.
 	 * @param targetType must not be {@literal null}.
 	 * @return {@link Document} with fields to be included.
 	 */
 	private Document addFieldsForProjection(Document fields, Class<?> domainType, Class<?> targetType) {
 
-		if ((fields != null && !fields.isEmpty()) || !targetType.isInterface()
-				|| ClassUtils.isAssignable(domainType, targetType)) {
+		if (!fields.isEmpty() || !targetType.isInterface() || ClassUtils.isAssignable(domainType, targetType)) {
 			return fields;
 		}
 
@@ -1910,9 +1938,10 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		return fields;
 	}
 
-	protected CreateCollectionOptions convertToCreateCollectionOptions(CollectionOptions collectionOptions) {
+	protected CreateCollectionOptions convertToCreateCollectionOptions(@Nullable CollectionOptions collectionOptions) {
 
 		CreateCollectionOptions result = new CreateCollectionOptions();
+
 		if (collectionOptions != null) {
 
 			collectionOptions.getCapped().ifPresent(result::capped);
@@ -1920,6 +1949,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 			collectionOptions.getMaxDocuments().ifPresent(result::maxDocuments);
 			collectionOptions.getCollation().map(Collation::toMongoCollation).ifPresent(result::collation);
 		}
+
 		return result;
 	}
 
@@ -1936,7 +1966,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * @return the List of converted objects.
 	 */
 	protected <T> Mono<T> doFindAndRemove(String collectionName, Document query, Document fields, Document sort,
-			Collation collation, Class<T> entityClass) {
+			@Nullable Collation collation, Class<T> entityClass) {
 
 		if (LOGGER.isDebugEnabled()) {
 			LOGGER.debug(String.format("findAndRemove using query: %s fields: %s sort: %s for class: %s in collection: %s",
@@ -1953,8 +1983,6 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	protected <T> Mono<T> doFindAndModify(String collectionName, Document query, Document fields, Document sort,
 			Class<T> entityClass, Update update, FindAndModifyOptions options) {
 
-		FindAndModifyOptions optionsToUse = options != null ? options : new FindAndModifyOptions();
-
 		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(entityClass);
 
 		return Mono.defer(() -> {
@@ -1971,7 +1999,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 						collectionName));
 			}
 
-			return executeFindOneInternal(new FindAndModifyCallback(mappedQuery, fields, sort, mappedUpdate, optionsToUse),
+			return executeFindOneInternal(new FindAndModifyCallback(mappedQuery, fields, sort, mappedUpdate, options),
 					new ReadDocumentCallback<T>(this.mongoConverter, entityClass, collectionName), collectionName);
 		});
 	}
@@ -1988,7 +2016,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * @param savedObject
 	 * @param id
 	 */
-	private void populateIdIfNecessary(Object savedObject, Object id) {
+	private void populateIdIfNecessary(Object savedObject, @Nullable Object id) {
 
 		if (id == null) {
 			return;
@@ -2028,22 +2056,20 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	}
 
 	protected void ensureNotIterable(Object o) {
-		if (null != o) {
 
-			boolean isIterable = o.getClass().isArray();
+		boolean isIterable = o.getClass().isArray();
 
-			if (!isIterable) {
-				for (Class iterableClass : ITERABLE_CLASSES) {
-					if (iterableClass.isAssignableFrom(o.getClass()) || o.getClass().getName().equals(iterableClass.getName())) {
-						isIterable = true;
-						break;
-					}
+		if (!isIterable) {
+			for (Class iterableClass : ITERABLE_CLASSES) {
+				if (iterableClass.isAssignableFrom(o.getClass()) || o.getClass().getName().equals(iterableClass.getName())) {
+					isIterable = true;
+					break;
 				}
 			}
+		}
 
-			if (isIterable) {
-				throw new IllegalArgumentException("Cannot use a collection here.");
-			}
+		if (isIterable) {
+			throw new IllegalArgumentException("Cannot use a collection here.");
 		}
 	}
 
@@ -2066,18 +2092,20 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 * The returned {@link WriteConcern} will be defaulted to {@link WriteConcern#ACKNOWLEDGED} when
 	 * {@link WriteResultChecking} is set to {@link WriteResultChecking#EXCEPTION}.
 	 *
-	 * @param mongoAction any WriteConcern already configured or null
-	 * @return The prepared WriteConcern or null
+	 * @param mongoAction any WriteConcern already configured or {@literal null}.
+	 * @return The prepared WriteConcern or {@literal null}.
 	 * @see #setWriteConcern(WriteConcern)
 	 * @see #setWriteConcernResolver(WriteConcernResolver)
 	 */
+	@Nullable
 	protected WriteConcern prepareWriteConcern(MongoAction mongoAction) {
 
 		WriteConcern wc = writeConcernResolver.resolve(mongoAction);
 		return potentiallyForceAcknowledgedWrite(wc);
 	}
 
-	private WriteConcern potentiallyForceAcknowledgedWrite(WriteConcern wc) {
+	@Nullable
+	private WriteConcern potentiallyForceAcknowledgedWrite(@Nullable WriteConcern wc) {
 
 		if (ObjectUtils.nullSafeEquals(WriteResultChecking.EXCEPTION, writeResultChecking)
 				&& MongoClientVersion.isMongo3Driver()) {
@@ -2121,14 +2149,14 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 *
 	 * @param collectionCallback the callback to retrieve the {@link FindPublisher} with, must not be {@literal null}.
 	 * @param preparer the {@link FindPublisherPreparer} to potentially modify the {@link FindPublisher} before iterating
-	 *          over it, may be {@literal null}
+	 *          over it, may be {@literal null}.
 	 * @param objectCallback the {@link DocumentCallback} to transform {@link Document}s into the actual domain type, must
 	 *          not be {@literal null}.
 	 * @param collectionName the collection to be queried, must not be {@literal null}.
 	 * @return
 	 */
 	private <T> Flux<T> executeFindMultiInternal(ReactiveCollectionQueryCallback<Document> collectionCallback,
-			FindPublisherPreparer preparer, DocumentCallback<T> objectCallback, String collectionName) {
+			@Nullable FindPublisherPreparer preparer, DocumentCallback<T> objectCallback, String collectionName) {
 
 		return createFlux(collectionName, collection -> {
 
@@ -2184,17 +2212,23 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		return resolved == null ? ex : resolved;
 	}
 
-	private MongoPersistentEntity<?> getPersistentEntity(Class<?> type) {
+	@Nullable
+	private MongoPersistentEntity<?> getPersistentEntity(@Nullable Class<?> type) {
 		return type == null ? null : mappingContext.getPersistentEntity(type);
 	}
 
-	private MongoPersistentProperty getIdPropertyFor(Class<?> type) {
+	@Nullable
+	private MongoPersistentProperty getIdPropertyFor(@Nullable Class<?> type) {
+
+		if (type == null) {
+			return null;
+		}
 
 		MongoPersistentEntity<?> persistentEntity = mappingContext.getPersistentEntity(type);
 		return persistentEntity != null ? persistentEntity.getIdProperty() : null;
 	}
 
-	private <T> String determineEntityCollectionName(T obj) {
+	private <T> String determineEntityCollectionName(@Nullable T obj) {
 
 		if (null != obj) {
 			return determineCollectionName(obj.getClass());
@@ -2203,7 +2237,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		return null;
 	}
 
-	String determineCollectionName(Class<?> entityClass) {
+	String determineCollectionName(@Nullable Class<?> entityClass) {
 
 		if (entityClass == null) {
 			throw new InvalidDataAccessApiUsageException(
@@ -2291,7 +2325,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		private final Optional<Document> fields;
 		private final Optional<Collation> collation;
 
-		FindOneCallback(Document query, Document fields, Collation collation) {
+		FindOneCallback(Document query, @Nullable Document fields, @Nullable Collation collation) {
 			this.query = query;
 			this.fields = Optional.ofNullable(fields);
 			this.collation = Optional.ofNullable(collation);
@@ -2327,10 +2361,10 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	private static class FindCallback implements ReactiveCollectionQueryCallback<Document> {
 
-		private final Document query;
-		private final Document fields;
+		private final @Nullable Document query;
+		private final @Nullable Document fields;
 
-		FindCallback(Document query) {
+		FindCallback(@Nullable Document query) {
 			this(query, null);
 		}
 
@@ -2370,7 +2404,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		private final Document sort;
 		private final Optional<Collation> collation;
 
-		FindAndRemoveCallback(Document query, Document fields, Document sort, Collation collation) {
+		FindAndRemoveCallback(Document query, Document fields, Document sort, @Nullable Collation collation) {
 
 			this.query = query;
 			this.fields = fields;
@@ -2509,7 +2543,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 			this.collectionName = collectionName;
 		}
 
-		public T doWith(Document object) {
+		public T doWith(@Nullable Document object) {
 
 			if (null != object) {
 				maybeEmitEvent(new AfterLoadEvent<T>(object, type, collectionName));
@@ -2540,7 +2574,8 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 		private final @NonNull Class<T> targetType;
 		private final @NonNull String collectionName;
 
-		public T doWith(Document object) {
+		@Nullable
+		public T doWith(@Nullable Document object) {
 
 			if (object == null) {
 				return null;
@@ -2604,10 +2639,10 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	 */
 	class QueryFindPublisherPreparer implements FindPublisherPreparer {
 
-		private final Query query;
-		private final Class<?> type;
+		private final @Nullable Query query;
+		private final @Nullable Class<?> type;
 
-		QueryFindPublisherPreparer(Query query, Class<?> type) {
+		QueryFindPublisherPreparer(@Nullable Query query, @Nullable Class<?> type) {
 
 			this.query = query;
 			this.type = type;
@@ -2687,12 +2722,14 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 	static class NoOpDbRefResolver implements DbRefResolver {
 
 		@Override
-		public Object resolveDbRef(MongoPersistentProperty property, DBRef dbref, DbRefResolverCallback callback,
-				DbRefProxyHandler proxyHandler) {
+		@Nullable
+		public Object resolveDbRef(@Nonnull MongoPersistentProperty property, @Nonnull DBRef dbref,
+				@Nonnull DbRefResolverCallback callback, @Nonnull DbRefProxyHandler proxyHandler) {
 			return null;
 		}
 
 		@Override
+		@Nullable
 		public DBRef createDbRef(org.springframework.data.mongodb.core.mapping.DBRef annotation,
 				MongoPersistentEntity<?> entity, Object id) {
 			return null;
@@ -2705,7 +2742,7 @@ public class ReactiveMongoTemplate implements ReactiveMongoOperations, Applicati
 
 		@Override
 		public List<Document> bulkFetch(List<DBRef> dbRefs) {
-			return null;
+			return Collections.emptyList();
 		}
 	}
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2015 the original author or authors.
+ * Copyright 2014-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@ import java.util.Set;
 
 import org.springframework.data.mongodb.core.script.ExecutableMongoScript;
 import org.springframework.data.mongodb.core.script.NamedMongoScript;
+import org.springframework.lang.Nullable;
 
 import com.mongodb.DB;
 
@@ -56,6 +57,7 @@ public interface ScriptOperations {
 	 * @return the script evaluation result.
 	 * @throws org.springframework.dao.DataAccessException
 	 */
+	@Nullable
 	Object execute(ExecutableMongoScript script, Object... args);
 
 	/**
@@ -65,6 +67,7 @@ public interface ScriptOperations {
 	 * @param args
 	 * @return
 	 */
+	@Nullable
 	Object call(String scriptName, Object... args);
 
 	/**

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

@@ -1,149 +1,149 @@
-/*
- * Copyright 2011-2017 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core;
-
-import java.net.UnknownHostException;
-
-import org.springframework.beans.factory.DisposableBean;
-import org.springframework.dao.DataAccessException;
-import org.springframework.dao.support.PersistenceExceptionTranslator;
-import org.springframework.data.mongodb.MongoDbFactory;
-import org.springframework.util.Assert;
-
-import com.mongodb.DB;
-import com.mongodb.MongoClient;
-import com.mongodb.MongoClientURI;
-import com.mongodb.WriteConcern;
-import com.mongodb.client.MongoDatabase;
-
-/**
- * Factory to create {@link DB} instances from a {@link MongoClient} instance.
- * 
- * @author Mark Pollack
- * @author Oliver Gierke
- * @author Thomas Darimont
- * @author Christoph Strobl
- */
-public class SimpleMongoDbFactory implements DisposableBean, MongoDbFactory {
-
-	private final MongoClient mongoClient;
-	private final String databaseName;
-	private final boolean mongoInstanceCreated;
-	private final PersistenceExceptionTranslator exceptionTranslator;
-
-	private WriteConcern writeConcern;
-
-	/**
-	 * Creates a new {@link SimpleMongoDbFactory} instance from the given {@link MongoClientURI}.
-	 * 
-	 * @param uri must not be {@literal null}.
-	 * @throws UnknownHostException
-	 * @since 1.7
-	 */
-	public SimpleMongoDbFactory(MongoClientURI uri) {
-		this(new MongoClient(uri), uri.getDatabase(), true);
-	}
-
-	/**
-	 * Creates a new {@link SimpleMongoDbFactory} instance from the given {@link MongoClient}.
-	 * 
-	 * @param mongoClient must not be {@literal null}.
-	 * @param databaseName must not be {@literal null}.
-	 * @since 1.7
-	 */
-	public SimpleMongoDbFactory(MongoClient mongoClient, String databaseName) {
-		this(mongoClient, databaseName, false);
-	}
-
-	/**
-	 * @param client
-	 * @param databaseName
-	 * @param mongoInstanceCreated
-	 * @since 1.7
-	 */
-	private SimpleMongoDbFactory(MongoClient mongoClient, String databaseName, boolean mongoInstanceCreated) {
-
-		Assert.notNull(mongoClient, "MongoClient must not be null!");
-		Assert.hasText(databaseName, "Database name must not be empty!");
-		Assert.isTrue(databaseName.matches("[\\w-]+"),
-				"Database name must only contain letters, numbers, underscores and dashes!");
-
-		this.mongoClient = mongoClient;
-		this.databaseName = databaseName;
-		this.mongoInstanceCreated = mongoInstanceCreated;
-		this.exceptionTranslator = new MongoExceptionTranslator();
-	}
-
-	/**
-	 * Configures the {@link WriteConcern} to be used on the {@link DB} instance being created.
-	 * 
-	 * @param writeConcern the writeConcern to set
-	 */
-	public void setWriteConcern(WriteConcern writeConcern) {
-		this.writeConcern = writeConcern;
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.MongoDbFactory#getDb()
-	 */
-	public MongoDatabase getDb() throws DataAccessException {
-		return getDb(databaseName);
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.MongoDbFactory#getDb(java.lang.String)
-	 */
-	public MongoDatabase getDb(String dbName) throws DataAccessException {
-
-		Assert.hasText(dbName, "Database name must not be empty.");
-
-		MongoDatabase db = mongoClient.getDatabase(dbName);
-
-		if (writeConcern == null) {
-			return db;
-		}
-
-		return db.withWriteConcern(writeConcern);
-	}
-
-	/**
-	 * Clean up the Mongo instance if it was created by the factory itself.
-	 * 
-	 * @see DisposableBean#destroy()
-	 */
-	public void destroy() throws Exception {
-		if (mongoInstanceCreated) {
-			mongoClient.close();
-		}
-	}
-
-	/* 
-	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.MongoDbFactory#getExceptionTranslator()
-	 */
-	@Override
-	public PersistenceExceptionTranslator getExceptionTranslator() {
-		return this.exceptionTranslator;
-	}
-
-	@SuppressWarnings("deprecation")
-	@Override
-	public DB getLegacyDb() {
-		return mongoClient.getDB(databaseName);
-	}
-}
+/*
+ * Copyright 2011-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core;
+
+import org.springframework.beans.factory.DisposableBean;
+import org.springframework.dao.DataAccessException;
+import org.springframework.dao.support.PersistenceExceptionTranslator;
+import org.springframework.data.mongodb.MongoDbFactory;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+
+import com.mongodb.DB;
+import com.mongodb.MongoClient;
+import com.mongodb.MongoClientURI;
+import com.mongodb.WriteConcern;
+import com.mongodb.client.MongoDatabase;
+
+/**
+ * Factory to create {@link MongoDatabase} instances from a {@link MongoClient} instance.
+ *
+ * @author Mark Pollack
+ * @author Oliver Gierke
+ * @author Thomas Darimont
+ * @author Christoph Strobl
+ * @author George Moraitis
+ * @author Mark Paluch
+ */
+public class SimpleMongoDbFactory implements DisposableBean, MongoDbFactory {
+
+	private final MongoClient mongoClient;
+	private final String databaseName;
+	private final boolean mongoInstanceCreated;
+	private final PersistenceExceptionTranslator exceptionTranslator;
+
+	private @Nullable WriteConcern writeConcern;
+
+	/**
+	 * Creates a new {@link SimpleMongoDbFactory} instance from the given {@link MongoClientURI}.
+	 *
+	 * @param uri must not be {@literal null}.
+	 * @since 1.7
+	 */
+	public SimpleMongoDbFactory(MongoClientURI uri) {
+		this(new MongoClient(uri), uri.getDatabase(), true);
+	}
+
+	/**
+	 * Creates a new {@link SimpleMongoDbFactory} instance from the given {@link MongoClient}.
+	 *
+	 * @param mongoClient must not be {@literal null}.
+	 * @param databaseName must not be {@literal null}.
+	 * @since 1.7
+	 */
+	public SimpleMongoDbFactory(MongoClient mongoClient, String databaseName) {
+		this(mongoClient, databaseName, false);
+	}
+
+	/**
+	 * @param mongoClient
+	 * @param databaseName
+	 * @param mongoInstanceCreated
+	 * @since 1.7
+	 */
+	private SimpleMongoDbFactory(MongoClient mongoClient, String databaseName, boolean mongoInstanceCreated) {
+
+		Assert.notNull(mongoClient, "MongoClient must not be null!");
+		Assert.hasText(databaseName, "Database name must not be empty!");
+		Assert.isTrue(databaseName.matches("[^/\\\\.$\"\\s]+"),
+				"Database name must not contain slashes, dots, spaces, quotes, or dollar signs!");
+
+		this.mongoClient = mongoClient;
+		this.databaseName = databaseName;
+		this.mongoInstanceCreated = mongoInstanceCreated;
+		this.exceptionTranslator = new MongoExceptionTranslator();
+	}
+
+	/**
+	 * Configures the {@link WriteConcern} to be used on the {@link DB} instance being created.
+	 *
+	 * @param writeConcern the writeConcern to set
+	 */
+	public void setWriteConcern(WriteConcern writeConcern) {
+		this.writeConcern = writeConcern;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.MongoDbFactory#getDb()
+	 */
+	public MongoDatabase getDb() throws DataAccessException {
+		return getDb(databaseName);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.MongoDbFactory#getDb(java.lang.String)
+	 */
+	public MongoDatabase getDb(String dbName) throws DataAccessException {
+
+		Assert.hasText(dbName, "Database name must not be empty.");
+
+		MongoDatabase db = mongoClient.getDatabase(dbName);
+
+		if (writeConcern == null) {
+			return db;
+		}
+
+		return db.withWriteConcern(writeConcern);
+	}
+
+	/**
+	 * Clean up the Mongo instance if it was created by the factory itself.
+	 *
+	 * @see DisposableBean#destroy()
+	 */
+	public void destroy() throws Exception {
+		if (mongoInstanceCreated) {
+			mongoClient.close();
+		}
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.MongoDbFactory#getExceptionTranslator()
+	 */
+	@Override
+	public PersistenceExceptionTranslator getExceptionTranslator() {
+		return this.exceptionTranslator;
+	}
+
+	@SuppressWarnings("deprecation")
+	@Override
+	public DB getLegacyDb() {
+		return mongoClient.getDB(databaseName);
+	}
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,6 +21,7 @@ import org.springframework.beans.factory.DisposableBean;
 import org.springframework.dao.DataAccessException;
 import org.springframework.dao.support.PersistenceExceptionTranslator;
 import org.springframework.data.mongodb.ReactiveMongoDatabaseFactory;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 import com.mongodb.ConnectionString;
@@ -41,9 +42,10 @@ public class SimpleReactiveMongoDatabaseFactory implements DisposableBean, React
 	private final MongoClient mongo;
 	private final String databaseName;
 	private final boolean mongoInstanceCreated;
+
 	private final PersistenceExceptionTranslator exceptionTranslator;
 
-	private WriteConcern writeConcern;
+	private @Nullable WriteConcern writeConcern;
 
 	/**
 	 * Creates a new {@link SimpleReactiveMongoDatabaseFactory} instance from the given {@link ConnectionString}.
@@ -70,8 +72,8 @@ public class SimpleReactiveMongoDatabaseFactory implements DisposableBean, React
 
 		Assert.notNull(client, "MongoClient must not be null!");
 		Assert.hasText(databaseName, "Database name must not be empty!");
-		Assert.isTrue(databaseName.matches("[\\w-]+"),
-				"Database name must only contain letters, numbers, underscores and dashes!");
+		Assert.isTrue(databaseName.matches("[^/\\\\.$\"\\s]+"),
+				"Database name must not contain slashes, dots, spaces, quotes, or dollar signs!");
 
 		this.mongo = client;
 		this.databaseName = databaseName;

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2012 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,6 +15,8 @@
  */
 package org.springframework.data.mongodb.core;
 
+import org.springframework.lang.Nullable;
+
 import com.mongodb.WriteConcern;
 
 /**
@@ -33,5 +35,6 @@ public interface WriteConcernResolver {
 	 *          should not be resolved.
 	 * @return a {@link WriteConcern} based on the passed in {@link MongoAction} value, maybe {@literal null}.
 	 */
+	@Nullable
 	WriteConcern resolve(MongoAction action);
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016. the original author or authors.
+ * Copyright 2016-2018. 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.
@@ -20,12 +20,15 @@ import java.util.Arrays;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
+import java.util.Map;
 
 import org.bson.Document;
+import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
 /**
  * @author Christoph Strobl
+ * @author Matt Morrissette
  * @since 1.10
  */
 abstract class AbstractAggregationExpression implements AggregationExpression {
@@ -46,29 +49,7 @@ abstract class AbstractAggregationExpression implements AggregationExpression {
 
 	@SuppressWarnings("unchecked")
 	public Document toDocument(Object value, AggregationOperationContext context) {
-
-		Object valueToUse;
-		if (value instanceof List) {
-
-			List<Object> arguments = (List<Object>) value;
-			List<Object> args = new ArrayList<Object>(arguments.size());
-
-			for (Object val : arguments) {
-				args.add(unpack(val, context));
-			}
-			valueToUse = args;
-		} else if (value instanceof java.util.Map) {
-
-			Document dbo = new Document();
-			for (java.util.Map.Entry<String, Object> entry : ((java.util.Map<String, Object>) value).entrySet()) {
-				dbo.put(entry.getKey(), unpack(entry.getValue(), context));
-			}
-			valueToUse = dbo;
-		} else {
-			valueToUse = unpack(value, context);
-		}
-
-		return new Document(getMongoMethod(), valueToUse);
+		return new Document(getMongoMethod(), unpack(value, context));
 	}
 
 	protected static List<Field> asFields(String... fieldRefs) {
@@ -94,14 +75,23 @@ abstract class AbstractAggregationExpression implements AggregationExpression {
 		if (value instanceof List) {
 
 			List<Object> sourceList = (List<Object>) value;
-			List<Object> mappedList = new ArrayList<Object>(sourceList.size());
+			List<Object> mappedList = new ArrayList<>(sourceList.size());
+
+			sourceList.stream().map((item) -> unpack(item, context)).forEach(mappedList::add);
 
-			for (Object item : sourceList) {
-				mappedList.add(unpack(item, context));
-			}
 			return mappedList;
 		}
 
+		if (value instanceof Map) {
+
+			Document targetDocument = new Document();
+
+			Map<String, Object> sourceMap = (Map<String, Object>) value;
+			sourceMap.forEach((k, v) -> targetDocument.append(k, unpack(v, context)));
+
+			return targetDocument;
+		}
+
 		return value;
 	}
 
@@ -112,9 +102,7 @@ abstract class AbstractAggregationExpression implements AggregationExpression {
 			List<Object> clone = new ArrayList<Object>((List) this.value);
 
 			if (value instanceof List) {
-				for (Object val : (List) value) {
-					clone.add(val);
-				}
+				clone.addAll((List) value);
 			} else {
 				clone.add(value);
 			}
@@ -127,10 +115,9 @@ abstract class AbstractAggregationExpression implements AggregationExpression {
 	@SuppressWarnings("unchecked")
 	protected java.util.Map<String, Object> append(String key, Object value) {
 
-		if (!(this.value instanceof java.util.Map)) {
-			throw new IllegalArgumentException("o_O");
-		}
-		java.util.Map<String, Object> clone = new LinkedHashMap<String, Object>((java.util.Map<String, Object>) this.value);
+		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);
 		clone.put(key, value);
 		return clone;
 
@@ -144,7 +131,67 @@ abstract class AbstractAggregationExpression implements AggregationExpression {
 		if (value instanceof java.util.Map) {
 			return new ArrayList<Object>(((java.util.Map) value).values());
 		}
-		return new ArrayList<Object>(Collections.singletonList(value));
+		return new ArrayList<>(Collections.singletonList(value));
+	}
+
+	/**
+	 * Get the value at a given index.
+	 *
+	 * @param index
+	 * @param <T>
+	 * @return
+	 * @since 2.1
+	 */
+	@SuppressWarnings("unchecked")
+	protected <T> T get(int index) {
+		return (T) values().get(index);
+	}
+
+	/**
+	 * Get the value for a given key.
+	 *
+	 * @param key
+	 * @param <T>
+	 * @return
+	 * @since 2.1
+	 */
+	@SuppressWarnings("unchecked")
+	protected <T> T get(Object key) {
+
+		Assert.isInstanceOf(Map.class, this.value, "Value must be a type of Map!");
+
+		return (T) ((java.util.Map<String, Object>) this.value).get(key);
+	}
+
+	/**
+	 * Get the argument map.
+	 *
+	 * @since 2.1
+	 * @return
+	 */
+	@SuppressWarnings("unchecked")
+	protected java.util.Map<String, Object> argumentMap() {
+
+		Assert.isInstanceOf(Map.class, this.value, "Value must be a type of Map!");
+
+		return Collections.unmodifiableMap((java.util.Map) value);
+	}
+
+	/**
+	 * Check if the given key is available.
+	 *
+	 * @param key
+	 * @return
+	 * @since 2.1
+	 */
+	@SuppressWarnings("unchecked")
+	protected boolean contains(Object key) {
+
+		if (!(this.value instanceof java.util.Map)) {
+			return false;
+		}
+
+		return ((java.util.Map<String, Object>) this.value).containsKey(key);
 	}
 
 	protected abstract String getMongoMethod();

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

@@ -32,6 +32,7 @@ import org.springframework.data.mongodb.core.query.Criteria;
 import org.springframework.data.mongodb.core.query.CriteriaDefinition;
 import org.springframework.data.mongodb.core.query.NearQuery;
 import org.springframework.data.mongodb.core.query.SerializationUtils;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -600,6 +601,16 @@ public class Aggregation {
 		return SerializationUtils.serializeToJsonSafely(toDocument("__collection__", DEFAULT_CONTEXT));
 	}
 
+	/**
+	 * Get {@link AggregationOptions} to apply.
+	 *
+	 * @return never {@literal null}.
+	 * @since 2.0.3
+	 */
+	public AggregationOptions getOptions() {
+		return options;
+	}
+
 	/**
 	 * Describes the system variables available in MongoDB aggregation framework pipeline expressions.
 	 *
@@ -619,7 +630,7 @@ public class Aggregation {
 		 * @param fieldRef may be {@literal null}.
 		 * @return
 		 */
-		public static boolean isReferingToSystemVariable(String fieldRef) {
+		public static boolean isReferingToSystemVariable(@Nullable String fieldRef) {
 
 			if (fieldRef == null || !fieldRef.startsWith(PREFIX) || fieldRef.length() <= 2) {
 				return false;

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,14 +21,16 @@ import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldRefe
 import org.springframework.data.mongodb.core.spel.ExpressionNode;
 import org.springframework.data.mongodb.core.spel.ExpressionTransformationContextSupport;
 import org.springframework.data.mongodb.core.spel.ExpressionTransformer;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
  * Interface to type an {@link ExpressionTransformer} to the contained
  * {@link AggregationExpressionTransformationContext}.
- * 
+ *
  * @author Oliver Gierke
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @since 1.4
  */
 interface AggregationExpressionTransformer
@@ -36,7 +38,7 @@ interface AggregationExpressionTransformer
 
 	/**
 	 * A special {@link ExpressionTransformationContextSupport} to be aware of the {@link AggregationOperationContext}.
-	 * 
+	 *
 	 * @author Oliver Gierke
 	 * @author Thomas Darimont
 	 */
@@ -47,14 +49,14 @@ interface AggregationExpressionTransformer
 
 		/**
 		 * Creates an {@link AggregationExpressionTransformationContext}.
-		 * 
+		 *
 		 * @param currentNode must not be {@literal null}.
-		 * @param parentNode
-		 * @param previousOperationObject
+		 * @param parentNode may be {@literal null}.
+		 * @param previousOperationObject may be {@literal null}.
 		 * @param aggregationContext must not be {@literal null}.
 		 */
-		public AggregationExpressionTransformationContext(T currentNode, ExpressionNode parentNode,
-				Document previousOperationObject, AggregationOperationContext context) {
+		public AggregationExpressionTransformationContext(T currentNode, @Nullable ExpressionNode parentNode,
+				@Nullable Document previousOperationObject, AggregationOperationContext context) {
 
 			super(currentNode, parentNode, previousOperationObject);
 
@@ -64,7 +66,7 @@ interface AggregationExpressionTransformer
 
 		/**
 		 * Returns the underlying {@link AggregationOperationContext}.
-		 * 
+		 *
 		 * @return
 		 */
 		public AggregationOperationContext getAggregationContext() {
@@ -73,7 +75,7 @@ interface AggregationExpressionTransformer
 
 		/**
 		 * Returns the {@link FieldReference} for the current {@link ExpressionNode}.
-		 * 
+		 *
 		 * @return
 		 */
 		public FieldReference getFieldReference() {

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

@@ -41,7 +41,7 @@ class AggregationOperationRenderer {
 	 * {@link Document} representation.
 	 *
 	 * @param operations must not be {@literal null}.
-	 * @param context must not be {@literal null}.
+	 * @param rootContext must not be {@literal null}.
 	 * @return the {@link List} of {@link Document}.
 	 */
 	static List<Document> toDocument(List<AggregationOperation> operations, AggregationOperationContext rootContext) {
@@ -59,7 +59,7 @@ class AggregationOperationRenderer {
 				FieldsExposingAggregationOperation exposedFieldsOperation = (FieldsExposingAggregationOperation) operation;
 				ExposedFields fields = exposedFieldsOperation.getFields();
 
-				if (operation instanceof InheritsFieldsAggregationOperation) {
+				if (operation instanceof InheritsFieldsAggregationOperation || exposedFieldsOperation.inheritsFields()) {
 					contextToUse = new InheritingExposedFieldsAggregationOperationContext(fields, contextToUse);
 				} else {
 					contextToUse = fields.exposesNoFields() ? DEFAULT_CONTEXT

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

@@ -19,6 +19,7 @@ import java.util.Optional;
 
 import org.bson.Document;
 import org.springframework.data.mongodb.core.query.Collation;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 import com.mongodb.DBObject;
@@ -70,7 +71,8 @@ public class AggregationOptions {
 	 * @param collation collation for string comparison. Can be {@literal null}.
 	 * @since 2.0
 	 */
-	public AggregationOptions(boolean allowDiskUse, boolean explain, Document cursor, Collation collation) {
+	public AggregationOptions(boolean allowDiskUse, boolean explain, @Nullable Document cursor,
+			@Nullable Collation collation) {
 
 		this.allowDiskUse = allowDiskUse;
 		this.explain = explain;
@@ -242,8 +244,8 @@ public class AggregationOptions {
 
 		private boolean allowDiskUse;
 		private boolean explain;
-		private Document cursor;
-		private Collation collation;
+		private @Nullable Document cursor;
+		private @Nullable Collation collation;
 
 		/**
 		 * Defines whether to off-load intensive sort-operations to disk.
@@ -300,7 +302,7 @@ public class AggregationOptions {
 		 * @param collation can be {@literal null}.
 		 * @return
 		 */
-		public Builder collation(Collation collation) {
+		public Builder collation(@Nullable Collation collation) {
 
 			this.collation = collation;
 			return this;

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

@@ -20,11 +20,12 @@ import java.util.Iterator;
 import java.util.List;
 
 import org.bson.Document;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
  * Collects the results of executing an aggregation operation.
- * 
+ *
  * @author Tobias Trelle
  * @author Oliver Gierke
  * @author Thomas Darimont
@@ -37,11 +38,11 @@ public class AggregationResults<T> implements Iterable<T> {
 
 	private final List<T> mappedResults;
 	private final Document rawResults;
-	private final String serverUsed;
+	private final @Nullable String serverUsed;
 
 	/**
 	 * Creates a new {@link AggregationResults} instance from the given mapped and raw results.
-	 * 
+	 *
 	 * @param mappedResults must not be {@literal null}.
 	 * @param rawResults must not be {@literal null}.
 	 */
@@ -57,7 +58,7 @@ public class AggregationResults<T> implements Iterable<T> {
 
 	/**
 	 * Returns the aggregation results.
-	 * 
+	 *
 	 * @return
 	 */
 	public List<T> getMappedResults() {
@@ -66,10 +67,11 @@ public class AggregationResults<T> implements Iterable<T> {
 
 	/**
 	 * Returns the unique mapped result. Assumes no result or exactly one.
-	 * 
+	 *
 	 * @return
 	 * @throws IllegalArgumentException in case more than one result is available.
 	 */
+	@Nullable
 	public T getUniqueMappedResult() {
 		Assert.isTrue(mappedResults.size() < 2, "Expected unique result or null, but got more than one!");
 		return mappedResults.size() == 1 ? mappedResults.get(0) : null;
@@ -85,16 +87,17 @@ public class AggregationResults<T> implements Iterable<T> {
 
 	/**
 	 * Returns the server that has been used to perform the aggregation.
-	 * 
+	 *
 	 * @return
 	 */
+	@Nullable
 	public String getServerUsed() {
 		return serverUsed;
 	}
 
 	/**
 	 * Returns the raw result that was returned by the server.
-	 * 
+	 *
 	 * @return
 	 * @since 1.6
 	 */
@@ -102,6 +105,7 @@ public class AggregationResults<T> implements Iterable<T> {
 		return rawResults;
 	}
 
+	@Nullable
 	private String parseServerUsed() {
 
 		Object object = rawResults.get("serverUsed");

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016. the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,7 +20,7 @@ import org.springframework.util.Assert;
 
 /**
  * An {@link AggregationExpression} that renders a MongoDB Aggregation Framework expression from the AST of a
- * <a href="http://docs.spring.io/spring/docs/current/spring-framework-reference/html/expressions.html">SpEL
+ * <a href="http://docs.spring.io/spring/docs/current/spring-framework-reference/core.html#expressions">SpEL
  * expression</a>. <br />
  * <br />
  * <strong>Samples:</strong> <br />
@@ -35,6 +35,7 @@ import org.springframework.util.Assert;
  * </code>
  * 
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @see SpelExpressionTransformer
  * @since 1.10
  */

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

@@ -92,7 +92,7 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public Abs abs() {
-			return fieldReference != null ? Abs.absoluteValueOf(fieldReference) : Abs.absoluteValueOf(expression);
+			return usesFieldRef() ? Abs.absoluteValueOf(fieldReference) : Abs.absoluteValueOf(expression);
 		}
 
 		/**
@@ -134,7 +134,7 @@ public class ArithmeticOperators {
 		}
 
 		private Add createAdd() {
-			return fieldReference != null ? Add.valueOf(fieldReference) : Add.valueOf(expression);
+			return usesFieldRef() ? Add.valueOf(fieldReference) : Add.valueOf(expression);
 		}
 
 		/**
@@ -144,7 +144,7 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public Ceil ceil() {
-			return fieldReference != null ? Ceil.ceilValueOf(fieldReference) : Ceil.ceilValueOf(expression);
+			return usesFieldRef() ? Ceil.ceilValueOf(fieldReference) : Ceil.ceilValueOf(expression);
 		}
 
 		/**
@@ -186,7 +186,7 @@ public class ArithmeticOperators {
 		}
 
 		private Divide createDivide() {
-			return fieldReference != null ? Divide.valueOf(fieldReference) : Divide.valueOf(expression);
+			return usesFieldRef() ? Divide.valueOf(fieldReference) : Divide.valueOf(expression);
 		}
 
 		/**
@@ -195,7 +195,7 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public Exp exp() {
-			return fieldReference != null ? Exp.expValueOf(fieldReference) : Exp.expValueOf(expression);
+			return usesFieldRef() ? Exp.expValueOf(fieldReference) : Exp.expValueOf(expression);
 		}
 
 		/**
@@ -205,7 +205,7 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public Floor floor() {
-			return fieldReference != null ? Floor.floorValueOf(fieldReference) : Floor.floorValueOf(expression);
+			return usesFieldRef() ? Floor.floorValueOf(fieldReference) : Floor.floorValueOf(expression);
 		}
 
 		/**
@@ -215,7 +215,7 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public Ln ln() {
-			return fieldReference != null ? Ln.lnValueOf(fieldReference) : Ln.lnValueOf(expression);
+			return usesFieldRef() ? Ln.lnValueOf(fieldReference) : Ln.lnValueOf(expression);
 		}
 
 		/**
@@ -258,7 +258,7 @@ public class ArithmeticOperators {
 		}
 
 		private Log createLog() {
-			return fieldReference != null ? Log.valueOf(fieldReference) : Log.valueOf(expression);
+			return usesFieldRef() ? Log.valueOf(fieldReference) : Log.valueOf(expression);
 		}
 
 		/**
@@ -267,7 +267,7 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public Log10 log10() {
-			return fieldReference != null ? Log10.log10ValueOf(fieldReference) : Log10.log10ValueOf(expression);
+			return usesFieldRef() ? Log10.log10ValueOf(fieldReference) : Log10.log10ValueOf(expression);
 		}
 
 		/**
@@ -310,7 +310,7 @@ public class ArithmeticOperators {
 		}
 
 		private Mod createMod() {
-			return fieldReference != null ? Mod.valueOf(fieldReference) : Mod.valueOf(expression);
+			return usesFieldRef() ? Mod.valueOf(fieldReference) : Mod.valueOf(expression);
 		}
 
 		/**
@@ -350,7 +350,7 @@ public class ArithmeticOperators {
 		}
 
 		private Multiply createMultiply() {
-			return fieldReference != null ? Multiply.valueOf(fieldReference) : Multiply.valueOf(expression);
+			return usesFieldRef() ? Multiply.valueOf(fieldReference) : Multiply.valueOf(expression);
 		}
 
 		/**
@@ -390,7 +390,7 @@ public class ArithmeticOperators {
 		}
 
 		private Pow createPow() {
-			return fieldReference != null ? Pow.valueOf(fieldReference) : Pow.valueOf(expression);
+			return usesFieldRef() ? Pow.valueOf(fieldReference) : Pow.valueOf(expression);
 		}
 
 		/**
@@ -399,7 +399,7 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public Sqrt sqrt() {
-			return fieldReference != null ? Sqrt.sqrtOf(fieldReference) : Sqrt.sqrtOf(expression);
+			return usesFieldRef() ? Sqrt.sqrtOf(fieldReference) : Sqrt.sqrtOf(expression);
 		}
 
 		/**
@@ -439,7 +439,7 @@ public class ArithmeticOperators {
 		}
 
 		private Subtract createSubtract() {
-			return fieldReference != null ? Subtract.valueOf(fieldReference) : Subtract.valueOf(expression);
+			return usesFieldRef() ? Subtract.valueOf(fieldReference) : Subtract.valueOf(expression);
 		}
 
 		/**
@@ -448,7 +448,7 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public Trunc trunc() {
-			return fieldReference != null ? Trunc.truncValueOf(fieldReference) : Trunc.truncValueOf(expression);
+			return usesFieldRef() ? Trunc.truncValueOf(fieldReference) : Trunc.truncValueOf(expression);
 		}
 
 		/**
@@ -457,7 +457,7 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public Sum sum() {
-			return fieldReference != null ? AccumulatorOperators.Sum.sumOf(fieldReference)
+			return usesFieldRef() ? AccumulatorOperators.Sum.sumOf(fieldReference)
 					: AccumulatorOperators.Sum.sumOf(expression);
 		}
 
@@ -467,7 +467,7 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public Avg avg() {
-			return fieldReference != null ? AccumulatorOperators.Avg.avgOf(fieldReference)
+			return usesFieldRef() ? AccumulatorOperators.Avg.avgOf(fieldReference)
 					: AccumulatorOperators.Avg.avgOf(expression);
 		}
 
@@ -477,7 +477,7 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public Max max() {
-			return fieldReference != null ? AccumulatorOperators.Max.maxOf(fieldReference)
+			return usesFieldRef() ? AccumulatorOperators.Max.maxOf(fieldReference)
 					: AccumulatorOperators.Max.maxOf(expression);
 		}
 
@@ -487,7 +487,7 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public Min min() {
-			return fieldReference != null ? AccumulatorOperators.Min.minOf(fieldReference)
+			return usesFieldRef() ? AccumulatorOperators.Min.minOf(fieldReference)
 					: AccumulatorOperators.Min.minOf(expression);
 		}
 
@@ -497,7 +497,7 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public StdDevPop stdDevPop() {
-			return fieldReference != null ? AccumulatorOperators.StdDevPop.stdDevPopOf(fieldReference)
+			return usesFieldRef() ? AccumulatorOperators.StdDevPop.stdDevPopOf(fieldReference)
 					: AccumulatorOperators.StdDevPop.stdDevPopOf(expression);
 		}
 
@@ -507,9 +507,13 @@ public class ArithmeticOperators {
 		 * @return
 		 */
 		public StdDevSamp stdDevSamp() {
-			return fieldReference != null ? AccumulatorOperators.StdDevSamp.stdDevSampOf(fieldReference)
+			return usesFieldRef() ? AccumulatorOperators.StdDevSamp.stdDevSampOf(fieldReference)
 					: AccumulatorOperators.StdDevSamp.stdDevSampOf(expression);
 		}
+
+		private boolean usesFieldRef() {
+			return fieldReference != null;
+		}
 	}
 
 	/**

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016. the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,12 +25,14 @@ import org.springframework.data.domain.Range;
 import org.springframework.data.mongodb.core.aggregation.ArrayOperators.Filter.AsBuilder;
 import org.springframework.data.mongodb.core.aggregation.ArrayOperators.Reduce.PropertyExpression;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
  * Gateway to {@literal array} aggregation operations.
  *
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @since 1.0
  */
 public class ArrayOperators {
@@ -223,15 +225,10 @@ public class ArrayOperators {
 		 * @param expression must not be {@literal null}.
 		 * @return
 		 */
-		public ArrayOperatorFactory.ReduceInitialValueBuilder reduce(final AggregationExpression expression) {
-			return new ArrayOperatorFactory.ReduceInitialValueBuilder() {
+		public ArrayOperatorFactory.ReduceInitialValueBuilder reduce(AggregationExpression expression) {
 
-				@Override
-				public Reduce startingWith(Object initialValue) {
-					return (usesFieldRef() ? Reduce.arrayOf(fieldReference) : Reduce.arrayOf(expression))
-							.withInitialValue(initialValue).reduce(expression);
-				}
-			};
+			return initialValue -> (usesFieldRef() ? Reduce.arrayOf(fieldReference)
+					: Reduce.arrayOf(ArrayOperatorFactory.this.expression)).withInitialValue(initialValue).reduce(expression);
 		}
 
 		/**
@@ -241,16 +238,10 @@ public class ArrayOperators {
 		 * @param expressions
 		 * @return
 		 */
-		public ArrayOperatorFactory.ReduceInitialValueBuilder reduce(final PropertyExpression... expressions) {
+		public ArrayOperatorFactory.ReduceInitialValueBuilder reduce(PropertyExpression... expressions) {
 
-			return new ArrayOperatorFactory.ReduceInitialValueBuilder() {
-
-				@Override
-				public Reduce startingWith(Object initialValue) {
-					return (usesFieldRef() ? Reduce.arrayOf(fieldReference) : Reduce.arrayOf(expression))
-							.withInitialValue(initialValue).reduce(expressions);
-				}
-			};
+			return initialValue -> (usesFieldRef() ? Reduce.arrayOf(fieldReference) : Reduce.arrayOf(expression))
+					.withInitialValue(initialValue).reduce(expressions);
 		}
 
 		/**
@@ -414,9 +405,9 @@ public class ArrayOperators {
 	 */
 	public static class Filter implements AggregationExpression {
 
-		private Object input;
-		private ExposedField as;
-		private Object condition;
+		private @Nullable Object input;
+		private @Nullable ExposedField as;
+		private @Nullable Object condition;
 
 		private Filter() {
 			// used by builder
@@ -1103,12 +1094,10 @@ public class ArrayOperators {
 		/**
 		 * Start creating new {@link Reduce}.
 		 *
-		 * @param expression must not be {@literal null}.
+		 * @param arrayValueExpression must not be {@literal null}.
 		 * @return
 		 */
-		public static InitialValueBuilder arrayOf(final AggregationExpression expression) {
-
-			Assert.notNull(expression, "AggregationExpression must not be null");
+		public static InitialValueBuilder arrayOf(final AggregationExpression arrayValueExpression) {
 
 			return new InitialValueBuilder() {
 
@@ -1123,14 +1112,14 @@ public class ArrayOperators {
 						public Reduce reduce(AggregationExpression expression) {
 
 							Assert.notNull(expression, "AggregationExpression must not be null");
-							return new Reduce(expression, initialValue, Collections.singletonList(expression));
+							return new Reduce(arrayValueExpression, initialValue, Collections.singletonList(expression));
 						}
 
 						@Override
 						public Reduce reduce(PropertyExpression... expressions) {
 
 							Assert.notNull(expressions, "PropertyExpressions must not be null");
-							return new Reduce(expression, initialValue, Arrays.<AggregationExpression> asList(expressions));
+							return new Reduce(arrayValueExpression, initialValue, Arrays.asList(expressions));
 						}
 					};
 				}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016. the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016. the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,6 +26,7 @@ import org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Co
 import org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond.ThenBuilder;
 import org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Switch.CaseOperator;
 import org.springframework.data.mongodb.core.query.CriteriaDefinition;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 
@@ -33,6 +34,7 @@ import org.springframework.util.ClassUtils;
  * Gateway to {@literal conditional expressions} that evaluate their argument expressions as booleans to a value.
  *
  * @author Mark Paluch
+ * @author Christoph Strobl
  * @since 1.10
  */
 public class ConditionalOperators {
@@ -121,9 +123,11 @@ public class ConditionalOperators {
 
 	public static class ConditionalOperatorFactory {
 
-		private final String fieldReference;
-		private final AggregationExpression expression;
-		private final CriteriaDefinition criteriaDefinition;
+		private final @Nullable String fieldReference;
+
+		private final @Nullable AggregationExpression expression;
+
+		private final @Nullable CriteriaDefinition criteriaDefinition;
 
 		/**
 		 * Creates new {@link ConditionalOperatorFactory} for given {@literal fieldReference}.
@@ -358,7 +362,7 @@ public class ConditionalOperators {
 		 */
 		static final class IfNullOperatorBuilder implements IfNullBuilder, ThenBuilder {
 
-			private Object condition;
+			private @Nullable Object condition;
 
 			private IfNullOperatorBuilder() {}
 
@@ -850,8 +854,8 @@ public class ConditionalOperators {
 		 */
 		static class ConditionalExpressionBuilder implements WhenBuilder, ThenBuilder, OtherwiseBuilder {
 
-			private Object condition;
-			private Object thenValue;
+			private @Nullable Object condition;
+			private @Nullable Object thenValue;
 
 			private ConditionalExpressionBuilder() {}
 

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

@@ -0,0 +1,670 @@
+/*
+ * Copyright 2018 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.aggregation;
+
+import java.util.Collections;
+
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+
+/**
+ * Gateway to {@literal convert} aggregation operations.
+ *
+ * @author Christoph Strobl
+ * @since 2.0.10
+ */
+public class ConvertOperators {
+
+	/**
+	 * Take the field referenced by given {@literal fieldReference}.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return
+	 */
+	public static ConvertOperatorFactory valueOf(String fieldReference) {
+		return new ConvertOperatorFactory(fieldReference);
+	}
+
+	/**
+	 * Take the value resulting from the given {@link AggregationExpression}.
+	 *
+	 * @param expression must not be {@literal null}.
+	 * @return
+	 */
+	public static ConvertOperatorFactory valueOf(AggregationExpression expression) {
+		return new ConvertOperatorFactory(expression);
+	}
+
+	/**
+	 * @author Christoph Strobl
+	 */
+	public static class ConvertOperatorFactory {
+
+		private final @Nullable String fieldReference;
+		private final @Nullable AggregationExpression expression;
+
+		/**
+		 * Creates new {@link ConvertOperatorFactory} for given {@literal fieldReference}.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 */
+		public ConvertOperatorFactory(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+
+			this.fieldReference = fieldReference;
+			this.expression = null;
+		}
+
+		/**
+		 * Creates new {@link ConvertOperatorFactory} for given {@link AggregationExpression}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 */
+		public ConvertOperatorFactory(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+
+			this.fieldReference = null;
+			this.expression = expression;
+		}
+
+		/**
+		 * Creates new {@link Convert aggregation expression} that takes the associated value and converts it into the type
+		 * specified by the given {@code stringTypeIdentifier}. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param stringTypeIdentifier must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert convertTo(String stringTypeIdentifier) {
+			return createConvert().to(stringTypeIdentifier);
+		}
+
+		/**
+		 * Creates new {@link Convert aggregation expression} that takes the associated value and converts it into the type
+		 * specified by the given {@code numericTypeIdentifier}. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param numericTypeIdentifier must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert convertTo(int numericTypeIdentifier) {
+			return createConvert().to(numericTypeIdentifier);
+		}
+
+		/**
+		 * Creates new {@link Convert aggregation expression} that takes the associated value and converts it into the type
+		 * specified by the value of the given {@link Field field reference}. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert convertToTypeOf(String fieldReference) {
+			return createConvert().toTypeOf(fieldReference);
+		}
+
+		/**
+		 * Creates new {@link Convert aggregation expression} that takes the associated value and converts it into the type
+		 * specified by the given {@link AggregationExpression expression}. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert convertToTypeOf(AggregationExpression expression) {
+			return createConvert().toTypeOf(expression);
+		}
+
+		/**
+		 * Creates new {@link ToBool aggregation expression} for {@code $toBool} that converts a value to boolean. Shorthand
+		 * for {@link #convertTo(String) #convertTo("bool")}. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link ToBool}.
+		 */
+		public ToBool convertToBoolean() {
+			return ToBool.toBoolean(valueObject());
+		}
+
+		/**
+		 * Creates new {@link ToDate aggregation expression} for {@code $toDate} that converts a value to a date. Shorthand
+		 * for {@link #convertTo(String) #convertTo("date")}. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link ToDate}.
+		 */
+		public ToDate convertToDate() {
+			return ToDate.toDate(valueObject());
+		}
+
+		/**
+		 * Creates new {@link ToDecimal aggregation expression} for {@code $toDecimal} that converts a value to a decimal.
+		 * Shorthand for {@link #convertTo(String) #convertTo("decimal")}. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link ToDecimal}.
+		 */
+		public ToDecimal convertToDecimal() {
+			return ToDecimal.toDecimal(valueObject());
+		}
+
+		/**
+		 * Creates new {@link ToDouble aggregation expression} for {@code $toDouble} that converts a value to a decimal.
+		 * Shorthand for {@link #convertTo(String) #convertTo("double")}. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link ToDouble}.
+		 */
+		public ToDouble convertToDouble() {
+			return ToDouble.toDouble(valueObject());
+		}
+
+		/**
+		 * Creates new {@link ToInt aggregation expression} for {@code $toInt} that converts a value to an int. Shorthand
+		 * for {@link #convertTo(String) #convertTo("int")}. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link ToInt}.
+		 */
+		public ToInt convertToInt() {
+			return ToInt.toInt(valueObject());
+		}
+
+		/**
+		 * Creates new {@link ToInt aggregation expression} for {@code $toLong} that converts a value to a long. Shorthand
+		 * for {@link #convertTo(String) #convertTo("long")}. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link ToInt}.
+		 */
+		public ToLong convertToLong() {
+			return ToLong.toLong(valueObject());
+		}
+
+		/**
+		 * Creates new {@link ToInt aggregation expression} for {@code $toObjectId} that converts a value to a objectId. Shorthand
+		 * for {@link #convertTo(String) #convertTo("objectId")}. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link ToInt}.
+		 */
+		public ToObjectId convertToObjectId() {
+			return ToObjectId.toObjectId(valueObject());
+		}
+
+		/**
+		 * Creates new {@link ToInt aggregation expression} for {@code $toString} that converts a value to a string. Shorthand
+		 * for {@link #convertTo(String) #convertTo("string")}. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link ToInt}.
+		 */
+		public ToString convertToString() {
+			return ToString.toString(valueObject());
+		}
+
+		private Convert createConvert() {
+			return usesFieldRef() ? Convert.convertValueOf(fieldReference) : Convert.convertValueOf(expression);
+		}
+
+		private Object valueObject() {
+			return usesFieldRef() ? Fields.field(fieldReference) : expression;
+		}
+
+		private boolean usesFieldRef() {
+			return fieldReference != null;
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $convert} that converts a value to a specified type. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/convert/">https://docs.mongodb.com/manual/reference/operator/aggregation/convert/</a>
+	 * @since 2.0.10
+	 */
+	public static class Convert extends AbstractAggregationExpression {
+
+		private Convert(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link Convert} using the given value for the {@literal input} attribute.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public static Convert convertValue(Object value) {
+			return new Convert(Collections.singletonMap("input", value));
+		}
+
+		/**
+		 * Creates new {@link Convert} using the value of the provided {@link Field fieldReference} as {@literal input}
+		 * value.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public static Convert convertValueOf(String fieldReference) {
+			return convertValue(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link Convert} using the result of the provided {@link AggregationExpression expression} as
+		 * {@literal input} value.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public static Convert convertValueOf(AggregationExpression expression) {
+			return convertValue(expression);
+		}
+
+		/**
+		 * Specify the conversion target type via its {@link String} representation.
+		 * <ul>
+		 * <li>double</li>
+		 * <li>string</li>
+		 * <li>objectId</li>
+		 * <li>bool</li>
+		 * <li>date</li>
+		 * <li>int</li>
+		 * <li>long</li>
+		 * <li>decimal</li>
+		 * </ul>
+		 *
+		 * @param stringTypeIdentifier must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert to(String stringTypeIdentifier) {
+			return new Convert(append("to", stringTypeIdentifier));
+		}
+
+		/**
+		 * Specify the conversion target type via its numeric representation.
+		 * <dl>
+		 * <dt>1</dt>
+		 * <dd>double</dd>
+		 * <dt>2</dt>
+		 * <dd>string</li>
+		 * <dt>7</dt>
+		 * <dd>objectId</li>
+		 * <dt>8</dt>
+		 * <dd>bool</dd>
+		 * <dt>9</dt>
+		 * <dd>date</dd>
+		 * <dt>16</dt>
+		 * <dd>int</dd>
+		 * <dt>18</dt>
+		 * <dd>long</dd>
+		 * <dt>19</dt>
+		 * <dd>decimal</dd>
+		 * </dl>
+		 *
+		 * @param numericTypeIdentifier must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert to(int numericTypeIdentifier) {
+			return new Convert(append("to", numericTypeIdentifier));
+		}
+
+		/**
+		 * Specify the conversion target type via the value of the given field.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert toTypeOf(String fieldReference) {
+			return new Convert(append("to", Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Specify the conversion target type via the value of the given {@link AggregationExpression expression}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert toTypeOf(AggregationExpression expression) {
+			return new Convert(append("to", expression));
+		}
+
+		/**
+		 * Optionally specify the value to return on encountering an error during conversion.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert onErrorReturn(Object value) {
+			return new Convert(append("onError", value));
+		}
+
+		/**
+		 * Optionally specify the field holding the value to return on encountering an error during conversion.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert onErrorReturnValueOf(String fieldReference) {
+			return onErrorReturn(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Optionally specify the expression to evaluate and return on encountering an error during conversion.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert onErrorReturnValueOf(AggregationExpression expression) {
+			return onErrorReturn(expression);
+		}
+
+		/**
+		 * Optionally specify the value to return when the input is {@literal null} or missing.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert onNullReturn(Object value) {
+			return new Convert(append("onNull", value));
+		}
+
+		/**
+		 * Optionally specify the field holding the value to return when the input is {@literal null} or missing.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert onNullReturnValueOf(String fieldReference) {
+			return onNullReturn(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Optionally specify the expression to evaluate and return when the input is {@literal null} or missing.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert onNullReturnValueOf(AggregationExpression expression) {
+			return onNullReturn(expression);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$convert";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toBool} that converts a value to {@literal boolean}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("bool")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toBool/">https://docs.mongodb.com/manual/reference/operator/aggregation/toBool/</a>
+	 * @since 2.0.10
+	 */
+	public static class ToBool extends AbstractAggregationExpression {
+
+		private ToBool(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToBool} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToBool}.
+		 */
+		public static ToBool toBoolean(Object value) {
+			return new ToBool(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toBool";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toDate} that converts a value to {@literal date}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("date")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toDate/">https://docs.mongodb.com/manual/reference/operator/aggregation/toDate/</a>
+	 * @since 2.0.10
+	 */
+	public static class ToDate extends AbstractAggregationExpression {
+
+		private ToDate(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToDate} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToDate}.
+		 */
+		public static ToDate toDate(Object value) {
+			return new ToDate(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toDate";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toDecimal} that converts a value to {@literal decimal}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("decimal")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toDecimal/">https://docs.mongodb.com/manual/reference/operator/aggregation/toDecimal/</a>
+	 * @since 2.0.10
+	 */
+	public static class ToDecimal extends AbstractAggregationExpression {
+
+		private ToDecimal(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToDecimal} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToDecimal}.
+		 */
+		public static ToDecimal toDecimal(Object value) {
+			return new ToDecimal(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toDecimal";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toDouble} that converts a value to {@literal double}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("double")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toDouble/">https://docs.mongodb.com/manual/reference/operator/aggregation/toDouble/</a>
+	 * @since 2.0.10
+	 */
+	public static class ToDouble extends AbstractAggregationExpression {
+
+		private ToDouble(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToDouble} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToDouble}.
+		 */
+		public static ToDouble toDouble(Object value) {
+			return new ToDouble(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toDouble";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toInt} that converts a value to {@literal integer}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("int")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toInt/">https://docs.mongodb.com/manual/reference/operator/aggregation/toInt/</a>
+	 * @since 2.0.10
+	 */
+	public static class ToInt extends AbstractAggregationExpression {
+
+		private ToInt(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToInt} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToInt}.
+		 */
+		public static ToInt toInt(Object value) {
+			return new ToInt(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toInt";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toLong} that converts a value to {@literal long}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("long")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toLong/">https://docs.mongodb.com/manual/reference/operator/aggregation/toLong/</a>
+	 * @since 2.0.10
+	 */
+	public static class ToLong extends AbstractAggregationExpression {
+
+		private ToLong(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToLong} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToLong}.
+		 */
+		public static ToLong toLong(Object value) {
+			return new ToLong(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toLong";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toObjectId} that converts a value to {@literal objectId}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("objectId")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toObjectId/">https://docs.mongodb.com/manual/reference/operator/aggregation/toObjectId/</a>
+	 * @since 2.0.10
+	 */
+	public static class ToObjectId extends AbstractAggregationExpression {
+
+		private ToObjectId(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToObjectId} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToObjectId}.
+		 */
+		public static ToObjectId toObjectId(Object value) {
+			return new ToObjectId(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toObjectId";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toString} that converts a value to {@literal string}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("string")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toString/">https://docs.mongodb.com/manual/reference/operator/aggregation/toString/</a>
+	 * @since 2.0.10
+	 */
+	public static class ToString extends AbstractAggregationExpression {
+
+		private ToString(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToString} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToString}.
+		 */
+		public static ToString toString(Object value) {
+			return new ToString(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toString";
+		}
+	}
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,14 +22,14 @@ import java.util.Iterator;
 import java.util.List;
 
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
-import org.springframework.data.mongodb.core.aggregation.Fields.AggregationField;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.CompositeIterator;
 import org.springframework.util.ObjectUtils;
 
 /**
  * Value object to capture the fields exposed by an {@link AggregationOperation}.
- * 
+ *
  * @author Oliver Gierke
  * @author Thomas Darimont
  * @author Mark Paluch
@@ -43,9 +43,19 @@ public final class ExposedFields implements Iterable<ExposedField> {
 	private final List<ExposedField> originalFields;
 	private final List<ExposedField> syntheticFields;
 
+	/**
+	 * Returns an empty {@link ExposedFields} instance.
+	 *
+	 * @return
+	 * @since 2.0
+	 */
+	public static ExposedFields empty() {
+		return EMPTY;
+	}
+
 	/**
 	 * Creates a new {@link ExposedFields} instance from the given {@link ExposedField}s.
-	 * 
+	 *
 	 * @param fields must not be {@literal null}.
 	 * @return
 	 */
@@ -55,7 +65,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 	/**
 	 * Creates a new {@link ExposedFields} instance from the given {@link ExposedField}s.
-	 * 
+	 *
 	 * @param fields must not be {@literal null}.
 	 * @return
 	 */
@@ -72,7 +82,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 	/**
 	 * Creates synthetic {@link ExposedFields} from the given {@link Fields}.
-	 * 
+	 *
 	 * @param fields must not be {@literal null}.
 	 * @return
 	 */
@@ -82,7 +92,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 	/**
 	 * Creates non-synthetic {@link ExposedFields} from the given {@link Fields}.
-	 * 
+	 *
 	 * @param fields must not be {@literal null}.
 	 * @return
 	 */
@@ -92,7 +102,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 	/**
 	 * Creates a new {@link ExposedFields} instance for the given fields in either synthetic or non-synthetic way.
-	 * 
+	 *
 	 * @param fields must not be {@literal null}.
 	 * @param synthetic
 	 * @return
@@ -111,7 +121,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 	/**
 	 * Creates a new {@link ExposedFields} with the given originals and synthetics.
-	 * 
+	 *
 	 * @param originals must not be {@literal null}.
 	 * @param synthetic must not be {@literal null}.
 	 */
@@ -123,7 +133,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 	/**
 	 * Creates a new {@link ExposedFields} adding the given {@link ExposedField}.
-	 * 
+	 *
 	 * @param field must not be {@literal null}.
 	 * @return
 	 */
@@ -140,10 +150,11 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 	/**
 	 * Returns the field with the given name or {@literal null} if no field with the given name is available.
-	 * 
+	 *
 	 * @param name
 	 * @return
 	 */
+	@Nullable
 	public ExposedField getField(String name) {
 
 		for (ExposedField field : this) {
@@ -157,7 +168,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 	/**
 	 * Returns whether the {@link ExposedFields} exposes no non-synthetic fields at all.
-	 * 
+	 *
 	 * @return
 	 */
 	boolean exposesNoNonSyntheticFields() {
@@ -166,7 +177,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 	/**
 	 * Returns whether the {@link ExposedFields} exposes a single non-synthetic field only.
-	 * 
+	 *
 	 * @return
 	 */
 	boolean exposesSingleNonSyntheticFieldOnly() {
@@ -175,7 +186,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 	/**
 	 * Returns whether the {@link ExposedFields} exposes no fields at all.
-	 * 
+	 *
 	 * @return
 	 */
 	boolean exposesNoFields() {
@@ -184,7 +195,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 	/**
 	 * Returns whether the {@link ExposedFields} exposes a single field only.
-	 * 
+	 *
 	 * @return
 	 */
 	boolean exposesSingleFieldOnly() {
@@ -198,7 +209,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 		return originalFields.size() + syntheticFields.size();
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see java.lang.Iterable#iterator()
 	 */
@@ -219,7 +230,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 	/**
 	 * A single exposed field.
-	 * 
+	 *
 	 * @author Oliver Gierke
 	 */
 	static class ExposedField implements Field {
@@ -229,7 +240,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 		/**
 		 * Creates a new {@link ExposedField} with the given key.
-		 * 
+		 *
 		 * @param key must not be {@literal null} or empty.
 		 * @param synthetic whether the exposed field is synthetic.
 		 */
@@ -239,7 +250,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 		/**
 		 * Creates a new {@link ExposedField} for the given {@link Field}.
-		 * 
+		 *
 		 * @param delegate must not be {@literal null}.
 		 * @param synthetic whether the exposed field is synthetic.
 		 */
@@ -249,7 +260,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 			this.synthetic = synthetic;
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.aggregation.Field#getKey()
 		 */
@@ -285,7 +296,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 		/**
 		 * Returns whether the field can be referred to using the given name.
-		 * 
+		 *
 		 * @param name
 		 * @return
 		 */
@@ -302,7 +313,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 			return String.format("AggregationField: %s, synthetic: %s", field, synthetic);
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see java.lang.Object#equals(java.lang.Object)
 		 */
@@ -364,7 +375,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 	/**
 	 * A reference to an {@link ExposedField}.
-	 * 
+	 *
 	 * @author Oliver Gierke
 	 */
 	static class DirectFieldReference implements FieldReference {
@@ -373,7 +384,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 
 		/**
 		 * Creates a new {@link FieldReference} for the given {@link ExposedField}.
-		 * 
+		 *
 		 * @param field must not be {@literal null}.
 		 */
 		public DirectFieldReference(ExposedField field) {
@@ -408,14 +419,14 @@ public final class ExposedFields implements Iterable<ExposedField> {
 		@Override
 		public String toString() {
 
-			if(getRaw().startsWith("$")) {
+			if (getRaw().startsWith("$")) {
 				return getRaw();
 			}
 
 			return String.format("$%s", getRaw());
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see java.lang.Object#equals(java.lang.Object)
 		 */
@@ -435,7 +446,7 @@ public final class ExposedFields implements Iterable<ExposedField> {
 			return this.field.equals(that.field);
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see java.lang.Object#hashCode()
 		 */

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,9 +16,10 @@
 package org.springframework.data.mongodb.core.aggregation;
 
 import org.bson.Document;
-import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.DirectFieldReference;
+import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -53,7 +54,7 @@ class ExposedFieldsAggregationOperationContext implements AggregationOperationCo
 		this.rootContext = rootContext;
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getMappedObject(org.bson.Document)
 	 */
@@ -62,7 +63,7 @@ class ExposedFieldsAggregationOperationContext implements AggregationOperationCo
 		return rootContext.getMappedObject(document);
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getReference(org.springframework.data.mongodb.core.aggregation.ExposedFields.AvailableField)
 	 */
@@ -71,7 +72,7 @@ class ExposedFieldsAggregationOperationContext implements AggregationOperationCo
 		return getReference(field, field.getTarget());
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getReference(java.lang.String)
 	 */
@@ -83,11 +84,11 @@ class ExposedFieldsAggregationOperationContext implements AggregationOperationCo
 	/**
 	 * Returns a {@link FieldReference} to the given {@link Field} with the given {@code name}.
 	 *
-	 * @param field may be {@literal null}
-	 * @param name must not be {@literal null}
+	 * @param field may be {@literal null}.
+	 * @param name must not be {@literal null}.
 	 * @return
 	 */
-	private FieldReference getReference(Field field, String name) {
+	private FieldReference getReference(@Nullable Field field, String name) {
 
 		Assert.notNull(name, "Name must not be null!");
 
@@ -100,13 +101,15 @@ class ExposedFieldsAggregationOperationContext implements AggregationOperationCo
 	}
 
 	/**
-	 * Resolves a {@link field}/{@link name} for a {@link FieldReference} if possible.
+	 * Resolves a {@link Field}/{@code name} for a {@link FieldReference} if possible.
 	 *
-	 * @param field may be {@literal null}
-	 * @param name must not be {@literal null}
-	 * @return the resolved reference or {@literal null}
+	 * @param field may be {@literal null}.
+	 * @param name must not be {@literal null}.
+	 * @return the resolved reference or {@literal null}.
 	 */
-	protected FieldReference resolveExposedField(Field field, String name) {
+	@Nullable
+	protected FieldReference resolveExposedField(@Nullable Field field, String name) {
+
 		ExposedField exposedField = exposedFields.getField(name);
 
 		if (exposedField != null) {

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

@@ -23,13 +23,14 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
 /**
  * Value object to capture a list of {@link Field} instances.
- * 
+ *
  * @author Oliver Gierke
  * @author Thomas Darimont
  * @since 1.3
@@ -46,7 +47,7 @@ public final class Fields implements Iterable<Field> {
 
 	/**
 	 * Creates a new {@link Fields} instance from the given {@link Fields}.
-	 * 
+	 *
 	 * @param fields must not be {@literal null} or empty.
 	 * @return
 	 */
@@ -58,7 +59,7 @@ public final class Fields implements Iterable<Field> {
 
 	/**
 	 * Creates a new {@link Fields} instance for {@link Field}s with the given names.
-	 * 
+	 *
 	 * @param names must not be {@literal null}.
 	 * @return
 	 */
@@ -77,7 +78,7 @@ public final class Fields implements Iterable<Field> {
 
 	/**
 	 * Creates a {@link Field} with the given name.
-	 * 
+	 *
 	 * @param name must not be {@literal null} or empty.
 	 * @return
 	 */
@@ -101,7 +102,7 @@ public final class Fields implements Iterable<Field> {
 
 	/**
 	 * Creates a new {@link Fields} instance using the given {@link Field}s.
-	 * 
+	 *
 	 * @param fields must not be {@literal null}.
 	 */
 	private Fields(List<Field> fields) {
@@ -139,7 +140,7 @@ public final class Fields implements Iterable<Field> {
 
 	/**
 	 * Creates a new {@link Fields} instance with a new {@link Field} of the given name added.
-	 * 
+	 *
 	 * @param name must not be {@literal null}.
 	 * @return
 	 */
@@ -166,6 +167,7 @@ public final class Fields implements Iterable<Field> {
 		return result;
 	}
 
+	@Nullable
 	public Field getField(String name) {
 
 		for (Field field : fields) {
@@ -177,7 +179,7 @@ public final class Fields implements Iterable<Field> {
 		return null;
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see java.lang.Iterable#iterator()
 	 */
@@ -196,7 +198,7 @@ public final class Fields implements Iterable<Field> {
 
 	/**
 	 * Value object to encapsulate a field in an aggregation operation.
-	 * 
+	 *
 	 * @author Oliver Gierke
 	 */
 	static class AggregationField implements Field {
@@ -207,7 +209,7 @@ public final class Fields implements Iterable<Field> {
 
 		/**
 		 * Creates an aggregation field with the given {@code name}.
-		 * 
+		 *
 		 * @see AggregationField#AggregationField(String, String).
 		 * @param name must not be {@literal null} or empty
 		 */
@@ -220,15 +222,15 @@ public final class Fields implements Iterable<Field> {
 		 * <p>
 		 * The {@code name} serves as an alias for the actual backing document field denoted by {@code target}. If no target
 		 * is set explicitly, the name will be used as target.
-		 * 
+		 *
 		 * @param name must not be {@literal null} or empty
 		 * @param target
 		 */
-		public AggregationField(String name, String target) {
+		public AggregationField(String name, @Nullable String target) {
 
 			raw = name;
-			String nameToSet = cleanUp(name);
-			String targetToSet = cleanUp(target);
+			String nameToSet = name != null ? cleanUp(name) : null;
+			String targetToSet = target != null ? cleanUp(target) : null;
 
 			Assert.hasText(nameToSet, "AggregationField name must not be null or empty!");
 
@@ -241,11 +243,7 @@ public final class Fields implements Iterable<Field> {
 			}
 		}
 
-		private static final String cleanUp(String source) {
-
-			if (source == null) {
-				return source;
-			}
+		private static String cleanUp(String source) {
 
 			if (Aggregation.SystemVariable.isReferingToSystemVariable(source)) {
 				return source;
@@ -301,7 +299,7 @@ public final class Fields implements Iterable<Field> {
 			return raw;
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see java.lang.Object#toString()
 		 */
@@ -310,7 +308,7 @@ public final class Fields implements Iterable<Field> {
 			return String.format("AggregationField - name: %s, target: %s", name, target);
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see java.lang.Object#equals(java.lang.Object)
 		 */
@@ -330,7 +328,7 @@ public final class Fields implements Iterable<Field> {
 			return this.name.equals(that.name) && ObjectUtils.nullSafeEquals(this.target, that.target);
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see java.lang.Object#hashCode()
 		 */

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

@@ -34,10 +34,25 @@ public interface FieldsExposingAggregationOperation extends AggregationOperation
 	ExposedFields getFields();
 
 	/**
-	 * Marker interface for {@link AggregationOperation} that inherits fields from previous operations.
+	 * @return {@literal true} to conditionally inherit fields from previous operations.
+	 * @since 2.0.6
 	 */
-	static interface InheritsFieldsAggregationOperation extends FieldsExposingAggregationOperation {
-
+	default boolean inheritsFields() {
+		return false;
 	}
 
+	/**
+	 * Marker interface for {@link AggregationOperation} that inherits fields from previous operations.
+	 */
+	interface InheritsFieldsAggregationOperation extends FieldsExposingAggregationOperation {
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation#inheritsFields()
+		 */
+		@Override
+		default boolean inheritsFields() {
+			return true;
+		}
+	}
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2013-2016 the original author or authors.
+ * Copyright 2013-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,40 +17,71 @@ package org.springframework.data.mongodb.core.aggregation;
 
 import org.bson.Document;
 import org.springframework.data.mongodb.core.query.NearQuery;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
 
 /**
  * Represents a {@code geoNear} aggregation operation.
  * <p>
  * We recommend to use the static factory method {@link Aggregation#geoNear(NearQuery, String)} instead of creating
  * instances of this class directly.
- * 
+ *
  * @author Thomas Darimont
  * @author Christoph Strobl
  * @since 1.3
+ * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/geoNear/">MongoDB Aggregation Framework:
+ *      $geoNear</a>
  */
 public class GeoNearOperation implements AggregationOperation {
 
 	private final NearQuery nearQuery;
 	private final String distanceField;
+	private final @Nullable String indexKey;
 
 	/**
 	 * Creates a new {@link GeoNearOperation} from the given {@link NearQuery} and the given distance field. The
 	 * {@code distanceField} defines output field that contains the calculated distance.
-	 * 
-	 * @param query must not be {@literal null}.
+	 *
+	 * @param nearQuery must not be {@literal null}.
 	 * @param distanceField must not be {@literal null}.
 	 */
 	public GeoNearOperation(NearQuery nearQuery, String distanceField) {
+		this(nearQuery, distanceField, null);
+	}
+
+	/**
+	 * Creates a new {@link GeoNearOperation} from the given {@link NearQuery} and the given distance field. The
+	 * {@code distanceField} defines output field that contains the calculated distance.
+	 *
+	 * @param nearQuery must not be {@literal null}.
+	 * @param distanceField must not be {@literal null}.
+	 * @param indexKey can be {@literal null};
+	 * @since 2.0.10
+	 */
+	private GeoNearOperation(NearQuery nearQuery, String distanceField, @Nullable String indexKey) {
 
 		Assert.notNull(nearQuery, "NearQuery must not be null.");
 		Assert.hasLength(distanceField, "Distance field must not be null or empty.");
 
 		this.nearQuery = nearQuery;
 		this.distanceField = distanceField;
+		this.indexKey = indexKey;
 	}
 
-	/* 
+	/**
+	 * Optionally specify the geospatial index to use via the field to use in the calculation. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @param key the geospatial index field to use when calculating the distance.
+	 * @return new instance of {@link GeoNearOperation}.
+	 * @since 2.0.10
+	 */
+	public GeoNearOperation useIndex(String key) {
+		return new GeoNearOperation(nearQuery, distanceField, key);
+	}
+
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
 	 */
@@ -60,6 +91,10 @@ public class GeoNearOperation implements AggregationOperation {
 		Document command = context.getMappedObject(nearQuery.toDocument());
 		command.put("distanceField", distanceField);
 
+		if (StringUtils.hasText(indexKey)) {
+			command.put("key", indexKey);
+		}
+
 		return new Document("$geoNear", command);
 	}
 }

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

@@ -25,6 +25,7 @@ import org.bson.Document;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
 import org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation.InheritsFieldsAggregationOperation;
 import org.springframework.data.mongodb.core.query.CriteriaDefinition;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 
@@ -51,12 +52,12 @@ public class GraphLookupOperation implements InheritsFieldsAggregationOperation
 	private final Field connectFrom;
 	private final Field connectTo;
 	private final Field as;
-	private final Long maxDepth;
-	private final Field depthField;
-	private final CriteriaDefinition restrictSearchWithMatch;
+	private final @Nullable Long maxDepth;
+	private final @Nullable Field depthField;
+	private final @Nullable CriteriaDefinition restrictSearchWithMatch;
 
 	private GraphLookupOperation(String from, List<Object> startWith, Field connectFrom, Field connectTo, Field as,
-			Long maxDepth, Field depthField, CriteriaDefinition restrictSearchWithMatch) {
+			@Nullable Long maxDepth, @Nullable Field depthField, @Nullable CriteriaDefinition restrictSearchWithMatch) {
 
 		this.from = from;
 		this.startWith = startWith;
@@ -214,9 +215,9 @@ public class GraphLookupOperation implements InheritsFieldsAggregationOperation
 	static final class GraphLookupOperationFromBuilder
 			implements FromBuilder, StartWithBuilder, ConnectFromBuilder, ConnectToBuilder {
 
-		private String from;
-		private List<? extends Object> startWith;
-		private String connectFrom;
+		private @Nullable String from;
+		private @Nullable List<? extends Object> startWith;
+		private @Nullable String connectFrom;
 
 		/* (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.aggregation.GraphLookupOperation.FromBuilder#from(java.lang.String)
@@ -336,9 +337,9 @@ public class GraphLookupOperation implements InheritsFieldsAggregationOperation
 		private final List<Object> startWith;
 		private final Field connectFrom;
 		private final Field connectTo;
-		private Long maxDepth;
-		private Field depthField;
-		private CriteriaDefinition restrictSearchWithMatch;
+		private @Nullable Long maxDepth;
+		private @Nullable Field depthField;
+		private @Nullable CriteriaDefinition restrictSearchWithMatch;
 
 		protected GraphLookupOperationBuilder(String from, List<? extends Object> startWith, String connectFrom,
 				String connectTo) {

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

@@ -19,25 +19,26 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
-import java.util.Locale;
 
 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.lang.Nullable;
 import org.springframework.util.Assert;
-import org.springframework.util.StringUtils;
 
 /**
  * Encapsulates the aggregation framework {@code $group}-operation.
  * <p>
  * We recommend to use the static factory method {@link Aggregation#group(Fields)} instead of creating instances of this
  * class directly.
- * 
+ *
  * @author Sebastian Herold
  * @author Thomas Darimont
  * @author Oliver Gierke
  * @author Gustavo de Geus
  * @author Christoph Strobl
+ * @author Mark Paluch
+ * @author Sergey Shcherbakov
  * @since 1.3
  * @see <a href="https://docs.mongodb.org/manual/reference/aggregation/group/">MongoDB Aggregation Framework: $group</a>
  */
@@ -52,7 +53,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Creates a new {@link GroupOperation} including the given {@link Fields}.
-	 * 
+	 *
 	 * @param fields must not be {@literal null}.
 	 */
 	public GroupOperation(Fields fields) {
@@ -63,7 +64,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Creates a new {@link GroupOperation} from the given {@link GroupOperation}.
-	 * 
+	 *
 	 * @param groupOperation must not be {@literal null}.
 	 */
 	protected GroupOperation(GroupOperation groupOperation) {
@@ -72,7 +73,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Creates a new {@link GroupOperation} from the given {@link GroupOperation} and the given {@link Operation}s.
-	 * 
+	 *
 	 * @param groupOperation
 	 * @param nextOperations
 	 */
@@ -89,7 +90,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Creates a new {@link GroupOperation} from the current one adding the given {@link Operation}.
-	 * 
+	 *
 	 * @param operation must not be {@literal null}.
 	 * @return
 	 */
@@ -99,7 +100,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Builder for {@link GroupOperation}s on a field.
-	 * 
+	 *
 	 * @author Thomas Darimont
 	 */
 	public static final class GroupOperationBuilder {
@@ -109,7 +110,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Creates a new {@link GroupOperationBuilder} from the given {@link GroupOperation} and {@link Operation}.
-		 * 
+		 *
 		 * @param groupOperation
 		 * @param operation
 		 */
@@ -124,7 +125,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Allows to specify an alias for the new-operation operation.
-		 * 
+		 *
 		 * @param alias
 		 * @return
 		 */
@@ -138,7 +139,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	 * <p>
 	 * Count expressions are emulated via {@code $sum: 1}.
 	 * <p>
-	 * 
+	 *
 	 * @return
 	 */
 	public GroupOperationBuilder count() {
@@ -147,7 +148,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Generates an {@link GroupOperationBuilder} for a {@code $sum}-expression for the given field-reference.
-	 * 
+	 *
 	 * @param reference
 	 * @return
 	 */
@@ -155,13 +156,28 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 		return sum(reference, null);
 	}
 
-	private GroupOperationBuilder sum(String reference, Object value) {
+	/**
+	 * Generates an {@link GroupOperationBuilder} for an {@code $sum}-expression for the given
+	 * {@link AggregationExpression}.
+	 *
+	 * @param expr must not be {@literal null}.
+	 * @return new instance of {@link GroupOperationBuilder}. Never {@literal null}.
+	 * @throws IllegalArgumentException when {@code expr} is {@literal null}.
+	 * @since 1.10.8
+	 */
+	public GroupOperationBuilder sum(AggregationExpression expr) {
+
+		Assert.notNull(expr, "Expr must not be null!");
+		return newBuilder(GroupOps.SUM, null, expr);
+	}
+
+	private GroupOperationBuilder sum(@Nullable String reference, @Nullable Object value) {
 		return newBuilder(GroupOps.SUM, reference, value);
 	}
 
 	/**
 	 * Generates an {@link GroupOperationBuilder} for an {@code $add_to_set}-expression for the given field-reference.
-	 * 
+	 *
 	 * @param reference
 	 * @return
 	 */
@@ -171,7 +187,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Generates an {@link GroupOperationBuilder} for an {@code $add_to_set}-expression for the given value.
-	 * 
+	 *
 	 * @param value
 	 * @return
 	 */
@@ -179,13 +195,13 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 		return addToSet(null, value);
 	}
 
-	private GroupOperationBuilder addToSet(String reference, Object value) {
+	private GroupOperationBuilder addToSet(@Nullable String reference, @Nullable Object value) {
 		return newBuilder(GroupOps.ADD_TO_SET, reference, value);
 	}
 
 	/**
 	 * Generates an {@link GroupOperationBuilder} for an {@code $last}-expression for the given field-reference.
-	 * 
+	 *
 	 * @param reference
 	 * @return
 	 */
@@ -196,7 +212,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	/**
 	 * Generates an {@link GroupOperationBuilder} for an {@code $last}-expression for the given
 	 * {@link AggregationExpression}.
-	 * 
+	 *
 	 * @param expr
 	 * @return
 	 */
@@ -206,7 +222,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Generates an {@link GroupOperationBuilder} for a {@code $first}-expression for the given field-reference.
-	 * 
+	 *
 	 * @param reference
 	 * @return
 	 */
@@ -217,7 +233,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	/**
 	 * Generates an {@link GroupOperationBuilder} for a {@code $first}-expression for the given
 	 * {@link AggregationExpression}.
-	 * 
+	 *
 	 * @param expr
 	 * @return
 	 */
@@ -227,7 +243,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Generates an {@link GroupOperationBuilder} for an {@code $avg}-expression for the given field-reference.
-	 * 
+	 *
 	 * @param reference
 	 * @return
 	 */
@@ -238,7 +254,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	/**
 	 * Generates an {@link GroupOperationBuilder} for an {@code $avg}-expression for the given
 	 * {@link AggregationExpression}.
-	 * 
+	 *
 	 * @param expr
 	 * @return
 	 */
@@ -248,7 +264,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Generates an {@link GroupOperationBuilder} for an {@code $push}-expression for the given field-reference.
-	 * 
+	 *
 	 * @param reference
 	 * @return
 	 */
@@ -258,7 +274,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Generates an {@link GroupOperationBuilder} for an {@code $push}-expression for the given value.
-	 * 
+	 *
 	 * @param value
 	 * @return
 	 */
@@ -266,13 +282,13 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 		return push(null, value);
 	}
 
-	private GroupOperationBuilder push(String reference, Object value) {
+	private GroupOperationBuilder push(@Nullable String reference, @Nullable Object value) {
 		return newBuilder(GroupOps.PUSH, reference, value);
 	}
 
 	/**
 	 * Generates an {@link GroupOperationBuilder} for an {@code $min}-expression that for the given field-reference.
-	 * 
+	 *
 	 * @param reference
 	 * @return
 	 */
@@ -283,7 +299,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	/**
 	 * Generates an {@link GroupOperationBuilder} for an {@code $min}-expression that for the given
 	 * {@link AggregationExpression}.
-	 * 
+	 *
 	 * @param expr
 	 * @return
 	 */
@@ -293,7 +309,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Generates an {@link GroupOperationBuilder} for an {@code $max}-expression that for the given field-reference.
-	 * 
+	 *
 	 * @param reference
 	 * @return
 	 */
@@ -304,7 +320,7 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	/**
 	 * Generates an {@link GroupOperationBuilder} for an {@code $max}-expression that for the given
 	 * {@link AggregationExpression}.
-	 * 
+	 *
 	 * @param expr
 	 * @return
 	 */
@@ -325,7 +341,8 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	}
 
 	/**
-	 * Generates an {@link GroupOperationBuilder} for an {@code $stdDevSamp}-expression that for the given {@link AggregationExpression}.
+	 * Generates an {@link GroupOperationBuilder} for an {@code $stdDevSamp}-expression that for the given
+	 * {@link AggregationExpression}.
 	 *
 	 * @param expr must not be {@literal null}.
 	 * @return never {@literal null}.
@@ -347,7 +364,8 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	}
 
 	/**
-	 * Generates an {@link GroupOperationBuilder} for an {@code $stdDevPop}-expression that for the given {@link AggregationExpression}.
+	 * Generates an {@link GroupOperationBuilder} for an {@code $stdDevPop}-expression that for the given
+	 * {@link AggregationExpression}.
 	 *
 	 * @param expr must not be {@literal null}.
 	 * @return never {@literal null}.
@@ -357,11 +375,11 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 		return newBuilder(GroupOps.STD_DEV_POP, null, expr);
 	}
 
-	private GroupOperationBuilder newBuilder(Keyword keyword, String reference, Object value) {
+	private GroupOperationBuilder newBuilder(Keyword keyword, @Nullable String reference, @Nullable Object value) {
 		return new GroupOperationBuilder(this, new Operation(keyword, null, reference, value));
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getFields()
 	 */
@@ -421,7 +439,8 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 
 	private static enum GroupOps implements Keyword {
 
-		SUM("$sum"), LAST("$last"), FIRST("$first"), PUSH("$push"), AVG("$avg"), MIN("$min"), MAX("$max"), ADD_TO_SET("$addToSet"), STD_DEV_POP("$stdDevPop"), STD_DEV_SAMP("$stdDevSamp");
+		SUM("$sum"), LAST("$last"), FIRST("$first"), PUSH("$push"), AVG("$avg"), MIN("$min"), MAX("$max"), ADD_TO_SET(
+				"$addToSet"), STD_DEV_POP("$stdDevPop"), STD_DEV_SAMP("$stdDevSamp");
 
 		private String mongoOperator;
 
@@ -429,7 +448,6 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 			this.mongoOperator = mongoOperator;
 		}
 
-
 		@Override
 		public String toString() {
 			return mongoOperator;
@@ -439,11 +457,11 @@ public class GroupOperation implements FieldsExposingAggregationOperation {
 	static class Operation implements AggregationOperation {
 
 		private final Keyword op;
-		private final String key;
-		private final String reference;
-		private final Object value;
+		private final @Nullable String key;
+		private final @Nullable String reference;
+		private final @Nullable Object value;
 
-		public Operation(Keyword op, String key, String reference, Object value) {
+		public Operation(Keyword op, @Nullable String key, @Nullable String reference, @Nullable Object value) {
 
 			this.op = op;
 			this.key = key;

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

@@ -18,6 +18,7 @@ package org.springframework.data.mongodb.core.aggregation;
 import org.bson.Document;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
 import org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation.InheritsFieldsAggregationOperation;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -28,14 +29,15 @@ import org.springframework.util.Assert;
  * @author Christoph Strobl
  * @author Mark Paluch
  * @since 1.9
- * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/">MongoDB Aggregation Framework: $lookup</a>
+ * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/">MongoDB Aggregation Framework:
+ *      $lookup</a>
  */
 public class LookupOperation implements FieldsExposingAggregationOperation, InheritsFieldsAggregationOperation {
 
-	private Field from;
-	private Field localField;
-	private Field foreignField;
-	private ExposedField as;
+	private final Field from;
+	private final Field localField;
+	private final Field foreignField;
+	private final ExposedField as;
 
 	/**
 	 * Creates a new {@link LookupOperation} for the given {@link Field}s.
@@ -58,10 +60,6 @@ public class LookupOperation implements FieldsExposingAggregationOperation, Inhe
 		this.as = new ExposedField(as, true);
 	}
 
-	private LookupOperation() {
-		// used by builder
-	}
-
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation#getFields()
@@ -143,11 +141,10 @@ public class LookupOperation implements FieldsExposingAggregationOperation, Inhe
 	public static final class LookupOperationBuilder
 			implements FromBuilder, LocalFieldBuilder, ForeignFieldBuilder, AsBuilder {
 
-		private final LookupOperation lookupOperation;
-
-		private LookupOperationBuilder() {
-			this.lookupOperation = new LookupOperation();
-		}
+		private @Nullable Field from;
+		private @Nullable Field localField;
+		private @Nullable Field foreignField;
+		private @Nullable ExposedField as;
 
 		/**
 		 * Creates new builder for {@link LookupOperation}.
@@ -162,7 +159,7 @@ public class LookupOperation implements FieldsExposingAggregationOperation, Inhe
 		public LocalFieldBuilder from(String name) {
 
 			Assert.hasText(name, "'From' must not be null or empty!");
-			lookupOperation.from = Fields.field(name);
+			from = Fields.field(name);
 			return this;
 		}
 
@@ -170,16 +167,16 @@ public class LookupOperation implements FieldsExposingAggregationOperation, Inhe
 		public LookupOperation as(String name) {
 
 			Assert.hasText(name, "'As' must not be null or empty!");
-			lookupOperation.as = new ExposedField(Fields.field(name), true);
-			return new LookupOperation(lookupOperation.from, lookupOperation.localField, lookupOperation.foreignField,
-					lookupOperation.as);
+			as = new ExposedField(Fields.field(name), true);
+			return new LookupOperation(from, localField, foreignField,
+					as);
 		}
 
 		@Override
 		public AsBuilder foreignField(String name) {
 
 			Assert.hasText(name, "'ForeignField' must not be null or empty!");
-			lookupOperation.foreignField = Fields.field(name);
+			foreignField = Fields.field(name);
 			return this;
 		}
 
@@ -187,7 +184,7 @@ public class LookupOperation implements FieldsExposingAggregationOperation, Inhe
 		public ForeignFieldBuilder localField(String name) {
 
 			Assert.hasText(name, "'LocalField' must not be null or empty!");
-			lookupOperation.localField = Fields.field(name);
+			localField = Fields.field(name);
 			return this;
 		}
 	}

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

@@ -22,13 +22,13 @@ import java.util.Collections;
 import java.util.List;
 
 import org.bson.Document;
-import org.springframework.data.mongodb.core.aggregation.VariableOperators.Let.ExpressionVariable;
 import org.springframework.data.mongodb.core.aggregation.ConditionalOperators.Cond;
 import org.springframework.data.mongodb.core.aggregation.ConditionalOperators.IfNull;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
 import org.springframework.data.mongodb.core.aggregation.Fields.AggregationField;
 import org.springframework.data.mongodb.core.aggregation.ProjectionOperation.ProjectionOperationBuilder.FieldProjection;
 import org.springframework.data.mongodb.core.aggregation.VariableOperators.Let.ExpressionVariable;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -39,14 +39,15 @@ import org.springframework.util.Assert;
  * <p>
  * We recommend to use the static factory method {@link Aggregation#project(Fields)} instead of creating instances of
  * this class directly.
- * 
+ *
  * @author Tobias Trelle
  * @author Thomas Darimont
  * @author Oliver Gierke
  * @author Christoph Strobl
  * @author Mark Paluch
  * @since 1.3
- * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/project/">MongoDB Aggregation Framework: $project</a>
+ * @see <a href="https://docs.mongodb.com/manual/reference/operator/aggregation/project/">MongoDB Aggregation Framework:
+ *      $project</a>
  */
 public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
@@ -65,7 +66,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Creates a new {@link ProjectionOperation} including the given {@link Fields}.
-	 * 
+	 *
 	 * @param fields must not be {@literal null}.
 	 */
 	public ProjectionOperation(Fields fields) {
@@ -75,7 +76,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 	/**
 	 * Copy constructor to allow building up {@link ProjectionOperation} instances from already existing
 	 * {@link Projection}s.
-	 * 
+	 *
 	 * @param current must not be {@literal null}.
 	 * @param projections must not be {@literal null}.
 	 */
@@ -91,18 +92,18 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Creates a new {@link ProjectionOperation} with the current {@link Projection}s and the given one.
-	 * 
+	 *
 	 * @param projection must not be {@literal null}.
 	 * @return
 	 */
 	private ProjectionOperation and(Projection projection) {
-		return new ProjectionOperation(this.projections, Arrays.asList(projection));
+		return new ProjectionOperation(this.projections, Collections.singletonList(projection));
 	}
 
 	/**
 	 * Creates a new {@link ProjectionOperation} with the current {@link Projection}s replacing the last current one with
 	 * the given one.
-	 * 
+	 *
 	 * @param projection must not be {@literal null}.
 	 * @return
 	 */
@@ -110,12 +111,12 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		List<Projection> projections = this.projections.isEmpty() ? Collections.<Projection> emptyList()
 				: this.projections.subList(0, this.projections.size() - 1);
-		return new ProjectionOperation(projections, Arrays.asList(projection));
+		return new ProjectionOperation(projections, Collections.singletonList(projection));
 	}
 
 	/**
 	 * Creates a new {@link ProjectionOperationBuilder} to define a projection for the field with the given name.
-	 * 
+	 *
 	 * @param name must not be {@literal null} or empty.
 	 * @return
 	 */
@@ -133,24 +134,19 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Excludes the given fields from the projection.
-	 * 
+	 *
 	 * @param fieldNames must not be {@literal null}.
 	 * @return
 	 */
 	public ProjectionOperation andExclude(String... fieldNames) {
 
-		for (String fieldName : fieldNames) {
-			Assert.isTrue(Fields.UNDERSCORE_ID.equals(fieldName),
-					String.format(EXCLUSION_ERROR, fieldName, Fields.UNDERSCORE_ID));
-		}
-
 		List<FieldProjection> excludeProjections = FieldProjection.from(Fields.fields(fieldNames), false);
 		return new ProjectionOperation(this.projections, excludeProjections);
 	}
 
 	/**
 	 * Includes the given fields into the projection.
-	 * 
+	 *
 	 * @param fieldNames must not be {@literal null}.
 	 * @return
 	 */
@@ -162,7 +158,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Includes the given fields into the projection.
-	 * 
+	 *
 	 * @param fields must not be {@literal null}.
 	 * @return
 	 */
@@ -184,7 +180,19 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			fields = fields == null ? ExposedFields.from(field) : fields.and(field);
 		}
 
-		return fields;
+		return fields != null ? fields : ExposedFields.empty();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation#inheritsFields()
+	 */
+	@Override
+	public boolean inheritsFields() {
+
+		return projections.stream().filter(FieldProjection.class::isInstance) //
+				.map(FieldProjection.class::cast) //
+				.anyMatch(FieldProjection::isExcluded);
 	}
 
 	/*
@@ -205,7 +213,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Base class for {@link ProjectionOperationBuilder}s.
-	 * 
+	 *
 	 * @author Thomas Darimont
 	 */
 	private static abstract class AbstractProjectionOperationBuilder implements AggregationOperation {
@@ -215,7 +223,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Creates a new {@link AbstractProjectionOperationBuilder} fot the given value and {@link ProjectionOperation}.
-		 * 
+		 *
 		 * @param value must not be {@literal null}.
 		 * @param operation must not be {@literal null}.
 		 */
@@ -228,7 +236,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			this.operation = operation;
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
 		 */
@@ -239,7 +247,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Returns the finally to be applied {@link ProjectionOperation} with the given alias.
-		 * 
+		 *
 		 * @param alias will never be {@literal null} or empty.
 		 * @return
 		 */
@@ -266,7 +274,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * An {@link ProjectionOperationBuilder} that is used for SpEL expression based projections.
-	 * 
+	 *
 	 * @author Thomas Darimont
 	 */
 	public static class ExpressionProjectionOperationBuilder extends ProjectionOperationBuilder {
@@ -277,7 +285,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		/**
 		 * Creates a new {@link ExpressionProjectionOperationBuilder} for the given value, {@link ProjectionOperation} and
 		 * parameters.
-		 * 
+		 *
 		 * @param expression must not be {@literal null}.
 		 * @param operation must not be {@literal null}.
 		 * @param parameters
@@ -325,7 +333,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * A {@link Projection} based on a SpEL expression.
-		 * 
+		 *
 		 * @author Thomas Darimont
 		 * @author Oliver Gierke
 		 */
@@ -338,7 +346,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 			/**
 			 * Creates a new {@link ExpressionProjection} for the given field, SpEL expression and parameters.
-			 * 
+			 *
 			 * @param field must not be {@literal null}.
 			 * @param expression must not be {@literal null} or empty.
 			 * @param parameters must not be {@literal null}.
@@ -354,7 +362,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 				this.params = parameters.clone();
 			}
 
-			/* 
+			/*
 			 * (non-Javadoc)
 			 * @see org.springframework.data.mongodb.core.aggregation.ProjectionOperation.Projection#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
 			 */
@@ -372,7 +380,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Builder for {@link ProjectionOperation}s on a field.
-	 * 
+	 *
 	 * @author Oliver Gierke
 	 * @author Thomas Darimont
 	 * @author Christoph Strobl
@@ -382,19 +390,19 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		private static final String NUMBER_NOT_NULL = "Number must not be null!";
 		private static final String FIELD_REFERENCE_NOT_NULL = "Field reference must not be null!";
 
-		private final String name;
-		private final OperationProjection previousProjection;
+		private final @Nullable String name;
+		private final @Nullable OperationProjection previousProjection;
 
 		/**
 		 * Creates a new {@link ProjectionOperationBuilder} for the field with the given name on top of the given
 		 * {@link ProjectionOperation}.
-		 * 
+		 *
 		 * @param name must not be {@literal null} or empty.
 		 * @param operation must not be {@literal null}.
 		 * @param previousProjection the previous operation projection, may be {@literal null}.
 		 */
 		public ProjectionOperationBuilder(String name, ProjectionOperation operation,
-				OperationProjection previousProjection) {
+				@Nullable OperationProjection previousProjection) {
 			super(name, operation);
 
 			this.name = name;
@@ -404,13 +412,13 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		/**
 		 * Creates a new {@link ProjectionOperationBuilder} for the field with the given value on top of the given
 		 * {@link ProjectionOperation}.
-		 * 
+		 *
 		 * @param value
 		 * @param operation
 		 * @param previousProjection
 		 */
 		protected ProjectionOperationBuilder(Object value, ProjectionOperation operation,
-				OperationProjection previousProjection) {
+				@Nullable OperationProjection previousProjection) {
 
 			super(value, operation);
 
@@ -421,28 +429,28 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		/**
 		 * Projects the result of the previous operation onto the current field. Will automatically add an exclusion for
 		 * {@code _id} as what would be held in it by default will now go into the field just projected into.
-		 * 
+		 *
 		 * @return
 		 */
 		public ProjectionOperation previousOperation() {
 
 			return this.operation.andExclude(Fields.UNDERSCORE_ID) //
-					.and(new PreviousOperationProjection(name));
+					.and(new PreviousOperationProjection(getRequiredName()));
 		}
 
 		/**
 		 * Defines a nested field binding for the current field.
-		 * 
+		 *
 		 * @param fields must not be {@literal null}.
 		 * @return
 		 */
 		public ProjectionOperation nested(Fields fields) {
-			return this.operation.and(new NestedFieldProjection(name, fields));
+			return this.operation.and(new NestedFieldProjection(getRequiredName(), fields));
 		}
 
 		/**
 		 * Allows to specify an alias for the previous projection operation.
-		 * 
+		 *
 		 * @param alias
 		 * @return
 		 */
@@ -454,10 +462,10 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			}
 
 			if (value instanceof AggregationExpression) {
-				return this.operation.and(new ExpressionProjection(Fields.field(alias), (AggregationExpression) value));
+				return this.operation.and(new ExpressionProjection(Fields.field(alias, alias), (AggregationExpression) value));
 			}
 
-			return this.operation.and(new FieldProjection(Fields.field(alias, name), null));
+			return this.operation.and(new FieldProjection(Fields.field(alias, getRequiredName()), null));
 		}
 
 		/*
@@ -468,7 +476,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		public ProjectionOperation applyCondition(Cond cond) {
 
 			Assert.notNull(cond, "ConditionalOperator must not be null!");
-			return this.operation.and(new ExpressionProjection(Fields.field(name), cond));
+			return this.operation.and(new ExpressionProjection(Fields.field(getRequiredName()), cond));
 		}
 
 		/*
@@ -479,12 +487,12 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		public ProjectionOperation applyCondition(IfNull ifNull) {
 
 			Assert.notNull(ifNull, "IfNullOperator must not be null!");
-			return this.operation.and(new ExpressionProjection(Fields.field(name), ifNull));
+			return this.operation.and(new ExpressionProjection(Fields.field(getRequiredName()), ifNull));
 		}
 
 		/**
 		 * Generates an {@code $add} expression that adds the given number to the previously mentioned field.
-		 * 
+		 *
 		 * @param number
 		 * @return
 		 */
@@ -496,7 +504,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Generates an {@code $add} expression that adds the value of the given field to the previously mentioned field.
-		 * 
+		 *
 		 * @param fieldReference
 		 * @return
 		 */
@@ -508,7 +516,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Generates an {@code $subtract} expression that subtracts the given number to the previously mentioned field.
-		 * 
+		 *
 		 * @param number
 		 * @return
 		 */
@@ -521,7 +529,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		/**
 		 * Generates an {@code $subtract} expression that subtracts the value of the given field to the previously mentioned
 		 * field.
-		 * 
+		 *
 		 * @param fieldReference
 		 * @return
 		 */
@@ -547,7 +555,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Generates an {@code $multiply} expression that multiplies the given number with the previously mentioned field.
-		 * 
+		 *
 		 * @param number
 		 * @return
 		 */
@@ -560,7 +568,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		/**
 		 * Generates an {@code $multiply} expression that multiplies the value of the given field with the previously
 		 * mentioned field.
-		 * 
+		 *
 		 * @param fieldReference
 		 * @return
 		 */
@@ -586,7 +594,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Generates an {@code $divide} expression that divides the previously mentioned field by the given number.
-		 * 
+		 *
 		 * @param number
 		 * @return
 		 */
@@ -600,7 +608,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		/**
 		 * Generates an {@code $divide} expression that divides the value of the given field by the previously mentioned
 		 * field.
-		 * 
+		 *
 		 * @param fieldReference
 		 * @return
 		 */
@@ -627,7 +635,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		/**
 		 * Generates an {@code $mod} expression that divides the previously mentioned field by the given number and returns
 		 * the remainder.
-		 * 
+		 *
 		 * @param number
 		 * @return
 		 */
@@ -789,7 +797,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder filter(String as, AggregationExpression condition) {
-			return this.operation.and(ArrayOperators.Filter.filter(name).as(as).by(condition));
+			return this.operation.and(ArrayOperators.Filter.filter(getRequiredName()).as(as).by(condition));
 		}
 
 		// SET OPERATORS
@@ -894,7 +902,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder absoluteValue() {
-			return this.operation.and(ArithmeticOperators.Abs.absoluteValueOf(name));
+			return this.operation.and(ArithmeticOperators.Abs.absoluteValueOf(getRequiredName()));
 		}
 
 		/**
@@ -905,7 +913,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder ceil() {
-			return this.operation.and(ArithmeticOperators.Ceil.ceilValueOf(name));
+			return this.operation.and(ArithmeticOperators.Ceil.ceilValueOf(getRequiredName()));
 		}
 
 		/**
@@ -916,7 +924,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder exp() {
-			return this.operation.and(ArithmeticOperators.Exp.expValueOf(name));
+			return this.operation.and(ArithmeticOperators.Exp.expValueOf(getRequiredName()));
 		}
 
 		/**
@@ -927,7 +935,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder floor() {
-			return this.operation.and(ArithmeticOperators.Floor.floorValueOf(name));
+			return this.operation.and(ArithmeticOperators.Floor.floorValueOf(getRequiredName()));
 		}
 
 		/**
@@ -938,7 +946,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder ln() {
-			return this.operation.and(ArithmeticOperators.Ln.lnValueOf(name));
+			return this.operation.and(ArithmeticOperators.Ln.lnValueOf(getRequiredName()));
 		}
 
 		/**
@@ -950,7 +958,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder log(String baseFieldRef) {
-			return this.operation.and(ArithmeticOperators.Log.valueOf(name).log(baseFieldRef));
+			return this.operation.and(ArithmeticOperators.Log.valueOf(getRequiredName()).log(baseFieldRef));
 		}
 
 		/**
@@ -962,7 +970,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder log(Number base) {
-			return this.operation.and(ArithmeticOperators.Log.valueOf(name).log(base));
+			return this.operation.and(ArithmeticOperators.Log.valueOf(getRequiredName()).log(base));
 		}
 
 		/**
@@ -974,7 +982,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder log(AggregationExpression base) {
-			return this.operation.and(ArithmeticOperators.Log.valueOf(name).log(base));
+			return this.operation.and(ArithmeticOperators.Log.valueOf(getRequiredName()).log(base));
 		}
 
 		/**
@@ -985,7 +993,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder log10() {
-			return this.operation.and(ArithmeticOperators.Log10.log10ValueOf(name));
+			return this.operation.and(ArithmeticOperators.Log10.log10ValueOf(getRequiredName()));
 		}
 
 		/**
@@ -997,7 +1005,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder pow(String exponentFieldRef) {
-			return this.operation.and(ArithmeticOperators.Pow.valueOf(name).pow(exponentFieldRef));
+			return this.operation.and(ArithmeticOperators.Pow.valueOf(getRequiredName()).pow(exponentFieldRef));
 		}
 
 		/**
@@ -1009,7 +1017,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder pow(Number exponent) {
-			return this.operation.and(ArithmeticOperators.Pow.valueOf(name).pow(exponent));
+			return this.operation.and(ArithmeticOperators.Pow.valueOf(getRequiredName()).pow(exponent));
 		}
 
 		/**
@@ -1021,7 +1029,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder pow(AggregationExpression exponentExpression) {
-			return this.operation.and(ArithmeticOperators.Pow.valueOf(name).pow(exponentExpression));
+			return this.operation.and(ArithmeticOperators.Pow.valueOf(getRequiredName()).pow(exponentExpression));
 		}
 
 		/**
@@ -1032,7 +1040,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder sqrt() {
-			return this.operation.and(ArithmeticOperators.Sqrt.sqrtOf(name));
+			return this.operation.and(ArithmeticOperators.Sqrt.sqrtOf(getRequiredName()));
 		}
 
 		/**
@@ -1042,7 +1050,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder trunc() {
-			return this.operation.and(ArithmeticOperators.Trunc.truncValueOf(name));
+			return this.operation.and(ArithmeticOperators.Trunc.truncValueOf(getRequiredName()));
 		}
 
 		/**
@@ -1089,7 +1097,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder toLower() {
-			return this.operation.and(StringOperators.ToLower.lowerValueOf(name));
+			return this.operation.and(StringOperators.ToLower.lowerValueOf(getRequiredName()));
 		}
 
 		/**
@@ -1100,7 +1108,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder toUpper() {
-			return this.operation.and(StringOperators.ToUpper.upperValueOf(name));
+			return this.operation.and(StringOperators.ToUpper.upperValueOf(getRequiredName()));
 		}
 
 		/**
@@ -1171,7 +1179,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder isArray() {
-			return this.operation.and(ArrayOperators.IsArray.isArray(name));
+			return this.operation.and(ArrayOperators.IsArray.isArray(getRequiredName()));
 		}
 
 		/**
@@ -1181,7 +1189,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder asLiteral() {
-			return this.operation.and(LiteralOperators.Literal.asLiteral(name));
+			return this.operation.and(LiteralOperators.Literal.asLiteral(getRequiredName()));
 		}
 
 		/**
@@ -1193,7 +1201,19 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		 * @since 1.10
 		 */
 		public ProjectionOperationBuilder dateAsFormattedString(String format) {
-			return this.operation.and(DateOperators.DateToString.dateOf(name).toString(format));
+			return this.operation.and(DateOperators.DateToString.dateOf(getRequiredName()).toString(format));
+		}
+
+		/**
+		 * Generates a {@code $dateToString} expression that takes the date representation of the previously mentioned field
+		 * using the server default format. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return
+		 * @since 2.0.10
+		 */
+		public ProjectionOperationBuilder dateAsFormattedString() {
+			return this.operation.and(DateOperators.DateToString.dateOf(getRequiredName()).defaultFormat());
 		}
 
 		/**
@@ -1225,6 +1245,13 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			return this.operation.and(VariableOperators.Let.define(variables).andApply(in));
 		}
 
+		private String getRequiredName() {
+
+			Assert.state(name != null, "Projection field name must not be null!");
+
+			return name;
+		}
+
 		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
@@ -1236,7 +1263,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Adds a generic projection for the current field.
-		 * 
+		 *
 		 * @param operation the operation key, e.g. {@code $add}.
 		 * @param values the values to be set for the projection operation.
 		 * @return
@@ -1249,7 +1276,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * A {@link Projection} to pull in the result of the previous operation.
-		 * 
+		 *
 		 * @author Oliver Gierke
 		 */
 		static class PreviousOperationProjection extends Projection {
@@ -1258,7 +1285,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 			/**
 			 * Creates a new {@link PreviousOperationProjection} for the field with the given name.
-			 * 
+			 *
 			 * @param name must not be {@literal null} or empty.
 			 */
 			public PreviousOperationProjection(String name) {
@@ -1266,7 +1293,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 				this.name = name;
 			}
 
-			/* 
+			/*
 			 * (non-Javadoc)
 			 * @see org.springframework.data.mongodb.core.aggregation.ProjectionOperation.Projection#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
 			 */
@@ -1278,7 +1305,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * A {@link FieldProjection} to map a result of a previous {@link AggregationOperation} to a new field.
-		 * 
+		 *
 		 * @author Oliver Gierke
 		 * @author Thomas Darimont
 		 * @author Mark Paluch
@@ -1286,11 +1313,11 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		static class FieldProjection extends Projection {
 
 			private final Field field;
-			private final Object value;
+			private final @Nullable Object value;
 
 			/**
 			 * Creates a new {@link FieldProjection} for the field of the given name, assigning the given value.
-			 * 
+			 *
 			 * @param name must not be {@literal null} or empty.
 			 * @param value
 			 */
@@ -1298,7 +1325,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 				this(Fields.field(name), value);
 			}
 
-			private FieldProjection(Field field, Object value) {
+			private FieldProjection(Field field, @Nullable Object value) {
 
 				super(new ExposedField(field.getName(), true));
 
@@ -1309,7 +1336,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			/**
 			 * Factory method to easily create {@link FieldProjection}s for the given {@link Fields}. Fields are projected as
 			 * references with their given name. A field {@code foo} will be projected as: {@code foo : 1 } .
-			 * 
+			 *
 			 * @param fields the {@link Fields} to in- or exclude, must not be {@literal null}.
 			 * @return
 			 */
@@ -1319,12 +1346,12 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 			/**
 			 * Factory method to easily create {@link FieldProjection}s for the given {@link Fields}.
-			 * 
+			 *
 			 * @param fields the {@link Fields} to in- or exclude, must not be {@literal null}.
 			 * @param value to use for the given field.
 			 * @return
 			 */
-			public static List<FieldProjection> from(Fields fields, Object value) {
+			public static List<FieldProjection> from(Fields fields, @Nullable Object value) {
 
 				Assert.notNull(fields, "Fields must not be null!");
 				List<FieldProjection> projections = new ArrayList<FieldProjection>();
@@ -1336,7 +1363,14 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 				return projections;
 			}
 
-			/* 
+			/**
+			 * @return {@literal true} if this field is excluded.
+			 */
+			public boolean isExcluded() {
+				return Boolean.FALSE.equals(value);
+			}
+
+			/*
 			 * (non-Javadoc)
 			 * @see org.springframework.data.mongodb.core.aggregation.ProjectionOperation.Projection#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
 			 */
@@ -1375,12 +1409,12 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 			/**
 			 * Creates a new {@link OperationProjection} for the given field.
-			 * 
+			 *
 			 * @param field the name of the field to add the operation projection for, must not be {@literal null} or empty.
 			 * @param operation the actual operation key, must not be {@literal null} or empty.
 			 * @param values the values to pass into the operation, must not be {@literal null}.
 			 */
-			public OperationProjection(Field field, String operation, Object[] values) {
+			OperationProjection(Field field, String operation, Object[] values) {
 
 				super(field);
 
@@ -1407,7 +1441,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			protected List<Object> getOperationArguments(AggregationOperationContext context) {
 
 				List<Object> result = new ArrayList<Object>(values.size());
-				result.add(context.getReference(getField().getName()).toString());
+				result.add(context.getReference(getField()).toString());
 
 				for (Object element : values) {
 
@@ -1429,7 +1463,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 			/**
 			 * Returns the field that holds the {@link OperationProjection}.
-			 * 
+			 *
 			 * @return
 			 */
 			protected Field getField() {
@@ -1452,11 +1486,11 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 			/**
 			 * Creates a new instance of this {@link OperationProjection} with the given alias.
-			 * 
+			 *
 			 * @param alias the alias to set
 			 * @return
 			 */
-			public OperationProjection withAlias(String alias) {
+			OperationProjection withAlias(String alias) {
 
 				final Field aliasedField = Fields.field(alias, this.field.getName());
 				return new OperationProjection(aliasedField, operation, values.toArray()) {
@@ -1486,14 +1520,14 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			private final String name;
 			private final Fields fields;
 
-			public NestedFieldProjection(String name, Fields fields) {
+			NestedFieldProjection(String name, Fields fields) {
 
 				super(Fields.field(name));
 				this.name = name;
 				this.fields = fields;
 			}
 
-			/* 
+			/*
 			 * (non-Javadoc)
 			 * @see org.springframework.data.mongodb.core.aggregation.ProjectionOperation.Projection#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
 			 */
@@ -1512,7 +1546,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Extracts the minute from a date expression.
-		 * 
+		 *
 		 * @return
 		 */
 		public ProjectionOperationBuilder extractMinute() {
@@ -1521,7 +1555,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Extracts the hour from a date expression.
-		 * 
+		 *
 		 * @return
 		 */
 		public ProjectionOperationBuilder extractHour() {
@@ -1530,7 +1564,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Extracts the second from a date expression.
-		 * 
+		 *
 		 * @return
 		 */
 		public ProjectionOperationBuilder extractSecond() {
@@ -1539,7 +1573,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Extracts the millisecond from a date expression.
-		 * 
+		 *
 		 * @return
 		 */
 		public ProjectionOperationBuilder extractMillisecond() {
@@ -1548,7 +1582,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Extracts the year from a date expression.
-		 * 
+		 *
 		 * @return
 		 */
 		public ProjectionOperationBuilder extractYear() {
@@ -1557,7 +1591,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Extracts the month from a date expression.
-		 * 
+		 *
 		 * @return
 		 */
 		public ProjectionOperationBuilder extractMonth() {
@@ -1566,7 +1600,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Extracts the week from a date expression.
-		 * 
+		 *
 		 * @return
 		 */
 		public ProjectionOperationBuilder extractWeek() {
@@ -1575,7 +1609,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Extracts the dayOfYear from a date expression.
-		 * 
+		 *
 		 * @return
 		 */
 		public ProjectionOperationBuilder extractDayOfYear() {
@@ -1584,7 +1618,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Extracts the dayOfMonth from a date expression.
-		 * 
+		 *
 		 * @return
 		 */
 		public ProjectionOperationBuilder extractDayOfMonth() {
@@ -1593,7 +1627,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Extracts the dayOfWeek from a date expression.
-		 * 
+		 *
 		 * @return
 		 */
 		public ProjectionOperationBuilder extractDayOfWeek() {
@@ -1603,7 +1637,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 	/**
 	 * Base class for {@link Projection} implementations.
-	 * 
+	 *
 	 * @author Oliver Gierke
 	 */
 	private static abstract class Projection {
@@ -1612,7 +1646,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Creates new {@link Projection} for the given {@link Field}.
-		 * 
+		 *
 		 * @param field must not be {@literal null}.
 		 */
 		public Projection(Field field) {
@@ -1623,7 +1657,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Returns the field exposed by the {@link Projection}.
-		 * 
+		 *
 		 * @return will never be {@literal null}.
 		 */
 		public ExposedField getExposedField() {
@@ -1633,7 +1667,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 		/**
 		 * Renders the current {@link Projection} into a {@link Document} based on the given
 		 * {@link AggregationOperationContext}.
-		 * 
+		 *
 		 * @param context will never be {@literal null}.
 		 * @return
 		 */
@@ -1650,7 +1684,7 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 
 		/**
 		 * Creates a new {@link ExpressionProjection}.
-		 * 
+		 *
 		 * @param field
 		 * @param expression
 		 */

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

@@ -43,6 +43,7 @@ import org.springframework.expression.spel.ast.PropertyOrFieldReference;
 import org.springframework.expression.spel.standard.SpelExpression;
 import org.springframework.expression.spel.standard.SpelExpressionParser;
 import org.springframework.expression.spel.support.StandardEvaluationContext;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.NumberUtils;
 import org.springframework.util.ObjectUtils;
@@ -64,7 +65,7 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 	/**
 	 * Creates a new {@link SpelExpressionTransformer}.
 	 */
-	public SpelExpressionTransformer() {
+	SpelExpressionTransformer() {
 
 		List<ExpressionNodeConversion<? extends ExpressionNode>> conversions = new ArrayList<ExpressionNodeConversion<? extends ExpressionNode>>();
 		conversions.add(new OperatorNodeConversion(this));
@@ -190,12 +191,12 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 		 * the previous context.
 		 *
 		 * @param node must not be {@literal null}.
-		 * @param parent
-		 * @param operation
+		 * @param parent may be {@literal null}.
+		 * @param operation may be {@literal null}.
 		 * @param context must not be {@literal null}.
 		 * @return
 		 */
-		protected Object transform(ExpressionNode node, ExpressionNode parent, Document operation,
+		protected Object transform(ExpressionNode node, @Nullable ExpressionNode parent, @Nullable Document operation,
 				AggregationExpressionTransformationContext<?> context) {
 
 			Assert.notNull(node, "ExpressionNode must not be null!");
@@ -290,7 +291,7 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 		}
 
 		private Object convertUnaryMinusOp(ExpressionTransformationContextSupport<OperatorNode> context,
-				Object leftResult) {
+				@Nullable Object leftResult) {
 
 			Object result = leftResult instanceof Number ? leftResult
 					: new Document("$multiply", Arrays.<Object> asList(Integer.valueOf(-1), leftResult));
@@ -320,7 +321,7 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 	 */
 	private static class IndexerNodeConversion extends ExpressionNodeConversion<ExpressionNode> {
 
-		public IndexerNodeConversion(AggregationExpressionTransformer transformer) {
+		IndexerNodeConversion(AggregationExpressionTransformer transformer) {
 			super(transformer);
 		}
 
@@ -350,7 +351,7 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 	 */
 	private static class InlineListNodeConversion extends ExpressionNodeConversion<ExpressionNode> {
 
-		public InlineListNodeConversion(AggregationExpressionTransformer transformer) {
+		InlineListNodeConversion(AggregationExpressionTransformer transformer) {
 			super(transformer);
 		}
 
@@ -358,6 +359,7 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.aggregation.SpelExpressionTransformer.SpelNodeWrapper#convertSpelNodeToMongoObjectExpression(org.springframework.data.mongodb.core.aggregation.SpelExpressionTransformer.ExpressionConversionContext)
 		 */
+		@Nullable
 		@Override
 		protected Object convert(AggregationExpressionTransformationContext<ExpressionNode> context) {
 
@@ -389,7 +391,7 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 	 */
 	private static class PropertyOrFieldReferenceNodeConversion extends ExpressionNodeConversion<ExpressionNode> {
 
-		public PropertyOrFieldReferenceNodeConversion(AggregationExpressionTransformer transformer) {
+		PropertyOrFieldReferenceNodeConversion(AggregationExpressionTransformer transformer) {
 			super(transformer);
 		}
 
@@ -422,7 +424,7 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 	 */
 	private static class LiteralNodeConversion extends ExpressionNodeConversion<LiteralNode> {
 
-		public LiteralNodeConversion(AggregationExpressionTransformer transformer) {
+		LiteralNodeConversion(AggregationExpressionTransformer transformer) {
 			super(transformer);
 		}
 
@@ -469,7 +471,7 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 	 */
 	private static class MethodReferenceNodeConversion extends ExpressionNodeConversion<MethodReferenceNode> {
 
-		public MethodReferenceNodeConversion(AggregationExpressionTransformer transformer) {
+		MethodReferenceNodeConversion(AggregationExpressionTransformer transformer) {
 			super(transformer);
 		}
 
@@ -483,6 +485,8 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 			MethodReferenceNode node = context.getCurrentNode();
 			AggregationMethodReference methodReference = node.getMethodReference();
 
+			Assert.state(methodReference != null, "Cannot resolve current node to AggregationMethodReference!");
+
 			Object args = null;
 
 			if (ObjectUtils.nullSafeEquals(methodReference.getArgumentType(), ArgumentType.SINGLE)) {
@@ -519,7 +523,7 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 	 */
 	private static class CompoundExpressionNodeConversion extends ExpressionNodeConversion<ExpressionNode> {
 
-		public CompoundExpressionNodeConversion(AggregationExpressionTransformer transformer) {
+		CompoundExpressionNodeConversion(AggregationExpressionTransformer transformer) {
 			super(transformer);
 		}
 
@@ -561,7 +565,7 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 		 *
 		 * @param transformer must not be {@literal null}.
 		 */
-		public NotOperatorNodeConversion(AggregationExpressionTransformer transformer) {
+		NotOperatorNodeConversion(AggregationExpressionTransformer transformer) {
 			super(transformer);
 		}
 
@@ -603,7 +607,7 @@ class SpelExpressionTransformer implements AggregationExpressionTransformer {
 		 *
 		 * @param transformer must not be {@literal null}.
 		 */
-		public ValueRetrievingNodeConversion(AggregationExpressionTransformer transformer) {
+		ValueRetrievingNodeConversion(AggregationExpressionTransformer transformer) {
 			super(transformer);
 		}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016. the original author or authors.
+ * Copyright 2016-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -26,6 +26,7 @@ import org.springframework.util.Assert;
  * Gateway to {@literal String} aggregation operations.
  *
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @since 1.10
  */
 public class StringOperators {
@@ -122,7 +123,7 @@ public class StringOperators {
 		}
 
 		private Concat createConcat() {
-			return fieldReference != null ? Concat.valueOf(fieldReference) : Concat.valueOf(expression);
+			return usesFieldRef() ? Concat.valueOf(fieldReference) : Concat.valueOf(expression);
 		}
 
 		/**
@@ -149,7 +150,7 @@ public class StringOperators {
 		}
 
 		private Substr createSubstr() {
-			return fieldReference != null ? Substr.valueOf(fieldReference) : Substr.valueOf(expression);
+			return usesFieldRef() ? Substr.valueOf(fieldReference) : Substr.valueOf(expression);
 		}
 
 		/**
@@ -158,7 +159,7 @@ public class StringOperators {
 		 * @return
 		 */
 		public ToLower toLower() {
-			return fieldReference != null ? ToLower.lowerValueOf(fieldReference) : ToLower.lowerValueOf(expression);
+			return usesFieldRef() ? ToLower.lowerValueOf(fieldReference) : ToLower.lowerValueOf(expression);
 		}
 
 		/**
@@ -167,7 +168,7 @@ public class StringOperators {
 		 * @return
 		 */
 		public ToUpper toUpper() {
-			return fieldReference != null ? ToUpper.upperValueOf(fieldReference) : ToUpper.upperValueOf(expression);
+			return usesFieldRef() ? ToUpper.upperValueOf(fieldReference) : ToUpper.upperValueOf(expression);
 		}
 
 		/**
@@ -210,7 +211,7 @@ public class StringOperators {
 		}
 
 		private StrCaseCmp createStrCaseCmp() {
-			return fieldReference != null ? StrCaseCmp.valueOf(fieldReference) : StrCaseCmp.valueOf(expression);
+			return usesFieldRef() ? StrCaseCmp.valueOf(fieldReference) : StrCaseCmp.valueOf(expression);
 		}
 
 		/**
@@ -256,7 +257,7 @@ public class StringOperators {
 		}
 
 		private IndexOfBytes.SubstringBuilder createIndexOfBytesSubstringBuilder() {
-			return fieldReference != null ? IndexOfBytes.valueOf(fieldReference) : IndexOfBytes.valueOf(expression);
+			return usesFieldRef() ? IndexOfBytes.valueOf(fieldReference) : IndexOfBytes.valueOf(expression);
 		}
 
 		/**
@@ -302,7 +303,7 @@ public class StringOperators {
 		}
 
 		private IndexOfCP.SubstringBuilder createIndexOfCPSubstringBuilder() {
-			return fieldReference != null ? IndexOfCP.valueOf(fieldReference) : IndexOfCP.valueOf(expression);
+			return usesFieldRef() ? IndexOfCP.valueOf(fieldReference) : IndexOfCP.valueOf(expression);
 		}
 
 		/**
@@ -339,7 +340,7 @@ public class StringOperators {
 		}
 
 		private Split createSplit() {
-			return fieldReference != null ? Split.valueOf(fieldReference) : Split.valueOf(expression);
+			return usesFieldRef() ? Split.valueOf(fieldReference) : Split.valueOf(expression);
 		}
 
 		/**
@@ -349,8 +350,7 @@ public class StringOperators {
 		 * @return
 		 */
 		public StrLenBytes length() {
-			return fieldReference != null ? StrLenBytes.stringLengthOf(fieldReference)
-					: StrLenBytes.stringLengthOf(expression);
+			return usesFieldRef() ? StrLenBytes.stringLengthOf(fieldReference) : StrLenBytes.stringLengthOf(expression);
 		}
 
 		/**
@@ -360,7 +360,7 @@ public class StringOperators {
 		 * @return
 		 */
 		public StrLenCP lengthCP() {
-			return fieldReference != null ? StrLenCP.stringLengthOfCP(fieldReference) : StrLenCP.stringLengthOfCP(expression);
+			return usesFieldRef() ? StrLenCP.stringLengthOfCP(fieldReference) : StrLenCP.stringLengthOfCP(expression);
 		}
 
 		/**
@@ -387,7 +387,137 @@ public class StringOperators {
 		}
 
 		private SubstrCP createSubstrCP() {
-			return fieldReference != null ? SubstrCP.valueOf(fieldReference) : SubstrCP.valueOf(expression);
+			return usesFieldRef() ? SubstrCP.valueOf(fieldReference) : SubstrCP.valueOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated string representation and trims whitespaces
+		 * from the beginning and end. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link Trim}.
+		 * @since 2.0.10
+		 */
+		public Trim trim() {
+			return createTrim();
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated string representation and trims the given
+		 * character sequence from the beginning and end. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param chars must not be {@literal null}.
+		 * @return new instance of {@link Trim}.
+		 * @since 2.0.10
+		 */
+		public Trim trim(String chars) {
+			return trim().chars(chars);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated string representation and trims the character
+		 * sequence resulting from the given {@link AggregationExpression} from the beginning and end. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link Trim}.
+		 * @since 2.0.10
+		 */
+		public Trim trim(AggregationExpression expression) {
+			return trim().charsOf(expression);
+		}
+
+		private Trim createTrim() {
+			return usesFieldRef() ? Trim.valueOf(fieldReference) : Trim.valueOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated string representation and trims whitespaces
+		 * from the beginning. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link LTrim}.
+		 * @since 2.0.10
+		 */
+		public LTrim ltrim() {
+			return createLTrim();
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated string representation and trims the given
+		 * character sequence from the beginning. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param chars must not be {@literal null}.
+		 * @return new instance of {@link LTrim}.
+		 * @since 2.0.10
+		 */
+		public LTrim ltrim(String chars) {
+			return ltrim().chars(chars);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated string representation and trims the character
+		 * sequence resulting from the given {@link AggregationExpression} from the beginning. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link LTrim}.
+		 * @since 2.0.10
+		 */
+		public LTrim ltrim(AggregationExpression expression) {
+			return ltrim().charsOf(expression);
+		}
+
+		private LTrim createLTrim() {
+			return usesFieldRef() ? LTrim.valueOf(fieldReference) : LTrim.valueOf(expression);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated string representation and trims whitespaces
+		 * from the end. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link RTrim}.
+		 * @since 2.0.10
+		 */
+		public RTrim rtrim() {
+			return createRTrim();
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated string representation and trims the given
+		 * character sequence from the end. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param chars must not be {@literal null}.
+		 * @return new instance of {@link RTrim}.
+		 * @since 2.0.10
+		 */
+		public RTrim rtrim(String chars) {
+			return rtrim().chars(chars);
+		}
+
+		/**
+		 * Creates new {@link AggregationExpression} that takes the associated string representation and trims the character
+		 * sequence resulting from the given {@link AggregationExpression} from the end. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link RTrim}.
+		 * @since 2.0.10
+		 */
+		public RTrim rtrim(AggregationExpression expression) {
+			return rtrim().charsOf(expression);
+		}
+
+		private RTrim createRTrim() {
+			return usesFieldRef() ? RTrim.valueOf(fieldReference) : RTrim.valueOf(expression);
+		}
+
+		private boolean usesFieldRef() {
+			return fieldReference != null;
 		}
 	}
 
@@ -1067,4 +1197,257 @@ public class StringOperators {
 			return new SubstrCP(append(Arrays.asList(start, nrOfChars)));
 		}
 	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $trim} which removes whitespace or the specified characters from the
+	 * beginning and end of a string. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @since 2.0.10
+	 */
+	public static class Trim extends AbstractAggregationExpression {
+
+		private Trim(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link Trim} using the value of the provided {@link Field fieldReference} as {@literal input} value.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link LTrim}.
+		 */
+		public static Trim valueOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new Trim(Collections.singletonMap("input", Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link Trim} using the result of the provided {@link AggregationExpression} as {@literal input}
+		 * value.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link Trim}.
+		 */
+		public static Trim valueOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new Trim(Collections.singletonMap("input", expression));
+		}
+
+		/**
+		 * Optional specify the character(s) to trim from the beginning.
+		 *
+		 * @param chars must not be {@literal null}.
+		 * @return new instance of {@link Trim}.
+		 */
+		public Trim chars(String chars) {
+
+			Assert.notNull(chars, "Chars must not be null!");
+			return new Trim(append("chars", chars));
+		}
+
+		/**
+		 * Optional specify the reference to the {@link Field field} holding the character values to trim from the
+		 * beginning.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link Trim}.
+		 */
+		public Trim charsOf(String fieldReference) {
+			return new Trim(append("chars", Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Optional specify the {@link AggregationExpression} evaluating to the character sequence to trim from the
+		 * beginning.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link Trim}.
+		 */
+		public Trim charsOf(AggregationExpression expression) {
+			return new Trim(append("chars", expression));
+		}
+
+		/**
+		 * Remove whitespace or the specified characters from the beginning of a string.<br />
+		 *
+		 * @return new instance of {@link LTrim}.
+		 */
+		public LTrim left() {
+			return new LTrim(argumentMap());
+		}
+
+		/**
+		 * Remove whitespace or the specified characters from the end of a string.<br />
+		 *
+		 * @return new instance of {@link RTrim}.
+		 */
+		public RTrim right() {
+			return new RTrim(argumentMap());
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$trim";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $ltrim} which removes whitespace or the specified characters from the
+	 * beginning of a string. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @since 2.0.10
+	 */
+	public static class LTrim extends AbstractAggregationExpression {
+
+		private LTrim(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link LTrim} using the value of the provided {@link Field fieldReference} as {@literal input} value.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link LTrim}.
+		 */
+		public static LTrim valueOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new LTrim(Collections.singletonMap("input", Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link LTrim} using the result of the provided {@link AggregationExpression} as {@literal input}
+		 * value.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link LTrim}.
+		 */
+		public static LTrim valueOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new LTrim(Collections.singletonMap("input", expression));
+		}
+
+		/**
+		 * Optional specify the character(s) to trim from the beginning.
+		 *
+		 * @param chars must not be {@literal null}.
+		 * @return new instance of {@link LTrim}.
+		 */
+		public LTrim chars(String chars) {
+
+			Assert.notNull(chars, "Chars must not be null!");
+			return new LTrim(append("chars", chars));
+		}
+
+		/**
+		 * Optional specify the reference to the {@link Field field} holding the character values to trim from the
+		 * beginning.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link LTrim}.
+		 */
+		public LTrim charsOf(String fieldReference) {
+			return new LTrim(append("chars", Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Optional specify the {@link AggregationExpression} evaluating to the character sequence to trim from the
+		 * beginning.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link LTrim}.
+		 */
+		public LTrim charsOf(AggregationExpression expression) {
+			return new LTrim(append("chars", expression));
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$ltrim";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $rtrim} which removes whitespace or the specified characters from the end
+	 * of a string. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @since 2.0.10
+	 */
+	public static class RTrim extends AbstractAggregationExpression {
+
+		private RTrim(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link RTrim} using the value of the provided {@link Field fieldReference} as {@literal input} value.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link RTrim}.
+		 */
+		public static RTrim valueOf(String fieldReference) {
+
+			Assert.notNull(fieldReference, "FieldReference must not be null!");
+			return new RTrim(Collections.singletonMap("input", Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Creates new {@link RTrim} using the result of the provided {@link AggregationExpression} as {@literal input}
+		 * value.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link RTrim}.
+		 */
+		public static RTrim valueOf(AggregationExpression expression) {
+
+			Assert.notNull(expression, "Expression must not be null!");
+			return new RTrim(Collections.singletonMap("input", expression));
+		}
+
+		/**
+		 * Optional specify the character(s) to trim from the end.
+		 *
+		 * @param chars must not be {@literal null}.
+		 * @return new instance of {@link RTrim}.
+		 */
+		public RTrim chars(String chars) {
+
+			Assert.notNull(chars, "Chars must not be null!");
+			return new RTrim(append("chars", chars));
+		}
+
+		/**
+		 * Optional specify the reference to the {@link Field field} holding the character values to trim from the end.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link RTrim}.
+		 */
+		public RTrim charsOf(String fieldReference) {
+			return new RTrim(append("chars", Fields.field(fieldReference)));
+		}
+
+		/**
+		 * Optional specify the {@link AggregationExpression} evaluating to the character sequence to trim from the end.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link RTrim}.
+		 */
+		public RTrim charsOf(AggregationExpression expression) {
+			return new RTrim(append("chars", expression));
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$rtrim";
+		}
+	}
 }

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

@@ -17,6 +17,7 @@ package org.springframework.data.mongodb.core.aggregation;
 
 import org.bson.Document;
 import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -36,7 +37,7 @@ public class UnwindOperation
 		implements AggregationOperation, FieldsExposingAggregationOperation.InheritsFieldsAggregationOperation {
 
 	private final ExposedField field;
-	private final ExposedField arrayIndex;
+	private final @Nullable ExposedField arrayIndex;
 	private final boolean preserveNullAndEmptyArrays;
 
 	/**
@@ -185,8 +186,8 @@ public class UnwindOperation
 	 */
 	public static final class UnwindOperationBuilder implements PathBuilder, IndexBuilder, EmptyArraysBuilder {
 
-		private Field field;
-		private Field arrayIndex;
+		private @Nullable Field field;
+		private @Nullable Field arrayIndex;
 
 		private UnwindOperationBuilder() {}
 

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

@@ -22,6 +22,7 @@ import java.util.List;
 
 import org.bson.Document;
 import org.springframework.data.mongodb.core.aggregation.VariableOperators.Let.ExpressionVariable;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -334,8 +335,8 @@ public class VariableOperators {
 		 */
 		public static class ExpressionVariable {
 
-			private final String variableName;
-			private final Object expression;
+			private final @Nullable String variableName;
+			private final @Nullable Object expression;
 
 			/**
 			 * Creates new {@link ExpressionVariable}.
@@ -343,7 +344,7 @@ public class VariableOperators {
 			 * @param variableName can be {@literal null}.
 			 * @param expression can be {@literal null}.
 			 */
-			private ExpressionVariable(String variableName, Object expression) {
+			private ExpressionVariable(@Nullable String variableName, @Nullable Object expression) {
 
 				this.variableName = variableName;
 				this.expression = expression;

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

@@ -1,5 +1,8 @@
 /**
  * Support for the MongoDB aggregation framework.
+ * 
  * @since 1.3
  */
-package org.springframework.data.mongodb.core.aggregation;
+@org.springframework.lang.NonNullApi
+package org.springframework.data.mongodb.core.aggregation;
+

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

@@ -28,6 +28,8 @@ import org.springframework.data.mongodb.core.convert.MongoConverters.BigIntegerT
 import org.springframework.data.mongodb.core.convert.MongoConverters.ObjectIdToBigIntegerConverter;
 import org.springframework.data.mongodb.core.convert.MongoConverters.ObjectIdToStringConverter;
 import org.springframework.data.mongodb.core.convert.MongoConverters.StringToObjectIdConverter;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 
 /**
  * Base class for {@link MongoConverter} implementations. Sets up a {@link GenericConversionService} and populates basic
@@ -36,6 +38,7 @@ import org.springframework.data.mongodb.core.convert.MongoConverters.StringToObj
  * @author Jon Brisbin
  * @author Oliver Gierke
  * @author Mark Paluch
+ * @author Christoph Strobl
  */
 public abstract class AbstractMongoConverter implements MongoConverter, InitializingBean {
 
@@ -46,18 +49,20 @@ public abstract class AbstractMongoConverter implements MongoConverter, Initiali
 	/**
 	 * Creates a new {@link AbstractMongoConverter} using the given {@link GenericConversionService}.
 	 *
-	 * @param conversionService
+	 * @param conversionService can be {@literal null} and defaults to {@link DefaultConversionService}.
 	 */
-	public AbstractMongoConverter(GenericConversionService conversionService) {
+	public AbstractMongoConverter(@Nullable GenericConversionService conversionService) {
 		this.conversionService = conversionService == null ? new DefaultConversionService() : conversionService;
 	}
 
 	/**
 	 * Registers the given custom conversions with the converter.
 	 *
-	 * @param conversions
+	 * @param conversions must not be {@literal null}.
 	 */
 	public void setCustomConversions(CustomConversions conversions) {
+
+		Assert.notNull(conversions, "Conversions must not be null!");
 		this.conversions = conversions;
 	}
 
@@ -66,7 +71,7 @@ public abstract class AbstractMongoConverter implements MongoConverter, Initiali
 	 *
 	 * @param instantiators
 	 */
-	public void setInstantiators(EntityInstantiators instantiators) {
+	public void setInstantiators(@Nullable EntityInstantiators instantiators) {
 		this.instantiators = instantiators == null ? new EntityInstantiators() : instantiators;
 	}
 
@@ -91,18 +96,11 @@ public abstract class AbstractMongoConverter implements MongoConverter, Initiali
 		conversions.registerConvertersIn(conversionService);
 	}
 
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.core.convert.MongoWriter#convertToMongoType(java.lang.Object)
-	 */
-	public Object convertToMongoType(Object obj) {
-		return convertToMongoType(obj, null);
-	}
-
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.core.convert.MongoConverter#getConversionService()
 	 */
+	@Override
 	public ConversionService getConversionService() {
 		return conversionService;
 	}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 the original author or authors.
+ * Copyright 2014-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,13 +16,15 @@
 package org.springframework.data.mongodb.core.convert;
 
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+import org.springframework.lang.Nullable;
 
 import com.mongodb.DBRef;
 
 /**
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 public interface DbRefProxyHandler {
 
-	Object populateId(MongoPersistentProperty property, DBRef source, Object proxy);
+	Object populateId(MongoPersistentProperty property, @Nullable DBRef source, Object proxy);
 }

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

@@ -21,6 +21,7 @@ import org.bson.Document;
 import org.springframework.dao.InvalidDataAccessApiUsageException;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+import org.springframework.lang.Nullable;
 
 import com.mongodb.DBRef;
 
@@ -45,6 +46,7 @@ public interface DbRefResolver {
 	 * @param callback will never be {@literal null}.
 	 * @return
 	 */
+	@Nullable
 	Object resolveDbRef(MongoPersistentProperty property, DBRef dbref, DbRefResolverCallback callback,
 			DbRefProxyHandler proxyHandler);
 
@@ -67,6 +69,7 @@ public interface DbRefResolver {
 	 * @return
 	 * @since 1.7
 	 */
+	@Nullable
 	Document fetch(DBRef dbRef);
 
 	/**

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

@@ -23,6 +23,7 @@ import org.springframework.data.mapping.model.SpELContext;
 import org.springframework.data.mapping.model.SpELExpressionEvaluator;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+import org.springframework.lang.Nullable;
 
 import com.mongodb.DBRef;
 
@@ -56,7 +57,7 @@ class DefaultDbRefProxyHandler implements DbRefProxyHandler {
 	 * @see org.springframework.data.mongodb.core.convert.DbRefProxyHandler#populateId(com.mongodb.DBRef, java.lang.Object)
 	 */
 	@Override
-	public Object populateId(MongoPersistentProperty property, DBRef source, Object proxy) {
+	public Object populateId(MongoPersistentProperty property, @Nullable DBRef source, Object proxy) {
 
 		if (source == null) {
 			return proxy;

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

@@ -23,9 +23,11 @@ import java.io.ObjectOutputStream;
 import java.io.Serializable;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
-import java.util.Comparator;
 import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 import org.aopalliance.intercept.MethodInterceptor;
 import org.aopalliance.intercept.MethodInvocation;
@@ -42,6 +44,7 @@ import org.springframework.data.mongodb.LazyLoadingException;
 import org.springframework.data.mongodb.MongoDbFactory;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+import org.springframework.lang.Nullable;
 import org.springframework.objenesis.ObjenesisStd;
 import org.springframework.util.Assert;
 import org.springframework.util.ReflectionUtils;
@@ -91,6 +94,7 @@ public class DefaultDbRefResolver implements DbRefResolver {
 
 		Assert.notNull(property, "Property must not be null!");
 		Assert.notNull(callback, "Callback must not be null!");
+		Assert.notNull(handler, "Handler must not be null!");
 
 		if (isLazyDbRef(property)) {
 			return createLazyLoadingProxy(property, dbref, callback, handler);
@@ -142,8 +146,8 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		}
 
 		String collection = refs.iterator().next().getCollectionName();
+		List<Object> ids = new ArrayList<>(refs.size());
 
-		List<Object> ids = new ArrayList<Object>(refs.size());
 		for (DBRef ref : refs) {
 
 			if (!collection.equals(ref.getCollectionName())) {
@@ -155,10 +159,14 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		}
 
 		MongoDatabase db = mongoDbFactory.getDb();
-		List<Document> result = new ArrayList<>();
-		db.getCollection(collection).find(new Document("_id", new Document("$in", ids))).into(result);
-		result.sort(new DbRefByReferencePositionComparator(ids));
-		return result;
+
+		List<Document> result = db.getCollection(collection) //
+				.find(new Document("_id", new Document("$in", ids))) //
+				.into(new ArrayList<>());
+
+		return ids.stream() //
+				.flatMap(id -> documentWithId(id, result)) //
+				.collect(Collectors.toList());
 	}
 
 	/**
@@ -170,8 +178,8 @@ public class DefaultDbRefResolver implements DbRefResolver {
 	 * @param callback must not be {@literal null}.
 	 * @return
 	 */
-	private Object createLazyLoadingProxy(MongoPersistentProperty property, DBRef dbref, DbRefResolverCallback callback,
-			DbRefProxyHandler handler) {
+	private Object createLazyLoadingProxy(MongoPersistentProperty property, @Nullable DBRef dbref,
+			DbRefResolverCallback callback, DbRefProxyHandler handler) {
 
 		Class<?> propertyType = property.getType();
 		LazyLoadingInterceptor interceptor = new LazyLoadingInterceptor(property, dbref, exceptionTranslator, callback);
@@ -223,6 +231,20 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		return property.getDBRef() != null && property.getDBRef().lazy();
 	}
 
+	/**
+	 * Returns document with the given identifier from the given list of {@link Document}s.
+	 *
+	 * @param identifier
+	 * @param documents
+	 * @return
+	 */
+	private static Stream<Document> documentWithId(Object identifier, Collection<Document> documents) {
+
+		return documents.stream() //
+				.filter(it -> it.get("_id").equals(identifier)) //
+				.limit(1);
+	}
+
 	/**
 	 * A {@link MethodInterceptor} that is used within a lazy loading proxy. The property resolving is delegated to a
 	 * {@link DbRefResolverCallback}. The resolving process is triggered by a method invocation on the proxy and is
@@ -242,8 +264,8 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		private final PersistenceExceptionTranslator exceptionTranslator;
 
 		private volatile boolean resolved;
-		private Object result;
-		private DBRef dbref;
+		private final @Nullable DBRef dbref;
+		private @Nullable Object result;
 
 		static {
 			try {
@@ -263,7 +285,7 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		 * @param dbref can be {@literal null}.
 		 * @param callback must not be {@literal null}.
 		 */
-		public LazyLoadingInterceptor(MongoPersistentProperty property, DBRef dbref,
+		public LazyLoadingInterceptor(MongoPersistentProperty property, @Nullable DBRef dbref,
 				PersistenceExceptionTranslator exceptionTranslator, DbRefResolverCallback callback) {
 
 			Assert.notNull(property, "Property must not be null!");
@@ -281,7 +303,7 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		 * @see org.aopalliance.intercept.MethodInterceptor#invoke(org.aopalliance.intercept.MethodInvocation)
 		 */
 		@Override
-		public Object invoke(MethodInvocation invocation) throws Throwable {
+		public Object invoke(@Nullable MethodInvocation invocation) throws Throwable {
 			return intercept(invocation.getThis(), invocation.getMethod(), invocation.getArguments(), null);
 		}
 
@@ -289,8 +311,9 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		 * (non-Javadoc)
 		 * @see org.springframework.cglib.proxy.MethodInterceptor#intercept(java.lang.Object, java.lang.reflect.Method, java.lang.Object[], org.springframework.cglib.proxy.MethodProxy)
 		 */
+		@Nullable
 		@Override
-		public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
+		public Object intercept(Object obj, Method method, Object[] args, @Nullable MethodProxy proxy) throws Throwable {
 
 			if (INITIALIZE_METHOD.equals(method)) {
 				return ensureResolved();
@@ -337,7 +360,7 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		 * @param proxy
 		 * @return
 		 */
-		private String proxyToString(Object proxy) {
+		private String proxyToString(@Nullable Object proxy) {
 
 			StringBuilder description = new StringBuilder();
 			if (dbref != null) {
@@ -358,7 +381,7 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		 * @param proxy
 		 * @return
 		 */
-		private int proxyHashCode(Object proxy) {
+		private int proxyHashCode(@Nullable Object proxy) {
 			return proxyToString(proxy).hashCode();
 		}
 
@@ -369,7 +392,7 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		 * @param that
 		 * @return
 		 */
-		private boolean proxyEquals(Object proxy, Object that) {
+		private boolean proxyEquals(@Nullable Object proxy, Object that) {
 
 			if (!(that instanceof LazyLoadingProxy)) {
 				return false;
@@ -387,6 +410,7 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		 *
 		 * @return
 		 */
+		@Nullable
 		private Object ensureResolved() {
 
 			if (!resolved) {
@@ -430,6 +454,7 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		 *
 		 * @return
 		 */
+		@Nullable
 		private synchronized Object resolve() {
 
 			if (!resolved) {
@@ -449,37 +474,4 @@ public class DefaultDbRefResolver implements DbRefResolver {
 			return result;
 		}
 	}
-
-	/**
-	 * {@link Comparator} for sorting {@link Document} that have been loaded in random order by a predefined list of
-	 * reference identifiers.
-	 *
-	 * @author Christoph Strobl
-	 * @author Oliver Gierke
-	 * @since 1.10
-	 */
-	private static class DbRefByReferencePositionComparator implements Comparator<Document> {
-
-		private final List<Object> reference;
-
-		/**
-		 * Creates a new {@link DbRefByReferencePositionComparator} for the given list of reference identifiers.
-		 *
-		 * @param referenceIds must not be {@literal null}.
-		 */
-		public DbRefByReferencePositionComparator(List<Object> referenceIds) {
-
-			Assert.notNull(referenceIds, "Reference identifiers must not be null!");
-			this.reference = new ArrayList<Object>(referenceIds);
-		}
-
-		/*
-		 * (non-Javadoc)
-		 * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
-		 */
-		@Override
-		public int compare(Document o1, Document o2) {
-			return Integer.compare(reference.indexOf(o1.get("_id")), reference.indexOf(o2.get("_id")));
-		}
-	}
 }

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

@@ -18,7 +18,6 @@ package org.springframework.data.mongodb.core.convert;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
-import java.util.Optional;
 import java.util.Set;
 
 import org.bson.Document;
@@ -32,6 +31,7 @@ import org.springframework.data.mapping.PersistentEntity;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.util.ClassTypeInformation;
 import org.springframework.data.util.TypeInformation;
+import org.springframework.lang.Nullable;
 import org.springframework.util.ObjectUtils;
 
 import com.mongodb.BasicDBList;
@@ -57,26 +57,27 @@ public class DefaultMongoTypeMapper extends DefaultTypeMapper<Bson> implements M
 	private static final TypeInformation<Map> MAP_TYPE_INFO = ClassTypeInformation.from(Map.class);
 
 	private final TypeAliasAccessor<Bson> accessor;
-	private final String typeKey;
+	private final @Nullable String typeKey;
 
 	public DefaultMongoTypeMapper() {
 		this(DEFAULT_TYPE_KEY);
 	}
 
-	public DefaultMongoTypeMapper(String typeKey) {
+	public DefaultMongoTypeMapper(@Nullable String typeKey) {
 		this(typeKey, Arrays.asList(new SimpleTypeInformationMapper()));
 	}
 
-	public DefaultMongoTypeMapper(String typeKey, MappingContext<? extends PersistentEntity<?, ?>, ?> mappingContext) {
+	public DefaultMongoTypeMapper(@Nullable String typeKey,
+			MappingContext<? extends PersistentEntity<?, ?>, ?> mappingContext) {
 		this(typeKey, new DocumentTypeAliasAccessor(typeKey), mappingContext,
 				Arrays.asList(new SimpleTypeInformationMapper()));
 	}
 
-	public DefaultMongoTypeMapper(String typeKey, List<? extends TypeInformationMapper> mappers) {
+	public DefaultMongoTypeMapper(@Nullable String typeKey, List<? extends TypeInformationMapper> mappers) {
 		this(typeKey, new DocumentTypeAliasAccessor(typeKey), null, mappers);
 	}
 
-	private DefaultMongoTypeMapper(String typeKey, TypeAliasAccessor<Bson> accessor,
+	private DefaultMongoTypeMapper(@Nullable String typeKey, TypeAliasAccessor<Bson> accessor,
 			MappingContext<? extends PersistentEntity<?, ?>, ?> mappingContext,
 			List<? extends TypeInformationMapper> mappers) {
 
@@ -99,9 +100,9 @@ public class DefaultMongoTypeMapper extends DefaultTypeMapper<Bson> implements M
 	 * @see org.springframework.data.mongodb.core.convert.MongoTypeMapper#writeTypeRestrictions(java.util.Set)
 	 */
 	@Override
-	public void writeTypeRestrictions(Document result, Set<Class<?>> restrictedTypes) {
+	public void writeTypeRestrictions(Document result, @Nullable Set<Class<?>> restrictedTypes) {
 
-		if (restrictedTypes == null || restrictedTypes.isEmpty()) {
+		if (ObjectUtils.isEmpty(restrictedTypes)) {
 			return;
 		}
 
@@ -111,7 +112,7 @@ public class DefaultMongoTypeMapper extends DefaultTypeMapper<Bson> implements M
 
 			Alias typeAlias = getAliasFor(ClassTypeInformation.from(restrictedType));
 
-			if (typeAlias != null && !ObjectUtils.nullSafeEquals(Alias.NONE, typeAlias) && typeAlias.isPresent()) {
+			if (!ObjectUtils.nullSafeEquals(Alias.NONE, typeAlias) && typeAlias.isPresent()) {
 				restrictedMappedTypes.add(typeAlias.getValue());
 			}
 		}
@@ -135,9 +136,9 @@ public class DefaultMongoTypeMapper extends DefaultTypeMapper<Bson> implements M
 	 */
 	public static final class DocumentTypeAliasAccessor implements TypeAliasAccessor<Bson> {
 
-		private final String typeKey;
+		private final @Nullable String typeKey;
 
-		public DocumentTypeAliasAccessor(String typeKey) {
+		public DocumentTypeAliasAccessor(@Nullable String typeKey) {
 			this.typeKey = typeKey;
 		}
 

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

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.mongodb.core.convert;
 
+import lombok.Getter;
+
 import java.util.Arrays;
 import java.util.Iterator;
 import java.util.Map;
@@ -23,6 +25,7 @@ import org.bson.Document;
 import org.bson.conversions.Bson;
 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;
@@ -39,7 +42,7 @@ import com.mongodb.DBObject;
  */
 class DocumentAccessor {
 
-	private final Bson document;
+	private final @Getter Bson document;
 
 	/**
 	 * Creates a new {@link DocumentAccessor} for the given {@link Document}.
@@ -65,7 +68,7 @@ class DocumentAccessor {
 	 * @param prop must not be {@literal null}.
 	 * @param value
 	 */
-	public void put(MongoPersistentProperty prop, Object value) {
+	public void put(MongoPersistentProperty prop, @Nullable Object value) {
 
 		Assert.notNull(prop, "MongoPersistentProperty must not be null!");
 		String fieldName = prop.getFieldName();
@@ -98,6 +101,7 @@ class DocumentAccessor {
 	 * @param property must not be {@literal null}.
 	 * @return
 	 */
+	@Nullable
 	public Object get(MongoPersistentProperty property) {
 
 		String fieldName = property.getFieldName();
@@ -135,15 +139,21 @@ class DocumentAccessor {
 
 		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(".")) {
-
-			if (this.document instanceof Document) {
-				return ((Document) this.document).containsKey(fieldName);
-			}
-
-			if (this.document instanceof DBObject) {
-				return ((DBObject) this.document).containsField(fieldName);
-			}
+			return false;
 		}
 
 		String[] parts = fieldName.split("\\.");
@@ -176,6 +186,7 @@ class DocumentAccessor {
 	 * @param source can be {@literal null}.
 	 * @return
 	 */
+	@Nullable
 	@SuppressWarnings("unchecked")
 	private static Map<String, Object> getAsMap(Object source) {
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2016 the original author or authors.
+ * Copyright 2012-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,6 +22,7 @@ import org.springframework.context.expression.MapAccessor;
 import org.springframework.expression.EvaluationContext;
 import org.springframework.expression.PropertyAccessor;
 import org.springframework.expression.TypedValue;
+import org.springframework.lang.Nullable;
 
 /**
  * {@link PropertyAccessor} to allow entity based field access to {@link Document}s.
@@ -47,7 +48,7 @@ class DocumentPropertyAccessor extends MapAccessor {
 	 * @see org.springframework.context.expression.MapAccessor#canRead(org.springframework.expression.EvaluationContext, java.lang.Object, java.lang.String)
 	 */
 	@Override
-	public boolean canRead(EvaluationContext context, Object target, String name) {
+	public boolean canRead(EvaluationContext context, @Nullable Object target, String name) {
 		return true;
 	}
 
@@ -57,7 +58,11 @@ class DocumentPropertyAccessor extends MapAccessor {
 	 */
 	@Override
 	@SuppressWarnings("unchecked")
-	public TypedValue read(EvaluationContext context, Object target, String name) {
+	public TypedValue read(EvaluationContext context, @Nullable Object target, String name) {
+
+		if (target == null) {
+			return TypedValue.NULL;
+		}
 
 		Map<String, Object> source = (Map<String, Object>) target;
 

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

@@ -15,10 +15,13 @@
  */
 package org.springframework.data.mongodb.core.convert;
 
+import java.text.Collator;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
 
 import org.bson.Document;
 import org.springframework.core.convert.converter.Converter;
@@ -41,15 +44,17 @@ import org.springframework.data.mongodb.core.geo.GeoJsonPoint;
 import org.springframework.data.mongodb.core.geo.GeoJsonPolygon;
 import org.springframework.data.mongodb.core.geo.Sphere;
 import org.springframework.data.mongodb.core.query.GeoCommand;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.NumberUtils;
 import org.springframework.util.ObjectUtils;
 
 import com.mongodb.BasicDBList;
+import com.mongodb.Function;
 
 /**
  * Wrapper class to contain useful geo structure converters for the usage with Mongo.
- * 
+ *
  * @author Thomas Darimont
  * @author Oliver Gierke
  * @author Christoph Strobl
@@ -58,6 +63,26 @@ import com.mongodb.BasicDBList;
  */
 abstract class GeoConverters {
 
+
+	private final static Map<String, Function<Document, GeoJson<?>>> converters;
+
+	static {
+
+		Collator caseInsensitive = Collator.getInstance();
+		caseInsensitive.setStrength(Collator.PRIMARY);
+
+		Map<String, Function<Document, GeoJson<?>>> geoConverters = new TreeMap<>(caseInsensitive);
+		geoConverters.put("point", DocumentToGeoJsonPointConverter.INSTANCE::convert);
+		geoConverters.put("multipoint", DocumentToGeoJsonMultiPointConverter.INSTANCE::convert);
+		geoConverters.put("linestring", DocumentToGeoJsonLineStringConverter.INSTANCE::convert);
+		geoConverters.put("multilinestring", DocumentToGeoJsonMultiLineStringConverter.INSTANCE::convert);
+		geoConverters.put("polygon", DocumentToGeoJsonPolygonConverter.INSTANCE::convert);
+		geoConverters.put("multipolygon", DocumentToGeoJsonMultiPolygonConverter.INSTANCE::convert);
+		geoConverters.put("geometrycollection", DocumentToGeoJsonGeometryCollectionConverter.INSTANCE::convert);
+
+		converters = geoConverters;
+	}
+
 	/**
 	 * Private constructor to prevent instantiation.
 	 */
@@ -65,7 +90,7 @@ abstract class GeoConverters {
 
 	/**
 	 * Returns the geo converters to be registered.
-	 * 
+	 *
 	 * @return
 	 */
 	@SuppressWarnings("unchecked")
@@ -91,17 +116,18 @@ abstract class GeoConverters {
 				, DocumentToGeoJsonMultiLineStringConverter.INSTANCE //
 				, DocumentToGeoJsonMultiPointConverter.INSTANCE //
 				, DocumentToGeoJsonMultiPolygonConverter.INSTANCE //
-				, DocumentToGeoJsonGeometryCollectionConverter.INSTANCE);
+				, DocumentToGeoJsonGeometryCollectionConverter.INSTANCE //
+				, DocumentToGeoJsonConverter.INSTANCE);
 	}
 
 	/**
 	 * Converts a {@link List} of {@link Double}s into a {@link Point}.
-	 * 
+	 *
 	 * @author Thomas Darimont
 	 * @since 1.5
 	 */
 	@ReadingConverter
-	static enum DocumentToPointConverter implements Converter<Document, Point> {
+	enum DocumentToPointConverter implements Converter<Document, Point> {
 
 		INSTANCE;
 
@@ -128,11 +154,11 @@ abstract class GeoConverters {
 
 	/**
 	 * Converts a {@link Point} into a {@link List} of {@link Double}s.
-	 * 
+	 *
 	 * @author Thomas Darimont
 	 * @since 1.5
 	 */
-	static enum PointToDocumentConverter implements Converter<Point, Document> {
+	enum PointToDocumentConverter implements Converter<Point, Document> {
 
 		INSTANCE;
 
@@ -147,13 +173,13 @@ abstract class GeoConverters {
 	}
 
 	/**
-	 * Converts a {@link Box} into a {@link BasicDBList}.
-	 * 
+	 * Converts a {@link Box} into a {@link Document}.
+	 *
 	 * @author Thomas Darimont
 	 * @since 1.5
 	 */
 	@WritingConverter
-	static enum BoxToDocumentConverter implements Converter<Box, Document> {
+	enum BoxToDocumentConverter implements Converter<Box, Document> {
 
 		INSTANCE;
 
@@ -176,13 +202,13 @@ abstract class GeoConverters {
 	}
 
 	/**
-	 * Converts a {@link BasicDBList} into a {@link Box}.
-	 * 
+	 * Converts a {@link Document} into a {@link Box}.
+	 *
 	 * @author Thomas Darimont
 	 * @since 1.5
 	 */
 	@ReadingConverter
-	static enum DocumentToBoxConverter implements Converter<Document, Box> {
+	enum DocumentToBoxConverter implements Converter<Document, Box> {
 
 		INSTANCE;
 
@@ -205,12 +231,12 @@ abstract class GeoConverters {
 	}
 
 	/**
-	 * Converts a {@link Circle} into a {@link BasicDBList}.
-	 * 
+	 * Converts a {@link Circle} into a {@link Document}.
+	 *
 	 * @author Thomas Darimont
 	 * @since 1.5
 	 */
-	static enum CircleToDocumentConverter implements Converter<Circle, Document> {
+	enum CircleToDocumentConverter implements Converter<Circle, Document> {
 
 		INSTANCE;
 
@@ -235,7 +261,7 @@ abstract class GeoConverters {
 
 	/**
 	 * Converts a {@link Document} into a {@link Circle}.
-	 * 
+	 *
 	 * @author Thomas Darimont
 	 * @since 1.5
 	 */
@@ -276,8 +302,8 @@ abstract class GeoConverters {
 	}
 
 	/**
-	 * Converts a {@link Sphere} into a {@link BasicDBList}.
-	 * 
+	 * Converts a {@link Sphere} into a {@link Document}.
+	 *
 	 * @author Thomas Darimont
 	 * @since 1.5
 	 */
@@ -305,13 +331,13 @@ abstract class GeoConverters {
 	}
 
 	/**
-	 * Converts a {@link BasicDBList} into a {@link Sphere}.
-	 * 
+	 * Converts a {@link Document} into a {@link Sphere}.
+	 *
 	 * @author Thomas Darimont
 	 * @since 1.5
 	 */
 	@ReadingConverter
-	static enum DocumentToSphereConverter implements Converter<Document, Sphere> {
+	enum DocumentToSphereConverter implements Converter<Document, Sphere> {
 
 		INSTANCE;
 
@@ -347,12 +373,12 @@ abstract class GeoConverters {
 	}
 
 	/**
-	 * Converts a {@link Polygon} into a {@link BasicDBList}.
-	 * 
+	 * Converts a {@link Polygon} into a {@link Document}.
+	 *
 	 * @author Thomas Darimont
 	 * @since 1.5
 	 */
-	static enum PolygonToDocumentConverter implements Converter<Polygon, Document> {
+	enum PolygonToDocumentConverter implements Converter<Polygon, Document> {
 
 		INSTANCE;
 
@@ -368,7 +394,7 @@ abstract class GeoConverters {
 			}
 
 			List<Point> points = source.getPoints();
-			List<Document> pointTuples = new ArrayList<Document>(points.size());
+			List<Document> pointTuples = new ArrayList<>(points.size());
 
 			for (Point point : points) {
 				pointTuples.add(PointToDocumentConverter.INSTANCE.convert(point));
@@ -381,13 +407,13 @@ abstract class GeoConverters {
 	}
 
 	/**
-	 * Converts a {@link BasicDBList} into a {@link Polygon}.
-	 * 
+	 * Converts a {@link Document} into a {@link Polygon}.
+	 *
 	 * @author Thomas Darimont
 	 * @since 1.5
 	 */
 	@ReadingConverter
-	static enum DocumentToPolygonConverter implements Converter<Document, Polygon> {
+	enum DocumentToPolygonConverter implements Converter<Document, Polygon> {
 
 		INSTANCE;
 
@@ -404,7 +430,7 @@ abstract class GeoConverters {
 			}
 
 			List<Document> points = (List<Document>) source.get("points");
-			List<Point> newPoints = new ArrayList<Point>(points.size());
+			List<Point> newPoints = new ArrayList<>(points.size());
 
 			for (Document element : points) {
 
@@ -417,12 +443,12 @@ abstract class GeoConverters {
 	}
 
 	/**
-	 * Converts a {@link Sphere} into a {@link BasicDBList}.
-	 * 
+	 * Converts a {@link Sphere} into a {@link Document}.
+	 *
 	 * @author Thomas Darimont
 	 * @since 1.5
 	 */
-	static enum GeoCommandToDocumentConverter implements Converter<GeoCommand, Document> {
+	enum GeoCommandToDocumentConverter implements Converter<GeoCommand, Document> {
 
 		INSTANCE;
 
@@ -482,7 +508,7 @@ abstract class GeoConverters {
 	 * @since 1.7
 	 */
 	@SuppressWarnings("rawtypes")
-	static enum GeoJsonToDocumentConverter implements Converter<GeoJson, Document> {
+	enum GeoJsonToDocumentConverter implements Converter<GeoJson, Document> {
 
 		INSTANCE;
 
@@ -545,7 +571,7 @@ abstract class GeoConverters {
 	 * @author Christoph Strobl
 	 * @since 1.7
 	 */
-	static enum GeoJsonPointToDocumentConverter implements Converter<GeoJsonPoint, Document> {
+	enum GeoJsonPointToDocumentConverter implements Converter<GeoJsonPoint, Document> {
 
 		INSTANCE;
 
@@ -563,7 +589,7 @@ abstract class GeoConverters {
 	 * @author Christoph Strobl
 	 * @since 1.7
 	 */
-	static enum GeoJsonPolygonToDocumentConverter implements Converter<GeoJsonPolygon, Document> {
+	enum GeoJsonPolygonToDocumentConverter implements Converter<GeoJsonPolygon, Document> {
 
 		INSTANCE;
 
@@ -581,7 +607,7 @@ abstract class GeoConverters {
 	 * @author Christoph Strobl
 	 * @since 1.7
 	 */
-	static enum DocumentToGeoJsonPointConverter implements Converter<Document, GeoJsonPoint> {
+	enum DocumentToGeoJsonPointConverter implements Converter<Document, GeoJsonPoint> {
 
 		INSTANCE;
 
@@ -609,7 +635,7 @@ abstract class GeoConverters {
 	 * @author Christoph Strobl
 	 * @since 1.7
 	 */
-	static enum DocumentToGeoJsonPolygonConverter implements Converter<Document, GeoJsonPolygon> {
+	enum DocumentToGeoJsonPolygonConverter implements Converter<Document, GeoJsonPolygon> {
 
 		INSTANCE;
 
@@ -654,7 +680,7 @@ abstract class GeoConverters {
 					String.format("Cannot convert type '%s' to MultiPolygon.", source.get("type")));
 
 			List dbl = (List) source.get("coordinates");
-			List<GeoJsonPolygon> polygones = new ArrayList<GeoJsonPolygon>();
+			List<GeoJsonPolygon> polygones = new ArrayList<>();
 
 			for (Object polygon : dbl) {
 				polygones.add(toGeoJsonPolygon((List) polygon));
@@ -668,7 +694,7 @@ abstract class GeoConverters {
 	 * @author Christoph Strobl
 	 * @since 1.7
 	 */
-	static enum DocumentToGeoJsonLineStringConverter implements Converter<Document, GeoJsonLineString> {
+	enum DocumentToGeoJsonLineStringConverter implements Converter<Document, GeoJsonLineString> {
 
 		INSTANCE;
 
@@ -696,7 +722,7 @@ abstract class GeoConverters {
 	 * @author Christoph Strobl
 	 * @since 1.7
 	 */
-	static enum DocumentToGeoJsonMultiPointConverter implements Converter<Document, GeoJsonMultiPoint> {
+	enum DocumentToGeoJsonMultiPointConverter implements Converter<Document, GeoJsonMultiPoint> {
 
 		INSTANCE;
 
@@ -724,7 +750,7 @@ abstract class GeoConverters {
 	 * @author Christoph Strobl
 	 * @since 1.7
 	 */
-	static enum DocumentToGeoJsonMultiLineStringConverter implements Converter<Document, GeoJsonMultiLineString> {
+	enum DocumentToGeoJsonMultiLineStringConverter implements Converter<Document, GeoJsonMultiLineString> {
 
 		INSTANCE;
 
@@ -756,7 +782,7 @@ abstract class GeoConverters {
 	 * @author Christoph Strobl
 	 * @since 1.7
 	 */
-	static enum DocumentToGeoJsonGeometryCollectionConverter implements Converter<Document, GeoJsonGeometryCollection> {
+	enum DocumentToGeoJsonGeometryCollectionConverter implements Converter<Document, GeoJsonGeometryCollection> {
 
 		INSTANCE;
 
@@ -775,41 +801,12 @@ abstract class GeoConverters {
 			Assert.isTrue(ObjectUtils.nullSafeEquals(source.get("type"), "GeometryCollection"),
 					String.format("Cannot convert type '%s' to GeometryCollection.", source.get("type")));
 
-			List<GeoJson<?>> geometries = new ArrayList<GeoJson<?>>();
+			List<GeoJson<?>> geometries = new ArrayList<>();
 			for (Object o : (List) source.get("geometries")) {
-				geometries.add(convertGeometries((Document) o));
+				geometries.add(toGenericGeoJson((Document) o));
 			}
+
 			return new GeoJsonGeometryCollection(geometries);
-
-		}
-
-		private static GeoJson<?> convertGeometries(Document source) {
-
-			Object type = source.get("type");
-			if (ObjectUtils.nullSafeEquals(type, "Point")) {
-				return DocumentToGeoJsonPointConverter.INSTANCE.convert(source);
-			}
-
-			if (ObjectUtils.nullSafeEquals(type, "MultiPoint")) {
-				return DocumentToGeoJsonMultiPointConverter.INSTANCE.convert(source);
-			}
-
-			if (ObjectUtils.nullSafeEquals(type, "LineString")) {
-				return DocumentToGeoJsonLineStringConverter.INSTANCE.convert(source);
-			}
-
-			if (ObjectUtils.nullSafeEquals(type, "MultiLineString")) {
-				return DocumentToGeoJsonMultiLineStringConverter.INSTANCE.convert(source);
-			}
-
-			if (ObjectUtils.nullSafeEquals(type, "Polygon")) {
-				return DocumentToGeoJsonPolygonConverter.INSTANCE.convert(source);
-			}
-			if (ObjectUtils.nullSafeEquals(type, "MultiPolygon")) {
-				return DocumentToGeoJsonMultiPolygonConverter.INSTANCE.convert(source);
-			}
-
-			throw new IllegalArgumentException(String.format("Cannot convert unknown GeoJson type %s", type));
 		}
 	}
 
@@ -819,7 +816,7 @@ abstract class GeoConverters {
 
 	/**
 	 * Converts a coordinate pairs nested in in {@link BasicDBList} into {@link GeoJsonPoint}s.
-	 * 
+	 *
 	 * @param listOfCoordinatePairs
 	 * @return
 	 * @since 1.7
@@ -827,7 +824,7 @@ abstract class GeoConverters {
 	@SuppressWarnings("unchecked")
 	static List<Point> toListOfPoint(List listOfCoordinatePairs) {
 
-		List<Point> points = new ArrayList<Point>();
+		List<Point> points = new ArrayList<>();
 
 		for (Object point : listOfCoordinatePairs) {
 
@@ -843,7 +840,7 @@ abstract class GeoConverters {
 
 	/**
 	 * Converts a coordinate pairs nested in in {@link BasicDBList} into {@link GeoJsonPolygon}.
-	 * 
+	 *
 	 * @param dbList
 	 * @return
 	 * @since 1.7
@@ -852,6 +849,46 @@ abstract class GeoConverters {
 		return new GeoJsonPolygon(toListOfPoint((List) dbList.get(0)));
 	}
 
+	/**
+	 * Converter implementation transforming a {@link Document} into a concrete {@link GeoJson} based on the embedded
+	 * {@literal type} information.
+	 *
+	 * @since 2.1
+	 * @author Christoph Strobl
+	 */
+	@ReadingConverter
+	enum DocumentToGeoJsonConverter implements Converter<Document, GeoJson> {
+		INSTANCE;
+
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.core.convert.converter.Converter#convert(java.lang.Object)
+		 */
+		@Nullable
+		@Override
+		public GeoJson convert(Document source) {
+			return toGenericGeoJson(source);
+		}
+	}
+
+	private static GeoJson<?> toGenericGeoJson(Document source) {
+
+		String type = source.get("type", String.class);
+
+		if(type != null) {
+
+			Function<Document, GeoJson<?>> converter = converters.get(type);
+
+			if(converter != null){
+				return converter.apply(source);
+			}
+		}
+
+		throw new IllegalArgumentException(
+				String.format("No converter found capable of converting GeoJson type %s.", type));
+	}
+
 	private static double toPrimitiveDoubleValue(Object value) {
 
 		Assert.isInstanceOf(Number.class, value, "Argument must be a Number.");

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 the original author or authors.
+ * Copyright 2014-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,21 +16,23 @@
 package org.springframework.data.mongodb.core.convert;
 
 import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver.LazyLoadingInterceptor;
+import org.springframework.lang.Nullable;
 
 import com.mongodb.DBRef;
 
 /**
  * Allows direct interaction with the underlying {@link LazyLoadingInterceptor}.
- * 
+ *
  * @author Thomas Darimont
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @since 1.5
  */
 public interface LazyLoadingProxy {
 
 	/**
 	 * Initializes the proxy and returns the wrapped value.
-	 * 
+	 *
 	 * @return
 	 * @since 1.5
 	 */
@@ -38,9 +40,10 @@ public interface LazyLoadingProxy {
 
 	/**
 	 * Returns the {@link DBRef} represented by this {@link LazyLoadingProxy}, may be null.
-	 * 
+	 *
 	 * @return
 	 * @since 1.5
 	 */
+	@Nullable
 	DBRef toDBRef();
 }

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

@@ -15,17 +15,8 @@
  */
 package org.springframework.data.mongodb.core.convert;
 
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashSet;
-import java.util.LinkedHashMap;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 import java.util.Map.Entry;
-import java.util.Optional;
-import java.util.Set;
 
 import org.bson.Document;
 import org.bson.conversions.Bson;
@@ -40,13 +31,13 @@ import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.data.convert.EntityInstantiator;
 import org.springframework.data.convert.TypeMapper;
 import org.springframework.data.mapping.Association;
-import org.springframework.data.mapping.PersistentProperty;
+import org.springframework.data.mapping.MappingException;
 import org.springframework.data.mapping.PersistentPropertyAccessor;
+import org.springframework.data.mapping.PreferredConstructor;
 import org.springframework.data.mapping.PreferredConstructor.Parameter;
 import org.springframework.data.mapping.context.MappingContext;
 import org.springframework.data.mapping.model.ConvertingPropertyAccessor;
 import org.springframework.data.mapping.model.DefaultSpELExpressionEvaluator;
-import org.springframework.data.mapping.MappingException;
 import org.springframework.data.mapping.model.ParameterValueProvider;
 import org.springframework.data.mapping.model.PersistentEntityParameterValueProvider;
 import org.springframework.data.mapping.model.PropertyValueProvider;
@@ -61,6 +52,7 @@ import org.springframework.data.mongodb.core.mapping.event.AfterLoadEvent;
 import org.springframework.data.mongodb.core.mapping.event.MongoMappingEvent;
 import org.springframework.data.util.ClassTypeInformation;
 import org.springframework.data.util.TypeInformation;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.CollectionUtils;
@@ -86,6 +78,7 @@ import com.mongodb.DBRef;
 public class MappingMongoConverter extends AbstractMongoConverter implements ApplicationContextAware, ValueResolver {
 
 	private static final String INCOMPATIBLE_TYPES = "Cannot convert %1$s of type %2$s into an instance of %3$s! Implement a custom Converter<%2$s, %3$s> and register it with the CustomConversions. Parent object was: %4$s";
+	private static final String INVALID_TYPE_TO_READ = "Expected to read Document %s into type %s but didn't find a PersistentEntity for the latter!";
 
 	protected static final Logger LOGGER = LoggerFactory.getLogger(MappingMongoConverter.class);
 
@@ -94,9 +87,9 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	protected final DbRefResolver dbRefResolver;
 	protected final DefaultDbRefProxyHandler dbRefProxyHandler;
 
-	protected ApplicationContext applicationContext;
+	protected @Nullable ApplicationContext applicationContext;
 	protected MongoTypeMapper typeMapper;
-	protected String mapKeyDotReplacement = null;
+	protected @Nullable String mapKeyDotReplacement = null;
 
 	private SpELContext spELContext;
 
@@ -142,11 +135,12 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * {@link DefaultMongoTypeMapper} by default. Setting this to {@literal null} will reset the {@link TypeMapper} to the
 	 * default one.
 	 *
-	 * @param typeMapper the typeMapper to set
+	 * @param typeMapper the typeMapper to set. Can be {@literal null}.
 	 */
-	public void setTypeMapper(MongoTypeMapper typeMapper) {
+	public void setTypeMapper(@Nullable MongoTypeMapper typeMapper) {
 		this.typeMapper = typeMapper == null
-				? new DefaultMongoTypeMapper(DefaultMongoTypeMapper.DEFAULT_TYPE_KEY, mappingContext) : typeMapper;
+				? new DefaultMongoTypeMapper(DefaultMongoTypeMapper.DEFAULT_TYPE_KEY, mappingContext)
+				: typeMapper;
 	}
 
 	/*
@@ -164,9 +158,9 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * object to fail. If further customization of the translation is needed, have a look at
 	 * {@link #potentiallyEscapeMapKey(String)} as well as {@link #potentiallyUnescapeMapKey(String)}.
 	 *
-	 * @param mapKeyDotReplacement the mapKeyDotReplacement to set
+	 * @param mapKeyDotReplacement the mapKeyDotReplacement to set. Can be {@literal null}.
 	 */
-	public void setMapKeyDotReplacement(String mapKeyDotReplacement) {
+	public void setMapKeyDotReplacement(@Nullable String mapKeyDotReplacement) {
 		this.mapKeyDotReplacement = mapKeyDotReplacement;
 	}
 
@@ -200,8 +194,9 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		return read(type, bson, ObjectPath.ROOT);
 	}
 
+	@Nullable
 	@SuppressWarnings("unchecked")
-	private <S extends Object> S read(TypeInformation<S> type, Bson bson, ObjectPath path) {
+	private <S extends Object> S read(TypeInformation<S> type, @Nullable Bson bson, ObjectPath path) {
 
 		if (null == bson) {
 			return null;
@@ -241,11 +236,17 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 
 		Document target = bson instanceof BasicDBObject ? new Document((BasicDBObject) bson) : (Document) bson;
 
-		return read((MongoPersistentEntity<S>) mappingContext.getRequiredPersistentEntity(typeToUse), target, path);
+		MongoPersistentEntity<?> entity = mappingContext.getPersistentEntity(typeToUse);
+
+		if (entity == null) {
+			throw new MappingException(String.format(INVALID_TYPE_TO_READ, target, typeToUse.getType()));
+		}
+
+		return read((MongoPersistentEntity<S>) entity, target, path);
 	}
 
 	private ParameterValueProvider<MongoPersistentProperty> getParameterProvider(MongoPersistentEntity<?> entity,
-			Bson source, DefaultSpELExpressionEvaluator evaluator, ObjectPath path) {
+			DocumentAccessor source, DefaultSpELExpressionEvaluator evaluator, ObjectPath path) {
 
 		MongoDbPropertyValueProvider provider = new MongoDbPropertyValueProvider(source, evaluator, path);
 		PersistentEntityParameterValueProvider<MongoPersistentProperty> parameterProvider = new PersistentEntityParameterValueProvider<>(
@@ -258,8 +259,14 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	private <S extends Object> S read(final MongoPersistentEntity<S> entity, final Document bson, final ObjectPath path) {
 
 		DefaultSpELExpressionEvaluator evaluator = new DefaultSpELExpressionEvaluator(bson, spELContext);
+		DocumentAccessor documentAccessor = new DocumentAccessor(bson);
+
+		PreferredConstructor<S, MongoPersistentProperty> constructor = entity.getPersistenceConstructor();
+
+		ParameterValueProvider<MongoPersistentProperty> provider = constructor != null && constructor.hasParameters() //
+				? getParameterProvider(entity, documentAccessor, evaluator, path) //
+				: NoOpParameterValueProvider.INSTANCE;
 
-		ParameterValueProvider<MongoPersistentProperty> provider = getParameterProvider(entity, bson, evaluator, path);
 		EntityInstantiator instantiator = instantiators.getInstantiatorFor(entity);
 		S instance = instantiator.createInstance(entity, provider);
 
@@ -267,7 +274,6 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 				conversionService);
 
 		MongoPersistentProperty idProperty = entity.getIdProperty();
-		DocumentAccessor documentAccessor = new DocumentAccessor(bson);
 
 		// make sure id property is set before all other properties
 		Object idValue = null;
@@ -283,9 +289,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		MongoDbPropertyValueProvider valueProvider = new MongoDbPropertyValueProvider(documentAccessor, evaluator,
 				currentPath);
 
-		DbRefResolverCallback callback = new DefaultDbRefResolverCallback(bson, currentPath, evaluator,
-				MappingMongoConverter.this);
-		readProperties(entity, accessor, idProperty, documentAccessor, valueProvider, callback);
+		readProperties(entity, accessor, idProperty, documentAccessor, valueProvider, currentPath, evaluator);
 
 		return instance;
 	}
@@ -300,14 +304,19 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	}
 
 	private void readProperties(MongoPersistentEntity<?> entity, PersistentPropertyAccessor accessor,
-			MongoPersistentProperty idProperty, DocumentAccessor documentAccessor,
-			MongoDbPropertyValueProvider valueProvider, DbRefResolverCallback callback) {
+			@Nullable MongoPersistentProperty idProperty, DocumentAccessor documentAccessor,
+			MongoDbPropertyValueProvider valueProvider, ObjectPath currentPath, SpELExpressionEvaluator evaluator) {
 
+		DbRefResolverCallback callback = null;
 
 		for (MongoPersistentProperty prop : entity) {
 
-			if(prop.isAssociation() && !entity.isConstructorArgument(prop)) {
-				readAssociation(prop.getAssociation(), accessor, documentAccessor, dbRefProxyHandler, callback );
+			if (callback == null) {
+				callback = getDbRefResolverCallback(documentAccessor, currentPath, evaluator);
+			}
+
+			if (prop.isAssociation() && !entity.isConstructorArgument(prop)) {
+				readAssociation(prop.getRequiredAssociation(), accessor, documentAccessor, dbRefProxyHandler, callback);
 				continue;
 			}
 			// we skip the id property since it was already set
@@ -319,8 +328,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 				continue;
 			}
 
-			if(prop.isAssociation()) {
-				readAssociation(prop.getAssociation(), accessor, documentAccessor, dbRefProxyHandler, callback );
+			if (prop.isAssociation()) {
+				readAssociation(prop.getRequiredAssociation(), accessor, documentAccessor, dbRefProxyHandler, callback);
 				continue;
 			}
 
@@ -328,27 +337,34 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 	}
 
+	private DbRefResolverCallback getDbRefResolverCallback(DocumentAccessor documentAccessor, ObjectPath currentPath,
+			SpELExpressionEvaluator evaluator) {
+
+		return new DefaultDbRefResolverCallback(documentAccessor.getDocument(), currentPath, evaluator,
+				MappingMongoConverter.this);
+	}
+
 	private void readAssociation(Association<MongoPersistentProperty> association, PersistentPropertyAccessor accessor,
 			DocumentAccessor documentAccessor, DbRefProxyHandler handler, DbRefResolverCallback callback) {
 
-			MongoPersistentProperty property = association.getInverse();
-			Object value = documentAccessor.get(property);
+		MongoPersistentProperty property = association.getInverse();
+		Object value = documentAccessor.get(property);
 
-			if (value == null) {
-				return;
-			}
+		if (value == null) {
+			return;
+		}
 
-			DBRef dbref = value instanceof DBRef ? (DBRef) value : null;
-			accessor.setProperty(property, dbRefResolver.resolveDbRef(property, dbref, callback, handler));
+		DBRef dbref = value instanceof DBRef ? (DBRef) value : null;
+		accessor.setProperty(property, dbRefResolver.resolveDbRef(property, dbref, callback, handler));
 	}
 
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.convert.MongoWriter#toDBRef(java.lang.Object, org.springframework.data.mongodb.core.mapping.MongoPersistentProperty)
 	 */
-	public DBRef toDBRef(Object object, MongoPersistentProperty referringProperty) {
+	public DBRef toDBRef(Object object, @Nullable MongoPersistentProperty referringProperty) {
 
-		org.springframework.data.mongodb.core.mapping.DBRef annotation = null;
+		org.springframework.data.mongodb.core.mapping.DBRef annotation;
 
 		if (referringProperty != null) {
 			annotation = referringProperty.getDBRef();
@@ -369,7 +385,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 *
 	 * @see org.springframework.data.mongodb.core.convert.MongoWriter#write(java.lang.Object, com.mongodb.Document)
 	 */
-	public void write(final Object obj, final Bson bson) {
+	public void write(Object obj, Bson bson) {
 
 		if (null == obj) {
 			return;
@@ -385,20 +401,32 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			removeFromMap(bson, "_id");
 		}
 
-		boolean handledByCustomConverter = conversions.hasCustomWriteTarget(entityType, Document.class);
-		if (!handledByCustomConverter && !(bson instanceof Collection)) {
+		if (requiresTypeHint(entityType)) {
 			typeMapper.writeType(type, bson);
 		}
 	}
 
+	/**
+	 * Check if a given type requires a type hint (aka {@literal _class} attribute) when writing to the document.
+	 *
+	 * @param type must not be {@literal null}.
+	 * @return {@literal true} if not a simple type, {@link Collection} or type with custom write target.
+	 */
+	private boolean requiresTypeHint(Class<?> type) {
+
+		return !conversions.isSimpleType(type) && !ClassUtils.isAssignable(Collection.class, type)
+				&& !conversions.hasCustomWriteTarget(type, Document.class);
+	}
+
 	/**
 	 * Internal write conversion method which should be used for nested invocations.
 	 *
 	 * @param obj
 	 * @param bson
+	 * @param typeHint
 	 */
 	@SuppressWarnings("unchecked")
-	protected void writeInternal(final Object obj, final Bson bson, final TypeInformation<?> typeHint) {
+	protected void writeInternal(@Nullable Object obj, Bson bson, @Nullable TypeInformation<?> typeHint) {
 
 		if (null == obj) {
 			return;
@@ -419,7 +447,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 
 		if (Collection.class.isAssignableFrom(entityType)) {
-			writeCollectionInternal((Collection<?>) obj, ClassTypeInformation.LIST, (BasicDBList) bson);
+			writeCollectionInternal((Collection<?>) obj, ClassTypeInformation.LIST, (Collection) bson);
 			return;
 		}
 
@@ -428,7 +456,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		addCustomTypeKeyIfNecessary(typeHint, obj, bson);
 	}
 
-	protected void writeInternal(Object obj, final Bson bson, MongoPersistentEntity<?> entity) {
+	protected void writeInternal(@Nullable Object obj, Bson bson, @Nullable MongoPersistentEntity<?> entity) {
 
 		if (obj == null) {
 			return;
@@ -454,17 +482,16 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	}
 
 	private void writeProperties(Bson bson, MongoPersistentEntity<?> entity, PersistentPropertyAccessor accessor,
-			DocumentAccessor dbObjectAccessor, MongoPersistentProperty idProperty) {
+			DocumentAccessor dbObjectAccessor, @Nullable MongoPersistentProperty idProperty) {
 
 		// Write the properties
 		for (MongoPersistentProperty prop : entity) {
 
-
 			if (prop.equals(idProperty) || !prop.isWritable()) {
 				continue;
 			}
-			if(prop.isAssociation()) {
-				writeAssociation(prop.getAssociation(), accessor, dbObjectAccessor);
+			if (prop.isAssociation()) {
+				writeAssociation(prop.getRequiredAssociation(), accessor, dbObjectAccessor);
 				continue;
 			}
 
@@ -485,13 +512,13 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	private void writeAssociation(Association<MongoPersistentProperty> association, PersistentPropertyAccessor accessor,
 			DocumentAccessor dbObjectAccessor) {
 
-			MongoPersistentProperty inverseProp = association.getInverse();
+		MongoPersistentProperty inverseProp = association.getInverse();
 
-			writePropertyInternal(accessor.getProperty(inverseProp), dbObjectAccessor, inverseProp);
+		writePropertyInternal(accessor.getProperty(inverseProp), dbObjectAccessor, inverseProp);
 	}
 
 	@SuppressWarnings({ "unchecked" })
-	protected void writePropertyInternal(Object obj, DocumentAccessor accessor, MongoPersistentProperty prop) {
+	protected void writePropertyInternal(@Nullable Object obj, DocumentAccessor accessor, MongoPersistentProperty prop) {
 
 		if (obj == null) {
 			return;
@@ -549,7 +576,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 
 		MongoPersistentEntity<?> entity = isSubtype(prop.getType(), obj.getClass())
-				? mappingContext.getRequiredPersistentEntity(obj.getClass()) : mappingContext.getRequiredPersistentEntity(type);
+				? mappingContext.getRequiredPersistentEntity(obj.getClass())
+				: mappingContext.getRequiredPersistentEntity(type);
 
 		Object existingValue = accessor.get(prop);
 		Document document = existingValue instanceof Document ? (Document) existingValue : new Document();
@@ -645,17 +673,21 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	}
 
 	/**
-	 * Populates the given {@link BasicDBList} with values from the given {@link Collection}.
+	 * Populates the given {@link Collection sink} with converted values from the given {@link Collection source}.
 	 *
-	 * @param source the collection to create a {@link BasicDBList} for, must not be {@literal null}.
+	 * @param source the collection to create a {@link Collection} for, must not be {@literal null}.
 	 * @param type the {@link TypeInformation} to consider or {@literal null} if unknown.
-	 * @param sink the {@link BasicDBList} to write to.
+	 * @param sink the {@link Collection} to write to.
 	 * @return
 	 */
-	private BasicDBList writeCollectionInternal(Collection<?> source, TypeInformation<?> type, BasicDBList sink) {
+	@SuppressWarnings("unchecked")
+	private List<Object> writeCollectionInternal(Collection<?> source, @Nullable TypeInformation<?> type,
+			Collection<?> sink) {
 
 		TypeInformation<?> componentType = null;
 
+		List<Object> collection = sink instanceof List ? (List<Object>) sink : new ArrayList<>(sink);
+
 		if (type != null) {
 			componentType = type.getComponentType();
 		}
@@ -665,17 +697,17 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			Class<?> elementType = element == null ? null : element.getClass();
 
 			if (elementType == null || conversions.isSimpleType(elementType)) {
-				sink.add(getPotentiallyConvertedSimpleWrite(element));
+				collection.add(getPotentiallyConvertedSimpleWrite(element));
 			} else if (element instanceof Collection || elementType.isArray()) {
-				sink.add(writeCollectionInternal(asCollection(element), componentType, new BasicDBList()));
+				collection.add(writeCollectionInternal(asCollection(element), componentType, new BasicDBList()));
 			} else {
 				Document document = new Document();
 				writeInternal(element, document, componentType);
-				sink.add(document);
+				collection.add(document);
 			}
 		}
 
-		return sink;
+		return collection;
 	}
 
 	/**
@@ -768,7 +800,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 
 		return conversions.hasCustomWriteTarget(key.getClass(), String.class)
-				? (String) getPotentiallyConvertedSimpleWrite(key) : key.toString();
+				? (String) getPotentiallyConvertedSimpleWrite(key)
+				: key.toString();
 	}
 
 	/**
@@ -790,7 +823,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * @param value must not be {@literal null}.
 	 * @param bson must not be {@literal null}.
 	 */
-	protected void addCustomTypeKeyIfNecessary(TypeInformation<?> type, Object value, Bson bson) {
+	protected void addCustomTypeKeyIfNecessary(@Nullable TypeInformation<?> type, Object value, Bson bson) {
 
 		Class<?> reference = type != null ? type.getActualType().getType() : Object.class;
 		Class<?> valueType = ClassUtils.getUserClass(value.getClass());
@@ -824,7 +857,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * @param value
 	 * @return
 	 */
-	private Object getPotentiallyConvertedSimpleWrite(Object value) {
+	@Nullable
+	private Object getPotentiallyConvertedSimpleWrite(@Nullable Object value) {
 
 		if (value == null) {
 			return null;
@@ -855,10 +889,11 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * @param target must not be {@literal null}.
 	 * @return
 	 */
+	@Nullable
 	@SuppressWarnings({ "rawtypes", "unchecked" })
-	private Object getPotentiallyConvertedSimpleRead(Object value, Class<?> target) {
+	private Object getPotentiallyConvertedSimpleRead(@Nullable Object value, @Nullable Class<?> target) {
 
-		if (value == null || target == null || target.isAssignableFrom(value.getClass())) {
+		if (value == null || target == null || ClassUtils.isAssignableValue(target, value)) {
 			return value;
 		}
 
@@ -921,58 +956,61 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * Reads the given {@link BasicDBList} into a collection of the given {@link TypeInformation}.
 	 *
 	 * @param targetType must not be {@literal null}.
-	 * @param sourceValue must not be {@literal null}.
+	 * @param source must not be {@literal null}.
 	 * @param path must not be {@literal null}.
 	 * @return the converted {@link Collection} or array, will never be {@literal null}.
 	 */
-	@SuppressWarnings({ "rawtypes", "unchecked" })
-	private Object readCollectionOrArray(TypeInformation<?> targetType, List sourceValue, ObjectPath path) {
+	@SuppressWarnings("unchecked")
+	private Object readCollectionOrArray(TypeInformation<?> targetType, Collection<?> source, ObjectPath path) {
 
 		Assert.notNull(targetType, "Target type must not be null!");
 		Assert.notNull(path, "Object path must not be null!");
 
 		Class<?> collectionType = targetType.getType();
+		collectionType = Collection.class.isAssignableFrom(collectionType) //
+				? collectionType //
+				: List.class;
 
-		TypeInformation<?> componentType = targetType.getComponentType() != null ? targetType.getComponentType()
+		TypeInformation<?> componentType = targetType.getComponentType() != null //
+				? targetType.getComponentType() //
 				: ClassTypeInformation.OBJECT;
 		Class<?> rawComponentType = componentType.getType();
 
-		collectionType = Collection.class.isAssignableFrom(collectionType) ? collectionType : List.class;
-		Collection<Object> items = targetType.getType().isArray() ? new ArrayList<>(sourceValue.size())
-				: CollectionFactory.createCollection(collectionType, rawComponentType, sourceValue.size());
+		Collection<Object> items = targetType.getType().isArray() //
+				? new ArrayList<>(source.size()) //
+				: CollectionFactory.createCollection(collectionType, rawComponentType, source.size());
 
-		if (sourceValue.isEmpty()) {
-			return getPotentiallyConvertedSimpleRead(items, collectionType);
+		if (source.isEmpty()) {
+			return getPotentiallyConvertedSimpleRead(items, targetType.getType());
 		}
 
-		if (!DBRef.class.equals(rawComponentType) && isCollectionOfDbRefWhereBulkFetchIsPossible(sourceValue)) {
+		if (!DBRef.class.equals(rawComponentType) && isCollectionOfDbRefWhereBulkFetchIsPossible(source)) {
 
-			List<Object> objects = bulkReadAndConvertDBRefs((List<DBRef>) sourceValue, componentType, path, rawComponentType);
+			List<Object> objects = bulkReadAndConvertDBRefs((List<DBRef>) source, componentType, path, rawComponentType);
 			return getPotentiallyConvertedSimpleRead(objects, targetType.getType());
 		}
 
-		for (Object dbObjItem : sourceValue) {
+		for (Object element : source) {
 
-			if (dbObjItem instanceof DBRef) {
-				items.add(DBRef.class.equals(rawComponentType) ? dbObjItem
-						: readAndConvertDBRef((DBRef) dbObjItem, componentType, path, rawComponentType));
-			} else if (dbObjItem instanceof Document) {
-				items.add(read(componentType, (Document) dbObjItem, path));
-			} else if (dbObjItem instanceof BasicDBObject) {
-				items.add(read(componentType, (BasicDBObject) dbObjItem, path));
+			if (element instanceof DBRef) {
+				items.add(DBRef.class.equals(rawComponentType) ? element
+						: readAndConvertDBRef((DBRef) element, componentType, path, rawComponentType));
+			} else if (element instanceof Document) {
+				items.add(read(componentType, (Document) element, path));
+			} else if (element instanceof BasicDBObject) {
+				items.add(read(componentType, (BasicDBObject) element, path));
 			} else {
 
-				if (dbObjItem instanceof Collection) {
+				if (!Object.class.equals(rawComponentType) && element instanceof Collection) {
 					if (!rawComponentType.isArray() && !ClassUtils.isAssignable(Iterable.class, rawComponentType)) {
 						throw new MappingException(
-								String.format(INCOMPATIBLE_TYPES, dbObjItem, dbObjItem.getClass(), rawComponentType, path));
+								String.format(INCOMPATIBLE_TYPES, element, element.getClass(), rawComponentType, path));
 					}
 				}
-
-				if (dbObjItem instanceof List) {
-					items.add(readCollectionOrArray(ClassTypeInformation.OBJECT, (List) dbObjItem, path));
+				if (element instanceof List) {
+					items.add(readCollectionOrArray(componentType, (Collection<Object>) element, path));
 				} else {
-					items.add(getPotentiallyConvertedSimpleRead(dbObjItem, rawComponentType));
+					items.add(getPotentiallyConvertedSimpleRead(element, rawComponentType));
 				}
 			}
 		}
@@ -1033,8 +1071,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 				map.put(key, DBRef.class.equals(rawValueType) ? value
 						: readAndConvertDBRef((DBRef) value, defaultedValueType, ObjectPath.ROOT, rawValueType));
 			} else if (value instanceof List) {
-				map.put(key,
-						readCollectionOrArray(valueType != null ? valueType : ClassTypeInformation.LIST, (List) value, path));
+				map.put(key, readCollectionOrArray(valueType != null ? valueType : ClassTypeInformation.LIST,
+						(List<Object>) value, path));
 			} else {
 				map.put(key, getPotentiallyConvertedSimpleRead(value, rawValueType));
 			}
@@ -1058,7 +1096,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 				String.format("Cannot read %s. as map. Given Bson must be a Document or DBObject!", bson.getClass()));
 	}
 
-	private static void addToMap(Bson bson, String key, Object value) {
+	private static void addToMap(Bson bson, String key, @Nullable Object value) {
 
 		if (bson instanceof Document) {
 			((Document) bson).put(key, value);
@@ -1072,8 +1110,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 				"Cannot add key/value pair to %s. as map. Given Bson must be a Document or DBObject!", bson.getClass()));
 	}
 
-	@SuppressWarnings("unchecked")
-	private static void addAllToMap(Bson bson, Map value) {
+	private static void addAllToMap(Bson bson, Map<String, ?> value) {
 
 		if (bson instanceof Document) {
 			((Document) bson).putAll(value);
@@ -1109,8 +1146,10 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.convert.MongoWriter#convertToMongoType(java.lang.Object, org.springframework.data.util.TypeInformation)
 	 */
+	@Nullable
 	@SuppressWarnings("unchecked")
-	public Object convertToMongoType(Object obj, TypeInformation<?> typeInformation) {
+	@Override
+	public Object convertToMongoType(@Nullable Object obj, TypeInformation<?> typeInformation) {
 
 		if (obj == null) {
 			return null;
@@ -1126,10 +1165,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			return getPotentiallyConvertedSimpleWrite(obj);
 		}
 
-		TypeInformation<?> typeHint = typeInformation;
-
 		if (obj instanceof List) {
-			return maybeConvertList((List<Object>) obj, typeHint);
+			return maybeConvertList((List<Object>) obj, typeInformation);
 		}
 
 		if (obj instanceof Document) {
@@ -1137,7 +1174,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			Document newValueDocument = new Document();
 			for (String vk : ((Document) obj).keySet()) {
 				Object o = ((Document) obj).get(vk);
-				newValueDocument.put(vk, convertToMongoType(o, typeHint));
+				newValueDocument.put(vk, convertToMongoType(o, typeInformation));
 			}
 			return newValueDocument;
 		}
@@ -1148,7 +1185,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			for (String vk : ((DBObject) obj).keySet()) {
 
 				Object o = ((DBObject) obj).get(vk);
-				newValueDbo.put(vk, convertToMongoType(o, typeHint));
+				newValueDbo.put(vk, convertToMongoType(o, typeInformation));
 			}
 
 			return newValueDbo;
@@ -1159,18 +1196,18 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			Document result = new Document();
 
 			for (Map.Entry<Object, Object> entry : ((Map<Object, Object>) obj).entrySet()) {
-				result.put(entry.getKey().toString(), convertToMongoType(entry.getValue(), typeHint));
+				result.put(entry.getKey().toString(), convertToMongoType(entry.getValue(), typeInformation));
 			}
 
 			return result;
 		}
 
 		if (obj.getClass().isArray()) {
-			return maybeConvertList(Arrays.asList((Object[]) obj), typeHint);
+			return maybeConvertList(Arrays.asList((Object[]) obj), typeInformation);
 		}
 
 		if (obj instanceof Collection) {
-			return maybeConvertList((Collection<?>) obj, typeHint);
+			return maybeConvertList((Collection<?>) obj, typeInformation);
 		}
 
 		Document newDocument = new Document();
@@ -1205,6 +1242,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * @param recursively whether to apply the removal recursively
 	 * @return
 	 */
+	@SuppressWarnings("unchecked")
 	private Object removeTypeInfo(Object object, boolean recursively) {
 
 		if (!(object instanceof Document)) {
@@ -1225,7 +1263,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 						removeTypeInfo(element, recursively);
 					}
 				} else if (value instanceof List) {
-					for (Object element : (List) value) {
+					for (Object element : (List<Object>) value) {
 						removeTypeInfo(element, recursively);
 					}
 				} else {
@@ -1268,7 +1306,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		 *
 		 * @param source must not be {@literal null}.
 		 * @param evaluator must not be {@literal null}.
-		 * @param path can be {@literal null}.
+		 * @param path must not be {@literal null}.
 		 */
 		public MongoDbPropertyValueProvider(Bson source, SpELExpressionEvaluator evaluator, ObjectPath path) {
 
@@ -1287,7 +1325,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		 *
 		 * @param accessor must not be {@literal null}.
 		 * @param evaluator must not be {@literal null}.
-		 * @param path can be {@literal null}.
+		 * @param path must not be {@literal null}.
 		 */
 		public MongoDbPropertyValueProvider(DocumentAccessor accessor, SpELExpressionEvaluator evaluator, ObjectPath path) {
 
@@ -1304,6 +1342,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		 * (non-Javadoc)
 		 * @see org.springframework.data.convert.PropertyValueProvider#getPropertyValue(org.springframework.data.mapping.PersistentProperty)
 		 */
+		@Nullable
 		public <T> T getPropertyValue(MongoPersistentProperty property) {
 
 			String expression = property.getSpelExpression();
@@ -1353,6 +1392,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 	}
 
+	@Nullable
 	@SuppressWarnings("unchecked")
 	<T> T readValue(Object value, TypeInformation<?> type, ObjectPath path) {
 
@@ -1363,7 +1403,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		} else if (value instanceof DBRef) {
 			return potentiallyReadOrResolveDbRef((DBRef) value, type, path, rawType);
 		} else if (value instanceof List) {
-			return (T) readCollectionOrArray(type, (List) value, path);
+			return (T) readCollectionOrArray(type, (List<Object>) value, path);
 		} else if (value instanceof Document) {
 			return (T) read(type, (Document) value, path);
 		} else if (value instanceof DBObject) {
@@ -1373,18 +1413,22 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 	}
 
+	@Nullable
 	@SuppressWarnings("unchecked")
-	private <T> T potentiallyReadOrResolveDbRef(DBRef dbref, TypeInformation<?> type, ObjectPath path, Class<?> rawType) {
+	private <T> T potentiallyReadOrResolveDbRef(@Nullable DBRef dbref, TypeInformation<?> type, ObjectPath path,
+			Class<?> rawType) {
 
 		if (rawType.equals(DBRef.class)) {
 			return (T) dbref;
 		}
 
-		T object =  dbref == null ? null : path.getPathItem(dbref.getId(), dbref.getCollectionName(), (Class<T>) rawType);
+		T object = dbref == null ? null : path.getPathItem(dbref.getId(), dbref.getCollectionName(), (Class<T>) rawType);
 		return object != null ? object : readAndConvertDBRef(dbref, type, path, rawType);
 	}
 
-	private <T> T readAndConvertDBRef(DBRef dbref, TypeInformation<?> type, ObjectPath path, final Class<?> rawType) {
+	@Nullable
+	private <T> T readAndConvertDBRef(@Nullable DBRef dbref, TypeInformation<?> type, ObjectPath path,
+			final Class<?> rawType) {
 
 		List<T> result = bulkReadAndConvertDBRefs(Collections.singletonList(dbref), type, path, rawType);
 		return CollectionUtils.isEmpty(result) ? null : result.iterator().next();
@@ -1414,7 +1458,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 
 		List<Document> referencedRawDocuments = dbrefs.size() == 1
-				? Collections.singletonList(readRef(dbrefs.iterator().next())) : bulkReadRefs(dbrefs);
+				? Collections.singletonList(readRef(dbrefs.iterator().next()))
+				: bulkReadRefs(dbrefs);
 		String collectionName = dbrefs.iterator().next().getCollectionName();
 
 		List<T> targeList = new ArrayList<>(dbrefs.size());
@@ -1474,7 +1519,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * @param source must not be {@literal null}.
 	 * @return
 	 */
-	private static boolean isCollectionOfDbRefWhereBulkFetchIsPossible(Iterable<Object> source) {
+	private static boolean isCollectionOfDbRefWhereBulkFetchIsPossible(Iterable<?> source) {
 
 		Assert.notNull(source, "Iterable of DBRefs must not be null!");
 
@@ -1506,4 +1551,14 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	static class NestedDocument {
 
 	}
+
+	enum NoOpParameterValueProvider implements ParameterValueProvider<MongoPersistentProperty> {
+
+		INSTANCE;
+
+		@Override
+		public <T> T getParameterValue(Parameter<T, MongoPersistentProperty> parameter) {
+			return null;
+		}
+	}
 }

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

@@ -1,44 +1,44 @@
-/*
- * Copyright 2010-2016 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core.convert;
-
-import org.bson.Document;
-import org.bson.conversions.Bson;
-import org.springframework.data.convert.EntityConverter;
-import org.springframework.data.convert.EntityReader;
-import org.springframework.data.convert.TypeMapper;
-import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
-import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
-
-/**
- * Central Mongo specific converter interface which combines {@link MongoWriter} and {@link MongoReader}.
- * 
- * @author Oliver Gierke
- * @author Thomas Darimont
- * @author Christoph Strobl
- */
-public interface MongoConverter
-		extends EntityConverter<MongoPersistentEntity<?>, MongoPersistentProperty, Object, Bson>, MongoWriter<Object>,
-		EntityReader<Object, Bson> {
-
-	/**
-	 * Returns thw {@link TypeMapper} being used to write type information into {@link Document}s created with that
-	 * converter.
-	 * 
-	 * @return will never be {@literal null}.
-	 */
-	MongoTypeMapper getTypeMapper();
-}
+/*
+ * Copyright 2010-2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.convert;
+
+import org.bson.Document;
+import org.bson.conversions.Bson;
+import org.springframework.data.convert.EntityConverter;
+import org.springframework.data.convert.EntityReader;
+import org.springframework.data.convert.TypeMapper;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+
+/**
+ * Central Mongo specific converter interface which combines {@link MongoWriter} and {@link MongoReader}.
+ * 
+ * @author Oliver Gierke
+ * @author Thomas Darimont
+ * @author Christoph Strobl
+ */
+public interface MongoConverter
+		extends EntityConverter<MongoPersistentEntity<?>, MongoPersistentProperty, Object, Bson>, MongoWriter<Object>,
+		EntityReader<Object, Bson> {
+
+	/**
+	 * Returns thw {@link TypeMapper} being used to write type information into {@link Document}s created with that
+	 * converter.
+	 * 
+	 * @return will never be {@literal null}.
+	 */
+	MongoTypeMapper getTypeMapper();
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2016 the original author or authors.
+ * Copyright 2011-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,8 +15,6 @@
  */
 package org.springframework.data.mongodb.core.convert;
 
-import reactor.core.publisher.Flux;
-
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.net.MalformedURLException;
@@ -29,9 +27,9 @@ import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
 
 import org.bson.Document;
+import org.bson.types.Binary;
 import org.bson.types.Code;
 import org.bson.types.ObjectId;
-import org.reactivestreams.Publisher;
 import org.springframework.core.convert.ConversionFailedException;
 import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.core.convert.converter.ConditionalConverter;
@@ -41,6 +39,7 @@ import org.springframework.data.convert.ReadingConverter;
 import org.springframework.data.convert.WritingConverter;
 import org.springframework.data.mongodb.core.query.Term;
 import org.springframework.data.mongodb.core.script.NamedMongoScript;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.NumberUtils;
 import org.springframework.util.StringUtils;
@@ -66,9 +65,9 @@ abstract class MongoConverters {
 	 * @return
 	 * @since 1.9
 	 */
-	public static Collection<Object> getConvertersToRegister() {
+	static Collection<Object> getConvertersToRegister() {
 
-		List<Object> converters = new ArrayList<Object>();
+		List<Object> converters = new ArrayList<>();
 
 		converters.add(BigDecimalToStringConverter.INSTANCE);
 		converters.add(StringToBigDecimalConverter.INSTANCE);
@@ -86,6 +85,7 @@ abstract class MongoConverters {
 		converters.add(AtomicLongToLongConverter.INSTANCE);
 		converters.add(LongToAtomicLongConverter.INSTANCE);
 		converters.add(IntegerToAtomicIntegerConverter.INSTANCE);
+		converters.add(BinaryToByteArrayConverter.INSTANCE);
 
 		return converters;
 	}
@@ -95,7 +95,7 @@ abstract class MongoConverters {
 	 *
 	 * @author Oliver Gierke
 	 */
-	public static enum ObjectIdToStringConverter implements Converter<ObjectId, String> {
+	enum ObjectIdToStringConverter implements Converter<ObjectId, String> {
 		INSTANCE;
 
 		public String convert(ObjectId id) {
@@ -108,7 +108,7 @@ abstract class MongoConverters {
 	 *
 	 * @author Oliver Gierke
 	 */
-	public static enum StringToObjectIdConverter implements Converter<String, ObjectId> {
+	enum StringToObjectIdConverter implements Converter<String, ObjectId> {
 		INSTANCE;
 
 		public ObjectId convert(String source) {
@@ -121,7 +121,7 @@ abstract class MongoConverters {
 	 *
 	 * @author Oliver Gierke
 	 */
-	public static enum ObjectIdToBigIntegerConverter implements Converter<ObjectId, BigInteger> {
+	enum ObjectIdToBigIntegerConverter implements Converter<ObjectId, BigInteger> {
 		INSTANCE;
 
 		public BigInteger convert(ObjectId source) {
@@ -134,7 +134,7 @@ abstract class MongoConverters {
 	 *
 	 * @author Oliver Gierke
 	 */
-	public static enum BigIntegerToObjectIdConverter implements Converter<BigInteger, ObjectId> {
+	enum BigIntegerToObjectIdConverter implements Converter<BigInteger, ObjectId> {
 		INSTANCE;
 
 		public ObjectId convert(BigInteger source) {
@@ -142,7 +142,7 @@ abstract class MongoConverters {
 		}
 	}
 
-	public static enum BigDecimalToStringConverter implements Converter<BigDecimal, String> {
+	enum BigDecimalToStringConverter implements Converter<BigDecimal, String> {
 		INSTANCE;
 
 		public String convert(BigDecimal source) {
@@ -150,7 +150,7 @@ abstract class MongoConverters {
 		}
 	}
 
-	public static enum StringToBigDecimalConverter implements Converter<String, BigDecimal> {
+	enum StringToBigDecimalConverter implements Converter<String, BigDecimal> {
 		INSTANCE;
 
 		public BigDecimal convert(String source) {
@@ -158,7 +158,7 @@ abstract class MongoConverters {
 		}
 	}
 
-	public static enum BigIntegerToStringConverter implements Converter<BigInteger, String> {
+	enum BigIntegerToStringConverter implements Converter<BigInteger, String> {
 		INSTANCE;
 
 		public String convert(BigInteger source) {
@@ -166,7 +166,7 @@ abstract class MongoConverters {
 		}
 	}
 
-	public static enum StringToBigIntegerConverter implements Converter<String, BigInteger> {
+	enum StringToBigIntegerConverter implements Converter<String, BigInteger> {
 		INSTANCE;
 
 		public BigInteger convert(String source) {
@@ -174,7 +174,7 @@ abstract class MongoConverters {
 		}
 	}
 
-	public static enum URLToStringConverter implements Converter<URL, String> {
+	enum URLToStringConverter implements Converter<URL, String> {
 		INSTANCE;
 
 		public String convert(URL source) {
@@ -182,7 +182,7 @@ abstract class MongoConverters {
 		}
 	}
 
-	public static enum StringToURLConverter implements Converter<String, URL> {
+	enum StringToURLConverter implements Converter<String, URL> {
 		INSTANCE;
 
 		private static final TypeDescriptor SOURCE = TypeDescriptor.valueOf(String.class);
@@ -199,7 +199,7 @@ abstract class MongoConverters {
 	}
 
 	@ReadingConverter
-	public static enum DocumentToStringConverter implements Converter<Document, String> {
+	enum DocumentToStringConverter implements Converter<Document, String> {
 
 		INSTANCE;
 
@@ -219,7 +219,7 @@ abstract class MongoConverters {
 	 * @since 1.6
 	 */
 	@WritingConverter
-	public static enum TermToStringConverter implements Converter<Term, String> {
+	enum TermToStringConverter implements Converter<Term, String> {
 
 		INSTANCE;
 
@@ -233,7 +233,7 @@ abstract class MongoConverters {
 	 * @author Christoph Strobl
 	 * @since 1.7
 	 */
-	public static enum DocumentToNamedMongoScriptConverter implements Converter<Document, NamedMongoScript> {
+	enum DocumentToNamedMongoScriptConverter implements Converter<Document, NamedMongoScript> {
 
 		INSTANCE;
 
@@ -255,7 +255,7 @@ abstract class MongoConverters {
 	 * @author Christoph Strobl
 	 * @since 1.7
 	 */
-	public static enum NamedMongoScriptToDocumentConverter implements Converter<NamedMongoScript, Document> {
+	enum NamedMongoScriptToDocumentConverter implements Converter<NamedMongoScript, Document> {
 
 		INSTANCE;
 
@@ -282,7 +282,7 @@ abstract class MongoConverters {
 	 * @since 1.9
 	 */
 	@WritingConverter
-	public static enum CurrencyToStringConverter implements Converter<Currency, String> {
+	enum CurrencyToStringConverter implements Converter<Currency, String> {
 
 		INSTANCE;
 
@@ -303,7 +303,7 @@ abstract class MongoConverters {
 	 * @since 1.9
 	 */
 	@ReadingConverter
-	public static enum StringToCurrencyConverter implements Converter<String, Currency> {
+	enum StringToCurrencyConverter implements Converter<String, Currency> {
 
 		INSTANCE;
 
@@ -326,7 +326,7 @@ abstract class MongoConverters {
 	 * @since 1.9
 	 */
 	@WritingConverter
-	public static enum NumberToNumberConverterFactory implements ConverterFactory<Number, Number>, ConditionalConverter {
+	enum NumberToNumberConverterFactory implements ConverterFactory<Number, Number>, ConditionalConverter {
 
 		INSTANCE;
 
@@ -391,7 +391,7 @@ abstract class MongoConverters {
 	 * @since 1.10
 	 */
 	@WritingConverter
-	public static enum AtomicLongToLongConverter implements Converter<AtomicLong, Long> {
+	enum AtomicLongToLongConverter implements Converter<AtomicLong, Long> {
 		INSTANCE;
 
 		@Override
@@ -407,7 +407,7 @@ abstract class MongoConverters {
 	 * @since 1.10
 	 */
 	@WritingConverter
-	public static enum AtomicIntegerToIntegerConverter implements Converter<AtomicInteger, Integer> {
+	enum AtomicIntegerToIntegerConverter implements Converter<AtomicInteger, Integer> {
 		INSTANCE;
 
 		@Override
@@ -423,7 +423,7 @@ abstract class MongoConverters {
 	 * @since 1.10
 	 */
 	@ReadingConverter
-	public static enum LongToAtomicLongConverter implements Converter<Long, AtomicLong> {
+	enum LongToAtomicLongConverter implements Converter<Long, AtomicLong> {
 		INSTANCE;
 
 		@Override
@@ -439,7 +439,7 @@ abstract class MongoConverters {
 	 * @since 1.10
 	 */
 	@ReadingConverter
-	public static enum IntegerToAtomicIntegerConverter implements Converter<Integer, AtomicInteger> {
+	enum IntegerToAtomicIntegerConverter implements Converter<Integer, AtomicInteger> {
 		INSTANCE;
 
 		@Override
@@ -447,4 +447,22 @@ abstract class MongoConverters {
 			return source != null ? new AtomicInteger(source) : null;
 		}
 	}
+
+	/**
+	 * {@link Converter} implementation converting {@link Binary} into {@code byte[]}.
+	 *
+	 * @author Christoph Strobl
+	 * @since 2.0.1
+	 */
+	@ReadingConverter
+	enum BinaryToByteArrayConverter implements Converter<Binary, byte[]> {
+
+		INSTANCE;
+
+		@Nullable
+		@Override
+		public byte[] convert(Binary source) {
+			return source.getData();
+		}
+	}
 }

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

@@ -28,6 +28,7 @@ import org.springframework.core.convert.converter.GenericConverter;
 import org.springframework.data.convert.JodaTimeConverters;
 import org.springframework.data.convert.WritingConverter;
 import org.springframework.data.mongodb.core.mapping.MongoSimpleTypes;
+import org.springframework.lang.Nullable;
 
 /**
  * Value object to capture custom conversion. {@link MongoCustomConversions} also act as factory for
@@ -94,8 +95,8 @@ public class MongoCustomConversions extends org.springframework.data.convert.Cus
 		 * (non-Javadoc)
 		 * @see org.springframework.core.convert.converter.GenericConverter#convert(java.lang.Object, org.springframework.core.convert.TypeDescriptor, org.springframework.core.convert.TypeDescriptor)
 		 */
-		public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
-			return source.toString();
+		public Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+			return source != null ? source.toString() : null;
 		}
 	}
 }

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

@@ -39,23 +39,35 @@ import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
 import org.springframework.data.mongodb.core.query.MongoRegexCreator;
 import org.springframework.data.mongodb.core.query.MongoRegexCreator.MatchMode;
 import org.springframework.data.mongodb.core.query.SerializationUtils;
+import org.springframework.data.mongodb.core.query.UntypedExampleMatcher;
 import org.springframework.data.support.ExampleMatcherAccessor;
 import org.springframework.data.util.TypeInformation;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
 /**
+ * Mapper from {@link Example} to a query {@link Document}.
+ *
  * @author Christoph Strobl
  * @author Mark Paluch
  * @author Jens Schauder
  * @since 1.8
+ * @see Example
+ * @see org.springframework.data.domain.ExampleMatcher
+ * @see UntypedExampleMatcher
  */
 public class MongoExampleMapper {
 
 	private final MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext;
 	private final MongoConverter converter;
 
+	/**
+	 * Create a new {@link MongoTypeMapper} given {@link MongoConverter}.
+	 *
+	 * @param converter must not be {@literal null}.
+	 */
 	public MongoExampleMapper(MongoConverter converter) {
 
 		this.converter = converter;
@@ -91,7 +103,7 @@ public class MongoExampleMapper {
 
 		Document reference = (Document) converter.convertToMongoType(example.getProbe());
 
-		if (entity.getIdProperty() != null) {
+		if (entity.getIdProperty() != null && ClassUtils.isAssignable(entity.getType(), example.getProbeType())) {
 
 			Object identifier = entity.getIdentifierAccessor(example.getProbe()).getIdentifier();
 			if (identifier == null) {
@@ -107,85 +119,17 @@ public class MongoExampleMapper {
 				: new Document(SerializationUtils.flattenMap(reference));
 		Document result = example.getMatcher().isAllMatching() ? flattened : orConcatenate(flattened);
 
-		this.converter.getTypeMapper().writeTypeRestrictions(result, getTypesToMatch(example));
-
-		return result;
-	}
-
-	private static Document orConcatenate(Document source) {
-
-		List<Document> foo = new ArrayList<Document>(source.keySet().size());
-
-		for (String key : source.keySet()) {
-			foo.add(new Document(key, source.get(key)));
-		}
-
-		return new Document("$or", foo);
-	}
-
-	private Set<Class<?>> getTypesToMatch(Example<?> example) {
-
-		Set<Class<?>> types = new HashSet<Class<?>>();
-
-		for (TypeInformation<?> reference : mappingContext.getManagedTypes()) {
-			if (example.getProbeType().isAssignableFrom(reference.getType())) {
-				types.add(reference.getType());
-			}
-		}
-
-		return types;
-	}
-
-	private String getMappedPropertyPath(String path, Class<?> probeType) {
-
-		MongoPersistentEntity<?> entity = mappingContext.getRequiredPersistentEntity(probeType);
-
-		Iterator<String> parts = Arrays.asList(path.split("\\.")).iterator();
-
-		final Stack<MongoPersistentProperty> stack = new Stack<MongoPersistentProperty>();
-
-		List<String> resultParts = new ArrayList<String>();
-
-		while (parts.hasNext()) {
-
-			String part = parts.next();
-			MongoPersistentProperty prop = entity.getPersistentProperty(part);
-
-			if (prop == null) {
-
-				entity.doWithProperties((PropertyHandler<MongoPersistentProperty>) property -> {
-					if (property.getFieldName().equals(part)) {
-						stack.push(property);
-					}
-				});
-
-				if (stack.isEmpty()) {
-					return "";
-				}
-
-				prop = stack.pop();
-			}
-
-			resultParts.add(prop.getName());
-
-			if (prop.isEntity() && mappingContext.hasPersistentEntityFor(prop.getActualType())) {
-				entity = mappingContext.getRequiredPersistentEntity(prop.getActualType());
-			} else {
-				break;
-			}
-		}
-
-		return StringUtils.collectionToDelimitedString(resultParts, ".");
+		return updateTypeRestrictions(result, example);
 	}
 
 	private void applyPropertySpecs(String path, Document source, Class<?> probeType,
 			ExampleMatcherAccessor exampleSpecAccessor) {
 
-		if (!(source instanceof Document)) {
+		if (source == null) {
 			return;
 		}
 
-		Iterator<Map.Entry<String, Object>> iter = ((Document) source).entrySet().iterator();
+		Iterator<Map.Entry<String, Object>> iter = source.entrySet().iterator();
 
 		while (iter.hasNext()) {
 
@@ -237,11 +181,106 @@ public class MongoExampleMapper {
 		}
 	}
 
-	private boolean isEmptyIdProperty(Entry<String, Object> entry) {
+	private String getMappedPropertyPath(String path, Class<?> probeType) {
+
+		MongoPersistentEntity<?> entity = mappingContext.getRequiredPersistentEntity(probeType);
+
+		Iterator<String> parts = Arrays.asList(path.split("\\.")).iterator();
+
+		final Stack<MongoPersistentProperty> stack = new Stack<>();
+
+		List<String> resultParts = new ArrayList<>();
+
+		while (parts.hasNext()) {
+
+			String part = parts.next();
+			MongoPersistentProperty prop = entity.getPersistentProperty(part);
+
+			if (prop == null) {
+
+				entity.doWithProperties((PropertyHandler<MongoPersistentProperty>) property -> {
+					if (property.getFieldName().equals(part)) {
+						stack.push(property);
+					}
+				});
+
+				if (stack.isEmpty()) {
+					return "";
+				}
+
+				prop = stack.pop();
+			}
+
+			resultParts.add(prop.getName());
+
+			if (prop.isEntity() && mappingContext.hasPersistentEntityFor(prop.getActualType())) {
+				entity = mappingContext.getRequiredPersistentEntity(prop.getActualType());
+			} else {
+				break;
+			}
+		}
+
+		return StringUtils.collectionToDelimitedString(resultParts, ".");
+	}
+
+	private Document updateTypeRestrictions(Document query, Example example) {
+
+		Document result = new Document();
+
+		if (isTypeRestricting(example)) {
+
+			result.putAll(query);
+			this.converter.getTypeMapper().writeTypeRestrictions(result, getTypesToMatch(example));
+			return result;
+		}
+
+		for (Map.Entry<String, Object> entry : query.entrySet()) {
+			if (!this.converter.getTypeMapper().isTypeKey(entry.getKey())) {
+				result.put(entry.getKey(), entry.getValue());
+			}
+		}
+
+		return result;
+	}
+
+	private boolean isTypeRestricting(Example example) {
+
+		if (example.getMatcher() instanceof UntypedExampleMatcher) {
+			return false;
+		}
+
+		if (example.getMatcher().getIgnoredPaths().isEmpty()) {
+			return true;
+		}
+
+		for (String path : example.getMatcher().getIgnoredPaths()) {
+			if (this.converter.getTypeMapper().isTypeKey(path)) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+
+	private Set<Class<?>> getTypesToMatch(Example<?> example) {
+
+		Set<Class<?>> types = new HashSet<>();
+
+		for (TypeInformation<?> reference : mappingContext.getManagedTypes()) {
+			if (example.getProbeType().isAssignableFrom(reference.getType())) {
+				types.add(reference.getType());
+			}
+		}
+
+		return types;
+	}
+
+	private static boolean isEmptyIdProperty(Entry<String, Object> entry) {
 		return entry.getKey().equals("_id") && entry.getValue() == null || entry.getValue().equals(Optional.empty());
 	}
 
-	private void applyStringMatcher(Map.Entry<String, Object> entry, StringMatcher stringMatcher, boolean ignoreCase) {
+	private static void applyStringMatcher(Map.Entry<String, Object> entry, StringMatcher stringMatcher,
+			boolean ignoreCase) {
 
 		Document document = new Document();
 
@@ -264,9 +303,20 @@ public class MongoExampleMapper {
 		}
 	}
 
+	private static Document orConcatenate(Document source) {
+
+		List<Document> or = new ArrayList<>(source.keySet().size());
+
+		for (String key : source.keySet()) {
+			or.add(new Document(key, source.get(key)));
+		}
+
+		return new Document("$or", or);
+	}
+
 	/**
 	 * Return the {@link MatchMode} for the given {@link StringMatcher}.
-	 * 
+	 *
 	 * @param matcher must not be {@literal null}.
 	 * @return
 	 */

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

@@ -1,64 +1,69 @@
-/*
- * Copyright 2010-2016 the original author or authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-package org.springframework.data.mongodb.core.convert;
-
-import org.bson.conversions.Bson;
-import org.springframework.data.convert.EntityWriter;
-import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
-import org.springframework.data.util.TypeInformation;
-
-import com.mongodb.DBRef;
-
-/**
- * A MongoWriter is responsible for converting an object of type T to the native MongoDB representation Document.
- * 
- * @param <T> the type of the object to convert to a Document
- * @author Mark Pollack
- * @author Thomas Risberg
- * @author Oliver Gierke
- * @author Christoph Strobl
- */
-public interface MongoWriter<T> extends EntityWriter<T, Bson> {
-
-	/**
-	 * Converts the given object into one Mongo will be able to store natively. If the given object can already be stored
-	 * as is, no conversion will happen.
-	 * 
-	 * @param obj can be {@literal null}.
-	 * @return
-	 */
-	Object convertToMongoType(Object obj);
-
-	/**
-	 * Converts the given object into one Mongo will be able to store natively but retains the type information in case
-	 * the given {@link TypeInformation} differs from the given object type.
-	 * 
-	 * @param obj can be {@literal null}.
-	 * @param typeInformation can be {@literal null}.
-	 * @return
-	 */
-	Object convertToMongoType(Object obj, TypeInformation<?> typeInformation);
-
-	/**
-	 * Creates a {@link DBRef} to refer to the given object.
-	 * 
-	 * @param object the object to create a {@link DBRef} to link to. The object's type has to carry an id attribute.
-	 * @param referingProperty the client-side property referring to the object which might carry additional metadata for
-	 *          the {@link DBRef} object to create. Can be {@literal null}.
-	 * @return will never be {@literal null}.
-	 */
-	DBRef toDBRef(Object object, MongoPersistentProperty referingProperty);
-}
+/*
+ * Copyright 2010-2016 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core.convert;
+
+import org.bson.conversions.Bson;
+import org.springframework.data.convert.EntityWriter;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+import org.springframework.data.util.TypeInformation;
+import org.springframework.lang.Nullable;
+
+import com.mongodb.DBRef;
+
+/**
+ * A MongoWriter is responsible for converting an object of type T to the native MongoDB representation Document.
+ * 
+ * @param <T> the type of the object to convert to a Document
+ * @author Mark Pollack
+ * @author Thomas Risberg
+ * @author Oliver Gierke
+ * @author Christoph Strobl
+ */
+public interface MongoWriter<T> extends EntityWriter<T, Bson> {
+
+	/**
+	 * Converts the given object into one Mongo will be able to store natively. If the given object can already be stored
+	 * as is, no conversion will happen.
+	 * 
+	 * @param obj can be {@literal null}.
+	 * @return
+	 */
+	@Nullable
+	default Object convertToMongoType(@Nullable Object obj) {
+		return convertToMongoType(obj, null);
+	}
+
+	/**
+	 * Converts the given object into one Mongo will be able to store natively but retains the type information in case
+	 * the given {@link TypeInformation} differs from the given object type.
+	 * 
+	 * @param obj can be {@literal null}.
+	 * @param typeInformation can be {@literal null}.
+	 * @return
+	 */
+	@Nullable
+	Object convertToMongoType(@Nullable Object obj, @Nullable TypeInformation<?> typeInformation);
+
+	/**
+	 * Creates a {@link DBRef} to refer to the given object.
+	 * 
+	 * @param object the object to create a {@link DBRef} to link to. The object's type has to carry an id attribute.
+	 * @param referingProperty the client-side property referring to the object which might carry additional metadata for
+	 *          the {@link DBRef} object to create. Can be {@literal null}.
+	 * @return will never be {@literal null}.
+	 */
+	DBRef toDBRef(Object object, @Nullable MongoPersistentProperty referingProperty);
+}