DATAMONGO-2121 - Release version 2.1.3 (Lovelace SR3).

Convert anonymous JSON callback class into a private static one. Use an expressive Pattern constant.

Original pull request: #621.

.travis.yml

@@ -13,12 +13,12 @@ before_install:
   - |-
     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
   global:
-    - MONGO_VERSION=3.7.9
+    - MONGO_VERSION=4.0.0
 
 addons:
   apt:

pom.xml

@@ -5,7 +5,7 @@
 
 	<groupId>org.springframework.data</groupId>
 	<artifactId>spring-data-mongodb-parent</artifactId>
-	<version>2.1.0.M3</version>
+	<version>2.1.3.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>2.1.0.M3</version>
+		<version>2.1.3.RELEASE</version>
 	</parent>
 
 	<modules>
@@ -27,9 +27,9 @@
 	<properties>
 		<project.type>multi</project.type>
 		<dist.id>spring-data-mongodb</dist.id>
-		<springdata.commons>2.1.0.M3</springdata.commons>
-		<mongo>3.8.0-beta2</mongo>
-		<mongo.reactivestreams>1.9.0-beta1</mongo.reactivestreams>
+		<springdata.commons>2.1.3.RELEASE</springdata.commons>
+		<mongo>3.8.2</mongo>
+		<mongo.reactivestreams>1.9.2</mongo.reactivestreams>
 		<jmh.version>1.19</jmh.version>
 	</properties>
 
@@ -138,6 +138,24 @@
 			</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>
@@ -151,8 +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>2.1.0.M3</version>
+		<version>2.1.3.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>2.1.0.M3</version>
+		<version>2.1.3.RELEASE</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 
@@ -50,7 +50,7 @@
 		<dependency>
 			<groupId>org.springframework.data</groupId>
 			<artifactId>spring-data-mongodb</artifactId>
-			<version>2.1.0.M3</version>
+			<version>2.1.3.RELEASE</version>
 		</dependency>
 
 		<!-- reactive -->

spring-data-mongodb-distribution/pom.xml

@@ -13,7 +13,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>2.1.0.M3</version>
+		<version>2.1.3.RELEASE</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

spring-data-mongodb/pom.xml

@@ -11,7 +11,7 @@
 	<parent>
 		<groupId>org.springframework.data</groupId>
 		<artifactId>spring-data-mongodb-parent</artifactId>
-		<version>2.1.0.M3</version>
+		<version>2.1.3.RELEASE</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 

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

@@ -110,7 +110,7 @@ public class MongoDatabaseUtils {
 
 		ClientSession session = doGetSession(factory, sessionSynchronization);
 
-		if(session == null) {
+		if (session == null) {
 			return StringUtils.hasText(dbName) ? factory.getDb(dbName) : factory.getDb();
 		}
 
@@ -118,6 +118,25 @@ public class MongoDatabaseUtils {
 		return StringUtils.hasText(dbName) ? factoryToUse.getDb(dbName) : factoryToUse.getDb();
 	}
 
+	/**
+	 * Check if the {@link MongoDbFactory} is actually bound to a {@link ClientSession} that has an active transaction, or
+	 * if a {@link TransactionSynchronization} has been registered for the {@link MongoDbFactory resource} and if the
+	 * associated {@link ClientSession} has an {@link ClientSession#hasActiveTransaction() active transaction}.
+	 *
+	 * @param dbFactory the resource to check transactions for. Must not be {@literal null}.
+	 * @return {@literal true} if the factory has an ongoing transaction.
+	 * @since 2.1.3
+	 */
+	public static boolean isTransactionActive(MongoDbFactory dbFactory) {
+
+		if (dbFactory.isTransactionActive()) {
+			return true;
+		}
+
+		MongoResourceHolder resourceHolder = (MongoResourceHolder) TransactionSynchronizationManager.getResource(dbFactory);
+		return resourceHolder != null && resourceHolder.hasActiveTransaction();
+	}
+
 	@Nullable
 	private static ClientSession doGetSession(MongoDbFactory dbFactory, SessionSynchronization sessionSynchronization) {
 
@@ -140,7 +159,7 @@ public class MongoDatabaseUtils {
 		// init a non native MongoDB transaction by registering a MongoSessionSynchronization
 
 		resourceHolder = new MongoResourceHolder(createClientSession(dbFactory), dbFactory);
-		resourceHolder.getSession().startTransaction();
+		resourceHolder.getRequiredSession().startTransaction();
 
 		TransactionSynchronizationManager
 				.registerSynchronization(new MongoSessionSynchronization(resourceHolder, dbFactory));
@@ -187,8 +206,8 @@ public class MongoDatabaseUtils {
 		@Override
 		protected void processResourceAfterCommit(MongoResourceHolder resourceHolder) {
 
-			if (isTransactionActive(resourceHolder)) {
-				resourceHolder.getSession().commitTransaction();
+			if (resourceHolder.hasActiveTransaction()) {
+				resourceHolder.getRequiredSession().commitTransaction();
 			}
 		}
 
@@ -199,8 +218,8 @@ public class MongoDatabaseUtils {
 		@Override
 		public void afterCompletion(int status) {
 
-			if (status == TransactionSynchronization.STATUS_ROLLED_BACK && isTransactionActive(this.resourceHolder)) {
-				resourceHolder.getSession().abortTransaction();
+			if (status == TransactionSynchronization.STATUS_ROLLED_BACK && this.resourceHolder.hasActiveTransaction()) {
+				resourceHolder.getRequiredSession().abortTransaction();
 			}
 
 			super.afterCompletion(status);
@@ -214,17 +233,8 @@ public class MongoDatabaseUtils {
 		protected void releaseResource(MongoResourceHolder resourceHolder, Object resourceKey) {
 
 			if (resourceHolder.hasActiveSession()) {
-				resourceHolder.getSession().close();
+				resourceHolder.getRequiredSession().close();
 			}
 		}
-
-		private boolean isTransactionActive(MongoResourceHolder resourceHolder) {
-
-			if (!resourceHolder.hasSession()) {
-				return false;
-			}
-
-			return resourceHolder.getSession().hasActiveTransaction();
-		}
 	}
 }

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

@@ -62,7 +62,10 @@ public interface MongoDbFactory extends CodecRegistryProvider, MongoSessionProvi
 	 * Get the legacy database entry point. Please consider {@link #getDb()} instead.
 	 *
 	 * @return
+	 * @deprecated since 2.1, use {@link #getDb()}. This method will be removed with a future version as it works only
+	 *             with the legacy MongoDB driver.
 	 */
+	@Deprecated
 	DB getLegacyDb();
 
 	/**
@@ -105,4 +108,15 @@ public interface MongoDbFactory extends CodecRegistryProvider, MongoSessionProvi
 	 * @since 2.1
 	 */
 	MongoDbFactory withSession(ClientSession session);
+
+	/**
+	 * Returns if the given {@link MongoDbFactory} is bound to a {@link ClientSession} that has an
+	 * {@link ClientSession#hasActiveTransaction() active transaction}.
+	 *
+	 * @return {@literal true} if there's an active transaction, {@literal false} otherwise.
+	 * @since 2.1.3
+	 */
+	default boolean isTransactionActive() {
+		return false;
+	}
 }

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

@@ -28,6 +28,7 @@ import com.mongodb.client.ClientSession;
  * <strong>Note:</strong> Intended for internal usage only.
  *
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @since 2.1
  * @see MongoTransactionManager
  * @see org.springframework.data.mongodb.core.MongoTemplate
@@ -57,6 +58,22 @@ class MongoResourceHolder extends ResourceHolderSupport {
 		return session;
 	}
 
+	/**
+	 * @return the required associated {@link ClientSession}.
+	 * @throws IllegalStateException if no {@link ClientSession} is associated with this {@link MongoResourceHolder}.
+	 * @since 2.1.3
+	 */
+	ClientSession getRequiredSession() {
+
+		ClientSession session = getSession();
+
+		if (session == null) {
+			throw new IllegalStateException("No session available!");
+		}
+
+		return session;
+	}
+
 	/**
 	 * @return the associated {@link MongoDbFactory}.
 	 */
@@ -101,7 +118,21 @@ class MongoResourceHolder extends ResourceHolderSupport {
 			return false;
 		}
 
-		return hasServerSession() && !getSession().getServerSession().isClosed();
+		return hasServerSession() && !getRequiredSession().getServerSession().isClosed();
+	}
+
+	/**
+	 * @return {@literal true} if the session has an active transaction.
+	 * @since 2.1.3
+	 * @see #hasActiveSession()
+	 */
+	boolean hasActiveTransaction() {
+
+		if (!hasActiveSession()) {
+			return false;
+		}
+
+		return getRequiredSession().hasActiveTransaction();
 	}
 
 	/**
@@ -111,7 +142,7 @@ class MongoResourceHolder extends ResourceHolderSupport {
 	boolean hasServerSession() {
 
 		try {
-			return getSession().getServerSession() != null;
+			return getRequiredSession().getServerSession() != null;
 		} catch (IllegalStateException serverSessionClosed) {
 			// ignore
 		}

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

@@ -0,0 +1,47 @@
+/*
+ * 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;
+
+import org.springframework.lang.Nullable;
+
+/**
+ * A specific {@link ClientSessionException} related to issues with a transaction such as aborted or non existing
+ * transactions.
+ *
+ * @author Christoph Strobl
+ * @since 2.1
+ */
+public class MongoTransactionException extends ClientSessionException {
+
+	/**
+	 * Constructor for {@link MongoTransactionException}.
+	 *
+	 * @param msg the detail message. Must not be {@literal null}.
+	 */
+	public MongoTransactionException(String msg) {
+		super(msg);
+	}
+
+	/**
+	 * Constructor for {@link ClientSessionException}.
+	 *
+	 * @param msg the detail message. Can be {@literal null}.
+	 * @param cause the root cause. Can be {@literal null}.
+	 */
+	public MongoTransactionException(@Nullable String msg, @Nullable Throwable cause) {
+		super(msg, cause);
+	}
+}

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

@@ -47,13 +47,18 @@ import com.mongodb.client.ClientSession;
  * Application code is required to retrieve the {@link com.mongodb.client.MongoDatabase} via
  * {@link MongoDatabaseUtils#getDatabase(MongoDbFactory)} instead of a standard {@link MongoDbFactory#getDb()} call.
  * Spring classes such as {@link org.springframework.data.mongodb.core.MongoTemplate} use this strategy implicitly.
- * 
+ * <p />
+ * By default failure of a {@literal commit} operation raises a {@link TransactionSystemException}. One may override
+ * {@link #doCommit(MongoTransactionObject)} to implement the
+ * <a href="https://docs.mongodb.com/manual/core/transactions/#retry-commit-operation">Retry Commit Operation</a>
+ * behavior as outlined in the MongoDB reference manual.
+ *
  * @author Christoph Strobl
  * @author Mark Paluch
  * @currentRead Shadow's Edge - Brent Weeks
  * @since 2.1
  * @see <a href="https://www.mongodb.com/transactions">MongoDB Transaction Documentation</a>
- * @see MongoDatabaseUtils#getDatabase(MongoDbFactory, SessionSynchronization) 
+ * @see MongoDatabaseUtils#getDatabase(MongoDbFactory, SessionSynchronization)
  */
 public class MongoTransactionManager extends AbstractPlatformTransactionManager
 		implements ResourceTransactionManager, InitializingBean {
@@ -70,7 +75,7 @@ public class MongoTransactionManager extends AbstractPlatformTransactionManager
 	 * <p />
 	 * Optionally it is possible to set default {@link TransactionOptions transaction options} defining
 	 * {@link com.mongodb.ReadConcern} and {@link com.mongodb.WriteConcern}.
-	 * 
+	 *
 	 * @see #setDbFactory(MongoDbFactory)
 	 * @see #setTransactionSynchronization(int)
 	 */
@@ -181,7 +186,7 @@ public class MongoTransactionManager extends AbstractPlatformTransactionManager
 	 * org.springframework.transaction.support.AbstractPlatformTransactionManager#doCommit(org.springframework.transaction.support.DefaultTransactionStatus)
 	 */
 	@Override
-	protected void doCommit(DefaultTransactionStatus status) throws TransactionException {
+	protected final void doCommit(DefaultTransactionStatus status) throws TransactionException {
 
 		MongoTransactionObject mongoTransactionObject = extractMongoTransaction(status);
 
@@ -191,14 +196,45 @@ public class MongoTransactionManager extends AbstractPlatformTransactionManager
 		}
 
 		try {
-			mongoTransactionObject.commitTransaction();
-		} catch (MongoException ex) {
+			doCommit(mongoTransactionObject);
+		} catch (Exception ex) {
 
 			throw new TransactionSystemException(String.format("Could not commit Mongo transaction for session %s.",
 					debugString(mongoTransactionObject.getSession())), ex);
 		}
 	}
 
+	/**
+	 * Customization hook to perform an actual commit of the given transaction.<br />
+	 * If a commit operation encounters an error, the MongoDB driver throws a {@link MongoException} holding
+	 * {@literal error labels}. <br />
+	 * By default those labels are ignored, nevertheless one might check for
+	 * {@link MongoException#UNKNOWN_TRANSACTION_COMMIT_RESULT_LABEL transient commit errors labels} and retry the the
+	 * commit. <br />
+	 * <code>
+	 *     <pre>
+	 * int retries = 3;
+	 * do {
+	 *     try {
+	 *         transactionObject.commitTransaction();
+	 *         break;
+	 *     } catch (MongoException ex) {
+	 *         if (!ex.hasErrorLabel(MongoException.UNKNOWN_TRANSACTION_COMMIT_RESULT_LABEL)) {
+	 *             throw ex;
+	 *         }
+	 *     }
+	 *     Thread.sleep(500);
+	 * } while (--retries > 0);
+	 *     </pre>
+	 * </code>
+	 *
+	 * @param transactionObject never {@literal null}.
+	 * @throws Exception in case of transaction errors.
+	 */
+	protected void doCommit(MongoTransactionObject transactionObject) throws Exception {
+		transactionObject.commitTransaction();
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * org.springframework.transaction.support.AbstractPlatformTransactionManager#doRollback(org.springframework.transaction.support.DefaultTransactionStatus)
@@ -386,7 +422,7 @@ public class MongoTransactionManager extends AbstractPlatformTransactionManager
 	 * @since 2.1
 	 * @see MongoResourceHolder
 	 */
-	static class MongoTransactionObject implements SmartTransactionObject {
+	protected static class MongoTransactionObject implements SmartTransactionObject {
 
 		private @Nullable MongoResourceHolder resourceHolder;
 
@@ -406,7 +442,7 @@ public class MongoTransactionManager extends AbstractPlatformTransactionManager
 		/**
 		 * @return {@literal true} if a {@link MongoResourceHolder} is set.
 		 */
-		boolean hasResourceHolder() {
+		final boolean hasResourceHolder() {
 			return resourceHolder != null;
 		}
 
@@ -428,14 +464,14 @@ public class MongoTransactionManager extends AbstractPlatformTransactionManager
 		/**
 		 * Commit the transaction.
 		 */
-		void commitTransaction() {
+		public void commitTransaction() {
 			getRequiredSession().commitTransaction();
 		}
 
 		/**
 		 * Rollback (abort) the transaction.
 		 */
-		void abortTransaction() {
+		public void abortTransaction() {
 			getRequiredSession().abortTransaction();
 		}
 
@@ -451,7 +487,7 @@ public class MongoTransactionManager extends AbstractPlatformTransactionManager
 		}
 
 		@Nullable
-		ClientSession getSession() {
+		public ClientSession getSession() {
 			return resourceHolder != null ? resourceHolder.getSession() : null;
 		}
 

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

@@ -22,6 +22,7 @@ import org.springframework.data.mongodb.core.ReactiveMongoOperations;
 import org.springframework.data.mongodb.core.ReactiveMongoTemplate;
 import org.springframework.data.mongodb.core.SimpleReactiveMongoDatabaseFactory;
 import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
+import org.springframework.data.mongodb.core.convert.NoOpDbRefResolver;
 
 import com.mongodb.reactivestreams.client.MongoClient;
 
@@ -80,8 +81,7 @@ public abstract class AbstractReactiveMongoConfiguration extends MongoConfigurat
 	@Bean
 	public MappingMongoConverter mappingMongoConverter() throws Exception {
 
-		MappingMongoConverter converter = new MappingMongoConverter(ReactiveMongoTemplate.NO_OP_REF_RESOLVER,
-				mongoMappingContext());
+		MappingMongoConverter converter = new MappingMongoConverter(NoOpDbRefResolver.INSTANCE, mongoMappingContext());
 		converter.setCustomConversions(customConversions());
 
 		return converter;

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

@@ -60,6 +60,7 @@ import org.springframework.data.mongodb.core.index.MongoPersistentEntityIndexCre
 import org.springframework.data.mongodb.core.mapping.Document;
 import org.springframework.data.mongodb.core.mapping.MongoMappingContext;
 import org.springframework.data.mongodb.core.mapping.event.ValidatingMongoEventListener;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.StringUtils;
@@ -75,6 +76,7 @@ import org.w3c.dom.Element;
  * @author Thomas Darimont
  * @author Christoph Strobl
  * @author Mark Paluch
+ * @author Zied Yaich
  */
 public class MappingMongoConverterParser implements BeanDefinitionParser {
 
@@ -159,6 +161,7 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 		return null;
 	}
 
+	@Nullable
 	private BeanDefinition potentiallyCreateValidatingMongoEventListener(Element element, ParserContext parserContext) {
 
 		String disableValidation = element.getAttribute("disable-validation");
@@ -180,6 +183,7 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 		return null;
 	}
 
+	@Nullable
 	private RuntimeBeanReference getValidator(Object source, ParserContext parserContext) {
 
 		if (!JSR_303_PRESENT) {
@@ -197,7 +201,7 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 	}
 
 	public static String potentiallyCreateMappingContext(Element element, ParserContext parserContext,
-			BeanDefinition conversionsDefinition, String converterId) {
+			@Nullable BeanDefinition conversionsDefinition, @Nullable String converterId) {
 
 		String ctxRef = element.getAttribute("mapping-context-ref");
 
@@ -211,7 +215,7 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 		BeanDefinitionBuilder mappingContextBuilder = BeanDefinitionBuilder
 				.genericBeanDefinition(MongoMappingContext.class);
 
-		Set<String> classesToAdd = getInititalEntityClasses(element);
+		Set<String> classesToAdd = getInitialEntityClasses(element);
 
 		if (classesToAdd != null) {
 			mappingContextBuilder.addPropertyValue("initialEntitySet", classesToAdd);
@@ -262,6 +266,7 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 		}
 	}
 
+	@Nullable
 	private BeanDefinition getCustomConversions(Element element, ParserContext parserContext) {
 
 		List<Element> customConvertersElements = DomUtils.getChildElementsByTagName(element, "custom-converters");
@@ -269,7 +274,7 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 		if (customConvertersElements.size() == 1) {
 
 			Element customerConvertersElement = customConvertersElements.get(0);
-			ManagedList<BeanMetadataElement> converterBeans = new ManagedList<BeanMetadataElement>();
+			ManagedList<BeanMetadataElement> converterBeans = new ManagedList<>();
 			List<Element> converterElements = DomUtils.getChildElementsByTagName(customerConvertersElement, "converter");
 
 			if (converterElements != null) {
@@ -285,9 +290,7 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 				provider.addExcludeFilter(new NegatingFilter(new AssignableTypeFilter(Converter.class),
 						new AssignableTypeFilter(GenericConverter.class)));
 
-				for (BeanDefinition candidate : provider.findCandidateComponents(packageToScan)) {
-					converterBeans.add(candidate);
-				}
+				converterBeans.addAll(provider.findCandidateComponents(packageToScan));
 			}
 
 			BeanDefinitionBuilder conversionsBuilder = BeanDefinitionBuilder.rootBeanDefinition(MongoCustomConversions.class);
@@ -304,7 +307,8 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 		return null;
 	}
 
-	private static Set<String> getInititalEntityClasses(Element element) {
+	@Nullable
+	private static Set<String> getInitialEntityClasses(Element element) {
 
 		String basePackage = element.getAttribute(BASE_PACKAGE);
 
@@ -317,7 +321,7 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 		componentProvider.addIncludeFilter(new AnnotationTypeFilter(Document.class));
 		componentProvider.addIncludeFilter(new AnnotationTypeFilter(Persistent.class));
 
-		Set<String> classes = new ManagedSet<String>();
+		Set<String> classes = new ManagedSet<>();
 		for (BeanDefinition candidate : componentProvider.findCandidateComponents(basePackage)) {
 			classes.add(candidate.getBeanClassName());
 		}
@@ -325,6 +329,7 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 		return classes;
 	}
 
+	@Nullable
 	public BeanMetadataElement parseConverter(Element element, ParserContext parserContext) {
 
 		String converterRef = element.getAttribute("ref");
@@ -375,7 +380,7 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 
 			Assert.notNull(filters, "TypeFilters must not be null");
 
-			this.delegates = new HashSet<TypeFilter>(Arrays.asList(filters));
+			this.delegates = new HashSet<>(Arrays.asList(filters));
 		}
 
 		/*

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

@@ -35,6 +35,8 @@ 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 {
@@ -98,6 +100,12 @@ public class MongoCredentialPropertyEditor extends PropertyEditorSupport {
 						verifyDatabasePresent(database);
 						credentials.add(MongoCredential.createScramSha1Credential(userNameAndPassword[0], database,
 								userNameAndPassword[1].toCharArray()));
+					} else if (MongoCredential.SCRAM_SHA_256_MECHANISM.equals(authMechanism)) {
+
+						verifyUsernameAndPasswordPresent(userNameAndPassword);
+						verifyDatabasePresent(database);
+						credentials.add(MongoCredential.createScramSha256Credential(userNameAndPassword[0], database,
+								userNameAndPassword[1].toCharArray()));
 					} else {
 						throw new IllegalArgumentException(
 								String.format("Cannot create MongoCredentials for unknown auth mechanism '%s'!", authMechanism));
@@ -164,7 +172,7 @@ 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();
@@ -173,7 +181,13 @@ 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/core/AggregationUtil.java

@@ -0,0 +1,170 @@
+/*
+ * 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.Arrays;
+import java.util.Collections;
+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.AggregationOperation;
+import org.springframework.data.mongodb.core.aggregation.AggregationOperationContext;
+import org.springframework.data.mongodb.core.aggregation.AggregationOptions;
+import org.springframework.data.mongodb.core.aggregation.CountOperation;
+import org.springframework.data.mongodb.core.aggregation.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.data.mongodb.core.query.CriteriaDefinition;
+import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+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 2.1
+ */
+@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
+	 */
+	List<Document> createPipeline(Aggregation aggregation, AggregationOperationContext context) {
+
+		if (!ObjectUtils.nullSafeEquals(context, Aggregation.DEFAULT_CONTEXT)) {
+			return aggregation.toPipeline(context);
+		}
+
+		return mapAggregationPipeline(aggregation.toPipeline(context));
+	}
+
+	/**
+	 * 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;
+	}
+
+	/**
+	 * Create a {@code $count} aggregation for {@link Query} and optionally a {@link Class entity class}.
+	 *
+	 * @param query must not be {@literal null}.
+	 * @param entityClass can be {@literal null} if the {@link Query} object is empty.
+	 * @return the {@link Aggregation} pipeline definition to run a {@code $count} aggregation.
+	 */
+	Aggregation createCountAggregation(Query query, @Nullable Class<?> entityClass) {
+
+		List<AggregationOperation> pipeline = computeCountAggregationPipeline(query, entityClass);
+
+		Aggregation aggregation = entityClass != null ? Aggregation.newAggregation(entityClass, pipeline)
+				: Aggregation.newAggregation(pipeline);
+		aggregation.withOptions(AggregationOptions.builder().collation(query.getCollation().orElse(null)).build());
+
+		return aggregation;
+	}
+
+	private List<AggregationOperation> computeCountAggregationPipeline(Query query, @Nullable Class<?> entityType) {
+
+		CountOperation count = Aggregation.count().as("totalEntityCount");
+		if (query.getQueryObject().isEmpty()) {
+			return Collections.singletonList(count);
+		}
+
+		Assert.notNull(entityType, "Entity type must not be null!");
+
+		Document mappedQuery = queryMapper.getMappedObject(query.getQueryObject(),
+				mappingContext.getPersistentEntity(entityType));
+
+		CriteriaDefinition criteria = new CriteriaDefinition() {
+
+			@Override
+			public Document getCriteriaObject() {
+				return mappedQuery;
+			}
+
+			@Nullable
+			@Override
+			public String getKey() {
+				return null;
+			}
+		};
+
+		return Arrays.asList(Aggregation.match(criteria), count);
+	}
+
+	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/ChangeStreamEvent.java

@@ -17,8 +17,10 @@ package org.springframework.data.mongodb.core;
 
 import lombok.EqualsAndHashCode;
 
-import java.util.concurrent.atomic.AtomicReference;
+import java.time.Instant;
+import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
 
+import org.bson.BsonValue;
 import org.bson.Document;
 import org.springframework.data.mongodb.core.convert.MongoConverter;
 import org.springframework.data.mongodb.core.messaging.Message;
@@ -26,6 +28,7 @@ import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 
 import com.mongodb.client.model.changestream.ChangeStreamDocument;
+import com.mongodb.client.model.changestream.OperationType;
 
 /**
  * {@link Message} implementation specific to MongoDB <a href="https://docs.mongodb.com/manual/changeStreams/">Change
@@ -38,11 +41,17 @@ import com.mongodb.client.model.changestream.ChangeStreamDocument;
 @EqualsAndHashCode
 public class ChangeStreamEvent<T> {
 
+	@SuppressWarnings("rawtypes") //
+	private static final AtomicReferenceFieldUpdater<ChangeStreamEvent, Object> CONVERTED_UPDATER = AtomicReferenceFieldUpdater
+			.newUpdater(ChangeStreamEvent.class, Object.class, "converted");
+
 	private final @Nullable ChangeStreamDocument<Document> raw;
 
 	private final Class<T> targetType;
 	private final MongoConverter converter;
-	private final AtomicReference<T> converted = new AtomicReference<>();
+
+	// accessed through CONVERTED_UPDATER.
+	private volatile @Nullable T converted;
 
 	/**
 	 * @param raw can be {@literal null}.
@@ -67,6 +76,58 @@ public class ChangeStreamEvent<T> {
 		return raw;
 	}
 
+	/**
+	 * Get the {@link ChangeStreamDocument#getClusterTime() cluster time} as {@link Instant} the event was emitted at.
+	 *
+	 * @return can be {@literal null}.
+	 */
+	@Nullable
+	public Instant getTimestamp() {
+
+		return raw != null && raw.getClusterTime() != null
+				? converter.getConversionService().convert(raw.getClusterTime(), Instant.class) : null;
+	}
+
+	/**
+	 * Get the {@link ChangeStreamDocument#getResumeToken() resume token} for this event.
+	 *
+	 * @return can be {@literal null}.
+	 */
+	@Nullable
+	public BsonValue getResumeToken() {
+		return raw != null ? raw.getResumeToken() : null;
+	}
+
+	/**
+	 * Get the {@link ChangeStreamDocument#getOperationType() operation type} for this event.
+	 *
+	 * @return can be {@literal null}.
+	 */
+	@Nullable
+	public OperationType getOperationType() {
+		return raw != null ? raw.getOperationType() : null;
+	}
+
+	/**
+	 * Get the database name the event was originated at.
+	 *
+	 * @return can be {@literal null}.
+	 */
+	@Nullable
+	public String getDatabaseName() {
+		return raw != null ? raw.getNamespace().getDatabaseName() : null;
+	}
+
+	/**
+	 * Get the collection name the event was originated at.
+	 *
+	 * @return can be {@literal null}.
+	 */
+	@Nullable
+	public String getCollectionName() {
+		return raw != null ? raw.getNamespace().getCollectionName() : null;
+	}
+
 	/**
 	 * Get the potentially converted {@link ChangeStreamDocument#getFullDocument()}.
 	 *
@@ -80,36 +141,48 @@ public class ChangeStreamEvent<T> {
 			return null;
 		}
 
-		if (raw.getFullDocument() == null) {
-			return targetType.cast(raw.getFullDocument());
+		Document fullDocument = raw.getFullDocument();
+
+		if (fullDocument == null) {
+			return targetType.cast(fullDocument);
 		}
 
-		return getConverted();
+		return getConverted(fullDocument);
 	}
 
-	private T getConverted() {
+	@SuppressWarnings("unchecked")
+	private T getConverted(Document fullDocument) {
+		return (T) doGetConverted(fullDocument);
+	}
+
+	private Object doGetConverted(Document fullDocument) {
+
+		Object result = CONVERTED_UPDATER.get(this);
 
-		T result = converted.get();
 		if (result != null) {
 			return result;
 		}
 
-		if (ClassUtils.isAssignable(Document.class, raw.getFullDocument().getClass())) {
+		if (ClassUtils.isAssignable(Document.class, fullDocument.getClass())) {
 
-			result = converter.read(targetType, raw.getFullDocument());
-			return converted.compareAndSet(null, result) ? result : converted.get();
+			result = converter.read(targetType, fullDocument);
+			return CONVERTED_UPDATER.compareAndSet(this, null, result) ? result : CONVERTED_UPDATER.get(this);
 		}
 
-		if (converter.getConversionService().canConvert(raw.getFullDocument().getClass(), targetType)) {
+		if (converter.getConversionService().canConvert(fullDocument.getClass(), targetType)) {
 
-			result = converter.getConversionService().convert(raw.getFullDocument(), targetType);
-			return converted.compareAndSet(null, result) ? result : converted.get();
+			result = converter.getConversionService().convert(fullDocument, targetType);
+			return CONVERTED_UPDATER.compareAndSet(this, null, result) ? result : CONVERTED_UPDATER.get(this);
 		}
 
 		throw new IllegalArgumentException(String.format("No converter found capable of converting %s to %s",
-				raw.getFullDocument().getClass(), targetType));
+				fullDocument.getClass(), targetType));
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see java.lang.Object#toString()
+	 */
 	@Override
 	public String toString() {
 		return "ChangeStreamEvent {" + "raw=" + raw + ", targetType=" + targetType + '}';

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

@@ -17,6 +17,7 @@ package org.springframework.data.mongodb.core;
 
 import lombok.EqualsAndHashCode;
 
+import java.time.Instant;
 import java.util.Arrays;
 import java.util.Optional;
 
@@ -46,6 +47,7 @@ public class ChangeStreamOptions {
 	private @Nullable BsonValue resumeToken;
 	private @Nullable FullDocument fullDocumentLookup;
 	private @Nullable Collation collation;
+	private @Nullable Instant resumeTimestamp;
 
 	protected ChangeStreamOptions() {}
 
@@ -77,6 +79,13 @@ public class ChangeStreamOptions {
 		return Optional.ofNullable(collation);
 	}
 
+	/**
+	 * @return {@link Optional#empty()} if not set.
+	 */
+	public Optional<Instant> getResumeTimestamp() {
+		return Optional.ofNullable(resumeTimestamp);
+	}
+
 	/**
 	 * @return empty {@link ChangeStreamOptions}.
 	 */
@@ -106,6 +115,7 @@ public class ChangeStreamOptions {
 		private @Nullable BsonValue resumeToken;
 		private @Nullable FullDocument fullDocumentLookup;
 		private @Nullable Collation collation;
+		private @Nullable Instant resumeTimestamp;
 
 		private ChangeStreamOptionsBuilder() {}
 
@@ -200,6 +210,20 @@ public class ChangeStreamOptions {
 			return this;
 		}
 
+		/**
+		 * Set the cluster time to resume from.
+		 *
+		 * @param resumeTimestamp must not be {@literal null}.
+		 * @return this.
+		 */
+		public ChangeStreamOptionsBuilder resumeAt(Instant resumeTimestamp) {
+
+			Assert.notNull(resumeTimestamp, "ResumeTimestamp must not be null!");
+
+			this.resumeTimestamp = resumeTimestamp;
+			return this;
+		}
+
 		/**
 		 * @return the built {@link ChangeStreamOptions}
 		 */
@@ -211,6 +235,7 @@ public class ChangeStreamOptions {
 			options.resumeToken = resumeToken;
 			options.fullDocumentLookup = fullDocumentLookup;
 			options.collation = collation;
+			options.resumeTimestamp = resumeTimestamp;
 
 			return options;
 		}

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

@@ -0,0 +1,683 @@
+/*
+ * 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.AccessLevel;
+import lombok.NonNull;
+import lombok.RequiredArgsConstructor;
+
+import java.util.Collection;
+import java.util.Map;
+
+import org.bson.Document;
+import org.springframework.core.convert.ConversionService;
+import org.springframework.dao.InvalidDataAccessApiUsageException;
+import org.springframework.data.mapping.IdentifierAccessor;
+import org.springframework.data.mapping.MappingException;
+import org.springframework.data.mapping.PersistentPropertyAccessor;
+import org.springframework.data.mapping.context.MappingContext;
+import org.springframework.data.mapping.model.ConvertingPropertyAccessor;
+import org.springframework.data.mongodb.core.convert.MongoWriter;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+import org.springframework.data.mongodb.core.mapping.MongoSimpleTypes;
+import org.springframework.data.mongodb.core.query.Criteria;
+import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
+
+import com.mongodb.util.JSONParseException;
+
+/**
+ * Common operations performed on an entity in the context of it's mapping metadata.
+ *
+ * @author Oliver Gierke
+ * @author Mark Paluch
+ * @since 2.1
+ * @see MongoTemplate
+ * @see ReactiveMongoTemplate
+ */
+@RequiredArgsConstructor
+class EntityOperations {
+
+	private static final String ID_FIELD = "_id";
+
+	private final @NonNull MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> context;
+
+	/**
+	 * Creates a new {@link Entity} for the given bean.
+	 *
+	 * @param entity must not be {@literal null}.
+	 * @return
+	 */
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	public <T> Entity<T> forEntity(T entity) {
+
+		Assert.notNull(entity, "Bean must not be null!");
+
+		if (entity instanceof String) {
+			return new UnmappedEntity(parse(entity.toString()));
+		}
+
+		if (entity instanceof Map) {
+			return new SimpleMappedEntity((Map<String, Object>) entity);
+		}
+
+		return MappedEntity.of(entity, context);
+	}
+
+	/**
+	 * Creates a new {@link AdaptibleEntity} for the given bean and {@link ConversionService}.
+	 *
+	 * @param entity must not be {@literal null}.
+	 * @param conversionService must not be {@literal null}.
+	 * @return
+	 */
+	@SuppressWarnings({ "unchecked", "rawtypes" })
+	public <T> AdaptibleEntity<T> forEntity(T entity, ConversionService conversionService) {
+
+		Assert.notNull(entity, "Bean must not be null!");
+		Assert.notNull(conversionService, "ConversionService must not be null!");
+
+		if (entity instanceof String) {
+			return new UnmappedEntity(parse(entity.toString()));
+		}
+
+		if (entity instanceof Map) {
+			return new SimpleMappedEntity((Map<String, Object>) entity);
+		}
+
+		return AdaptibleMappedEntity.of(entity, context, conversionService);
+	}
+
+	public String determineCollectionName(@Nullable Class<?> entityClass) {
+
+		if (entityClass == null) {
+			throw new InvalidDataAccessApiUsageException(
+					"No class parameter provided, entity collection can't be determined!");
+		}
+
+		return context.getRequiredPersistentEntity(entityClass).getCollection();
+	}
+
+	/**
+	 * Returns the collection name to be used for the given entity.
+	 *
+	 * @param obj can be {@literal null}.
+	 * @return
+	 */
+	@Nullable
+	public String determineEntityCollectionName(@Nullable Object obj) {
+		return null == obj ? null : determineCollectionName(obj.getClass());
+	}
+
+	public Query getByIdInQuery(Collection<?> entities) {
+
+		MultiValueMap<String, Object> byIds = new LinkedMultiValueMap<>();
+
+		entities.stream() //
+				.map(this::forEntity) //
+				.forEach(it -> byIds.add(it.getIdFieldName(), it.getId()));
+
+		Criteria[] criterias = byIds.entrySet().stream() //
+				.map(it -> Criteria.where(it.getKey()).in(it.getValue())) //
+				.toArray(Criteria[]::new);
+
+		return new Query(criterias.length == 1 ? criterias[0] : new Criteria().orOperator(criterias));
+	}
+
+	/**
+	 * Returns the name of the identifier property. Considers mapping information but falls back to the MongoDB default of
+	 * {@code _id} if no identifier property can be found.
+	 *
+	 * @param type must not be {@literal null}.
+	 * @return
+	 */
+	public String getIdPropertyName(Class<?> type) {
+
+		Assert.notNull(type, "Type must not be null!");
+
+		MongoPersistentEntity<?> persistentEntity = context.getPersistentEntity(type);
+
+		if (persistentEntity != null && persistentEntity.getIdProperty() != null) {
+			return persistentEntity.getRequiredIdProperty().getName();
+		}
+
+		return ID_FIELD;
+	}
+
+	private static Document parse(String source) {
+
+		try {
+			return Document.parse(source);
+		} catch (JSONParseException | org.bson.json.JsonParseException o_O) {
+			throw new MappingException("Could not parse given String to save into a JSON document!", o_O);
+		}
+	}
+
+	/**
+	 * A representation of information about an entity.
+	 *
+	 * @author Oliver Gierke
+	 * @since 2.1
+	 */
+	interface Entity<T> {
+
+		/**
+		 * Returns the field name of the identifier of the entity.
+		 *
+		 * @return
+		 */
+		String getIdFieldName();
+
+		/**
+		 * Returns the identifier of the entity.
+		 *
+		 * @return
+		 */
+		Object getId();
+
+		/**
+		 * Returns the {@link Query} to find the entity by its identifier.
+		 *
+		 * @return
+		 */
+		Query getByIdQuery();
+
+		/**
+		 * Returns the {@link Query} to find the entity in its current version.
+		 *
+		 * @return
+		 */
+		Query getQueryForVersion();
+
+		/**
+		 * Maps the backing entity into a {@link MappedDocument} using the given {@link MongoWriter}.
+		 *
+		 * @param writer must not be {@literal null}.
+		 * @return
+		 */
+		MappedDocument toMappedDocument(MongoWriter<? super T> writer);
+
+		/**
+		 * Asserts that the identifier type is updatable in case its not already set.
+		 */
+		default void assertUpdateableIdIfNotSet() {}
+
+		/**
+		 * Returns whether the entity is versioned, i.e. if it contains a version property.
+		 *
+		 * @return
+		 */
+		default boolean isVersionedEntity() {
+			return false;
+		}
+
+		/**
+		 * Returns the value of the version if the entity has a version property, {@literal null} otherwise.
+		 *
+		 * @return
+		 */
+		@Nullable
+		Object getVersion();
+
+		/**
+		 * Returns the underlying bean.
+		 *
+		 * @return
+		 */
+		T getBean();
+
+		/**
+		 * Returns whether the entity is considered to be new.
+		 * 
+		 * @return
+		 * @since 2.1.2
+		 */
+		boolean isNew();
+	}
+
+	/**
+	 * Information and commands on an entity.
+	 *
+	 * @author Oliver Gierke
+	 * @since 2.1
+	 */
+	interface AdaptibleEntity<T> extends Entity<T> {
+
+		/**
+		 * Populates the identifier of the backing entity if it has an identifier property and there's no identifier
+		 * currently present.
+		 *
+		 * @param id must not be {@literal null}.
+		 * @return
+		 */
+		@Nullable
+		T populateIdIfNecessary(@Nullable Object id);
+
+		/**
+		 * Initializes the version property of the of the current entity if available.
+		 *
+		 * @return the entity with the version property updated if available.
+		 */
+		T initializeVersionProperty();
+
+		/**
+		 * Increments the value of the version property if available.
+		 *
+		 * @return the entity with the version property incremented if available.
+		 */
+		T incrementVersion();
+
+		/**
+		 * Returns the current version value if the entity has a version property.
+		 *
+		 * @return the current version or {@literal null} in case it's uninitialized or the entity doesn't expose a version
+		 *         property.
+		 */
+		@Nullable
+		Number getVersion();
+	}
+
+	@RequiredArgsConstructor
+	private static class UnmappedEntity<T extends Map<String, Object>> implements AdaptibleEntity<T> {
+
+		private final T map;
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#getIdPropertyName()
+		 */
+		@Override
+		public String getIdFieldName() {
+			return ID_FIELD;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#getId()
+		 */
+		@Override
+		public Object getId() {
+			return map.get(ID_FIELD);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#getByIdQuery()
+		 */
+		@Override
+		public Query getByIdQuery() {
+			return Query.query(Criteria.where(ID_FIELD).is(map.get(ID_FIELD)));
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.MutablePersistableSource#populateIdIfNecessary(java.lang.Object)
+		 */
+		@Nullable
+		@Override
+		public T populateIdIfNecessary(@Nullable Object id) {
+
+			map.put(ID_FIELD, id);
+
+			return map;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#getQueryForVersion()
+		 */
+		@Override
+		public Query getQueryForVersion() {
+			throw new MappingException("Cannot query for version on plain Documents!");
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#toMappedDocument(org.springframework.data.mongodb.core.convert.MongoWriter)
+		 */
+		@Override
+		public MappedDocument toMappedDocument(MongoWriter<? super T> writer) {
+			return MappedDocument.of(map instanceof Document //
+					? (Document) map //
+					: new Document(map));
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.MutablePersistableSource#initializeVersionProperty()
+		 */
+		@Override
+		public T initializeVersionProperty() {
+			return map;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.MutablePersistableSource#getVersion()
+		 */
+		@Override
+		@Nullable
+		public Number getVersion() {
+			return null;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.MutablePersistableSource#incrementVersion()
+		 */
+		@Override
+		public T incrementVersion() {
+			return map;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#getBean()
+		 */
+		@Override
+		public T getBean() {
+			return map;
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.Entity#isNew()
+		 */
+		@Override
+		public boolean isNew() {
+			return map.get(ID_FIELD) != null;
+		}
+	}
+
+	private static class SimpleMappedEntity<T extends Map<String, Object>> extends UnmappedEntity<T> {
+
+		SimpleMappedEntity(T map) {
+			super(map);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#toMappedDocument(org.springframework.data.mongodb.core.convert.MongoWriter)
+		 */
+		@Override
+		@SuppressWarnings("unchecked")
+		public MappedDocument toMappedDocument(MongoWriter<? super T> writer) {
+
+			T bean = getBean();
+			bean = (T) (bean instanceof Document //
+					? (Document) bean //
+					: new Document(bean));
+			Document document = new Document();
+			writer.write(bean, document);
+
+			return MappedDocument.of(document);
+		}
+	}
+
+	@RequiredArgsConstructor(access = AccessLevel.PROTECTED)
+	private static class MappedEntity<T> implements Entity<T> {
+
+		private final @NonNull MongoPersistentEntity<?> entity;
+		private final @NonNull IdentifierAccessor idAccessor;
+		private final @NonNull PersistentPropertyAccessor<T> propertyAccessor;
+
+		private static <T> MappedEntity<T> of(T bean,
+				MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> context) {
+
+			MongoPersistentEntity<?> entity = context.getRequiredPersistentEntity(bean.getClass());
+			IdentifierAccessor identifierAccessor = entity.getIdentifierAccessor(bean);
+			PersistentPropertyAccessor<T> propertyAccessor = entity.getPropertyAccessor(bean);
+
+			return new MappedEntity<>(entity, identifierAccessor, propertyAccessor);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#getIdPropertyName()
+		 */
+		@Override
+		public String getIdFieldName() {
+			return entity.getRequiredIdProperty().getFieldName();
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#getId()
+		 */
+		@Override
+		public Object getId() {
+			return idAccessor.getRequiredIdentifier();
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#getByIdQuery()
+		 */
+		@Override
+		public Query getByIdQuery() {
+
+			if (!entity.hasIdProperty()) {
+				throw new MappingException("No id property found for object of type " + entity.getType() + "!");
+			}
+
+			MongoPersistentProperty idProperty = entity.getRequiredIdProperty();
+
+			return Query.query(Criteria.where(idProperty.getName()).is(getId()));
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#getQueryForVersion(java.lang.Object)
+		 */
+		@Override
+		public Query getQueryForVersion() {
+
+			MongoPersistentProperty idProperty = entity.getRequiredIdProperty();
+			MongoPersistentProperty property = entity.getRequiredVersionProperty();
+
+			return new Query(Criteria.where(idProperty.getName()).is(getId())//
+					.and(property.getName()).is(getVersion()));
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#toMappedDocument(org.springframework.data.mongodb.core.convert.MongoWriter)
+		 */
+		@Override
+		public MappedDocument toMappedDocument(MongoWriter<? super T> writer) {
+
+			T bean = propertyAccessor.getBean();
+
+			Document document = new Document();
+			writer.write(bean, document);
+
+			if (document.containsKey(ID_FIELD) && document.get(ID_FIELD) == null) {
+				document.remove(ID_FIELD);
+			}
+
+			return MappedDocument.of(document);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.Entity#assertUpdateableIdIfNotSet()
+		 */
+		public void assertUpdateableIdIfNotSet() {
+
+			if (!entity.hasIdProperty()) {
+				return;
+			}
+
+			MongoPersistentProperty property = entity.getRequiredIdProperty();
+			Object propertyValue = idAccessor.getIdentifier();
+
+			if (propertyValue != null) {
+				return;
+			}
+
+			if (!MongoSimpleTypes.AUTOGENERATED_ID_TYPES.contains(property.getType())) {
+				throw new InvalidDataAccessApiUsageException(
+						String.format("Cannot autogenerate id of type %s for entity of type %s!", property.getType().getName(),
+								entity.getType().getName()));
+			}
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#isVersionedEntity()
+		 */
+		@Override
+		public boolean isVersionedEntity() {
+			return entity.hasVersionProperty();
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#getVersion()
+		 */
+		@Override
+		@Nullable
+		public Object getVersion() {
+			return propertyAccessor.getProperty(entity.getRequiredVersionProperty());
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.PersistableSource#getBean()
+		 */
+		@Override
+		public T getBean() {
+			return propertyAccessor.getBean();
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.Entity#isNew()
+		 */
+		@Override
+		public boolean isNew() {
+			return entity.isNew(propertyAccessor.getBean());
+		}
+	}
+
+	private static class AdaptibleMappedEntity<T> extends MappedEntity<T> implements AdaptibleEntity<T> {
+
+		private final MongoPersistentEntity<?> entity;
+		private final ConvertingPropertyAccessor<T> propertyAccessor;
+		private final IdentifierAccessor identifierAccessor;
+
+		private AdaptibleMappedEntity(MongoPersistentEntity<?> entity, IdentifierAccessor identifierAccessor,
+				ConvertingPropertyAccessor<T> propertyAccessor) {
+
+			super(entity, identifierAccessor, propertyAccessor);
+
+			this.entity = entity;
+			this.propertyAccessor = propertyAccessor;
+			this.identifierAccessor = identifierAccessor;
+		}
+
+		private static <T> AdaptibleEntity<T> of(T bean,
+				MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> context,
+				ConversionService conversionService) {
+
+			MongoPersistentEntity<?> entity = context.getRequiredPersistentEntity(bean.getClass());
+			IdentifierAccessor identifierAccessor = entity.getIdentifierAccessor(bean);
+			PersistentPropertyAccessor<T> propertyAccessor = entity.getPropertyAccessor(bean);
+
+			return new AdaptibleMappedEntity<>(entity, identifierAccessor,
+					new ConvertingPropertyAccessor<>(propertyAccessor, conversionService));
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.AdaptibleEntity#populateIdIfNecessary(java.lang.Object)
+		 */
+		@Nullable
+		@Override
+		public T populateIdIfNecessary(@Nullable Object id) {
+
+			if (id == null) {
+				return null;
+			}
+
+			T bean = propertyAccessor.getBean();
+			MongoPersistentProperty idProperty = entity.getIdProperty();
+
+			if (idProperty == null) {
+				return bean;
+			}
+
+			if (identifierAccessor.getIdentifier() != null) {
+				return bean;
+			}
+
+			propertyAccessor.setProperty(idProperty, id);
+
+			return propertyAccessor.getBean();
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.MappedEntity#getVersion()
+		 */
+		@Override
+		@Nullable
+		public Number getVersion() {
+
+			MongoPersistentProperty versionProperty = entity.getRequiredVersionProperty();
+
+			return propertyAccessor.getProperty(versionProperty, Number.class);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.AdaptibleEntity#initializeVersionProperty()
+		 */
+		@Override
+		public T initializeVersionProperty() {
+
+			if (!entity.hasVersionProperty()) {
+				return propertyAccessor.getBean();
+			}
+
+			MongoPersistentProperty versionProperty = entity.getRequiredVersionProperty();
+
+			propertyAccessor.setProperty(versionProperty, versionProperty.getType().isPrimitive() ? 1 : 0);
+
+			return propertyAccessor.getBean();
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.EntityOperations.AdaptibleEntity#incrementVersion()
+		 */
+		@Override
+		public T incrementVersion() {
+
+			MongoPersistentProperty versionProperty = entity.getRequiredVersionProperty();
+			Number version = getVersion();
+			Number nextVersion = version == null ? 0 : version.longValue() + 1;
+
+			propertyAccessor.setProperty(versionProperty, nextVersion);
+
+			return propertyAccessor.getBean();
+		}
+	}
+}

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

@@ -119,11 +119,11 @@ class ExecutableAggregationOperationSupport implements ExecutableAggregationOper
 				TypedAggregation<?> typedAggregation = (TypedAggregation<?>) aggregation;
 
 				if (typedAggregation.getInputType() != null) {
-					return template.determineCollectionName(typedAggregation.getInputType());
+					return template.getCollectionName(typedAggregation.getInputType());
 				}
 			}
 
-			return template.determineCollectionName(domainType);
+			return template.getCollectionName(domainType);
 		}
 	}
 }

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

@@ -230,7 +230,7 @@ class ExecutableFindOperationSupport implements ExecutableFindOperation {
 		}
 
 		private String getCollectionName() {
-			return StringUtils.hasText(collection) ? collection : template.determineCollectionName(domainType);
+			return StringUtils.hasText(collection) ? collection : template.getCollectionName(domainType);
 		}
 
 		private String asString() {

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

@@ -63,17 +63,19 @@ public interface ExecutableInsertOperation {
 		 * Insert exactly one object.
 		 *
 		 * @param object must not be {@literal null}.
+		 * @return the inserted object.
 		 * @throws IllegalArgumentException if object is {@literal null}.
 		 */
-		void one(T object);
+		T one(T object);
 
 		/**
 		 * Insert a collection of objects.
 		 *
 		 * @param objects must not be {@literal null}.
+		 * @return the inserted objects.
 		 * @throws IllegalArgumentException if objects is {@literal null}.
 		 */
-		void all(Collection<? extends T> objects);
+		Collection<? extends T> all(Collection<? extends T> objects);
 	}
 
 	/**

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

@@ -72,11 +72,11 @@ class ExecutableInsertOperationSupport implements ExecutableInsertOperation {
 		 * @see org.springframework.data.mongodb.core.ExecutableInsertOperation.TerminatingInsert#insert(java.lang.Class)
 		 */
 		@Override
-		public void one(T object) {
+		public T one(T object) {
 
 			Assert.notNull(object, "Object must not be null!");
 
-			template.insert(object, getCollectionName());
+			return template.insert(object, getCollectionName());
 		}
 
 		/*
@@ -84,11 +84,11 @@ class ExecutableInsertOperationSupport implements ExecutableInsertOperation {
 		 * @see org.springframework.data.mongodb.core.ExecutableInsertOperation.TerminatingInsert#all(java.util.Collection)
 		 */
 		@Override
-		public void all(Collection<? extends T> objects) {
+		public Collection<T> all(Collection<? extends T> objects) {
 
 			Assert.notNull(objects, "Objects must not be null!");
 
-			template.insert(objects, getCollectionName());
+			return template.insert(objects, getCollectionName());
 		}
 
 		/*
@@ -129,7 +129,7 @@ class ExecutableInsertOperationSupport implements ExecutableInsertOperation {
 		}
 
 		private String getCollectionName() {
-			return StringUtils.hasText(collection) ? collection : template.determineCollectionName(domainType);
+			return StringUtils.hasText(collection) ? collection : template.getCollectionName(domainType);
 		}
 	}
 }

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

@@ -15,10 +15,11 @@
  */
 package org.springframework.data.mongodb.core;
 
-import java.util.List;
-
 import lombok.NonNull;
 import lombok.RequiredArgsConstructor;
+
+import java.util.List;
+
 import org.springframework.data.mongodb.core.mapreduce.MapReduceOptions;
 import org.springframework.data.mongodb.core.query.Query;
 import org.springframework.lang.Nullable;
@@ -67,8 +68,9 @@ class ExecutableMapReduceOperationSupport implements ExecutableMapReduceOperatio
 		private final @Nullable String reduceFunction;
 		private final @Nullable MapReduceOptions options;
 
-		ExecutableMapReduceSupport(MongoTemplate template, Class<?> domainType, Class<T> returnType, @Nullable String collection,
-				Query query, @Nullable String mapFunction, @Nullable String reduceFunction, @Nullable MapReduceOptions options) {
+		ExecutableMapReduceSupport(MongoTemplate template, Class<?> domainType, Class<T> returnType,
+				@Nullable String collection, Query query, @Nullable String mapFunction, @Nullable String reduceFunction,
+				@Nullable MapReduceOptions options) {
 
 			this.template = template;
 			this.domainType = domainType;
@@ -169,7 +171,7 @@ class ExecutableMapReduceOperationSupport implements ExecutableMapReduceOperatio
 		}
 
 		private String getCollectionName() {
-			return StringUtils.hasText(collection) ? collection : template.determineCollectionName(domainType);
+			return StringUtils.hasText(collection) ? collection : template.getCollectionName(domainType);
 		}
 	}
 }

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

@@ -53,26 +53,6 @@ public interface ExecutableRemoveOperation {
 	 */
 	<T> ExecutableRemove<T> remove(Class<T> domainType);
 
-	/**
-	 * Collection override (optional).
-	 *
-	 * @param <T>
-	 * @author Christoph Strobl
-	 * @since 2.0
-	 */
-	interface RemoveWithCollection<T> extends RemoveWithQuery<T> {
-
-		/**
-		 * Explicitly set the name of the collection to perform the query on. <br />
-		 * Skip this step to use the default collection derived from the domain type.
-		 *
-		 * @param collection must not be {@literal null} nor {@literal empty}.
-		 * @return new instance of {@link RemoveWithCollection}.
-		 * @throws IllegalArgumentException if collection is {@literal null}.
-		 */
-		RemoveWithQuery<T> inCollection(String collection);
-	}
-
 	/**
 	 * @author Christoph Strobl
 	 * @since 2.0
@@ -104,6 +84,27 @@ public interface ExecutableRemoveOperation {
 		List<T> findAndRemove();
 	}
 
+	/**
+	 * Collection override (optional).
+	 *
+	 * @param <T>
+	 * @author Christoph Strobl
+	 * @since 2.0
+	 */
+	interface RemoveWithCollection<T> extends RemoveWithQuery<T> {
+
+		/**
+		 * Explicitly set the name of the collection to perform the query on. <br />
+		 * Skip this step to use the default collection derived from the domain type.
+		 *
+		 * @param collection must not be {@literal null} nor {@literal empty}.
+		 * @return new instance of {@link RemoveWithCollection}.
+		 * @throws IllegalArgumentException if collection is {@literal null}.
+		 */
+		RemoveWithQuery<T> inCollection(String collection);
+	}
+
+
 	/**
 	 * @author Christoph Strobl
 	 * @since 2.0

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

@@ -123,7 +123,7 @@ class ExecutableRemoveOperationSupport implements ExecutableRemoveOperation {
 		}
 
 		private String getCollectionName() {
-			return StringUtils.hasText(collection) ? collection : template.determineCollectionName(domainType);
+			return StringUtils.hasText(collection) ? collection : template.getCollectionName(domainType);
 		}
 	}
 }

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

@@ -19,13 +19,13 @@ import java.util.Optional;
 
 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;
 
+import com.mongodb.client.result.UpdateResult;
+
 /**
- * {@link ExecutableUpdateOperation} allows creation and execution of MongoDB update / findAndModify operations in a
- * fluent API style. <br />
+ * {@link ExecutableUpdateOperation} allows creation and execution of MongoDB update / findAndModify / findAndReplace
+ * operations in a fluent API style. <br />
  * The starting {@literal domainType} is used for mapping the {@link Query} provided via {@code matching}, as well as
  * the {@link Update} via {@code apply} into the MongoDB specific representations. The collection to operate on is by
  * default derived from the initial {@literal domainType} and can be defined there via
@@ -57,6 +57,91 @@ public interface ExecutableUpdateOperation {
 	 */
 	<T> ExecutableUpdate<T> update(Class<T> domainType);
 
+	/**
+	 * Trigger findAndModify execution by calling one of the terminating methods.
+	 *
+	 * @author Christoph Strobl
+	 * @author Mark Paluch
+	 * @since 2.0
+	 */
+	interface TerminatingFindAndModify<T> {
+
+		/**
+		 * Find, modify and return the first matching document.
+		 *
+		 * @return {@link Optional#empty()} if nothing found.
+		 */
+		default Optional<T> findAndModify() {
+			return Optional.ofNullable(findAndModifyValue());
+		}
+
+		/**
+		 * Find, modify and return the first matching document.
+		 *
+		 * @return {@literal null} if nothing found.
+		 */
+		@Nullable
+		T findAndModifyValue();
+	}
+
+	/**
+	 * Trigger
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * execution by calling one of the terminating methods.
+	 *
+	 * @author Mark Paluch
+	 * @since 2.1
+	 */
+	interface TerminatingFindAndReplace<T> {
+
+		/**
+		 * Find, replace and return the first matching document.
+		 *
+		 * @return {@link Optional#empty()} if nothing found.
+		 */
+		default Optional<T> findAndReplace() {
+			return Optional.ofNullable(findAndReplaceValue());
+		}
+
+		/**
+		 * Find, replace and return the first matching document.
+		 *
+		 * @return {@literal null} if nothing found.
+		 */
+		@Nullable
+		T findAndReplaceValue();
+	}
+
+	/**
+	 * Trigger update execution by calling one of the terminating methods.
+	 *
+	 * @author Christoph Strobl
+	 * @since 2.0
+	 */
+	interface TerminatingUpdate<T> extends TerminatingFindAndModify<T>, FindAndModifyWithOptions<T> {
+
+		/**
+		 * Update all matching documents in the collection.
+		 *
+		 * @return never {@literal null}.
+		 */
+		UpdateResult all();
+
+		/**
+		 * Update the first document in the collection.
+		 *
+		 * @return never {@literal null}.
+		 */
+		UpdateResult first();
+
+		/**
+		 * Creates a new document if no documents match the filter query or updates the matching ones.
+		 *
+		 * @return never {@literal null}.
+		 */
+		UpdateResult upsert();
+	}
+
 	/**
 	 * Declare the {@link Update} to apply.
 	 *
@@ -73,6 +158,16 @@ public interface ExecutableUpdateOperation {
 		 * @throws IllegalArgumentException if update is {@literal null}.
 		 */
 		TerminatingUpdate<T> apply(Update update);
+
+		/**
+		 * Specify {@code replacement} object.
+		 *
+		 * @param replacement must not be {@literal null}.
+		 * @return new instance of {@link FindAndReplaceOptions}.
+		 * @throws IllegalArgumentException if options is {@literal null}.
+		 * @since 2.1
+		 */
+		FindAndReplaceWithProjection<T> replaceWith(T replacement);
 	}
 
 	/**
@@ -131,56 +226,43 @@ public interface ExecutableUpdateOperation {
 	}
 
 	/**
-	 * Trigger findAndModify execution by calling one of the terminating methods.
+	 * Define {@link FindAndReplaceOptions}.
+	 *
+	 * @author Mark Paluch
+	 * @author Christoph Strobl
+	 * @since 2.1
 	 */
-	interface TerminatingFindAndModify<T> {
+	interface FindAndReplaceWithOptions<T> extends TerminatingFindAndReplace<T> {
 
 		/**
-		 * Find, modify and return the first matching document.
+		 * Explicitly define {@link FindAndReplaceOptions} for the {@link Update}.
 		 *
-		 * @return {@link Optional#empty()} if nothing found.
+		 * @param options must not be {@literal null}.
+		 * @return new instance of {@link FindAndReplaceOptions}.
+		 * @throws IllegalArgumentException if options is {@literal null}.
 		 */
-		default Optional<T> findAndModify() {
-			return Optional.ofNullable(findAndModifyValue());
-		}
-
-		/**
-		 * Find, modify and return the first matching document.
-		 *
-		 * @return {@literal null} if nothing found.
-		 */
-		@Nullable
-		T findAndModifyValue();
+		FindAndReplaceWithProjection<T> withOptions(FindAndReplaceOptions options);
 	}
 
 	/**
-	 * Trigger update execution by calling one of the terminating methods.
+	 * Result type override (Optional).
 	 *
 	 * @author Christoph Strobl
-	 * @since 2.0
+	 * @since 2.1
 	 */
-	interface TerminatingUpdate<T> extends TerminatingFindAndModify<T>, FindAndModifyWithOptions<T> {
+	interface FindAndReplaceWithProjection<T> extends FindAndReplaceWithOptions<T> {
 
 		/**
-		 * Update all matching documents in the collection.
+		 * Define the target type fields should be mapped to. <br />
+		 * Skip this step if you are anyway only interested in the original domain type.
 		 *
-		 * @return never {@literal null}.
+		 * @param resultType must not be {@literal null}.
+		 * @param <R> result type.
+		 * @return new instance of {@link FindAndReplaceWithProjection}.
+		 * @throws IllegalArgumentException if resultType is {@literal null}.
 		 */
-		UpdateResult all();
+		<R> FindAndReplaceWithOptions<R> as(Class<R> resultType);
 
-		/**
-		 * Update the first document in the collection.
-		 *
-		 * @return never {@literal null}.
-		 */
-		UpdateResult first();
-
-		/**
-		 * Creates a new document if no documents match the filter query or updates the matching ones.
-		 *
-		 * @return never {@literal null}.
-		 */
-		UpdateResult upsert();
 	}
 
 	/**

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

@@ -51,7 +51,7 @@ class ExecutableUpdateOperationSupport implements ExecutableUpdateOperation {
 
 		Assert.notNull(domainType, "DomainType must not be null!");
 
-		return new ExecutableUpdateSupport<>(template, domainType, ALL_QUERY, null, null, null);
+		return new ExecutableUpdateSupport<>(template, domainType, ALL_QUERY, null, null, null, null, null, domainType);
 	}
 
 	/**
@@ -61,14 +61,18 @@ class ExecutableUpdateOperationSupport implements ExecutableUpdateOperation {
 	@RequiredArgsConstructor
 	@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
 	static class ExecutableUpdateSupport<T>
-			implements ExecutableUpdate<T>, UpdateWithCollection<T>, UpdateWithQuery<T>, TerminatingUpdate<T> {
+			implements ExecutableUpdate<T>, UpdateWithCollection<T>, UpdateWithQuery<T>, TerminatingUpdate<T>,
+			FindAndReplaceWithOptions<T>, TerminatingFindAndReplace<T>, FindAndReplaceWithProjection<T> {
 
 		@NonNull MongoTemplate template;
-		@NonNull Class<T> domainType;
+		@NonNull Class domainType;
 		Query query;
 		@Nullable Update update;
 		@Nullable String collection;
-		@Nullable FindAndModifyOptions options;
+		@Nullable FindAndModifyOptions findAndModifyOptions;
+		@Nullable FindAndReplaceOptions findAndReplaceOptions;
+		@Nullable Object replacement;
+		@NonNull Class<T> targetType;
 
 		/*
 		 * (non-Javadoc)
@@ -79,7 +83,8 @@ class ExecutableUpdateOperationSupport implements ExecutableUpdateOperation {
 
 			Assert.notNull(update, "Update must not be null!");
 
-			return new ExecutableUpdateSupport<>(template, domainType, query, update, collection, options);
+			return new ExecutableUpdateSupport<>(template, domainType, query, update, collection, findAndModifyOptions,
+					findAndReplaceOptions, replacement, targetType);
 		}
 
 		/*
@@ -91,7 +96,8 @@ class ExecutableUpdateOperationSupport implements ExecutableUpdateOperation {
 
 			Assert.hasText(collection, "Collection must not be null nor empty!");
 
-			return new ExecutableUpdateSupport<>(template, domainType, query, update, collection, options);
+			return new ExecutableUpdateSupport<>(template, domainType, query, update, collection, findAndModifyOptions,
+					findAndReplaceOptions, replacement, targetType);
 		}
 
 		/*
@@ -103,7 +109,34 @@ class ExecutableUpdateOperationSupport implements ExecutableUpdateOperation {
 
 			Assert.notNull(options, "Options must not be null!");
 
-			return new ExecutableUpdateSupport<>(template, domainType, query, update, collection, options);
+			return new ExecutableUpdateSupport<>(template, domainType, query, update, collection, options,
+					findAndReplaceOptions, replacement, targetType);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.ExecutableUpdateOperation.UpdateWithUpdate#replaceWith(Object)
+		 */
+		@Override
+		public FindAndReplaceWithProjection<T> replaceWith(T replacement) {
+
+			Assert.notNull(replacement, "Replacement must not be null!");
+
+			return new ExecutableUpdateSupport<>(template, domainType, query, update, collection, findAndModifyOptions,
+					findAndReplaceOptions, replacement, targetType);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.ExecutableUpdateOperation.FindAndReplaceWithOptions#withOptions(org.springframework.data.mongodb.core.FindAndReplaceOptions)
+		 */
+		@Override
+		public FindAndReplaceWithProjection<T> withOptions(FindAndReplaceOptions options) {
+
+			Assert.notNull(options, "Options must not be null!");
+
+			return new ExecutableUpdateSupport<>(template, domainType, query, update, collection, findAndModifyOptions,
+					options, replacement, targetType);
 		}
 
 		/*
@@ -115,7 +148,21 @@ class ExecutableUpdateOperationSupport implements ExecutableUpdateOperation {
 
 			Assert.notNull(query, "Query must not be null!");
 
-			return new ExecutableUpdateSupport<>(template, domainType, query, update, collection, options);
+			return new ExecutableUpdateSupport<>(template, domainType, query, update, collection, findAndModifyOptions,
+					findAndReplaceOptions, replacement, targetType);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.ReactiveUpdateOperation.FindAndReplaceWithProjection#as(java.lang.Class)
+		 */
+		@Override
+		public <R> FindAndReplaceWithOptions<R> as(Class<R> resultType) {
+
+			Assert.notNull(resultType, "ResultType must not be null!");
+
+			return new ExecutableUpdateSupport<>(template, domainType, query, update, collection, findAndModifyOptions,
+					findAndReplaceOptions, replacement, resultType);
 		}
 
 		/*
@@ -151,7 +198,22 @@ class ExecutableUpdateOperationSupport implements ExecutableUpdateOperation {
 		 */
 		@Override
 		public @Nullable T findAndModifyValue() {
-			return template.findAndModify(query, update, options != null ? options : new FindAndModifyOptions(), domainType, getCollectionName());
+
+			return template.findAndModify(query, update,
+					findAndModifyOptions != null ? findAndModifyOptions : new FindAndModifyOptions(), targetType,
+					getCollectionName());
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.ExecutableUpdateOperation.TerminatingFindAndReplace#findAndReplaceValue()
+		 */
+		@Override
+		public @Nullable T findAndReplaceValue() {
+
+			return (T) template.findAndReplace(query, replacement,
+					findAndReplaceOptions != null ? findAndReplaceOptions : FindAndReplaceOptions.empty(), domainType,
+					getCollectionName(), targetType);
 		}
 
 		private UpdateResult doUpdate(boolean multi, boolean upsert) {
@@ -159,7 +221,7 @@ class ExecutableUpdateOperationSupport implements ExecutableUpdateOperation {
 		}
 
 		private String getCollectionName() {
-			return StringUtils.hasText(collection) ? collection : template.determineCollectionName(domainType);
+			return StringUtils.hasText(collection) ? collection : template.getCollectionName(domainType);
 		}
 	}
 }

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

@@ -36,15 +36,17 @@ public class FindAndModifyOptions {
 	/**
 	 * Static factory method to create a FindAndModifyOptions instance
 	 *
-	 * @return a new instance
+	 * @return new instance of {@link FindAndModifyOptions}.
 	 */
 	public static FindAndModifyOptions options() {
 		return new FindAndModifyOptions();
 	}
 
 	/**
-	 * @param options
-	 * @return
+	 * Create new {@link FindAndModifyOptions} based on option of given {@litearl source}.
+	 * 
+	 * @param source can be {@literal null}.
+	 * @return new instance of {@link FindAndModifyOptions}.
 	 * @since 2.0
 	 */
 	public static FindAndModifyOptions of(@Nullable FindAndModifyOptions source) {

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

@@ -0,0 +1,109 @@
+/*
+ * 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;
+
+/**
+ * Options for
+ * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>.
+ * <br />
+ * Defaults to
+ * <dl>
+ * <dt>returnNew</dt>
+ * <dd>false</dd>
+ * <dt>upsert</dt>
+ * <dd>false</dd>
+ * </dl>
+ *
+ * @author Mark Paluch
+ * @author Christoph Strobl
+ * @since 2.1
+ */
+public class FindAndReplaceOptions {
+
+	private boolean returnNew;
+	private boolean upsert;
+
+	/**
+	 * Static factory method to create a {@link FindAndReplaceOptions} instance.
+	 * <dl>
+	 * <dt>returnNew</dt>
+	 * <dd>false</dd>
+	 * <dt>upsert</dt>
+	 * <dd>false</dd>
+	 * </dl>
+	 *
+	 * @return new instance of {@link FindAndReplaceOptions}.
+	 */
+	public static FindAndReplaceOptions options() {
+		return new FindAndReplaceOptions();
+	}
+
+	/**
+	 * Static factory method to create a {@link FindAndReplaceOptions} instance with
+	 * <dl>
+	 * <dt>returnNew</dt>
+	 * <dd>false</dd>
+	 * <dt>upsert</dt>
+	 * <dd>false</dd>
+	 * </dl>
+	 *
+	 * @return new instance of {@link FindAndReplaceOptions}.
+	 */
+	public static FindAndReplaceOptions empty() {
+		return new FindAndReplaceOptions();
+	}
+
+	/**
+	 * Return the replacement document.
+	 *
+	 * @return this.
+	 */
+	public FindAndReplaceOptions returnNew() {
+
+		this.returnNew = true;
+		return this;
+	}
+
+	/**
+	 * Insert a new document if not exists.
+	 *
+	 * @return this.
+	 */
+	public FindAndReplaceOptions upsert() {
+
+		this.upsert = true;
+		return this;
+	}
+
+	/**
+	 * Get the bit indicating to return the replacement document.
+	 *
+	 * @return
+	 */
+	public boolean isReturnNew() {
+		return returnNew;
+	}
+
+	/**
+	 * Get the bit indicating if to create a new document if not exists.
+	 *
+	 * @return
+	 */
+	public boolean isUpsert() {
+		return upsert;
+	}
+
+}

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

@@ -0,0 +1,88 @@
+/*
+ * 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.Getter;
+import lombok.RequiredArgsConstructor;
+
+import java.util.Collection;
+import java.util.List;
+
+import org.bson.Document;
+import org.bson.conversions.Bson;
+import org.springframework.data.mongodb.core.query.Update;
+import org.springframework.data.util.StreamUtils;
+
+import com.mongodb.client.model.Filters;
+
+/**
+ * A MongoDB document in its mapped state. I.e. after a source document has been mapped using mapping information of the
+ * entity the source document was supposed to represent.
+ *
+ * @author Oliver Gierke
+ * @since 2.1
+ */
+@RequiredArgsConstructor(staticName = "of")
+public class MappedDocument {
+
+	private static final String ID_FIELD = "_id";
+	private static final Document ID_ONLY_PROJECTION = new Document(ID_FIELD, 1);
+
+	private final @Getter Document document;
+
+	public static Document getIdOnlyProjection() {
+		return ID_ONLY_PROJECTION;
+	}
+
+	public static Document getIdIn(Collection<?> ids) {
+		return new Document(ID_FIELD, new Document("$in", ids));
+	}
+
+	public static List<Object> toIds(Collection<Document> documents) {
+
+		return documents.stream()//
+				.map(it -> it.get(ID_FIELD))//
+				.collect(StreamUtils.toUnmodifiableList());
+	}
+
+	public boolean hasId() {
+		return document.containsKey(ID_FIELD);
+	}
+
+	public boolean hasNonNullId() {
+		return hasId() && document.get(ID_FIELD) != null;
+	}
+
+	public Object getId() {
+		return document.get(ID_FIELD);
+	}
+
+	public <T> T getId(Class<T> type) {
+		return document.get(ID_FIELD, type);
+	}
+
+	public boolean isIdPresent(Class<?> type) {
+		return type.isInstance(getId());
+	}
+
+	public Bson getIdFilter() {
+		return Filters.eq(ID_FIELD, document.get(ID_FIELD));
+	}
+
+	public Update updateWithoutId() {
+		return Update.fromDocument(document, ID_FIELD);
+	}
+}

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

@@ -233,6 +233,15 @@ public abstract class MongoDbFactorySupport<C> implements MongoDbFactory {
 			return delegate.withSession(session);
 		}
 
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.MongoDbFactory#isTransactionActive()
+		 */
+		@Override
+		public boolean isTransactionActive() {
+			return session != null && session.hasActiveTransaction();
+		}
+
 		private MongoDatabase proxyMongoDatabase(MongoDatabase database) {
 			return createProxyInstance(session, database, MongoDatabase.class);
 		}
@@ -241,7 +250,8 @@ public abstract class MongoDbFactorySupport<C> implements MongoDbFactory {
 			return createProxyInstance(session, database, MongoDatabase.class);
 		}
 
-		private MongoCollection<?> proxyCollection(com.mongodb.session.ClientSession session, MongoCollection<?> collection) {
+		private MongoCollection<?> proxyCollection(com.mongodb.session.ClientSession session,
+				MongoCollection<?> collection) {
 			return createProxyInstance(session, collection, MongoCollection.class);
 		}
 

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

@@ -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;
 
@@ -30,6 +31,7 @@ import org.springframework.dao.PermissionDeniedDataAccessException;
 import org.springframework.dao.support.PersistenceExceptionTranslator;
 import org.springframework.data.mongodb.BulkOperationException;
 import org.springframework.data.mongodb.ClientSessionException;
+import org.springframework.data.mongodb.MongoTransactionException;
 import org.springframework.data.mongodb.UncategorizedMongoDbException;
 import org.springframework.data.mongodb.util.MongoDbErrorCodes;
 import org.springframework.lang.Nullable;
@@ -52,17 +54,17 @@ 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"));
 
 	/*
@@ -80,7 +82,7 @@ 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);
 		}
 
@@ -92,7 +94,7 @@ 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) {
@@ -128,6 +130,10 @@ public class MongoExceptionTranslator implements PersistenceExceptionTranslator
 				return new InvalidDataAccessApiUsageException(ex.getMessage(), ex);
 			} else if (MongoDbErrorCodes.isPermissionDeniedCode(code)) {
 				return new PermissionDeniedDataAccessException(ex.getMessage(), ex);
+			} else if (MongoDbErrorCodes.isClientSessionFailureCode(code)) {
+				return new ClientSessionException(ex.getMessage(), ex);
+			} else if (MongoDbErrorCodes.isTransactionFailureCode(code)) {
+				return new MongoTransactionException(ex.getMessage(), ex);
 			}
 			return new UncategorizedMongoDbException(ex.getMessage(), ex);
 		}

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

@@ -28,6 +28,7 @@ import org.springframework.data.mongodb.core.aggregation.Aggregation;
 import org.springframework.data.mongodb.core.aggregation.AggregationOptions;
 import org.springframework.data.mongodb.core.aggregation.AggregationResults;
 import org.springframework.data.mongodb.core.aggregation.TypedAggregation;
+import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
 import org.springframework.data.mongodb.core.convert.MongoConverter;
 import org.springframework.data.mongodb.core.index.IndexOperations;
 import org.springframework.data.mongodb.core.mapreduce.GroupBy;
@@ -42,6 +43,7 @@ import org.springframework.data.mongodb.core.query.Update;
 import org.springframework.data.util.CloseableIterator;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ClassUtils;
 
 import com.mongodb.ClientSessionOptions;
 import com.mongodb.Cursor;
@@ -381,7 +383,7 @@ public interface MongoOperations extends FluentMongoOperations {
 	 * Returns a new {@link BulkOperations} for the given entity type and collection name.
 	 *
 	 * @param mode the {@link BulkMode} to use for bulk operations, must not be {@literal null}.
-	 * @param entityClass the name of the entity class. Can be {@literal null}.
+	 * @param entityType the name of the entity class. Can be {@literal null}.
 	 * @param collectionName the name of the collection to work on, must not be {@literal null} or empty.
 	 * @return {@link BulkOperations} on the named collection associated with the given entity class.
 	 */
@@ -420,8 +422,6 @@ public interface MongoOperations extends FluentMongoOperations {
 	 * Execute a group operation over the entire collection. The group operation entity class should match the 'shape' of
 	 * the returned object that takes int account the initial document structure as well as any finalize functions.
 	 *
-	 * @param criteria The criteria that restricts the row that are considered for grouping. If not specified all rows are
-	 *          considered.
 	 * @param inputCollectionName the collection where the group operation will read from
 	 * @param groupBy the conditions under which the group operation will be performed, e.g. keys, initial document,
 	 *          reduce function.
@@ -894,6 +894,167 @@ public interface MongoOperations extends FluentMongoOperations {
 	<T> T findAndModify(Query query, Update update, FindAndModifyOptions options, Class<T> entityClass,
 			String collectionName);
 
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement}
+	 * document. <br />
+	 * The collection name is derived from the {@literal replacement} type. <br />
+	 * Options are defaulted to {@link FindAndReplaceOptions#empty()}. <br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @return the converted object that was updated or {@literal null}, if not found.
+	 * @since 2.1
+	 */
+	@Nullable
+	default <T> T findAndReplace(Query query, T replacement) {
+		return findAndReplace(query, replacement, FindAndReplaceOptions.empty());
+	}
+
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement}
+	 * document.<br />
+	 * Options are defaulted to {@link FindAndReplaceOptions#empty()}. <br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @param collectionName the collection to query. Must not be {@literal null}.
+	 * @return the converted object that was updated or {@literal null}, if not found.
+	 * @since 2.1
+	 */
+	@Nullable
+	default <T> T findAndReplace(Query query, T replacement, String collectionName) {
+		return findAndReplace(query, replacement, FindAndReplaceOptions.empty(), collectionName);
+	}
+
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement} document
+	 * taking {@link FindAndReplaceOptions} into account.<br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @param options the {@link FindAndModifyOptions} holding additional information. Must not be {@literal null}.
+	 * @return the converted object that was updated or {@literal null}, if not found. Depending on the value of
+	 *         {@link FindAndReplaceOptions#isReturnNew()} this will either be the object as it was before the update or
+	 *         as it is after the update.
+	 * @since 2.1
+	 */
+	@Nullable
+	default <T> T findAndReplace(Query query, T replacement, FindAndReplaceOptions options) {
+		return findAndReplace(query, replacement, options, getCollectionName(ClassUtils.getUserClass(replacement)));
+	}
+
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement} document
+	 * taking {@link FindAndReplaceOptions} into account.<br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @param options the {@link FindAndModifyOptions} holding additional information. Must not be {@literal null}.
+	 * @return the converted object that was updated or {@literal null}, if not found. Depending on the value of
+	 *         {@link FindAndReplaceOptions#isReturnNew()} this will either be the object as it was before the update or
+	 *         as it is after the update.
+	 * @since 2.1
+	 */
+	@Nullable
+	default <T> T findAndReplace(Query query, T replacement, FindAndReplaceOptions options, String collectionName) {
+
+		Assert.notNull(replacement, "Replacement must not be null!");
+		return findAndReplace(query, replacement, options, (Class<T>) ClassUtils.getUserClass(replacement), collectionName);
+	}
+
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement} document
+	 * taking {@link FindAndReplaceOptions} into account.<br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @param options the {@link FindAndModifyOptions} holding additional information. Must not be {@literal null}.
+	 * @param entityType 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 or {@literal null}, if not found. Depending on the value of
+	 *         {@link FindAndReplaceOptions#isReturnNew()} this will either be the object as it was before the update or
+	 *         as it is after the update.
+	 * @since 2.1
+	 */
+	@Nullable
+	default <T> T findAndReplace(Query query, T replacement, FindAndReplaceOptions options, Class<T> entityType,
+			String collectionName) {
+
+		return findAndReplace(query, replacement, options, entityType, collectionName, entityType);
+	}
+
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement} document
+	 * taking {@link FindAndReplaceOptions} into account.<br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @param options the {@link FindAndModifyOptions} holding additional information. Must not be {@literal null}.
+	 * @param entityType the type used for mapping the {@link Query} to domain type fields and deriving the collection
+	 *          from. Must not be {@literal null}.
+	 * @param resultType the parametrized type projection return type. Must not be {@literal null}, use the domain type of
+	 *          {@code Object.class} instead.
+	 * @return the converted object that was updated or {@literal null}, if not found. Depending on the value of
+	 *         {@link FindAndReplaceOptions#isReturnNew()} this will either be the object as it was before the update or
+	 *         as it is after the update.
+	 * @since 2.1
+	 */
+	@Nullable
+	default <S, T> T findAndReplace(Query query, S replacement, FindAndReplaceOptions options, Class<S> entityType,
+			Class<T> resultType) {
+
+		return findAndReplace(query, replacement, options, entityType,
+				getCollectionName(ClassUtils.getUserClass(entityType)), resultType);
+	}
+
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement} document
+	 * taking {@link FindAndReplaceOptions} into account.<br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @param options the {@link FindAndModifyOptions} holding additional information. Must not be {@literal null}.
+	 * @param entityType the type used for mapping the {@link Query} to domain type fields. Must not be {@literal null}.
+	 * @param collectionName the collection to query. Must not be {@literal null}.
+	 * @param resultType the parametrized type projection return type. Must not be {@literal null}, use the domain type of
+	 *          {@code Object.class} instead.
+	 * @return the converted object that was updated or {@literal null}, if not found. Depending on the value of
+	 *         {@link FindAndReplaceOptions#isReturnNew()} this will either be the object as it was before the update or
+	 *         as it is after the update.
+	 * @since 2.1
+	 */
+	@Nullable
+	<S, T> T findAndReplace(Query query, S replacement, FindAndReplaceOptions options, Class<S> entityType,
+			String collectionName, Class<T> resultType);
+
 	/**
 	 * Map the results of an ad-hoc query on the collection for the entity type to a single instance of an object of the
 	 * specified type. The first document that matches the query is returned and also removed from the collection in the
@@ -980,8 +1141,9 @@ public interface MongoOperations extends FluentMongoOperations {
 	 * 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. Must not be {@literal null}.
+	 * @return the inserted object.
 	 */
-	void insert(Object objectToSave);
+	<T> T insert(T objectToSave);
 
 	/**
 	 * Insert the object into the specified collection.
@@ -993,32 +1155,36 @@ public interface MongoOperations extends FluentMongoOperations {
 	 *
 	 * @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 inserted object.
 	 */
-	void insert(Object objectToSave, String collectionName);
+	<T> 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. Must not be {@literal null}.
 	 * @param entityClass class that determines the collection to use. Must not be {@literal null}.
+	 * @return the inserted objects that.
 	 */
-	void insert(Collection<? extends Object> batchToSave, Class<?> entityClass);
+	<T> Collection<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. Must not be {@literal null}.
 	 * @param collectionName name of the collection to store the object in. Must not be {@literal null}.
+	 * @return the inserted objects that.
 	 */
-	void insert(Collection<? extends Object> batchToSave, String collectionName);
+	<T> Collection<T> insert(Collection<? extends T> batchToSave, String collectionName);
 
 	/**
 	 * 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. Must not be {@literal null}.
+	 * @return the inserted objects.
 	 */
-	void insertAll(Collection<? extends Object> objectsToSave);
+	<T> Collection<T> insertAll(Collection<? extends T> objectsToSave);
 
 	/**
 	 * Save the object to the collection for the entity type of the object to save. This will perform an insert if the
@@ -1034,8 +1200,9 @@ public interface MongoOperations extends FluentMongoOperations {
 	 * Conversion"</a> for more details.
 	 *
 	 * @param objectToSave the object to store in the collection. Must not be {@literal null}.
+	 * @return the saved object.
 	 */
-	void save(Object objectToSave);
+	<T> T save(T objectToSave);
 
 	/**
 	 * Save the object to the specified collection. This will perform an insert if the object is not already present, that
@@ -1052,8 +1219,9 @@ public interface MongoOperations extends FluentMongoOperations {
 	 *
 	 * @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.
 	 */
-	void save(Object objectToSave, String collectionName);
+	<T> T save(T objectToSave, String collectionName);
 
 	/**
 	 * Performs an upsert. If no document is found that matches the query, a new document is created and inserted by

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

@@ -0,0 +1,75 @@
+/*
+ * 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.AccessLevel;
+import lombok.RequiredArgsConstructor;
+
+import org.bson.Document;
+import org.springframework.data.mapping.SimplePropertyHandler;
+import org.springframework.data.mapping.context.MappingContext;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+import org.springframework.data.projection.ProjectionFactory;
+import org.springframework.data.projection.ProjectionInformation;
+import org.springframework.util.ClassUtils;
+
+/**
+ * Common operations performed on properties of an entity like extracting fields information for projection creation.
+ *
+ * @author Christoph Strobl
+ * @since 2.1
+ */
+@RequiredArgsConstructor(access = AccessLevel.PACKAGE)
+class PropertyOperations {
+
+	private final MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext;
+
+	/**
+	 * For cases where {@code fields} is {@link Document#isEmpty() empty} include only fields that are required for
+	 * creating the projection (target) type if the {@code targetType} is a {@literal DTO projection} or a
+	 * {@literal closed interface projection}.
+	 *
+	 * @param projectionFactory must not 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.
+	 */
+	Document computeFieldsForProjection(ProjectionFactory projectionFactory, Document fields, Class<?> domainType,
+			Class<?> targetType) {
+
+		if (!fields.isEmpty() || ClassUtils.isAssignable(domainType, targetType)) {
+			return fields;
+		}
+
+		Document projectedFields = new Document();
+
+		if (targetType.isInterface()) {
+
+			ProjectionInformation projectionInformation = projectionFactory.getProjectionInformation(targetType);
+
+			if (projectionInformation.isClosed()) {
+				projectionInformation.getInputProperties().forEach(it -> projectedFields.append(it.getName(), 1));
+			}
+		} else {
+			mappingContext.getRequiredPersistentEntity(targetType).doWithProperties(
+					(SimplePropertyHandler) persistentProperty -> projectedFields.append(persistentProperty.getName(), 1));
+		}
+
+		return projectedFields;
+	}
+}

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

@@ -30,5 +30,4 @@ import com.mongodb.reactivestreams.client.MongoCollection;
 public interface ReactiveCollectionCallback<T> {
 
 	Publisher<T> doInCollection(MongoCollection<Document> collection) throws MongoException, DataAccessException;
-
 }

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

@@ -85,6 +85,23 @@ public interface ReactiveFindOperation {
 		 */
 		Flux<T> all();
 
+		/**
+		 * Get all matching elements using a {@link com.mongodb.CursorType#TailableAwait tailable cursor}. The stream will
+		 * not be completed unless the {@link org.reactivestreams.Subscription} is
+		 * {@link org.reactivestreams.Subscription#cancel() canceled}.
+		 * <p />
+		 * However, the stream may become dead, or invalid, if either the query returns no match or the cursor returns the
+		 * document at the "end" of the collection and then the application deletes that document.
+		 * <p />
+		 * A stream that is no longer in use must be {@link reactor.core.Disposable#dispose()} disposed} otherwise the
+		 * streams will linger and exhaust resources. <br/>
+		 * <strong>NOTE:</strong> Requires a capped collection.
+		 *
+		 * @return the {@link Flux} emitting converted objects.
+		 * @since 2.1
+		 */
+		Flux<T> tail();
+
 		/**
 		 * Get the number of matching elements.
 		 *

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

@@ -169,6 +169,15 @@ class ReactiveFindOperationSupport implements ReactiveFindOperation {
 			return doFind(null);
 		}
 
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.ReactiveFindOperation.TerminatingFind#tail()
+		 */
+		@Override
+		public Flux<T> tail() {
+			return doFind(template.new TailingQueryFindPublisherPreparer(query, domainType));
+		}
+
 		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.ReactiveFindOperation.FindWithQuery#near(org.springframework.data.mongodb.core.query.NearQuery)

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

@@ -19,7 +19,6 @@ import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 import java.util.Collection;
-import java.util.List;
 import java.util.function.Consumer;
 import java.util.function.Supplier;
 
@@ -27,6 +26,7 @@ import org.bson.Document;
 import org.reactivestreams.Publisher;
 import org.reactivestreams.Subscription;
 import org.springframework.data.geo.GeoResult;
+import org.springframework.data.mongodb.ReactiveMongoDatabaseFactory;
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
 import org.springframework.data.mongodb.core.aggregation.AggregationOptions;
 import org.springframework.data.mongodb.core.aggregation.TypedAggregation;
@@ -41,6 +41,7 @@ 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.ClassUtils;
 
 import com.mongodb.ClientSessionOptions;
 import com.mongodb.ReadPreference;
@@ -688,6 +689,160 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	<T> Mono<T> findAndModify(Query query, Update update, FindAndModifyOptions options, Class<T> entityClass,
 			String collectionName);
 
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement}
+	 * document. <br />
+	 * Options are defaulted to {@link FindAndReplaceOptions#empty()}. <br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @return the converted object that was updated or {@link Mono#empty()}, if not found.
+	 * @since 2.1
+	 */
+	default <T> Mono<T> findAndReplace(Query query, T replacement) {
+		return findAndReplace(query, replacement, FindAndReplaceOptions.empty());
+	}
+
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement}
+	 * document. <br />
+	 * Options are defaulted to {@link FindAndReplaceOptions#empty()}. <br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @param collectionName the collection to query. Must not be {@literal null}.
+	 * @return the converted object that was updated or {@link Mono#empty()}, if not found.
+	 * @since 2.1
+	 */
+	default <T> Mono<T> findAndReplace(Query query, T replacement, String collectionName) {
+		return findAndReplace(query, replacement, FindAndReplaceOptions.empty(), collectionName);
+	}
+
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement} document
+	 * taking {@link FindAndReplaceOptions} into account. <br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @param options the {@link FindAndModifyOptions} holding additional information. Must not be {@literal null}.
+	 * @return the converted object that was updated or {@link Mono#empty()}, if not found. Depending on the value of
+	 *         {@link FindAndReplaceOptions#isReturnNew()} this will either be the object as it was before the update or
+	 *         as it is after the update.
+	 * @since 2.1
+	 */
+	default <T> Mono<T> findAndReplace(Query query, T replacement, FindAndReplaceOptions options) {
+		return findAndReplace(query, replacement, options, getCollectionName(ClassUtils.getUserClass(replacement)));
+	}
+
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement} document
+	 * taking {@link FindAndReplaceOptions} into account. <br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @param options the {@link FindAndModifyOptions} holding additional information. Must not be {@literal null}.
+	 * @return the converted object that was updated or {@link Mono#empty()}, if not found. Depending on the value of
+	 *         {@link FindAndReplaceOptions#isReturnNew()} this will either be the object as it was before the update or
+	 *         as it is after the update.
+	 * @since 2.1
+	 */
+	default <T> Mono<T> findAndReplace(Query query, T replacement, FindAndReplaceOptions options, String collectionName) {
+
+		Assert.notNull(replacement, "Replacement must not be null!");
+		return findAndReplace(query, replacement, options, (Class<T>) ClassUtils.getUserClass(replacement), collectionName);
+	}
+
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement} document
+	 * taking {@link FindAndReplaceOptions} into account. <br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @param options the {@link FindAndModifyOptions} holding additional information. Must not be {@literal null}.
+	 * @param entityType 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 or {@link Mono#empty()}, if not found. Depending on the value of
+	 *         {@link FindAndReplaceOptions#isReturnNew()} this will either be the object as it was before the update or
+	 *         as it is after the update.
+	 * @since 2.1
+	 */
+	default <T> Mono<T> findAndReplace(Query query, T replacement, FindAndReplaceOptions options, Class<T> entityType,
+			String collectionName) {
+
+		return findAndReplace(query, replacement, options, entityType, collectionName, entityType);
+	}
+
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement} document
+	 * taking {@link FindAndReplaceOptions} into account. <br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @param options the {@link FindAndModifyOptions} holding additional information. Must not be {@literal null}.
+	 * @param entityType the type used for mapping the {@link Query} to domain type fields and deriving the collection
+	 *          from. Must not be {@literal null}.
+	 * @param resultType the parametrized type projection return type. Must not be {@literal null}, use the domain type of
+	 *          {@code Object.class} instead.
+	 * @return the converted object that was updated or {@link Mono#empty()}, if not found. Depending on the value of
+	 *         {@link FindAndReplaceOptions#isReturnNew()} this will either be the object as it was before the update or
+	 *         as it is after the update.
+	 * @since 2.1
+	 */
+	default <S, T> Mono<T> findAndReplace(Query query, S replacement, FindAndReplaceOptions options, Class<S> entityType,
+			Class<T> resultType) {
+
+		return findAndReplace(query, replacement, options, entityType,
+				getCollectionName(ClassUtils.getUserClass(entityType)), resultType);
+	}
+
+	/**
+	 * Triggers
+	 * <a href="https://docs.mongodb.com/manual/reference/method/db.collection.findOneAndReplace/">findOneAndReplace<a/>
+	 * to replace a single document matching {@link Criteria} of given {@link Query} with the {@code replacement} document
+	 * taking {@link FindAndReplaceOptions} into account. <br />
+	 * <strong>NOTE:</strong> The replacement entity must not hold an {@literal id}.
+	 *
+	 * @param query the {@link Query} class that specifies the {@link Criteria} used to find a record and also an optional
+	 *          fields specification. Must not be {@literal null}.
+	 * @param replacement the replacement document. Must not be {@literal null}.
+	 * @param options the {@link FindAndModifyOptions} holding additional information. Must not be {@literal null}.
+	 * @param entityType the type used for mapping the {@link Query} to domain type fields and deriving the collection
+	 *          from. Must not be {@literal null}.
+	 * @param collectionName the collection to query. Must not be {@literal null}.
+	 * @param resultType resultType the parametrized type projection return type. Must not be {@literal null}, use the
+	 *          domain type of {@code Object.class} instead.
+	 * @return the converted object that was updated or {@link Mono#empty()}, if not found. Depending on the value of
+	 *         {@link FindAndReplaceOptions#isReturnNew()} this will either be the object as it was before the update or
+	 *         as it is after the update.
+	 * @since 2.1
+	 */
+	<S, T> Mono<T> findAndReplace(Query query, S replacement, FindAndReplaceOptions options, Class<S> entityType,
+			String collectionName, Class<T> resultType);
+
 	/**
 	 * Map the results of an ad-hoc query on the collection for the entity type to a single instance of an object of the
 	 * specified type. The first document that matches the query is returned and also removed from the collection in the
@@ -772,7 +927,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * 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. Must not be {@literal null}.
-	 * @return the saved object.
+	 * @return the inserted object.
 	 */
 	<T> Mono<T> insert(T objectToSave);
 
@@ -786,7 +941,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 *
 	 * @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.
+	 * @return the inserted object.
 	 */
 	<T> Mono<T> insert(T objectToSave, String collectionName);
 
@@ -795,7 +950,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 *
 	 * @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.
+	 * @return the inserted objects .
 	 */
 	<T> Flux<T> insert(Collection<? extends T> batchToSave, Class<?> entityClass);
 
@@ -804,7 +959,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 *
 	 * @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.
+	 * @return the inserted objects.
 	 */
 	<T> Flux<T> insert(Collection<? extends T> batchToSave, String collectionName);
 
@@ -832,7 +987,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * 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. Must not be {@literal null}.
-	 * @return the saved object.
+	 * @return the inserted objects.
 	 */
 	<T> Mono<T> insert(Mono<? extends T> objectToSave);
 
@@ -841,7 +996,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 *
 	 * @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.
+	 * @return the inserted objects.
 	 */
 	<T> Flux<T> insertAll(Mono<? extends Collection<? extends T>> batchToSave, Class<?> entityClass);
 
@@ -850,7 +1005,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 *
 	 * @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.
+	 * @return the inserted objects.
 	 */
 	<T> Flux<T> insertAll(Mono<? extends Collection<? extends T>> batchToSave, String collectionName);
 
@@ -859,7 +1014,7 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * class.
 	 *
 	 * @param objectsToSave the publisher which provides objects to save. Must not be {@literal null}.
-	 * @return the saved objects.
+	 * @return the inserted objects.
 	 */
 	<T> Flux<T> insertAll(Mono<? extends Collection<? extends T>> objectsToSave);
 
@@ -1202,7 +1357,57 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	<T> Flux<T> tail(Query query, Class<T> entityClass, String collectionName);
 
 	/**
-	 * Subscribe to a MongoDB <a href="https://docs.mongodb.com/manual/changeStreams/">Change Streams</a> via the reactive
+	 * Subscribe to a MongoDB <a href="https://docs.mongodb.com/manual/changeStreams/">Change Stream</a> for all events in
+	 * the configured default database via the reactive infrastructure. Use the optional provided {@link Aggregation} to
+	 * filter events. The stream will not be completed unless the {@link org.reactivestreams.Subscription} is
+	 * {@link Subscription#cancel() canceled}.
+	 * <p />
+	 * The {@link ChangeStreamEvent#getBody()} is mapped to the {@literal resultType} while the
+	 * {@link ChangeStreamEvent#getRaw()} contains the unmodified payload.
+	 * <p />
+	 * Use {@link ChangeStreamOptions} to set arguments like {@link ChangeStreamOptions#getResumeToken() the resumseToken}
+	 * for resuming change streams.
+	 *
+	 * @param options must not be {@literal null}. Use {@link ChangeStreamOptions#empty()}.
+	 * @param targetType the result type to use.
+	 * @param <T>
+	 * @return the {@link Flux} emitting {@link ChangeStreamEvent events} as they arrive.
+	 * @since 2.1
+	 * @see ReactiveMongoDatabaseFactory#getMongoDatabase()
+	 * @see ChangeStreamOptions#getFilter()
+	 */
+	default <T> Flux<ChangeStreamEvent<T>> changeStream(ChangeStreamOptions options, Class<T> targetType) {
+		return changeStream(null, options, targetType);
+	}
+
+	/**
+	 * Subscribe to a MongoDB <a href="https://docs.mongodb.com/manual/changeStreams/">Change Stream</a> for all events in
+	 * the given collection via the reactive infrastructure. Use the optional provided {@link Aggregation} to filter
+	 * events. The stream will not be completed unless the {@link org.reactivestreams.Subscription} is
+	 * {@link Subscription#cancel() canceled}.
+	 * <p />
+	 * The {@link ChangeStreamEvent#getBody()} is mapped to the {@literal resultType} while the
+	 * {@link ChangeStreamEvent#getRaw()} contains the unmodified payload.
+	 * <p />
+	 * Use {@link ChangeStreamOptions} to set arguments like {@link ChangeStreamOptions#getResumeToken() the resumseToken}
+	 * for resuming change streams.
+	 *
+	 * @param collectionName the collection to watch. Can be {@literal null} to watch all collections.
+	 * @param options must not be {@literal null}. Use {@link ChangeStreamOptions#empty()}.
+	 * @param targetType the result type to use.
+	 * @param <T>
+	 * @return the {@link Flux} emitting {@link ChangeStreamEvent events} as they arrive.
+	 * @since 2.1
+	 * @see ChangeStreamOptions#getFilter()
+	 */
+	default <T> Flux<ChangeStreamEvent<T>> changeStream(@Nullable String collectionName, ChangeStreamOptions options,
+			Class<T> targetType) {
+
+		return changeStream(null, collectionName, options, targetType);
+	}
+
+	/**
+	 * Subscribe to a MongoDB <a href="https://docs.mongodb.com/manual/changeStreams/">Change Stream</a> via the reactive
 	 * infrastructure. Use the optional provided {@link Aggregation} to filter events. The stream will not be completed
 	 * unless the {@link org.reactivestreams.Subscription} is {@link Subscription#cancel() canceled}.
 	 * <p />
@@ -1212,38 +1417,17 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 * Use {@link ChangeStreamOptions} to set arguments like {@link ChangeStreamOptions#getResumeToken() the resumseToken}
 	 * for resuming change streams.
 	 *
-	 * @param filter can be {@literal null}.
-	 * @param resultType must not be {@literal null}.
-	 * @param options must not be {@literal null}.
-	 * @param collectionName must not be {@literal null} nor empty.
+	 * @param database the database to watch. Can be {@literal null}, uses configured default if so.
+	 * @param collectionName the collection to watch. Can be {@literal null}, watches all collections if so.
+	 * @param options must not be {@literal null}. Use {@link ChangeStreamOptions#empty()}.
+	 * @param targetType the result type to use.
 	 * @param <T>
-	 * @return
+	 * @return the {@link Flux} emitting {@link ChangeStreamEvent events} as they arrive.
 	 * @since 2.1
+	 * @see ChangeStreamOptions#getFilter()
 	 */
-	<T> Flux<ChangeStreamEvent<T>> changeStream(@Nullable Aggregation filter, Class<T> resultType,
-			ChangeStreamOptions options, String collectionName);
-
-	/**
-	 * Subscribe to a MongoDB <a href="https://docs.mongodb.com/manual/changeStreams/">Change Streams</a> via the reactive
-	 * infrastructure. Use the optional provided aggregation chain to filter events. The stream will not be completed
-	 * unless the {@link org.reactivestreams.Subscription} is {@link Subscription#cancel() canceled}.
-	 * <p />
-	 * The {@link ChangeStreamEvent#getBody()} is mapped to the {@literal resultType} while the
-	 * {@link ChangeStreamEvent#getRaw()} contains the unmodified payload.
-	 * <p />
-	 * Use {@link ChangeStreamOptions} to set arguments like {@link ChangeStreamOptions#getResumeToken() the resumeToken}
-	 * for resuming change streams.
-	 *
-	 * @param filter can be empty, must not be {@literal null}.
-	 * @param resultType must not be {@literal null}.
-	 * @param options must not be {@literal null}.
-	 * @param collectionName must not be {@literal null} nor empty.
-	 * @param <T>
-	 * @return
-	 * @since 2.1
-	 */
-	<T> Flux<ChangeStreamEvent<T>> changeStream(List<Document> filter, Class<T> resultType, ChangeStreamOptions options,
-			String collectionName);
+	<T> Flux<ChangeStreamEvent<T>> changeStream(@Nullable String database, @Nullable String collectionName,
+			ChangeStreamOptions options, Class<T> targetType);
 
 	/**
 	 * Execute a map-reduce operation. Use {@link MapReduceOptions} to optionally specify an output collection and other
@@ -1288,4 +1472,13 @@ public interface ReactiveMongoOperations extends ReactiveFluentMongoOperations {
 	 */
 	MongoConverter getConverter();
 
+	/**
+	 * The collection name used for the specified class by this template.
+	 *
+	 * @param entityClass must not be {@literal null}.
+	 * @return
+	 * @since 2.1
+	 */
+	String getCollectionName(Class<?> entityClass);
+
 }

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

@@ -18,12 +18,13 @@ package org.springframework.data.mongodb.core;
 import reactor.core.publisher.Mono;
 
 import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.data.mongodb.core.query.Update;
 
 import com.mongodb.client.result.UpdateResult;
 
 /**
- * {@link ReactiveUpdateOperation} allows creation and execution of reactive MongoDB update / findAndModify operations
- * in a fluent API style. <br />
+ * {@link ReactiveUpdateOperation} allows creation and execution of reactive MongoDB update / findAndModify /
+ * findAndReplace operations in a fluent API style. <br />
  * The starting {@literal domainType} is used for mapping the {@link Query} provided via {@code matching}, as well as
  * the {@link org.springframework.data.mongodb.core.query.Update} via {@code apply} into the MongoDB specific
  * representations. The collection to operate on is by default derived from the initial {@literal domainType} and can be
@@ -68,6 +69,22 @@ public interface ReactiveUpdateOperation {
 		Mono<T> findAndModify();
 	}
 
+	/**
+	 * Compose findAndReplace execution by calling one of the terminating methods.
+	 *
+	 * @author Mark Paluch
+	 * @since 2.1
+	 */
+	interface TerminatingFindAndReplace<T> {
+
+		/**
+		 * Find, replace and return the first matching document.
+		 *
+		 * @return {@link Mono#empty()} if nothing found. Never {@literal null}.
+		 */
+		Mono<T> findAndReplace();
+	}
+
 	/**
 	 * Compose update execution by calling one of the terminating methods.
 	 */
@@ -108,6 +125,16 @@ public interface ReactiveUpdateOperation {
 		 * @throws IllegalArgumentException if update is {@literal null}.
 		 */
 		TerminatingUpdate<T> apply(org.springframework.data.mongodb.core.query.Update update);
+
+		/**
+		 * Specify {@code replacement} object.
+		 *
+		 * @param replacement must not be {@literal null}.
+		 * @return new instance of {@link FindAndReplaceOptions}.
+		 * @throws IllegalArgumentException if options is {@literal null}.
+		 * @since 2.1
+		 */
+		FindAndReplaceWithProjection<T> replaceWith(T replacement);
 	}
 
 	/**
@@ -157,5 +184,45 @@ public interface ReactiveUpdateOperation {
 		TerminatingFindAndModify<T> withOptions(FindAndModifyOptions options);
 	}
 
+	/**
+	 * Define {@link FindAndReplaceOptions}.
+	 *
+	 * @author Mark Paluch
+	 * @author Christoph Strobl
+	 * @since 2.1
+	 */
+	interface FindAndReplaceWithOptions<T> extends TerminatingFindAndReplace<T> {
+
+		/**
+		 * Explicitly define {@link FindAndReplaceOptions} for the {@link Update}.
+		 *
+		 * @param options must not be {@literal null}.
+		 * @return new instance of {@link FindAndReplaceOptions}.
+		 * @throws IllegalArgumentException if options is {@literal null}.
+		 */
+		FindAndReplaceWithProjection<T> withOptions(FindAndReplaceOptions options);
+	}
+
+	/**
+	 * Result type override (Optional).
+	 *
+	 * @author Christoph Strobl
+	 * @since 2.1
+	 */
+	interface FindAndReplaceWithProjection<T> extends FindAndReplaceWithOptions<T> {
+
+		/**
+		 * Define the target type fields should be mapped to. <br />
+		 * Skip this step if you are anyway only interested in the original domain type.
+		 *
+		 * @param resultType must not be {@literal null}.
+		 * @param <R> result type.
+		 * @return new instance of {@link FindAndReplaceWithProjection}.
+		 * @throws IllegalArgumentException if resultType is {@literal null}.
+		 */
+		<R> FindAndReplaceWithOptions<R> as(Class<R> resultType);
+
+	}
+
 	interface ReactiveUpdate<T> extends UpdateWithCollection<T>, UpdateWithQuery<T>, UpdateWithUpdate<T> {}
 }

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

@@ -22,6 +22,7 @@ import lombok.experimental.FieldDefaults;
 import reactor.core.publisher.Mono;
 
 import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -50,20 +51,24 @@ class ReactiveUpdateOperationSupport implements ReactiveUpdateOperation {
 
 		Assert.notNull(domainType, "DomainType must not be null!");
 
-		return new ReactiveUpdateSupport<>(template, domainType, ALL_QUERY, null, null, null);
+		return new ReactiveUpdateSupport<>(template, domainType, ALL_QUERY, null, null, null, null, null, domainType);
 	}
 
 	@RequiredArgsConstructor
 	@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
 	static class ReactiveUpdateSupport<T>
-			implements ReactiveUpdate<T>, UpdateWithCollection<T>, UpdateWithQuery<T>, TerminatingUpdate<T> {
+			implements ReactiveUpdate<T>, UpdateWithCollection<T>, UpdateWithQuery<T>, TerminatingUpdate<T>,
+			FindAndReplaceWithOptions<T>, FindAndReplaceWithProjection<T>, TerminatingFindAndReplace<T> {
 
 		@NonNull ReactiveMongoTemplate template;
-		@NonNull Class<T> domainType;
+		@NonNull Class<?> domainType;
 		Query query;
 		org.springframework.data.mongodb.core.query.Update update;
-		String collection;
-		FindAndModifyOptions options;
+		@Nullable String collection;
+		@Nullable FindAndModifyOptions findAndModifyOptions;
+		@Nullable FindAndReplaceOptions findAndReplaceOptions;
+		@Nullable Object replacement;
+		@NonNull Class<T> targetType;
 
 		/*
 		 * (non-Javadoc)
@@ -74,7 +79,8 @@ class ReactiveUpdateOperationSupport implements ReactiveUpdateOperation {
 
 			Assert.notNull(update, "Update must not be null!");
 
-			return new ReactiveUpdateSupport<>(template, domainType, query, update, collection, options);
+			return new ReactiveUpdateSupport<>(template, domainType, query, update, collection, findAndModifyOptions,
+					findAndReplaceOptions, replacement, targetType);
 		}
 
 		/*
@@ -86,7 +92,8 @@ class ReactiveUpdateOperationSupport implements ReactiveUpdateOperation {
 
 			Assert.hasText(collection, "Collection must not be null nor empty!");
 
-			return new ReactiveUpdateSupport<>(template, domainType, query, update, collection, options);
+			return new ReactiveUpdateSupport<>(template, domainType, query, update, collection, findAndModifyOptions,
+					findAndReplaceOptions, replacement, targetType);
 		}
 
 		/*
@@ -116,7 +123,18 @@ class ReactiveUpdateOperationSupport implements ReactiveUpdateOperation {
 
 			String collectionName = getCollectionName();
 
-			return template.findAndModify(query, update, options, domainType, collectionName);
+			return template.findAndModify(query, update, findAndModifyOptions, targetType, collectionName);
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.ReactiveUpdateOperation.TerminatingFindAndReplace#findAndReplace()
+		 */
+		@Override
+		public Mono<T> findAndReplace() {
+			return template.findAndReplace(query, replacement,
+					findAndReplaceOptions != null ? findAndReplaceOptions : new FindAndReplaceOptions(), (Class) domainType,
+					getCollectionName(), targetType);
 		}
 
 		/*
@@ -128,7 +146,8 @@ class ReactiveUpdateOperationSupport implements ReactiveUpdateOperation {
 
 			Assert.notNull(query, "Query must not be null!");
 
-			return new ReactiveUpdateSupport<>(template, domainType, query, update, collection, options);
+			return new ReactiveUpdateSupport<>(template, domainType, query, update, collection, findAndModifyOptions,
+					findAndReplaceOptions, replacement, targetType);
 		}
 
 		/*
@@ -149,7 +168,47 @@ class ReactiveUpdateOperationSupport implements ReactiveUpdateOperation {
 
 			Assert.notNull(options, "Options must not be null!");
 
-			return new ReactiveUpdateSupport<>(template, domainType, query, update, collection, options);
+			return new ReactiveUpdateSupport<>(template, domainType, query, update, collection, options,
+					findAndReplaceOptions, replacement, targetType);
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.ReactiveUpdateOperation.UpdateWithUpdate#replaceWith(java.lang.Object)
+		 */
+		@Override
+		public FindAndReplaceWithProjection<T> replaceWith(T replacement) {
+
+			Assert.notNull(replacement, "Replacement must not be null!");
+
+			return new ReactiveUpdateSupport<>(template, domainType, query, update, collection, findAndModifyOptions,
+					findAndReplaceOptions, replacement, targetType);
+		}
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.ReactiveUpdateOperation.FindAndReplaceWithOptions#withOptions(org.springframework.data.mongodb.core.FindAndReplaceOptions)
+		 */
+		@Override
+		public FindAndReplaceWithProjection<T> withOptions(FindAndReplaceOptions options) {
+
+			Assert.notNull(options, "Options must not be null!");
+
+			return new ReactiveUpdateSupport<>(template, domainType, query, update, collection, findAndModifyOptions, options,
+					replacement, targetType);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.ReactiveUpdateOperation.FindAndReplaceWithProjection#as(java.lang.Class)
+		 */
+		@Override
+		public <R> FindAndReplaceWithOptions<R> as(Class<R> resultType) {
+
+			Assert.notNull(resultType, "ResultType must not be null!");
+
+			return new ReactiveUpdateSupport<>(template, domainType, query, update, collection, findAndModifyOptions,
+					findAndReplaceOptions, replacement, resultType);
 		}
 
 		private Mono<UpdateResult> doUpdate(boolean multi, boolean upsert) {

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

@@ -23,6 +23,7 @@ import java.util.List;
 import java.util.Map;
 
 import org.bson.Document;
+import org.springframework.data.mongodb.core.aggregation.Aggregation.SystemVariable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 
@@ -92,6 +93,10 @@ abstract class AbstractAggregationExpression implements AggregationExpression {
 			return targetDocument;
 		}
 
+		if (value instanceof SystemVariable) {
+			return value.toString();
+		}
+
 		return value;
 	}
 

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) {

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

@@ -267,6 +267,19 @@ public class ArrayOperators {
 			return (usesFieldRef() ? In.arrayOf(fieldReference) : In.arrayOf(expression)).containsValue(value);
 		}
 
+		/**
+		 * Creates new {@link AggregationExpression} that converts the associated expression into an object.
+		 * <strong>NOTE:</strong> Requires MongoDB 3.6 or later.
+		 *
+		 * @return new instance of {@link ArrayToObject}.
+		 * @since 2.1
+		 */
+		public ArrayToObject toObject() {
+
+			return usesFieldRef() ? ArrayToObject.arrayValueOfToObject(fieldReference)
+					: ArrayToObject.arrayValueOfToObject(expression);
+		}
+
 		/**
 		 * @author Christoph Strobl
 		 */
@@ -1497,4 +1510,59 @@ public class ArrayOperators {
 			In containsValue(Object value);
 		}
 	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $arrayToObject} that transforms an array into a single document. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 3.6 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/arrayToObject/">https://docs.mongodb.com/manual/reference/operator/aggregation/arrayToObject/</a>
+	 * @since 2.1
+	 */
+	public static class ArrayToObject extends AbstractAggregationExpression {
+
+		private ArrayToObject(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Converts the given array (e.g. an array of two-element arrays, a field reference to an array,...) to an object.
+		 *
+		 * @param array must not be {@literal null}.
+		 * @return new instance of {@link ArrayToObject}.
+		 */
+		public static ArrayToObject arrayToObject(Object array) {
+			return new ArrayToObject(array);
+		}
+
+		/**
+		 * Converts the array pointed to by the given {@link Field field reference} to an object.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link ArrayToObject}.
+		 */
+		public static ArrayToObject arrayValueOfToObject(String fieldReference) {
+			return new ArrayToObject(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Converts the result array of the given {@link AggregationExpression expression} to an object.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link ArrayToObject}.
+		 */
+		public static ArrayToObject arrayValueOfToObject(AggregationExpression expression) {
+			return new ArrayToObject(expression);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AbstractAggregationExpression#getMongoMethod()
+		 */
+		@Override
+		protected String getMongoMethod() {
+			return "$arrayToObject";
+		}
+	}
 }

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

@@ -0,0 +1,695 @@
+/*
+ * 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.data.mongodb.core.schema.JsonSchemaObject.Type;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+
+/**
+ * Gateway to {@literal convert} aggregation operations.
+ *
+ * @author Christoph Strobl
+ * @since 2.1
+ */
+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 given {@link Type}. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param type must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert convertTo(Type type) {
+			return createConvert().to(type);
+		}
+
+		/**
+		 * 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 2.1
+	 */
+	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.
+		 *
+		 * @param type must not be {@literal null}.
+		 * @return new instance of {@link Convert}.
+		 */
+		public Convert to(Type type) {
+
+			String typeString = Type.BOOLEAN.equals(type) ? "bool" : type.value().toString();
+			return to(typeString);
+		}
+
+		/**
+		 * 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 $toBool} that converts a value to {@literal boolean}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("bool")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toBool/">https://docs.mongodb.com/manual/reference/operator/aggregation/toBool/</a>
+	 * @since 2.1
+	 */
+	public static class ToBool extends AbstractAggregationExpression {
+
+		private ToBool(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToBool} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToBool}.
+		 */
+		public static ToBool toBoolean(Object value) {
+			return new ToBool(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toBool";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toDate} that converts a value to {@literal date}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("date")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toDate/">https://docs.mongodb.com/manual/reference/operator/aggregation/toDate/</a>
+	 * @since 2.1
+	 */
+	public static class ToDate extends AbstractAggregationExpression {
+
+		private ToDate(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToDate} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToDate}.
+		 */
+		public static ToDate toDate(Object value) {
+			return new ToDate(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toDate";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toDecimal} that converts a value to {@literal decimal}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("decimal")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toDecimal/">https://docs.mongodb.com/manual/reference/operator/aggregation/toDecimal/</a>
+	 * @since 2.1
+	 */
+	public static class ToDecimal extends AbstractAggregationExpression {
+
+		private ToDecimal(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToDecimal} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToDecimal}.
+		 */
+		public static ToDecimal toDecimal(Object value) {
+			return new ToDecimal(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toDecimal";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toDouble} that converts a value to {@literal double}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("double")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toDouble/">https://docs.mongodb.com/manual/reference/operator/aggregation/toDouble/</a>
+	 * @since 2.1
+	 */
+	public static class ToDouble extends AbstractAggregationExpression {
+
+		private ToDouble(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToDouble} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToDouble}.
+		 */
+		public static ToDouble toDouble(Object value) {
+			return new ToDouble(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toDouble";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toInt} that converts a value to {@literal integer}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("int")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toInt/">https://docs.mongodb.com/manual/reference/operator/aggregation/toInt/</a>
+	 * @since 2.1
+	 */
+	public static class ToInt extends AbstractAggregationExpression {
+
+		private ToInt(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToInt} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToInt}.
+		 */
+		public static ToInt toInt(Object value) {
+			return new ToInt(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toInt";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toLong} that converts a value to {@literal long}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("long")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toLong/">https://docs.mongodb.com/manual/reference/operator/aggregation/toLong/</a>
+	 * @since 2.1
+	 */
+	public static class ToLong extends AbstractAggregationExpression {
+
+		private ToLong(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToLong} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToLong}.
+		 */
+		public static ToLong toLong(Object value) {
+			return new ToLong(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toLong";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toObjectId} that converts a value to {@literal objectId}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("objectId")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toObjectId/">https://docs.mongodb.com/manual/reference/operator/aggregation/toObjectId/</a>
+	 * @since 2.1
+	 */
+	public static class ToObjectId extends AbstractAggregationExpression {
+
+		private ToObjectId(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToObjectId} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToObjectId}.
+		 */
+		public static ToObjectId toObjectId(Object value) {
+			return new ToObjectId(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toObjectId";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $toString} that converts a value to {@literal string}. Shorthand for
+	 * {@link Convert#to(String) Convert#to("string")}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/toString/">https://docs.mongodb.com/manual/reference/operator/aggregation/toString/</a>
+	 * @since 2.1
+	 */
+	public static class ToString extends AbstractAggregationExpression {
+
+		private ToString(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ToString} using the given value as input.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ToString}.
+		 */
+		public static ToString toString(Object value) {
+			return new ToString(value);
+		}
+
+		@Override
+		protected String getMongoMethod() {
+			return "$toString";
+		}
+	}
+}

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

@@ -22,6 +22,7 @@ import java.util.Map;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
+import org.springframework.util.StringUtils;
 
 /**
  * Gateway to {@literal Date} aggregation operations.
@@ -178,7 +179,7 @@ public class DateOperators {
 		 * Create a {@link Timezone} for the {@link AggregationExpression} resulting in the Olson Timezone Identifier or UTC
 		 * Offset.
 		 *
-		 * @param value the {@link AggregationExpression} resulting in the timezone.
+		 * @param expression the {@link AggregationExpression} resulting in the timezone.
 		 * @return new instance of {@link Timezone}.
 		 */
 		public static Timezone ofExpression(AggregationExpression expression) {
@@ -380,6 +381,17 @@ public class DateOperators {
 			return applyTimezone(DateToString.dateToString(dateReference()).toString(format), timezone);
 		}
 
+		/**
+		 * Creates new {@link AggregationExpression} that converts a date object to a string according to the server default
+		 * format.
+		 *
+		 * @return new instance of {@link DateToString}.
+		 * @since 2.1
+		 */
+		public DateToString toStringWithDefaultFormat() {
+			return applyTimezone(DateToString.dateToString(dateReference()).defaultFormat(), timezone);
+		}
+
 		/**
 		 * Creates new {@link AggregationExpression} that returns the weekday number in ISO 8601-2018 format, ranging from 1
 		 * (for Monday) to 7 (for Sunday).
@@ -1352,6 +1364,11 @@ public class DateOperators {
 					Assert.notNull(format, "Format must not be null!");
 					return new DateToString(argumentMap(value, format, Timezone.none()));
 				}
+
+				@Override
+				public DateToString defaultFormat() {
+					return new DateToString(argumentMap(value, null, Timezone.none()));
+				}
 			};
 		}
 
@@ -1392,7 +1409,43 @@ public class DateOperators {
 		public DateToString withTimezone(Timezone timezone) {
 
 			Assert.notNull(timezone, "Timezone must not be null.");
-			return new DateToString(argumentMap(get("date"), get("format"), timezone));
+			return new DateToString(append("timezone", timezone));
+		}
+
+		/**
+		 * Optionally specify the value to return when the date is {@literal null} or missing. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link DateToString}.
+		 * @since 2.1
+		 */
+		public DateToString onNullReturn(Object value) {
+			return new DateToString(append("onNull", value));
+		}
+
+		/**
+		 * Optionally specify the field holding the value to return when the date is {@literal null} or missing. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link DateToString}.
+		 * @since 2.1
+		 */
+		public DateToString onNullReturnValueOf(String fieldReference) {
+			return onNullReturn(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Optionally specify the expression to evaluate and return when the date is {@literal null} or missing. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link DateToString}.
+		 * @since 2.1
+		 */
+		public DateToString onNullReturnValueOf(AggregationExpression expression) {
+			return onNullReturn(expression);
 		}
 
 		@Override
@@ -1400,10 +1453,14 @@ public class DateOperators {
 			return "$dateToString";
 		}
 
-		private static java.util.Map<String, Object> argumentMap(Object date, String format, Timezone timezone) {
+		private static java.util.Map<String, Object> argumentMap(Object date, @Nullable String format, Timezone timezone) {
+
+			java.util.Map<String, Object> args = new LinkedHashMap<>(2);
+
+			if (StringUtils.hasText(format)) {
+				args.put("format", format);
+			}
 
-			java.util.Map<String, Object> args = new LinkedHashMap<String, Object>(2);
-			args.put("format", format);
 			args.put("date", date);
 
 			if (!ObjectUtils.nullSafeEquals(timezone, Timezone.none())) {
@@ -1412,6 +1469,25 @@ public class DateOperators {
 			return args;
 		}
 
+		protected java.util.Map<String, Object> append(String key, Object value) {
+
+			java.util.Map<String, Object> clone = new LinkedHashMap<>(argumentMap());
+
+			if (value instanceof Timezone) {
+
+				if (ObjectUtils.nullSafeEquals(value, Timezone.none())) {
+					clone.remove("timezone");
+				} else {
+					clone.put("timezone", ((Timezone) value).value);
+				}
+
+			} else {
+				clone.put(key, value);
+			}
+
+			return clone;
+		}
+
 		public interface FormatBuilder {
 
 			/**
@@ -1421,6 +1497,16 @@ public class DateOperators {
 			 * @return
 			 */
 			DateToString toString(String format);
+
+			/**
+			 * Creates new {@link DateToString} using the server default string format ({@code %Y-%m-%dT%H:%M:%S.%LZ}) for
+			 * dates. <br />
+			 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+			 *
+			 * @return new instance of {@link DateToString}.
+			 * @since 2.1
+			 */
+			DateToString defaultFormat();
 		}
 	}
 
@@ -2269,6 +2355,20 @@ public class DateOperators {
 			return new DateFromString(appendTimezone(argumentMap(), timezone));
 		}
 
+		/**
+		 * Optionally set the date format to use. If not specified {@code %Y-%m-%dT%H:%M:%S.%LZ} is used.<br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @param format must not be {@literal null}.
+		 * @return new instance of {@link DateFromString}.
+		 * @throws IllegalArgumentException if given {@literal format} is {@literal null}.
+		 */
+		public DateFromString withFormat(String format) {
+
+			Assert.notNull(format, "Format must not be null!");
+			return new DateFromString(append("format", format));
+		}
+
 		@Override
 		protected String getMongoMethod() {
 			return "$dateFromString";

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

@@ -17,7 +17,9 @@ 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.
@@ -28,26 +30,55 @@ import org.springframework.util.Assert;
  * @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 2.1
+	 */
+	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 2.1
+	 */
+	public GeoNearOperation useIndex(String key) {
+		return new GeoNearOperation(nearQuery, distanceField, key);
 	}
 
 	/*
@@ -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

@@ -103,8 +103,8 @@ public class GraphLookupOperation implements InheritsFieldsAggregationOperation
 
 		graphLookup.put("startWith", mappedStartWith.size() == 1 ? mappedStartWith.iterator().next() : mappedStartWith);
 
-		graphLookup.put("connectFromField", connectFrom.getName());
-		graphLookup.put("connectToField", connectTo.getName());
+		graphLookup.put("connectFromField", connectFrom.getTarget());
+		graphLookup.put("connectToField", connectTo.getTarget());
 		graphLookup.put("as", as.getName());
 
 		if (maxDepth != null) {
@@ -112,7 +112,7 @@ public class GraphLookupOperation implements InheritsFieldsAggregationOperation
 		}
 
 		if (depthField != null) {
-			graphLookup.put("depthField", depthField.getName());
+			graphLookup.put("depthField", depthField.getTarget());
 		}
 
 		if (restrictSearchWithMatch != null) {

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

@@ -0,0 +1,298 @@
+/*
+ * 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.Arrays;
+import java.util.Collection;
+
+import org.bson.Document;
+import org.springframework.util.Assert;
+
+/**
+ * Gateway for
+ * <a href="https://docs.mongodb.com/manual/meta/aggregation-quick-reference/#object-expression-operators">object
+ * expression operators</a>.
+ *
+ * @author Christoph Strobl
+ * @since 2.1
+ */
+public class ObjectOperators {
+
+	/**
+	 * Take the value referenced by given {@literal fieldReference}.
+	 *
+	 * @param fieldReference must not be {@literal null}.
+	 * @return new instance of {@link ObjectOperatorFactory}.
+	 */
+	public static ObjectOperatorFactory valueOf(String fieldReference) {
+		return new ObjectOperatorFactory(Fields.field(fieldReference));
+	}
+
+	/**
+	 * Take the value provided by the given {@link AggregationExpression}.
+	 *
+	 * @param expression must not be {@literal null}.
+	 * @return new instance of {@link ObjectOperatorFactory}.
+	 */
+	public static ObjectOperatorFactory valueOf(AggregationExpression expression) {
+		return new ObjectOperatorFactory(expression);
+	}
+
+	/**
+	 * @author Christoph Strobl
+	 */
+	public static class ObjectOperatorFactory {
+
+		private final Object value;
+
+		/**
+		 * Creates new {@link ObjectOperatorFactory} for given {@literal value}.
+		 *
+		 * @param value must not be {@literal null}.
+		 */
+		public ObjectOperatorFactory(Object value) {
+
+			Assert.notNull(value, "Value must not be null!");
+
+			this.value = value;
+		}
+
+		/**
+		 * Creates new {@link MergeObjects aggregation expression} that takes the associated value and uses
+		 * {@literal $mergeObjects} as an accumulator within the {@literal $group} stage. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link MergeObjects}.
+		 */
+		public MergeObjects merge() {
+			return MergeObjects.merge(value);
+		}
+
+		/**
+		 * Creates new {@link MergeObjects aggregation expression} that takes the associated value and combines it with the
+		 * given values (documents or mapped objects) into a single document. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link MergeObjects}.
+		 */
+		public MergeObjects mergeWith(Object... values) {
+			return merge().mergeWith(values);
+		}
+
+		/**
+		 * Creates new {@link MergeObjects aggregation expression} that takes the associated value and combines it with the
+		 * values of the given {@link Field field references} into a single document. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link MergeObjects}.
+		 */
+		public MergeObjects mergeWithValuesOf(String... fieldReferences) {
+			return merge().mergeWithValuesOf(fieldReferences);
+		}
+
+		/**
+		 * Creates new {@link MergeObjects aggregation expression} that takes the associated value and combines it with the
+		 * result values of the given {@link Aggregation expressions} into a single document. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+		 *
+		 * @return new instance of {@link MergeObjects}.
+		 */
+		public MergeObjects mergeWithValuesOf(AggregationExpression... expression) {
+			return merge().mergeWithValuesOf(expression);
+		}
+
+		/**
+		 * Creates new {@link ObjectToArray aggregation expression} that takes the associated value and converts it to an
+		 * array of {@link Document documents} that contain two fields {@literal k} and {@literal v} each. <br />
+		 * <strong>NOTE:</strong> Requires MongoDB 3.6 or later.
+		 * 
+		 * @since 2.1
+		 */
+		public ObjectToArray toArray() {
+			return ObjectToArray.toArray(value);
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $mergeObjects} that combines multiple documents into a single document.
+	 * <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 4.0 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/mergeObjects/">https://docs.mongodb.com/manual/reference/operator/aggregation/mergeObjects/</a>
+	 * @since 2.1
+	 */
+	public static class MergeObjects extends AbstractAggregationExpression {
+
+		private MergeObjects(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link MergeObjects aggregation expression} that takes given values and combines them into a single
+		 * document. <br />
+		 *
+		 * @param values must not be {@literal null}.
+		 * @return new instance of {@link MergeObjects}.
+		 */
+		public static MergeObjects merge(Object... values) {
+			return new MergeObjects(Arrays.asList(values));
+		}
+
+		/**
+		 * Creates new {@link MergeObjects aggregation expression} that takes the given {@link Field field references} and
+		 * combines them into a single document.
+		 *
+		 * @param fieldReferences must not be {@literal null}.
+		 * @return new instance of {@link MergeObjects}.
+		 */
+		public static MergeObjects mergeValuesOf(String... fieldReferences) {
+			return merge(Arrays.stream(fieldReferences).map(Fields::field).toArray());
+		}
+
+		/**
+		 * Creates new {@link MergeObjects aggregation expression} that takes the result of the given {@link Aggregation
+		 * expressions} and combines them into a single document.
+		 *
+		 * @param expressions must not be {@literal null}.
+		 * @return new instance of {@link MergeObjects}.
+		 */
+		public static MergeObjects mergeValuesOf(AggregationExpression... expressions) {
+			return merge(expressions);
+		}
+
+		/**
+		 * Creates new {@link MergeObjects aggregation expression} by adding the given {@link Field field references}.
+		 *
+		 * @param fieldReferences must not be {@literal null}.
+		 * @return new instance of {@link MergeObjects}.
+		 */
+		public MergeObjects mergeWithValuesOf(String... fieldReferences) {
+			return mergeWith(Arrays.stream(fieldReferences).map(Fields::field).toArray());
+		}
+
+		/**
+		 * Creates new {@link MergeObjects aggregation expression} by adding the given {@link AggregationExpression
+		 * expressions}.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link MergeObjects}.
+		 */
+		public MergeObjects mergeWithValuesOf(AggregationExpression... expression) {
+			return mergeWith(expression);
+		}
+
+		/**
+		 * Creates new {@link MergeObjects aggregation expression} by adding the given values (documents or mapped objects).
+		 *
+		 * @param values must not be {@literal null}.
+		 * @return new instance of {@link MergeObjects}.
+		 */
+		public MergeObjects mergeWith(Object... values) {
+			return new MergeObjects(append(Arrays.asList(values)));
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AbstractAggregationExpression#toDocument(java.lang.Object, org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
+		 */
+		@Override
+		public Document toDocument(Object value, AggregationOperationContext context) {
+			return super.toDocument(potentiallyExtractSingleValue(value), context);
+		}
+
+		@SuppressWarnings("unchecked")
+		private Object potentiallyExtractSingleValue(Object value) {
+
+			if (value instanceof Collection) {
+
+				Collection<Object> collection = ((Collection<Object>) value);
+				if (collection.size() == 1) {
+					return collection.iterator().next();
+				}
+			}
+			return value;
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AbstractAggregationExpression#getMongoMethod()
+		 */
+		@Override
+		protected String getMongoMethod() {
+			return "$mergeObjects";
+		}
+	}
+
+	/**
+	 * {@link AggregationExpression} for {@code $objectToArray} that converts a document to an array of {@link Document
+	 * documents} that each contains two fields {@literal k} and {@literal v}. <br />
+	 * <strong>NOTE:</strong> Requires MongoDB 3.6 or later.
+	 *
+	 * @author Christoph Strobl
+	 * @see <a href=
+	 *      "https://docs.mongodb.com/manual/reference/operator/aggregation/objectToArray/">https://docs.mongodb.com/manual/reference/operator/aggregation/objectToArray/</a>
+	 * @since 2.1
+	 */
+	public static class ObjectToArray extends AbstractAggregationExpression {
+
+		private ObjectToArray(Object value) {
+			super(value);
+		}
+
+		/**
+		 * Creates new {@link ObjectToArray aggregation expression} that takes the value pointed to by given {@link Field
+		 * fieldReference} and converts it to an array.
+		 *
+		 * @param fieldReference must not be {@literal null}.
+		 * @return new instance of {@link ObjectToArray}.
+		 */
+		public static ObjectToArray valueOfToArray(String fieldReference) {
+			return toArray(Fields.field(fieldReference));
+		}
+
+		/**
+		 * Creates new {@link ObjectToArray aggregation expression} that takes the result value of the given
+		 * {@link AggregationExpression expression} and converts it to an array.
+		 *
+		 * @param expression must not be {@literal null}.
+		 * @return new instance of {@link ObjectToArray}.
+		 */
+		public static ObjectToArray valueOfToArray(AggregationExpression expression) {
+			return toArray(expression);
+		}
+
+		/**
+		 * Creates new {@link ObjectToArray aggregation expression} that takes the given value and converts it to an array.
+		 *
+		 * @param value must not be {@literal null}.
+		 * @return new instance of {@link ObjectToArray}.
+		 */
+		public static ObjectToArray toArray(Object value) {
+			return new ObjectToArray(value);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.core.aggregation.AbstractAggregationExpression#getMongoMethod()
+		 */
+		@Override
+		protected String getMongoMethod() {
+			return "$objectToArray";
+		}
+	}
+}

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

@@ -102,7 +102,7 @@ public class PrefixingDelegatingAggregationOperationContext implements Aggregati
 	}
 
 	private String prefixKey(String key) {
-		return (key.startsWith("$") || blacklist.contains(key)) ? key : (prefix + "." + key);
+		return (key.startsWith("$") || isBlacklisted(key)) ? key : (prefix + "." + key);
 	}
 
 	private Object prefixCollection(Collection<Object> sourceCollection) {
@@ -119,4 +119,23 @@ public class PrefixingDelegatingAggregationOperationContext implements Aggregati
 
 		return prefixed;
 	}
+
+	private boolean isBlacklisted(String key) {
+
+		if (blacklist.contains(key)) {
+			return true;
+		}
+
+		if (!key.contains(".")) {
+			return false;
+		}
+
+		for (String blacklisted : blacklist) {
+			if (key.startsWith(blacklisted + ".")) {
+				return true;
+			}
+		}
+
+		return false;
+	}
 }

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

@@ -1204,6 +1204,18 @@ public class ProjectionOperation implements FieldsExposingAggregationOperation {
 			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 2.1
+		 */
+		public ProjectionOperationBuilder dateAsFormattedString() {
+			return this.operation.and(DateOperators.DateToString.dateOf(getRequiredName()).defaultFormat());
+		}
+
 		/**
 		 * Generates a {@code $let} expression that binds variables for use in the specified expression, and returns the
 		 * result of the expression.

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

@@ -350,8 +350,7 @@ public class StringOperators {
 		 * @return
 		 */
 		public StrLenBytes length() {
-			return usesFieldRef() ? StrLenBytes.stringLengthOf(fieldReference)
-					: StrLenBytes.stringLengthOf(expression);
+			return usesFieldRef() ? StrLenBytes.stringLengthOf(fieldReference) : StrLenBytes.stringLengthOf(expression);
 		}
 
 		/**
@@ -391,6 +390,132 @@ public class StringOperators {
 			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 2.1
+		 */
+		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 2.1
+		 */
+		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 2.1
+		 */
+		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 2.1
+		 */
+		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 2.1
+		 */
+		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 2.1
+		 */
+		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 2.1
+		 */
+		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 2.1
+		 */
+		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 2.1
+		 */
+		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;
 		}
@@ -1072,4 +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 2.1
+	 */
+	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 2.1
+	 */
+	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 2.1
+	 */
+	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/convert/DbRefResolver.java

@@ -22,6 +22,7 @@ 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 org.springframework.util.StringUtils;
 
 import com.mongodb.DBRef;
 
@@ -59,9 +60,15 @@ public interface DbRefResolver {
 	 * @param id will never be {@literal null}.
 	 * @return
 	 */
-	DBRef createDbRef(@Nullable org.springframework.data.mongodb.core.mapping.DBRef annotation,
-			MongoPersistentEntity<?> entity,
-			Object id);
+	default DBRef createDbRef(@Nullable org.springframework.data.mongodb.core.mapping.DBRef annotation,
+			MongoPersistentEntity<?> entity, Object id) {
+
+		if (annotation != null && StringUtils.hasText(annotation.db())) {
+			return new DBRef(annotation.db(), entity.getCollection(), id);
+		}
+
+		return new DBRef(entity.getCollection(), id);
+	}
 
 	/**
 	 * Actually loads the {@link DBRef} from the datasource.

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

@@ -43,7 +43,6 @@ import org.springframework.dao.support.PersistenceExceptionTranslator;
 import org.springframework.data.mongodb.ClientSessionException;
 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;
@@ -104,21 +103,6 @@ public class DefaultDbRefResolver implements DbRefResolver {
 		return callback.resolve(property);
 	}
 
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.core.convert.DbRefResolver#created(org.springframework.data.mongodb.core.mapping.MongoPersistentProperty, org.springframework.data.mongodb.core.mapping.MongoPersistentEntity, java.lang.Object)
-	 */
-	@Override
-	public DBRef createDbRef(@Nullable org.springframework.data.mongodb.core.mapping.DBRef annotation,
-			MongoPersistentEntity<?> entity, Object id) {
-
-		if (annotation != null && StringUtils.hasText(annotation.db())) {
-			return new DBRef(annotation.db(), entity.getCollection(), id);
-		}
-
-		return new DBRef(entity.getCollection(), id);
-	}
-
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.convert.DbRefResolver#fetch(com.mongodb.DBRef)

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

@@ -21,6 +21,7 @@ import java.util.Map;
 
 import org.bson.Document;
 import org.bson.conversions.Bson;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
 import org.springframework.data.mongodb.util.BsonUtils;
 import org.springframework.lang.Nullable;
@@ -58,6 +59,14 @@ class DocumentAccessor {
 		this.document = document;
 	}
 
+	/**
+	 * @return the underlying {@link Bson document}.
+	 * @since 2.1
+	 */
+	Bson getDocument() {
+		return this.document;
+	}
+
 	/**
 	 * Puts the given value into the backing {@link Document} based on the coordinates defined through the given
 	 * {@link MongoPersistentProperty}. By default this will be the plain field name. But field names might also consist
@@ -103,13 +112,14 @@ class DocumentAccessor {
 	public Object get(MongoPersistentProperty property) {
 
 		String fieldName = property.getFieldName();
+		Map<String, Object> map = BsonUtils.asMap(document);
 
 		if (!fieldName.contains(".")) {
-			return BsonUtils.asMap(this.document).get(fieldName);
+			return map.get(fieldName);
 		}
 
 		Iterator<String> parts = Arrays.asList(fieldName.split("\\.")).iterator();
-		Map<String, Object> source = BsonUtils.asMap(this.document);
+		Map<String, Object> source = map;
 		Object result = null;
 
 		while (source != null && parts.hasNext()) {
@@ -124,6 +134,17 @@ class DocumentAccessor {
 		return result;
 	}
 
+	/**
+	 * Returns the raw identifier for the given {@link MongoPersistentEntity} or the value of the default identifier
+	 * field.
+	 *
+	 * @param entity must not be {@literal null}.
+	 * @return
+	 */
+	public Object getRawId(MongoPersistentEntity<?> entity) {
+		return entity.hasIdProperty() ? get(entity.getRequiredIdProperty()) : BsonUtils.asMap(document).get("_id");
+	}
+
 	/**
 	 * Returns whether the underlying {@link Document} has a value ({@literal null} or non-{@literal null}) for the given
 	 * {@link MongoPersistentProperty}.
@@ -131,21 +152,27 @@ class DocumentAccessor {
 	 * @param property must not be {@literal null}.
 	 * @return
 	 */
+	@SuppressWarnings("unchecked")
 	public boolean hasValue(MongoPersistentProperty property) {
 
 		Assert.notNull(property, "Property must not be null!");
 
 		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("\\.");

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;
@@ -42,6 +33,7 @@ import org.springframework.data.convert.TypeMapper;
 import org.springframework.data.mapping.Association;
 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;
@@ -147,7 +139,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 */
 	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;
 	}
 
 	/*
@@ -249,13 +242,14 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			throw new MappingException(String.format(INVALID_TYPE_TO_READ, target, typeToUse.getType()));
 		}
 
-		return read((MongoPersistentEntity<S>) mappingContext.getRequiredPersistentEntity(typeToUse), target, path);
+		return read((MongoPersistentEntity<S>) entity, target, path);
 	}
 
 	private ParameterValueProvider<MongoPersistentProperty> getParameterProvider(MongoPersistentEntity<?> entity,
-			Bson source, DefaultSpELExpressionEvaluator evaluator, ObjectPath path) {
+			DocumentAccessor source, SpELExpressionEvaluator evaluator, ObjectPath path) {
 
-		MongoDbPropertyValueProvider provider = new MongoDbPropertyValueProvider(source, evaluator, path);
+		AssociationAwareMongoDbPropertyValueProvider provider = new AssociationAwareMongoDbPropertyValueProvider(source,
+				evaluator, path);
 		PersistentEntityParameterValueProvider<MongoPersistentProperty> parameterProvider = new PersistentEntityParameterValueProvider<>(
 				entity, provider, path.getCurrentObject());
 
@@ -265,60 +259,105 @@ 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);
+		SpELExpressionEvaluator evaluator = new DefaultSpELExpressionEvaluator(bson, spELContext);
+		DocumentAccessor documentAccessor = new DocumentAccessor(bson);
+
+		PreferredConstructor<S, MongoPersistentProperty> persistenceConstructor = entity.getPersistenceConstructor();
+
+		ParameterValueProvider<MongoPersistentProperty> provider = persistenceConstructor != null
+				&& persistenceConstructor.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);
 
-		PersistentPropertyAccessor accessor = new ConvertingPropertyAccessor(entity.getPropertyAccessor(instance),
-				conversionService);
-
-		MongoPersistentProperty idProperty = entity.getIdProperty();
-		DocumentAccessor documentAccessor = new DocumentAccessor(bson);
-
-		// make sure id property is set before all other properties
-		Object idValue = null;
-
-		if (idProperty != null && documentAccessor.hasValue(idProperty)) {
-
-			idValue = readIdValue(path, evaluator, idProperty, documentAccessor);
-			accessor.setProperty(idProperty, idValue);
+		if (entity.requiresPropertyPopulation()) {
+			return populateProperties(entity, documentAccessor, path, evaluator, instance);
 		}
 
-		ObjectPath currentPath = path.push(instance, entity, idValue != null ? bson.get(idProperty.getFieldName()) : null);
-
-		MongoDbPropertyValueProvider valueProvider = new MongoDbPropertyValueProvider(documentAccessor, evaluator,
-				currentPath);
-
-		DbRefResolverCallback callback = new DefaultDbRefResolverCallback(bson, currentPath, evaluator,
-				MappingMongoConverter.this);
-		readProperties(entity, accessor, idProperty, documentAccessor, valueProvider, callback);
-
 		return instance;
 	}
 
-	private Object readIdValue(ObjectPath path, DefaultSpELExpressionEvaluator evaluator,
-			MongoPersistentProperty idProperty, DocumentAccessor documentAccessor) {
+	private <S> S populateProperties(MongoPersistentEntity<S> entity, DocumentAccessor documentAccessor, ObjectPath path,
+			SpELExpressionEvaluator evaluator, S instance) {
+
+		PersistentPropertyAccessor<S> accessor = new ConvertingPropertyAccessor<>(entity.getPropertyAccessor(instance),
+				conversionService);
+
+		// Make sure id property is set before all other properties
+
+		Object rawId = readAndPopulateIdentifier(accessor, documentAccessor, entity, path, evaluator);
+		ObjectPath currentPath = path.push(accessor.getBean(), entity, rawId);
+
+		MongoDbPropertyValueProvider valueProvider = new MongoDbPropertyValueProvider(documentAccessor, evaluator,
+				currentPath);
+
+		readProperties(entity, accessor, documentAccessor, valueProvider, currentPath, evaluator);
+
+		return accessor.getBean();
+	}
+
+	/**
+	 * Reads the identifier from either the bean backing the {@link PersistentPropertyAccessor} or the source document in
+	 * case the identifier has not be populated yet. In this case the identifier is set on the bean for further reference.
+	 *
+	 * @param accessor must not be {@literal null}.
+	 * @param document must not be {@literal null}.
+	 * @param entity must not be {@literal null}.
+	 * @param path
+	 * @param evaluator
+	 * @return
+	 */
+	private Object readAndPopulateIdentifier(PersistentPropertyAccessor<?> accessor, DocumentAccessor document,
+			MongoPersistentEntity<?> entity, ObjectPath path, SpELExpressionEvaluator evaluator) {
+
+		Object rawId = document.getRawId(entity);
+
+		if (!entity.hasIdProperty() || rawId == null) {
+			return rawId;
+		}
+
+		MongoPersistentProperty idProperty = entity.getRequiredIdProperty();
+
+		if (idProperty.isImmutable() && entity.isConstructorArgument(idProperty)) {
+			return rawId;
+		}
+
+		accessor.setProperty(idProperty, readIdValue(path, evaluator, idProperty, rawId));
+
+		return rawId;
+	}
+
+	private Object readIdValue(ObjectPath path, SpELExpressionEvaluator evaluator, MongoPersistentProperty idProperty,
+			Object rawId) {
 
 		String expression = idProperty.getSpelExpression();
-		Object resolvedValue = expression != null ? evaluator.evaluate(expression) : documentAccessor.get(idProperty);
+		Object resolvedValue = expression != null ? evaluator.evaluate(expression) : rawId;
 
 		return resolvedValue != null ? readValue(resolvedValue, idProperty.getTypeInformation(), path) : null;
 	}
 
-	private void readProperties(MongoPersistentEntity<?> entity, PersistentPropertyAccessor accessor,
-			@Nullable MongoPersistentProperty idProperty, DocumentAccessor documentAccessor,
-			MongoDbPropertyValueProvider valueProvider, DbRefResolverCallback callback) {
+	private void readProperties(MongoPersistentEntity<?> entity, PersistentPropertyAccessor<?> accessor,
+			DocumentAccessor documentAccessor, MongoDbPropertyValueProvider valueProvider, ObjectPath currentPath,
+			SpELExpressionEvaluator evaluator) {
+
+		DbRefResolverCallback callback = null;
 
 		for (MongoPersistentProperty prop : entity) {
 
 			if (prop.isAssociation() && !entity.isConstructorArgument(prop)) {
+
+				if (callback == null) {
+					callback = getDbRefResolverCallback(documentAccessor, currentPath, evaluator);
+				}
+
 				readAssociation(prop.getRequiredAssociation(), accessor, documentAccessor, dbRefProxyHandler, callback);
 				continue;
 			}
-			// we skip the id property since it was already set
-			if (idProperty != null && idProperty.equals(prop)) {
+
+			// We skip the id property since it was already set
+
+			if (entity.isIdProperty(prop)) {
 				continue;
 			}
 
@@ -327,6 +366,11 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			}
 
 			if (prop.isAssociation()) {
+
+				if (callback == null) {
+					callback = getDbRefResolverCallback(documentAccessor, currentPath, evaluator);
+				}
+
 				readAssociation(prop.getRequiredAssociation(), accessor, documentAccessor, dbRefProxyHandler, callback);
 				continue;
 			}
@@ -335,7 +379,14 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 	}
 
-	private void readAssociation(Association<MongoPersistentProperty> association, PersistentPropertyAccessor accessor,
+	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();
@@ -392,12 +443,23 @@ 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.
 	 *
@@ -427,7 +489,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 
 		if (Collection.class.isAssignableFrom(entityType)) {
-			writeCollectionInternal((Collection<?>) obj, ClassTypeInformation.LIST, (Collection) bson);
+			writeCollectionInternal((Collection<?>) obj, ClassTypeInformation.LIST, (Collection<?>) bson);
 			return;
 		}
 
@@ -446,10 +508,10 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			throw new MappingException("No mapping metadata found for entity of type " + obj.getClass().getName());
 		}
 
-		PersistentPropertyAccessor accessor = entity.getPropertyAccessor(obj);
+		PersistentPropertyAccessor<?> accessor = entity.getPropertyAccessor(obj);
 		DocumentAccessor dbObjectAccessor = new DocumentAccessor(bson);
-
 		MongoPersistentProperty idProperty = entity.getIdProperty();
+
 		if (idProperty != null && !dbObjectAccessor.hasValue(idProperty)) {
 
 			Object value = idMapper.convertId(accessor.getProperty(idProperty));
@@ -458,10 +520,11 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 				dbObjectAccessor.put(idProperty, value);
 			}
 		}
+
 		writeProperties(bson, entity, accessor, dbObjectAccessor, idProperty);
 	}
 
-	private void writeProperties(Bson bson, MongoPersistentEntity<?> entity, PersistentPropertyAccessor accessor,
+	private void writeProperties(Bson bson, MongoPersistentEntity<?> entity, PersistentPropertyAccessor<?> accessor,
 			DocumentAccessor dbObjectAccessor, @Nullable MongoPersistentProperty idProperty) {
 
 		// Write the properties
@@ -489,8 +552,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 	}
 
-	private void writeAssociation(Association<MongoPersistentProperty> association, PersistentPropertyAccessor accessor,
-			DocumentAccessor dbObjectAccessor) {
+	private void writeAssociation(Association<MongoPersistentProperty> association,
+			PersistentPropertyAccessor<?> accessor, DocumentAccessor dbObjectAccessor) {
 
 		MongoPersistentProperty inverseProp = association.getInverse();
 
@@ -555,8 +618,9 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 			return;
 		}
 
-		MongoPersistentEntity<?> entity = isSubtype(prop.getType(), obj.getClass())
-				? mappingContext.getRequiredPersistentEntity(obj.getClass()) : mappingContext.getRequiredPersistentEntity(type);
+		MongoPersistentEntity<?> entity = isSubTypeOf(obj.getClass(), prop.getType())
+				? mappingContext.getRequiredPersistentEntity(obj.getClass())
+				: mappingContext.getRequiredPersistentEntity(type);
 
 		Object existingValue = accessor.get(prop);
 		Document document = existingValue instanceof Document ? (Document) existingValue : new Document();
@@ -566,10 +630,6 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		accessor.put(prop, document);
 	}
 
-	private boolean isSubtype(Class<?> left, Class<?> right) {
-		return left.isAssignableFrom(right) && !left.equals(right);
-	}
-
 	/**
 	 * Returns given object as {@link Collection}. Will return the {@link Collection} as is if the source is a
 	 * {@link Collection} already, will convert an array into a {@link Collection} or simply create a single element
@@ -659,11 +719,13 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * @param sink the {@link Collection} to write to.
 	 * @return
 	 */
-	private List<Object> writeCollectionInternal(Collection<?> source, @Nullable TypeInformation<?> type, Collection<?> sink) {
+	@SuppressWarnings("unchecked")
+	private List<Object> writeCollectionInternal(Collection<?> source, @Nullable TypeInformation<?> type,
+			Collection<?> sink) {
 
 		TypeInformation<?> componentType = null;
 
-		List<Object> collection = sink instanceof List ? (List) sink : new ArrayList<>(sink);
+		List<Object> collection = sink instanceof List ? (List<Object>) sink : new ArrayList<>(sink);
 
 		if (type != null) {
 			componentType = type.getComponentType();
@@ -777,7 +839,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 
 		return conversions.hasCustomWriteTarget(key.getClass(), String.class)
-				? (String) getPotentiallyConvertedSimpleWrite(key) : key.toString();
+				? (String) getPotentiallyConvertedSimpleWrite(key)
+				: key.toString();
 	}
 
 	/**
@@ -867,7 +930,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 */
 	@Nullable
 	@SuppressWarnings({ "rawtypes", "unchecked" })
-	private Object getPotentiallyConvertedSimpleRead(@Nullable Object value, @Nullable  Class<?> target) {
+	private Object getPotentiallyConvertedSimpleRead(@Nullable Object value, @Nullable Class<?> target) {
 
 		if (value == null || target == null || ClassUtils.isAssignableValue(target, value)) {
 			return value;
@@ -943,7 +1006,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		Assert.notNull(path, "Object path must not be null!");
 
 		Class<?> collectionType = targetType.getType();
-		collectionType = Collection.class.isAssignableFrom(collectionType) //
+		collectionType = isSubTypeOf(collectionType, Collection.class) //
 				? collectionType //
 				: List.class;
 
@@ -977,13 +1040,12 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 				items.add(read(componentType, (BasicDBObject) element, path));
 			} else {
 
-				if (element 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, element, element.getClass(), rawComponentType, path));
 					}
 				}
-
 				if (element instanceof List) {
 					items.add(readCollectionOrArray(componentType, (Collection<Object>) element, path));
 				} else {
@@ -1270,12 +1332,14 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 	 * of the configured source {@link Document}.
 	 *
 	 * @author Oliver Gierke
+	 * @author Mark Paluch
+	 * @author Christoph Strobl
 	 */
 	class MongoDbPropertyValueProvider implements PropertyValueProvider<MongoPersistentProperty> {
 
-		private final DocumentAccessor source;
-		private final SpELExpressionEvaluator evaluator;
-		private final ObjectPath path;
+		final DocumentAccessor accessor;
+		final SpELExpressionEvaluator evaluator;
+		final ObjectPath path;
 
 		/**
 		 * Creates a new {@link MongoDbPropertyValueProvider} for the given source, {@link SpELExpressionEvaluator} and
@@ -1285,15 +1349,8 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		 * @param evaluator must not be {@literal null}.
 		 * @param path must not be {@literal null}.
 		 */
-		public MongoDbPropertyValueProvider(Bson source, SpELExpressionEvaluator evaluator, ObjectPath path) {
-
-			Assert.notNull(source, "Source document must no be null!");
-			Assert.notNull(evaluator, "SpELExpressionEvaluator must not be null!");
-			Assert.notNull(path, "ObjectPath must not be null!");
-
-			this.source = new DocumentAccessor(source);
-			this.evaluator = evaluator;
-			this.path = path;
+		MongoDbPropertyValueProvider(Bson source, SpELExpressionEvaluator evaluator, ObjectPath path) {
+			this(new DocumentAccessor(source), evaluator, path);
 		}
 
 		/**
@@ -1304,13 +1361,13 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		 * @param evaluator must not be {@literal null}.
 		 * @param path must not be {@literal null}.
 		 */
-		public MongoDbPropertyValueProvider(DocumentAccessor accessor, SpELExpressionEvaluator evaluator, ObjectPath path) {
+		MongoDbPropertyValueProvider(DocumentAccessor accessor, SpELExpressionEvaluator evaluator, ObjectPath path) {
 
 			Assert.notNull(accessor, "DocumentAccessor must no be null!");
 			Assert.notNull(evaluator, "SpELExpressionEvaluator must not be null!");
 			Assert.notNull(path, "ObjectPath must not be null!");
 
-			this.source = accessor;
+			this.accessor = accessor;
 			this.evaluator = evaluator;
 			this.path = path;
 		}
@@ -1323,7 +1380,7 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		public <T> T getPropertyValue(MongoPersistentProperty property) {
 
 			String expression = property.getSpelExpression();
-			Object value = expression != null ? evaluator.evaluate(expression) : source.get(property);
+			Object value = expression != null ? evaluator.evaluate(expression) : accessor.get(property);
 
 			if (value == null) {
 				return null;
@@ -1333,6 +1390,55 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		}
 	}
 
+	/**
+	 * {@link PropertyValueProvider} that is aware of {@link MongoPersistentProperty#isAssociation()} and that delegates
+	 * resolution to {@link DbRefResolver}.
+	 *
+	 * @author Mark Paluch
+	 * @author Christoph Strobl
+	 * @since 2.1
+	 */
+	class AssociationAwareMongoDbPropertyValueProvider extends MongoDbPropertyValueProvider {
+
+		/**
+		 * Creates a new {@link AssociationAwareMongoDbPropertyValueProvider} for the given source,
+		 * {@link SpELExpressionEvaluator} and {@link ObjectPath}.
+		 *
+		 * @param source must not be {@literal null}.
+		 * @param evaluator must not be {@literal null}.
+		 * @param path must not be {@literal null}.
+		 */
+		AssociationAwareMongoDbPropertyValueProvider(DocumentAccessor source, SpELExpressionEvaluator evaluator,
+				ObjectPath path) {
+			super(source, evaluator, path);
+		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.convert.PropertyValueProvider#getPropertyValue(org.springframework.data.mapping.PersistentProperty)
+		 */
+		@Nullable
+		@SuppressWarnings("unchecked")
+		public <T> T getPropertyValue(MongoPersistentProperty property) {
+
+			if (property.isDbReference() && property.getDBRef().lazy()) {
+
+				Object rawRefValue = accessor.get(property);
+				if (rawRefValue == null) {
+					return null;
+				}
+
+				DbRefResolverCallback callback = new DefaultDbRefResolverCallback(accessor.getDocument(), path, evaluator,
+						MappingMongoConverter.this);
+
+				DBRef dbref = rawRefValue instanceof DBRef ? (DBRef) rawRefValue : null;
+				return (T) dbRefResolver.resolveDbRef(property, dbref, callback, dbRefProxyHandler);
+			}
+
+			return super.getPropertyValue(property);
+		}
+	}
+
 	/**
 	 * Extension of {@link SpELExpressionParameterValueProvider} to recursively trigger value conversion on the raw
 	 * resolved SpEL value.
@@ -1435,7 +1541,8 @@ 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());
@@ -1517,6 +1624,17 @@ public class MappingMongoConverter extends AbstractMongoConverter implements App
 		return true;
 	}
 
+	/**
+	 * Returns whether the given type is a sub type of the given reference, i.e. assignable but not the exact same type.
+	 * 
+	 * @param type must not be {@literal null}.
+	 * @param reference must not be {@literal null}.
+	 * @return
+	 */
+	private static boolean isSubTypeOf(Class<?> type, Class<?> reference) {
+		return !type.equals(reference) && reference.isAssignableFrom(type);
+	}
+
 	/**
 	 * Marker class used to indicate we have a non root document object here that might be used within an update - so we
 	 * need to preserve type hints for potential nested elements but need to remove it on top level.
@@ -1527,4 +1645,14 @@ 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/MongoConverters.java

@@ -19,6 +19,7 @@ import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.net.MalformedURLException;
 import java.net.URL;
+import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Currency;
@@ -26,6 +27,7 @@ import java.util.List;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
 
+import org.bson.BsonTimestamp;
 import org.bson.Document;
 import org.bson.types.Binary;
 import org.bson.types.Code;
@@ -86,6 +88,7 @@ abstract class MongoConverters {
 		converters.add(LongToAtomicLongConverter.INSTANCE);
 		converters.add(IntegerToAtomicIntegerConverter.INSTANCE);
 		converters.add(BinaryToByteArrayConverter.INSTANCE);
+		converters.add(BsonTimestampToInstantConverter.INSTANCE);
 
 		return converters;
 	}
@@ -465,4 +468,22 @@ abstract class MongoConverters {
 			return source.getData();
 		}
 	}
+
+	/**
+	 * {@link Converter} implementation converting {@link BsonTimestamp} into {@link Instant}.
+	 *
+	 * @author Christoph Strobl
+	 * @since 2.1.2
+	 */
+	@ReadingConverter
+	enum BsonTimestampToInstantConverter implements Converter<BsonTimestamp, Instant> {
+
+		INSTANCE;
+
+		@Nullable
+		@Override
+		public Instant convert(BsonTimestamp source) {
+			return Instant.ofEpochSecond(source.getTime(), 0);
+		}
+	}
 }

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

@@ -164,13 +164,14 @@ public class MongoExampleMapper {
 			if (exampleSpecAccessor.hasPropertySpecifier(mappedPropertyPath)) {
 
 				PropertyValueTransformer valueTransformer = exampleSpecAccessor.getValueTransformerForPath(mappedPropertyPath);
-				value = valueTransformer.convert(value);
-				if (value == null) {
+				Optional converted = valueTransformer.apply(Optional.ofNullable(value));
+
+				if(!converted.isPresent()) {
 					iter.remove();
 					continue;
 				}
 
-				entry.setValue(value);
+				entry.setValue(converted.get());
 			}
 
 			if (entry.getValue() instanceof String) {

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

@@ -0,0 +1,72 @@
+/*
+ * 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.convert;
+
+import java.util.List;
+
+import org.bson.Document;
+import org.springframework.data.mongodb.core.mapping.MongoPersistentProperty;
+import org.springframework.lang.Nullable;
+
+import com.mongodb.DBRef;
+
+/**
+ * No-Operation {@link org.springframework.data.mongodb.core.mapping.DBRef} resolver throwing
+ * {@link UnsupportedOperationException} when attempting to resolve database references.
+ *
+ * @author Mark Paluch
+ * @author Christoph Strobl
+ * @since 2.1
+ */
+public enum NoOpDbRefResolver implements DbRefResolver {
+
+	INSTANCE;
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.convert.DbRefResolver#resolveDbRef(org.springframework.data.mongodb.core.mapping.MongoPersistentProperty, org.springframework.data.mongodb.core.convert.DbRefResolverCallback, org.springframework.data.mongodb.core.convert.DbRefProxyHandler)
+	 */
+	@Override
+	@Nullable
+	public Object resolveDbRef(MongoPersistentProperty property, @Nullable DBRef dbref, DbRefResolverCallback callback,
+			DbRefProxyHandler proxyHandler) {
+
+		return handle();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.convert.DbRefResolver#fetch(com.mongodb.DBRef)
+	 */
+	@Override
+	@Nullable
+	public Document fetch(DBRef dbRef) {
+		return handle();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.convert.DbRefResolver#bulkFetch(java.util.List)
+	 */
+	@Override
+	public List<Document> bulkFetch(List<DBRef> dbRefs) {
+		return handle();
+	}
+
+	private <T> T handle() throws UnsupportedOperationException {
+		throw new UnsupportedOperationException("DBRef resolution is not supported!");
+	}
+}

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

@@ -15,8 +15,6 @@
  */
 package org.springframework.data.mongodb.core.convert;
 
-import lombok.Value;
-
 import java.util.ArrayList;
 import java.util.List;
 
@@ -45,26 +43,33 @@ class ObjectPath {
 
 	static final ObjectPath ROOT = new ObjectPath();
 
-	private final ObjectPathItem[] items;
+	private final @Nullable ObjectPath parent;
+	private final @Nullable Object object;
+	private final @Nullable Object idValue;
+	private final String collection;
 
 	private ObjectPath() {
-		this.items = new ObjectPathItem[0];
+
+		this.parent = null;
+		this.object = null;
+		this.idValue = null;
+		this.collection = "";
 	}
 
 	/**
-	 * Creates a new {@link ObjectPath} from the given parent {@link ObjectPath} by adding the provided
-	 * {@link ObjectPathItem} to it.
+	 * Creates a new {@link ObjectPath} from the given parent {@link ObjectPath} and adding the provided path values.
 	 *
 	 * @param parent must not be {@literal null}.
-	 * @param item
+	 * @param collection
+	 * @param idValue
+	 * @param collection
 	 */
-	private ObjectPath(ObjectPath parent, ObjectPath.ObjectPathItem item) {
+	private ObjectPath(ObjectPath parent, Object object, @Nullable Object idValue, String collection) {
 
-		ObjectPathItem[] items = new ObjectPathItem[parent.items.length + 1];
-		System.arraycopy(parent.items, 0, items, 0, parent.items.length);
-		items[parent.items.length] = item;
-
-		this.items = items;
+		this.parent = parent;
+		this.object = object;
+		this.idValue = idValue;
+		this.collection = collection;
 	}
 
 	/**
@@ -80,8 +85,7 @@ class ObjectPath {
 		Assert.notNull(object, "Object must not be null!");
 		Assert.notNull(entity, "MongoPersistentEntity must not be null!");
 
-		ObjectPathItem item = new ObjectPathItem(object, id, entity.getCollection());
-		return new ObjectPath(this, item);
+		return new ObjectPath(this, object, id, entity.getCollection());
 	}
 
 	/**
@@ -100,15 +104,15 @@ class ObjectPath {
 		Assert.notNull(id, "Id must not be null!");
 		Assert.hasText(collection, "Collection name must not be null!");
 
-		for (ObjectPathItem item : items) {
+		for (ObjectPath current = this; current != null; current = current.parent) {
 
-			Object object = item.getObject();
+			Object object = current.getObject();
 
-			if (object == null || item.getIdValue() == null) {
+			if (object == null || current.getIdValue() == null) {
 				continue;
 			}
 
-			if (collection.equals(item.getCollection()) && id.equals(item.getIdValue())) {
+			if (collection.equals(current.getCollection()) && id.equals(current.getIdValue())) {
 				return object;
 			}
 		}
@@ -133,15 +137,15 @@ class ObjectPath {
 		Assert.hasText(collection, "Collection name must not be null!");
 		Assert.notNull(type, "Type must not be null!");
 
-		for (ObjectPathItem item : items) {
+		for (ObjectPath current = this; current != null; current = current.parent) {
 
-			Object object = item.getObject();
+			Object object = current.getObject();
 
-			if (object == null || item.getIdValue() == null) {
+			if (object == null || current.getIdValue() == null) {
 				continue;
 			}
 
-			if (collection.equals(item.getCollection()) && id.equals(item.getIdValue())
+			if (collection.equals(current.getCollection()) && id.equals(current.getIdValue())
 					&& ClassUtils.isAssignable(type, object.getClass())) {
 				return type.cast(object);
 			}
@@ -157,7 +161,21 @@ class ObjectPath {
 	 */
 	@Nullable
 	Object getCurrentObject() {
-		return items.length == 0 ? null : items[items.length - 1].getObject();
+		return getObject();
+	}
+
+	@Nullable
+	private Object getObject() {
+		return object;
+	}
+
+	@Nullable
+	private Object getIdValue() {
+		return idValue;
+	}
+
+	private String getCollection() {
+		return collection;
 	}
 
 	/*
@@ -167,31 +185,16 @@ class ObjectPath {
 	@Override
 	public String toString() {
 
-		if (items.length == 0) {
+		if (parent == null) {
 			return "[empty]";
 		}
 
-		List<String> strings = new ArrayList<>(items.length);
+		List<String> strings = new ArrayList<>();
 
-		for (ObjectPathItem item : items) {
-			strings.add(ObjectUtils.nullSafeToString(item.object));
+		for (ObjectPath current = this; current != null; current = current.parent) {
+			strings.add(ObjectUtils.nullSafeToString(current.getObject()));
 		}
 
 		return StringUtils.collectionToDelimitedString(strings, " -> ");
 	}
-
-	/**
-	 * An item in an {@link ObjectPath}.
-	 *
-	 * @author Thomas Darimont
-	 * @author Oliver Gierke
-	 * @author Mark Paluch
-	 */
-	@Value
-	private static class ObjectPathItem {
-
-		Object object;
-		@Nullable Object idValue;
-		String collection;
-	}
 }

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

@@ -312,7 +312,7 @@ public class QueryMapper {
 	@SuppressWarnings("unchecked")
 	protected Object getMappedValue(Field documentField, Object value) {
 
-		if (documentField.isIdField()) {
+		if (documentField.isIdField() && !documentField.isAssociation()) {
 
 			if (isDBObject(value)) {
 				DBObject valueDbo = (DBObject) value;
@@ -850,15 +850,18 @@ public class QueryMapper {
 
 		/*
 		 * (non-Javadoc)
-		 * @see org.springframework.data.mongodb.core.convert.QueryMapper.Field#isIdKey()
+		 * @see org.springframework.data.mongodb.core.convert.QueryMapper.Field#isIdField()
 		 */
 		@Override
 		public boolean isIdField() {
 
-			MongoPersistentProperty idProperty = entity.getIdProperty();
+			MongoPersistentProperty idProperty = (property != null && property.isIdProperty()) ? property
+					: entity.getIdProperty();
 
 			if (idProperty != null) {
-				return idProperty.getName().equals(name) || idProperty.getFieldName().equals(name);
+
+				return name.equals(idProperty.getName()) || name.equals(idProperty.getFieldName())
+						|| name.endsWith("." + idProperty.getName()) || name.endsWith("." + idProperty.getFieldName());
 			}
 
 			return DEFAULT_ID_NAMES.contains(name);

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

@@ -70,7 +70,9 @@ public @interface CompoundIndex {
 	/**
 	 * @return
 	 * @see <a href="https://docs.mongodb.org/manual/core/index-creation/#index-creation-duplicate-dropping">https://docs.mongodb.org/manual/core/index-creation/#index-creation-duplicate-dropping</a>
+	 * @deprecated since 2.1. No longer supported by MongoDB as of server version 3.0.
 	 */
+	@Deprecated
 	boolean dropDups() default false;
 
 	/**

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

@@ -36,6 +36,10 @@ import org.springframework.util.StringUtils;
 @SuppressWarnings("deprecation")
 public class Index implements IndexDefinition {
 
+	/**
+	 * @deprecated since 2.1. No longer supported by MongoDB as of server version 3.0.
+	 */
+	@Deprecated
 	public enum Duplicates {
 		RETAIN
 	}
@@ -43,7 +47,6 @@ public class Index implements IndexDefinition {
 	private final Map<String, Direction> fieldSpec = new LinkedHashMap<String, Direction>();
 	private @Nullable String name;
 	private boolean unique = false;
-	private boolean dropDuplicates = false;
 	private boolean sparse = false;
 	private boolean background = false;
 	private long expire = -1;
@@ -183,9 +186,6 @@ public class Index implements IndexDefinition {
 		if (unique) {
 			document.put("unique", true);
 		}
-		if (dropDuplicates) {
-			document.put("dropDups", true);
-		}
 		if (sparse) {
 			document.put("sparse", true);
 		}

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

@@ -56,7 +56,9 @@ public @interface Indexed {
 	/**
 	 * @return
 	 * @see <a href="https://docs.mongodb.org/manual/core/index-creation/#index-creation-duplicate-dropping">https://docs.mongodb.org/manual/core/index-creation/#index-creation-duplicate-dropping</a>
+	 * @deprecated since 2.1. No longer supported by MongoDB as of server version 3.0.
 	 */
+	@Deprecated
 	boolean dropDups() default false;
 
 	/**

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

@@ -24,11 +24,14 @@ import org.springframework.lang.Nullable;
  * {@link MongoPersistentProperty} caching access to {@link #isIdProperty()} and {@link #getFieldName()}.
  *
  * @author Oliver Gierke
+ * @author Mark Paluch
  */
 public class CachingMongoPersistentProperty extends BasicMongoPersistentProperty {
 
 	private @Nullable Boolean isIdProperty;
 	private @Nullable Boolean isAssociation;
+	private @Nullable boolean dbRefResolved;
+	private @Nullable DBRef dbref;
 	private @Nullable String fieldName;
 	private @Nullable Boolean usePropertyAccess;
 	private @Nullable Boolean isTransient;
@@ -36,8 +39,7 @@ public class CachingMongoPersistentProperty extends BasicMongoPersistentProperty
 	/**
 	 * Creates a new {@link CachingMongoPersistentProperty}.
 	 *
-	 * @param field
-	 * @param propertyDescriptor
+	 * @param property
 	 * @param owner
 	 * @param simpleTypeHolder
 	 * @param fieldNamingStrategy
@@ -114,4 +116,28 @@ public class CachingMongoPersistentProperty extends BasicMongoPersistentProperty
 
 		return this.isTransient;
 	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.mapping.BasicMongoPersistentProperty#isDbReference()
+	 */
+	@Override
+	public boolean isDbReference() {
+		return getDBRef() != null;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.mapping.BasicMongoPersistentProperty#getDBRef()
+	 */
+	@Override
+	public DBRef getDBRef() {
+
+		if (!dbRefResolved) {
+			this.dbref = super.getDBRef();
+			this.dbRefResolved = true;
+		}
+
+		return this.dbref;
+	}
 }

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

@@ -22,13 +22,13 @@ import java.util.Set;
 import java.util.UUID;
 import java.util.regex.Pattern;
 
-import org.bson.BsonObjectId;
+import org.bson.*;
 import org.bson.types.Binary;
 import org.bson.types.CodeWScope;
+import org.bson.types.CodeWithScope;
+import org.bson.types.Decimal128;
 import org.bson.types.ObjectId;
 import org.springframework.data.mapping.model.SimpleTypeHolder;
-import org.springframework.data.mongodb.util.MongoClientVersion;
-import org.springframework.util.ClassUtils;
 
 import com.mongodb.DBRef;
 
@@ -54,15 +54,29 @@ public abstract class MongoSimpleTypes {
 		simpleTypes.add(ObjectId.class);
 		simpleTypes.add(BsonObjectId.class);
 		simpleTypes.add(CodeWScope.class);
+		simpleTypes.add(CodeWithScope.class);
 		simpleTypes.add(org.bson.Document.class);
 		simpleTypes.add(Pattern.class);
 		simpleTypes.add(Binary.class);
 		simpleTypes.add(UUID.class);
+		simpleTypes.add(Decimal128.class);
 
-		if (MongoClientVersion.isMongo34Driver()) {
-			simpleTypes
-					.add(ClassUtils.resolveClassName("org.bson.types.Decimal128", MongoSimpleTypes.class.getClassLoader()));
-		}
+		simpleTypes.add(BsonBinary.class);
+		simpleTypes.add(BsonBoolean.class);
+		simpleTypes.add(BsonDateTime.class);
+		simpleTypes.add(BsonDbPointer.class);
+		simpleTypes.add(BsonDecimal128.class);
+		simpleTypes.add(BsonDocument.class);
+		simpleTypes.add(BsonDocument.class);
+		simpleTypes.add(BsonDouble.class);
+		simpleTypes.add(BsonInt32.class);
+		simpleTypes.add(BsonInt64.class);
+		simpleTypes.add(BsonJavaScript.class);
+		simpleTypes.add(BsonJavaScriptWithScope.class);
+		simpleTypes.add(BsonObjectId.class);
+		simpleTypes.add(BsonRegularExpression.class);
+		simpleTypes.add(BsonString.class);
+		simpleTypes.add(BsonTimestamp.class);
 
 		MONGO_SIMPLE_TYPES = Collections.unmodifiableSet(simpleTypes);
 	}

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

@@ -15,8 +15,6 @@
  */
 package org.springframework.data.mongodb.core.mapping.event;
 
-import java.util.Optional;
-
 import org.springframework.beans.factory.ObjectFactory;
 import org.springframework.context.ApplicationListener;
 import org.springframework.core.Ordered;
@@ -53,9 +51,7 @@ public class AuditingEventListener implements ApplicationListener<BeforeConvertE
 	 */
 	@Override
 	public void onApplicationEvent(BeforeConvertEvent<Object> event) {
-
-		Optional.ofNullable(event.getSource())//
-				.ifPresent(it -> auditingHandlerFactory.getObject().markAudited(it));
+		event.mapSource(it -> auditingHandlerFactory.getObject().markAudited(it));
 	}
 
 	/*

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

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.mongodb.core.mapping.event;
 
+import java.util.function.Function;
+
 import org.bson.Document;
 import org.springframework.context.ApplicationEvent;
 import org.springframework.lang.Nullable;
@@ -72,4 +74,19 @@ public class MongoMappingEvent<T> extends ApplicationEvent {
 	public T getSource() {
 		return (T) super.getSource();
 	}
+
+	/**
+	 * Allows client code to change the underlying source instance by applying the given {@link Function}.
+	 * 
+	 * @param mapper the {@link Function} to apply, will only be applied if the source is not {@literal null}.
+	 * @since 2.1
+	 */
+	final void mapSource(Function<T, T> mapper) {
+
+		if (source == null) {
+			return;
+		}
+
+		this.source = mapper.apply(getSource());
+	}
 }

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

@@ -24,6 +24,8 @@ import org.springframework.data.mongodb.core.query.Collation;
 import org.springframework.lang.Nullable;
 
 import com.mongodb.MapReduceCommand;
+import com.mongodb.MapReduceCommand.OutputType;
+import com.mongodb.client.model.MapReduceAction;
 
 /**
  * @author Mark Pollack
@@ -295,6 +297,37 @@ public class MapReduceOptions {
 		return collation;
 	}
 
+	/**
+	 * Return the {@link MapReduceAction} derived from {@link com.mongodb.MapReduceCommand.OutputType}.
+	 *
+	 * @return the mapped action or {@literal null} if the action maps to inline output.
+	 * @since 2.0.10
+	 */
+	@Nullable
+	public MapReduceAction getMapReduceAction() {
+
+		switch (outputType) {
+			case MERGE:
+				return MapReduceAction.MERGE;
+			case REDUCE:
+				return MapReduceAction.REDUCE;
+			case REPLACE:
+				return MapReduceAction.REPLACE;
+			case INLINE:
+				return null;
+			default:
+				throw new IllegalStateException(String.format("Unknown output type %s for map reduce command.", outputType));
+		}
+	}
+
+	/**
+	 * @return {@literal true} if {@link OutputType#INLINE} is used.
+	 * @since 2.0.10
+	 */
+	public boolean usesInlineOutput() {
+		return OutputType.INLINE.equals(outputType);
+	}
+
 	public Document getOptionsObject() {
 
 		Document cmd = new Document();
@@ -328,7 +361,7 @@ public class MapReduceOptions {
 
 		Document out = new Document();
 
-		switch (outputType) {
+		switch (getOutputType()) {
 			case INLINE:
 				out.put("inline", 1);
 				break;

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

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.mongodb.core.messaging;
 
+import java.time.Instant;
+
 import org.bson.BsonValue;
 import org.bson.Document;
 import org.springframework.data.mongodb.core.ChangeStreamOptions;
@@ -34,7 +36,7 @@ import com.mongodb.client.model.changestream.FullDocument;
  * using the synchronous MongoDB Java driver.
  * <p/>
  * The most trivial use case is subscribing to all events of a specific {@link com.mongodb.client.MongoCollection
- * collection}.
+ * collection}
  *
  * <pre>
  * <code>
@@ -42,6 +44,15 @@ import com.mongodb.client.model.changestream.FullDocument;
  * </code>
  * </pre>
  *
+ * or {@link com.mongodb.client.MongoDatabase} which receives events from all {@link com.mongodb.client.MongoCollection
+ * collections} in that database.
+ *
+ * <pre>
+ * <code>
+ *     ChangeStreamRequest<Document> request = new ChangeStreamRequest<>(System.out::println, RequestOptions.justDatabase("test"));
+ * </code>
+ * </pre>
+ *
  * For more advanced scenarios {@link ChangeStreamOptions} offers abstractions for options like filtering, resuming,...
  *
  * <pre>
@@ -154,21 +165,23 @@ public class ChangeStreamRequest<T>
 	 */
 	public static class ChangeStreamRequestOptions implements SubscriptionRequest.RequestOptions {
 
-		private final String collectionName;
+		private final @Nullable String databaseName;
+		private final @Nullable String collectionName;
 		private final ChangeStreamOptions options;
 
 		/**
 		 * Create new {@link ChangeStreamRequestOptions}.
 		 *
-		 * @param collectionName must not be {@literal null}.
+		 * @param collectionName can be {@literal null}.
 		 * @param options must not be {@literal null}.
 		 */
-		public ChangeStreamRequestOptions(String collectionName, ChangeStreamOptions options) {
+		public ChangeStreamRequestOptions(@Nullable String databaseName, @Nullable String collectionName,
+				ChangeStreamOptions options) {
 
-			Assert.notNull(collectionName, "CollectionName must not be null!");
 			Assert.notNull(options, "Options must not be null!");
 
 			this.collectionName = collectionName;
+			this.databaseName = databaseName;
 			this.options = options;
 		}
 
@@ -176,7 +189,8 @@ public class ChangeStreamRequest<T>
 
 			Assert.notNull(options, "Options must not be null!");
 
-			return new ChangeStreamRequestOptions(options.getCollectionName(), ChangeStreamOptions.builder().build());
+			return new ChangeStreamRequestOptions(options.getDatabaseName(), options.getCollectionName(),
+					ChangeStreamOptions.builder().build());
 		}
 
 		/**
@@ -196,6 +210,15 @@ public class ChangeStreamRequest<T>
 		public String getCollectionName() {
 			return collectionName;
 		}
+
+		/*
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.monitor.SubscriptionRequest.RequestOptions#getDatabaseName()
+		 */
+		@Override
+		public String getDatabaseName() {
+			return databaseName;
+		}
 	}
 
 	/**
@@ -207,12 +230,27 @@ public class ChangeStreamRequest<T>
 	 */
 	public static class ChangeStreamRequestBuilder<T> {
 
+		private @Nullable String databaseName;
 		private @Nullable String collectionName;
 		private @Nullable MessageListener<ChangeStreamDocument<Document>, ? super T> listener;
 		private ChangeStreamOptionsBuilder delegate = ChangeStreamOptions.builder();
 
 		private ChangeStreamRequestBuilder() {}
 
+		/**
+		 * Set the name of the {@link com.mongodb.client.MongoDatabase} to listen to.
+		 *
+		 * @param databaseName must not be {@literal null} nor empty.
+		 * @return this.
+		 */
+		public ChangeStreamRequestBuilder<T> database(String databaseName) {
+
+			Assert.hasText(databaseName, "DatabaseName must not be null!");
+
+			this.databaseName = databaseName;
+			return this;
+		}
+
 		/**
 		 * Set the name of the {@link com.mongodb.client.MongoCollection} to listen to.
 		 *
@@ -317,6 +355,22 @@ public class ChangeStreamRequest<T>
 			return this;
 		}
 
+		/**
+		 * Set the cluster time at which to resume listening.
+		 *
+		 * @param clusterTime must not be {@literal null}.
+		 * @return this.
+		 * @see ChangeStreamOptions#getResumeTimestamp()
+		 * @see ChangeStreamOptionsBuilder#resumeAt(java.time.Instant)
+		 */
+		public ChangeStreamRequestBuilder<T> resumeAt(Instant clusterTime) {
+
+			Assert.notNull(clusterTime, "ClusterTime must not be null!");
+
+			this.delegate.resumeAt(clusterTime);
+			return this;
+		}
+
 		/**
 		 * Set the {@link FullDocument} lookup to {@link FullDocument#UPDATE_LOOKUP}.
 		 *
@@ -339,9 +393,9 @@ public class ChangeStreamRequest<T>
 		public ChangeStreamRequest<T> build() {
 
 			Assert.notNull(listener, "MessageListener must not be null!");
-			Assert.hasText(collectionName, "CollectionName must not be null!");
 
-			return new ChangeStreamRequest<>(listener, new ChangeStreamRequestOptions(collectionName, delegate.build()));
+			return new ChangeStreamRequest<>(listener,
+					new ChangeStreamRequestOptions(databaseName, collectionName, delegate.build()));
 		}
 	}
 }

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

@@ -17,14 +17,16 @@ package org.springframework.data.mongodb.core.messaging;
 
 import lombok.AllArgsConstructor;
 
+import java.time.Instant;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
-import java.util.Optional;
 import java.util.Set;
 
 import org.bson.BsonDocument;
+import org.bson.BsonTimestamp;
+import org.bson.BsonValue;
 import org.bson.Document;
 import org.springframework.data.mongodb.core.ChangeStreamEvent;
 import org.springframework.data.mongodb.core.ChangeStreamOptions;
@@ -42,10 +44,12 @@ import org.springframework.data.mongodb.core.messaging.SubscriptionRequest.Reque
 import org.springframework.lang.Nullable;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ErrorHandler;
+import org.springframework.util.StringUtils;
 
 import com.mongodb.MongoNamespace;
 import com.mongodb.client.ChangeStreamIterable;
 import com.mongodb.client.MongoCursor;
+import com.mongodb.client.MongoDatabase;
 import com.mongodb.client.model.Collation;
 import com.mongodb.client.model.changestream.ChangeStreamDocument;
 import com.mongodb.client.model.changestream.FullDocument;
@@ -54,6 +58,7 @@ import com.mongodb.client.model.changestream.FullDocument;
  * {@link Task} implementation for obtaining {@link ChangeStreamDocument ChangeStreamDocuments} from MongoDB.
  *
  * @author Christoph Strobl
+ * @author Mark Paluch
  * @since 2.1
  */
 class ChangeStreamTask extends CursorReadingTask<ChangeStreamDocument<Document>, Object> {
@@ -73,7 +78,7 @@ class ChangeStreamTask extends CursorReadingTask<ChangeStreamDocument<Document>,
 		mongoConverter = template.getConverter();
 	}
 
-	/* 
+	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.core.messaging.CursorReadingTask#initCursor(org.springframework.data.mongodb.core.MongoTemplate, org.springframework.data.mongodb.core.messaging.SubscriptionRequest.RequestOptions, java.lang.Class)
 	 */
@@ -84,7 +89,9 @@ class ChangeStreamTask extends CursorReadingTask<ChangeStreamDocument<Document>,
 		List<Document> filter = Collections.emptyList();
 		BsonDocument resumeToken = new BsonDocument();
 		Collation collation = null;
-		FullDocument fullDocument = FullDocument.DEFAULT;
+		FullDocument fullDocument = ClassUtils.isAssignable(Document.class, targetType) ? FullDocument.DEFAULT
+				: FullDocument.UPDATE_LOOKUP;
+		BsonTimestamp startAt = null;
 
 		if (options instanceof ChangeStreamRequest.ChangeStreamRequestOptions) {
 
@@ -107,16 +114,32 @@ class ChangeStreamTask extends CursorReadingTask<ChangeStreamDocument<Document>,
 			fullDocument = changeStreamOptions.getFullDocumentLookup()
 					.orElseGet(() -> ClassUtils.isAssignable(Document.class, targetType) ? FullDocument.DEFAULT
 							: FullDocument.UPDATE_LOOKUP);
+
+			startAt = changeStreamOptions.getResumeTimestamp().map(it -> new BsonTimestamp((int) it.getEpochSecond(), 0))
+					.orElse(null);
 		}
 
-		ChangeStreamIterable<Document> iterable = filter.isEmpty()
-				? template.getCollection(options.getCollectionName()).watch(Document.class)
-				: template.getCollection(options.getCollectionName()).watch(filter, Document.class);
+		MongoDatabase db = StringUtils.hasText(options.getDatabaseName())
+				? template.getMongoDbFactory().getDb(options.getDatabaseName()) : template.getDb();
+
+		ChangeStreamIterable<Document> iterable;
+
+		if (StringUtils.hasText(options.getCollectionName())) {
+			iterable = filter.isEmpty() ? db.getCollection(options.getCollectionName()).watch(Document.class)
+					: db.getCollection(options.getCollectionName()).watch(filter, Document.class);
+
+		} else {
+			iterable = filter.isEmpty() ? db.watch(Document.class) : db.watch(filter, Document.class);
+		}
 
 		if (!resumeToken.isEmpty()) {
 			iterable = iterable.resumeAfter(resumeToken);
 		}
 
+		if (startAt != null) {
+			iterable.startAtOperationTime(startAt);
+		}
+
 		if (collation != null) {
 			iterable = iterable.collation(collation);
 		}
@@ -126,13 +149,15 @@ class ChangeStreamTask extends CursorReadingTask<ChangeStreamDocument<Document>,
 		return iterable.iterator();
 	}
 
+	@SuppressWarnings("unchecked")
 	List<Document> prepareFilter(MongoTemplate template, ChangeStreamOptions options) {
 
 		if (!options.getFilter().isPresent()) {
 			return Collections.emptyList();
 		}
 
-		Object filter = options.getFilter().get();
+		Object filter = options.getFilter().orElse(null);
+
 		if (filter instanceof Aggregation) {
 			Aggregation agg = (Aggregation) filter;
 			AggregationOperationContext context = agg instanceof TypedAggregation
@@ -141,26 +166,39 @@ class ChangeStreamTask extends CursorReadingTask<ChangeStreamDocument<Document>,
 					: Aggregation.DEFAULT_CONTEXT;
 
 			return agg.toPipeline(new PrefixingDelegatingAggregationOperationContext(context, "fullDocument", blacklist));
-		} else if (filter instanceof List) {
-			return (List<Document>) filter;
-		} else {
-			throw new IllegalArgumentException(
-					"ChangeStreamRequestOptions.filter mut be either an Aggregation or a plain list of Documents");
 		}
+
+		if (filter instanceof List) {
+			return (List<Document>) filter;
+		}
+
+		throw new IllegalArgumentException(
+				"ChangeStreamRequestOptions.filter mut be either an Aggregation or a plain list of Documents");
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.core.messaging.CursorReadingTask#createMessage(java.lang.Object, java.lang.Class, org.springframework.data.mongodb.core.messaging.SubscriptionRequest.RequestOptions)
+	 */
 	@Override
 	protected Message<ChangeStreamDocument<Document>, Object> createMessage(ChangeStreamDocument<Document> source,
 			Class<Object> targetType, RequestOptions options) {
 
-		// namespace might be null for eg. OperationType.INVALIDATE
-		MongoNamespace namespace = Optional.ofNullable(source.getNamespace())
-				.orElse(new MongoNamespace("unknown", options.getCollectionName()));
+		MongoNamespace namespace = source.getNamespace() != null ? source.getNamespace()
+				: createNamespaceFromOptions(options);
 
 		return new ChangeStreamEventMessage<>(new ChangeStreamEvent<>(source, targetType, mongoConverter), MessageProperties
 				.builder().databaseName(namespace.getDatabaseName()).collectionName(namespace.getCollectionName()).build());
 	}
 
+	MongoNamespace createNamespaceFromOptions(RequestOptions options) {
+
+		String collectionName = StringUtils.hasText(options.getCollectionName()) ? options.getCollectionName() : "unknown";
+		String databaseName = StringUtils.hasText(options.getDatabaseName()) ? options.getDatabaseName() : "unknown";
+
+		return new MongoNamespace(databaseName, collectionName);
+	}
+
 	/**
 	 * {@link Message} implementation for ChangeStreams
 	 *
@@ -172,7 +210,7 @@ class ChangeStreamTask extends CursorReadingTask<ChangeStreamDocument<Document>,
 		private final ChangeStreamEvent<T> delegate;
 		private final MessageProperties messageProperties;
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.messaging.Message#getRaw()
 		 */
@@ -182,7 +220,7 @@ class ChangeStreamTask extends CursorReadingTask<ChangeStreamDocument<Document>,
 			return delegate.getRaw();
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.messaging.Message#getBody()
 		 */
@@ -192,7 +230,7 @@ class ChangeStreamTask extends CursorReadingTask<ChangeStreamDocument<Document>,
 			return delegate.getBody();
 		}
 
-		/* 
+		/*
 		 * (non-Javadoc)
 		 * @see org.springframework.data.mongodb.core.messaging.Message#getProperties()
 		 */
@@ -200,5 +238,32 @@ class ChangeStreamTask extends CursorReadingTask<ChangeStreamDocument<Document>,
 		public MessageProperties getProperties() {
 			return this.messageProperties;
 		}
+
+		/**
+		 * @return the resume token or {@literal null} if not set.
+		 * @see ChangeStreamEvent#getResumeToken()
+		 */
+		@Nullable
+		BsonValue getResumeToken() {
+			return delegate.getResumeToken();
+		}
+
+		/**
+		 * @return the cluster time of the event or {@literal null}.
+		 * @see ChangeStreamEvent#getTimestamp()
+		 */
+		@Nullable
+		Instant getTimestamp() {
+			return delegate.getTimestamp();
+		}
+
+		/**
+		 * Get the {@link ChangeStreamEvent} from the message.
+		 *
+		 * @return never {@literal null}.
+		 */
+		ChangeStreamEvent<T> getChangeStreamEvent() {
+			return delegate;
+		}
 	}
 }

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

@@ -24,10 +24,10 @@ import org.springframework.data.mongodb.core.MongoTemplate;
 import org.springframework.data.mongodb.core.messaging.Message.MessageProperties;
 import org.springframework.data.mongodb.core.messaging.SubscriptionRequest.RequestOptions;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.ErrorHandler;
 
 import com.mongodb.client.MongoCursor;
-import com.mysema.commons.lang.Assert;
 
 /**
  * @author Christoph Strobl
@@ -202,7 +202,7 @@ abstract class CursorReadingTask<T, R> implements Task {
 	public boolean awaitStart(Duration timeout) throws InterruptedException {
 
 		Assert.notNull(timeout, "Timeout must not be null!");
-		Assert.isFalse(timeout.isNegative(), "Timeout must not be negative!");
+		Assert.isTrue(!timeout.isNegative(), "Timeout must not be negative!");
 
 		return awaitStart.await(timeout.toNanos(), TimeUnit.NANOSECONDS);
 	}

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

@@ -15,7 +15,10 @@
  */
 package org.springframework.data.mongodb.core.messaging;
 
+import org.springframework.data.mongodb.MongoDbFactory;
 import org.springframework.data.mongodb.core.messaging.SubscriptionRequest.RequestOptions;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 
 /**
  * The actual {@link SubscriptionRequest} sent to the {@link MessageListenerContainer}. This wrapper type allows passing
@@ -51,8 +54,93 @@ public interface SubscriptionRequest<S, T, O extends RequestOptions> {
 	interface RequestOptions {
 
 		/**
-		 * @return the name of the collection to subscribe to. Never {@literal null}.
+		 * Get the database name of the db.
+		 *
+		 * @return the name of the database to subscribe to. Can be {@literal null} in which case the default
+		 *         {@link MongoDbFactory#getDb() database} is used.
 		 */
+		@Nullable
+		default String getDatabaseName() {
+			return null;
+		}
+
+		/**
+		 * Get the collection name.
+		 *
+		 * @return the name of the collection to subscribe to. Can be {@literal null}.
+		 */
+		@Nullable
 		String getCollectionName();
+
+		/**
+		 * Create empty options.
+		 *
+		 * @return new instance of empty {@link RequestOptions}.
+		 */
+		static RequestOptions none() {
+			return () -> null;
+		}
+
+		/**
+		 * Create options with the provided database.
+		 *
+		 * @param database must not be {@literal null}.
+		 * @return new instance of empty {@link RequestOptions}.
+		 */
+		static RequestOptions justDatabase(String database) {
+
+			Assert.notNull(database, "Database must not be null!");
+
+			return new RequestOptions() {
+
+				@Override
+				public String getCollectionName() {
+					return null;
+				}
+
+				@Override
+				public String getDatabaseName() {
+					return database;
+				}
+			};
+		}
+
+		/**
+		 * Create options with the provided collection.
+		 *
+		 * @param collection must not be {@literal null}.
+		 * @return new instance of empty {@link RequestOptions}.
+		 */
+		static RequestOptions justCollection(String collection) {
+
+			Assert.notNull(collection, "Collection must not be null!");
+			return () -> collection;
+		}
+
+		/**
+		 * Create options with the provided database and collection.
+		 *
+		 * @param database must not be {@literal null}.
+		 * @param collection must not be {@literal null}.
+		 * @return new instance of empty {@link RequestOptions}.
+		 */
+		static RequestOptions of(String database, String collection) {
+
+			Assert.notNull(database, "Database must not be null!");
+			Assert.notNull(collection, "Collection must not be null!");
+
+			return new RequestOptions() {
+
+				@Override
+				public String getCollectionName() {
+					return collection;
+				}
+
+				@Override
+				public String getDatabaseName() {
+					return database;
+				}
+			};
+		}
 	}
 }

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

@@ -868,8 +868,17 @@ public class Criteria implements CriteriaDefinition {
 			return right == null;
 		}
 
-		if (left instanceof Pattern) {
-			return right instanceof Pattern ? ((Pattern) left).pattern().equals(((Pattern) right).pattern()) : false;
+		if (Pattern.class.isInstance(left)) {
+
+			if (!Pattern.class.isInstance(right)) {
+				return false;
+			}
+
+			Pattern leftPattern = (Pattern) left;
+			Pattern rightPattern = (Pattern) right;
+
+			return leftPattern.pattern().equals(rightPattern.pattern()) //
+					&& leftPattern.flags() == rightPattern.flags();
 		}
 
 		return ObjectUtils.nullSafeEquals(left, right);

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

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.mongodb.core.query;
 
+import java.time.Duration;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
@@ -50,6 +51,7 @@ public class Meta {
 
 	private final Map<String, Object> values = new LinkedHashMap<String, Object>(2);
 	private final Set<CursorOption> flags = new LinkedHashSet<CursorOption>();
+	private Integer cursorBatchSize;
 
 	/**
 	 * @return {@literal null} if not set.
@@ -65,7 +67,7 @@ public class Meta {
 	 * @param maxTimeMsec
 	 */
 	public void setMaxTimeMsec(long maxTimeMsec) {
-		setMaxTime(maxTimeMsec, TimeUnit.MILLISECONDS);
+		setMaxTime(Duration.ofMillis(maxTimeMsec));
 	}
 
 	/**
@@ -73,11 +75,25 @@ public class Meta {
 	 *
 	 * @param timeout
 	 * @param timeUnit
+	 * @deprecated since 2.1. Use {@link #setMaxTime(Duration)} instead.
 	 */
+	@Deprecated
 	public void setMaxTime(long timeout, @Nullable TimeUnit timeUnit) {
 		setValue(MetaKey.MAX_TIME_MS.key, (timeUnit != null ? timeUnit : TimeUnit.MILLISECONDS).toMillis(timeout));
 	}
 
+	/**
+	 * Set the maximum time limit for processing operations.
+	 *
+	 * @param timeout must not be {@literal null}.
+	 * @since 2.1
+	 */
+	public void setMaxTime(Duration timeout) {
+
+		Assert.notNull(timeout, "Timeout must not be null!");
+		setValue(MetaKey.MAX_TIME_MS.key, timeout.toMillis());
+	}
+
 	/**
 	 * @return {@literal null} if not set.
 	 */
@@ -90,13 +106,15 @@ public class Meta {
 	 * Only scan the specified number of documents.
 	 *
 	 * @param maxScan
+	 * @deprecated since 2.1 due to deprecation in MongoDB 4.0.
 	 */
+	@Deprecated
 	public void setMaxScan(long maxScan) {
 		setValue(MetaKey.MAX_SCAN.key, maxScan);
 	}
 
 	/**
-	 * Add a comment to the query.
+	 * Add a comment to the query that is propagated to the profile log.
 	 *
 	 * @param comment
 	 */
@@ -116,7 +134,9 @@ public class Meta {
 	 * Using snapshot prevents the cursor from returning a document more than once.
 	 *
 	 * @param useSnapshot
+	 * @deprecated since 2.1 due to deprecation as of MongoDB 3.6
 	 */
+	@Deprecated
 	public void setSnapshot(boolean useSnapshot) {
 		setValue(MetaKey.SNAPSHOT.key, useSnapshot);
 	}
@@ -128,6 +148,27 @@ public class Meta {
 		return getValue(MetaKey.SNAPSHOT.key, false);
 	}
 
+	/**
+	 * @return {@literal null} if not set.
+	 * @since 2.1
+	 */
+	@Nullable
+	public Integer getCursorBatchSize() {
+		return cursorBatchSize;
+	}
+
+	/**
+	 * Apply the batch size (number of documents to return in each response) for a query. <br />
+	 * Use {@literal 0 (zero)} for no limit. A <strong>negative limit</strong> closes the cursor after returning a single
+	 * batch indicating to the server that the client will not ask for a subsequent one.
+	 *
+	 * @param cursorBatchSize The number of documents to return per batch.
+	 * @since 2.1
+	 */
+	public void setCursorBatchSize(int cursorBatchSize) {
+		this.cursorBatchSize = cursorBatchSize;
+	}
+
 	/**
 	 * Add {@link CursorOption} influencing behavior of the {@link com.mongodb.DBCursor}.
 	 *
@@ -153,7 +194,7 @@ public class Meta {
 	 * @return
 	 */
 	public boolean hasValues() {
-		return !this.values.isEmpty() || !this.flags.isEmpty();
+		return !this.values.isEmpty() || !this.flags.isEmpty() || this.cursorBatchSize != null;
 	}
 
 	/**

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

@@ -18,6 +18,7 @@ package org.springframework.data.mongodb.core.query;
 import static org.springframework.data.mongodb.core.query.SerializationUtils.*;
 import static org.springframework.util.ObjectUtils.*;
 
+import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashSet;
@@ -289,7 +290,7 @@ public class Query {
 
 	/**
 	 * @param maxTimeMsec
-	 * @return
+	 * @return this.
 	 * @see Meta#setMaxTimeMsec(long)
 	 * @since 1.6
 	 */
@@ -302,22 +303,38 @@ public class Query {
 	/**
 	 * @param timeout
 	 * @param timeUnit
-	 * @return
+	 * @return this.
 	 * @see Meta#setMaxTime(long, TimeUnit)
 	 * @since 1.6
+	 * @deprecated since 2.1. Use {@link #maxTime(Duration)} instead.
 	 */
+	@Deprecated
 	public Query maxTime(long timeout, TimeUnit timeUnit) {
 
 		meta.setMaxTime(timeout, timeUnit);
 		return this;
 	}
 
+	/**
+	 * @param timeout
+	 * @return this.
+	 * @see Meta#setMaxTime(Duration)
+	 * @since 2.1
+	 */
+	public Query maxTime(Duration timeout) {
+
+		meta.setMaxTime(timeout);
+		return this;
+	}
+
 	/**
 	 * @param maxScan
-	 * @return
+	 * @return this.
 	 * @see Meta#setMaxScan(long)
 	 * @since 1.6
+	 * @deprecated since 2.1 due to deprecation in MongoDB 4.0.
 	 */
+	@Deprecated
 	public Query maxScan(long maxScan) {
 
 		meta.setMaxScan(maxScan);
@@ -325,8 +342,10 @@ public class Query {
 	}
 
 	/**
+	 * Add a comment to the query that is propagated to the profile log.
+	 *
 	 * @param comment
-	 * @return
+	 * @return this.
 	 * @see Meta#setComment(String)
 	 * @since 1.6
 	 */
@@ -337,10 +356,12 @@ public class Query {
 	}
 
 	/**
-	 * @return
+	 * @return this.
 	 * @see Meta#setSnapshot(boolean)
 	 * @since 1.6
+	 * @deprecated since 2.1 due to deprecation as of MongoDB 3.6
 	 */
+	@Deprecated
 	public Query useSnapshot() {
 
 		meta.setSnapshot(true);
@@ -348,7 +369,23 @@ public class Query {
 	}
 
 	/**
-	 * @return
+	 * Set the number of documents to return in each response batch. <br />
+	 * Use {@literal 0 (zero)} for no limit. A <strong>negative limit</strong> closes the cursor after returning a single
+	 * batch indicating to the server that the client will not ask for a subsequent one.
+	 * 
+	 * @param batchSize The number of documents to return per batch.
+	 * @return this.
+	 * @see Meta#setCursorBatchSize(int)
+	 * @since 2.1
+	 */
+	public Query cursorBatchSize(int batchSize) {
+
+		meta.setCursorBatchSize(batchSize);
+		return this;
+	}
+
+	/**
+	 * @return this.
 	 * @see org.springframework.data.mongodb.core.query.Meta.CursorOption#NO_TIMEOUT
 	 * @since 1.10
 	 */
@@ -359,7 +396,7 @@ public class Query {
 	}
 
 	/**
-	 * @return
+	 * @return this.
 	 * @see org.springframework.data.mongodb.core.query.Meta.CursorOption#EXHAUST
 	 * @since 1.10
 	 */
@@ -370,7 +407,9 @@ public class Query {
 	}
 
 	/**
-	 * @return
+	 * Allows querying of a replica slave.
+	 *
+	 * @return this.
 	 * @see org.springframework.data.mongodb.core.query.Meta.CursorOption#SLAVE_OK
 	 * @since 1.10
 	 */
@@ -381,7 +420,7 @@ public class Query {
 	}
 
 	/**
-	 * @return
+	 * @return this.
 	 * @see org.springframework.data.mongodb.core.query.Meta.CursorOption#PARTIAL
 	 * @since 1.10
 	 */
@@ -392,7 +431,7 @@ public class Query {
 	}
 
 	/**
-	 * @return never {@literal null}.
+	 * @return never {@literal null}.ø
 	 * @since 1.6
 	 */
 	public Meta getMeta() {

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

@@ -893,18 +893,14 @@ public class Update {
 		/**
 		 * Forces values to be added at the given {@literal position}.
 		 *
-		 * @param position needs to be greater than or equal to zero.
+		 * @param position the position offset. As of MongoDB 3.6 use a negative value to indicate starting from the end,
+		 *          counting (but not including) the last element of the array.
 		 * @return never {@literal null}.
 		 * @since 1.7
 		 */
 		public PushOperatorBuilder atPosition(int position) {
 
-			if (position < 0) {
-				throw new IllegalArgumentException("Position must be greater than or equal to zero.");
-			}
-
 			this.modifiers.addModifier(new PositionModifier(position));
-
 			return this;
 		}
 

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

@@ -52,6 +52,7 @@ import com.mongodb.client.gridfs.model.GridFSUploadOptions;
  * @author Christoph Strobl
  * @author Mark Paluch
  * @author Hartmut Lang
+ * @author Niklas Helge Hanft
  */
 public class GridFsTemplate implements GridFsOperations, ResourcePatternResolver {
 
@@ -228,7 +229,8 @@ public class GridFsTemplate implements GridFsOperations, ResourcePatternResolver
 	 */
 	public GridFsResource getResource(String location) {
 
-		return Optional.ofNullable(findOne(query(whereFilename().is(location)))).map(this::getResource)
+		return Optional.ofNullable(findOne(query(whereFilename().is(location)))) //
+				.map(this::getResource) //
 				.orElseGet(() -> GridFsResource.absent(location));
 	}
 
@@ -240,7 +242,7 @@ public class GridFsTemplate implements GridFsOperations, ResourcePatternResolver
 
 		Assert.notNull(file, "GridFSFile must not be null!");
 
-		return new GridFsResource(file, getGridFs().openDownloadStream(file.getFilename()));
+		return new GridFsResource(file, getGridFs().openDownloadStream(file.getObjectId()));
 	}
 
 	/*
@@ -261,7 +263,7 @@ public class GridFsTemplate implements GridFsOperations, ResourcePatternResolver
 			List<GridFsResource> resources = new ArrayList<>();
 
 			for (GridFSFile file : files) {
-				resources.add(new GridFsResource(file, getGridFs().openDownloadStream(file.getFilename())));
+				resources.add(getResource(file));
 			}
 
 			return resources.toArray(new GridFsResource[0]);

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

@@ -21,7 +21,6 @@ import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
-import org.springframework.core.annotation.AliasFor;
 import org.springframework.data.annotation.QueryAnnotation;
 
 /**
@@ -50,6 +49,16 @@ public @interface Meta {
 	 */
 	long maxScanDocuments() default -1;
 
+	/**
+	 * Sets the number of documents to return per batch. <br />
+	 * Use {@literal 0 (zero)} for no limit. A <strong>negative limit</strong> closes the cursor after returning a single
+	 * batch indicating to the server that the client will not ask for a subsequent one.
+	 * 
+	 * @return {@literal 0 (zero)} by default.
+	 * @since 2.1
+	 */
+	int cursorBatchSize() default 0;
+
 	/**
 	 * Add a comment to the query.
 	 *

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

@@ -30,6 +30,7 @@ import org.springframework.data.repository.query.QueryByExampleExecutor;
  * @author Christoph Strobl
  * @author Thomas Darimont
  * @author Mark Paluch
+ * @author Khaled Baklouti
  */
 @NoRepositoryBean
 public interface MongoRepository<T, ID> extends PagingAndSortingRepository<T, ID>, QueryByExampleExecutor<T> {
@@ -39,7 +40,7 @@ public interface MongoRepository<T, ID> extends PagingAndSortingRepository<T, ID
 	 * @see org.springframework.data.repository.CrudRepository#saveAll(java.lang.Iterable)
 	 */
 	@Override
-	<S extends T> List<S> saveAll(Iterable<S> entites);
+	<S extends T> List<S> saveAll(Iterable<S> entities);
 
 	/*
 	 * (non-Javadoc)

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

@@ -77,4 +77,22 @@ public @interface Query {
 	 * @return
 	 */
 	boolean delete() default false;
+
+	/**
+	 * Defines a default sort order for the given query.<br />
+	 * <strong>NOTE:</strong> The so set defaults can be altered / overwritten using an explicit
+	 * {@link org.springframework.data.domain.Sort} argument of the query method.
+	 *
+	 * <pre>
+	 * <code>
+	 *
+	 * 		&#64;Query(sort = "{ age : -1 }") // order by age descending
+	 * 		List<Person> findByFirstname(String firstname);
+	 * </code>
+	 * </pre>
+	 *
+	 * @return
+	 * @since 2.1
+	 */
+	String sort() default "";
 }

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

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.mongodb.repository.query;
 
+import org.bson.Document;
 import org.springframework.data.mongodb.core.ExecutableFindOperation.ExecutableFind;
 import org.springframework.data.mongodb.core.ExecutableFindOperation.FindWithQuery;
 import org.springframework.data.mongodb.core.ExecutableFindOperation.TerminatingFind;
@@ -84,6 +85,7 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 		Query query = createQuery(accessor);
 
 		applyQueryMetaAttributesWhenPresent(query);
+		query = applyAnnotatedDefaultSortIfPresent(query);
 
 		ResultProcessor processor = method.getResultProcessor().withDynamicProjection(accessor);
 		Class<?> typeToRead = processor.getReturnedType().getTypeToRead();
@@ -110,7 +112,7 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 		} else if (method.isStreamQuery()) {
 			return q -> operation.matching(q).stream();
 		} else if (method.isCollectionQuery()) {
-			return q -> operation.matching(q.with(accessor.getPageable())).all();
+			return q -> operation.matching(q.with(accessor.getPageable()).with(accessor.getSort())).all();
 		} else if (method.isPageQuery()) {
 			return new PagedExecution(operation, accessor.getPageable());
 		} else if (isCountQuery()) {
@@ -135,6 +137,23 @@ public abstract class AbstractMongoQuery implements RepositoryQuery {
 		return query;
 	}
 
+	/**
+	 * Add a default sort derived from {@link org.springframework.data.mongodb.repository.Query#sort()} to the given
+	 * {@link Query} if present.
+	 *
+	 * @param query the {@link Query} to potentially apply the sort to.
+	 * @return the query with potential default sort applied.
+	 * @since 2.1
+	 */
+	Query applyAnnotatedDefaultSortIfPresent(Query query) {
+
+		if (!method.hasAnnotatedSort()) {
+			return query;
+		}
+
+		return QueryUtils.decorateSort(query, Document.parse(method.getAnnotatedSort()));
+	}
+
 	/**
 	 * Creates a {@link Query} instance using the given {@link ConvertingParameterAccessor}. Will delegate to
 	 * {@link #createQuery(ConvertingParameterAccessor)} by default but allows customization of the count query to be

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

@@ -18,6 +18,7 @@ package org.springframework.data.mongodb.repository.query;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
+import org.bson.Document;
 import org.reactivestreams.Publisher;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.data.convert.EntityInstantiators;
@@ -31,11 +32,9 @@ import org.springframework.data.mongodb.repository.query.ReactiveMongoQueryExecu
 import org.springframework.data.mongodb.repository.query.ReactiveMongoQueryExecution.GeoNearExecution;
 import org.springframework.data.mongodb.repository.query.ReactiveMongoQueryExecution.ResultProcessingConverter;
 import org.springframework.data.mongodb.repository.query.ReactiveMongoQueryExecution.ResultProcessingExecution;
-import org.springframework.data.mongodb.repository.query.ReactiveMongoQueryExecution.TailExecution;
 import org.springframework.data.repository.query.ParameterAccessor;
 import org.springframework.data.repository.query.RepositoryQuery;
 import org.springframework.data.repository.query.ResultProcessor;
-import org.springframework.data.repository.query.ReturnedType;
 import org.springframework.util.Assert;
 
 /**
@@ -109,6 +108,7 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 		Query query = createQuery(new ConvertingParameterAccessor(operations.getConverter(), parameterAccessor));
 
 		applyQueryMetaAttributesWhenPresent(query);
+		query = applyAnnotatedDefaultSortIfPresent(query);
 
 		ResultProcessor processor = method.getResultProcessor().withDynamicProjection(parameterAccessor);
 		Class<?> typeToRead = processor.getReturnedType().getTypeToRead();
@@ -119,7 +119,7 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 
 		String collection = method.getEntityInformation().getCollectionName();
 
-		ReactiveMongoQueryExecution execution = getExecution(query, parameterAccessor,
+		ReactiveMongoQueryExecution execution = getExecution(parameterAccessor,
 				new ResultProcessingConverter(processor, operations, instantiators), find);
 
 		return execution.execute(query, processor.getReturnedType().getDomainType(), collection);
@@ -128,12 +128,11 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 	/**
 	 * Returns the execution instance to use.
 	 *
-	 * @param query must not be {@literal null}.
 	 * @param accessor must not be {@literal null}.
 	 * @param resultProcessing must not be {@literal null}.
 	 * @return
 	 */
-	private ReactiveMongoQueryExecution getExecution(Query query, MongoParameterAccessor accessor,
+	private ReactiveMongoQueryExecution getExecution(MongoParameterAccessor accessor,
 			Converter<Object, Object> resultProcessing, FindWithQuery<?> operation) {
 		return new ResultProcessingExecution(getExecutionToWrap(accessor, operation), resultProcessing);
 	}
@@ -145,11 +144,13 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 		} else if (method.isGeoNearQuery()) {
 			return new GeoNearExecution(operations, accessor, method.getReturnType());
 		} else if (isTailable(method)) {
-			return new TailExecution(operations, accessor.getPageable());
+			return (q, t, c) -> operation.matching(q.with(accessor.getPageable())).tail();
 		} else if (method.isCollectionQuery()) {
 			return (q, t, c) -> operation.matching(q.with(accessor.getPageable())).all();
 		} else if (isCountQuery()) {
 			return (q, t, c) -> operation.matching(q).count();
+		} else if (isExistsQuery()) {
+			return (q, t, c) -> operation.matching(q).exists();
 		} else {
 			return (q, t, c) -> {
 
@@ -177,6 +178,23 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 		return query;
 	}
 
+	/**
+	 * Add a default sort derived from {@link org.springframework.data.mongodb.repository.Query#sort()} to the given
+	 * {@link Query} if present.
+	 *
+	 * @param query the {@link Query} to potentially apply the sort to.
+	 * @return the query with potential default sort applied.
+	 * @since 2.1
+	 */
+	Query applyAnnotatedDefaultSortIfPresent(Query query) {
+
+		if (!method.hasAnnotatedSort()) {
+			return query;
+		}
+
+		return QueryUtils.decorateSort(query, Document.parse(method.getAnnotatedSort()));
+	}
+
 	/**
 	 * Creates a {@link Query} instance using the given {@link ConvertingParameterAccessor}. Will delegate to
 	 * {@link #createQuery(ConvertingParameterAccessor)} by default but allows customization of the count query to be
@@ -204,6 +222,14 @@ public abstract class AbstractReactiveMongoQuery implements RepositoryQuery {
 	 */
 	protected abstract boolean isCountQuery();
 
+	/**
+	 * Returns whether the query should get an exists projection applied.
+	 *
+	 * @return
+	 * @since 2.0.9
+	 */
+	protected abstract boolean isExistsQuery();
+
 	/**
 	 * Return weather the query should delete matching documents.
 	 *

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

@@ -0,0 +1,48 @@
+/*
+ * 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.repository.query;
+
+import lombok.experimental.UtilityClass;
+
+/**
+ * Utility class containing methods to interact with boolean values.
+ *
+ * @author Mark Paluch
+ * @since 2.0.9
+ */
+@UtilityClass
+class BooleanUtil {
+
+	/**
+	 * Count the number of {@literal true} values.
+	 *
+	 * @param values
+	 * @return the number of values that are {@literal true}.
+	 */
+	static int countBooleanTrueValues(boolean... values) {
+
+		int count = 0;
+
+		for (boolean value : values) {
+
+			if (value) {
+				count++;
+			}
+		}
+
+		return count;
+	}
+}

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

@@ -16,16 +16,19 @@
 package org.springframework.data.mongodb.repository.query;
 
 import lombok.EqualsAndHashCode;
+import lombok.RequiredArgsConstructor;
 import lombok.Value;
 import lombok.experimental.UtilityClass;
 
 import java.io.StringWriter;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.NoSuchElementException;
 import java.util.UUID;
+import java.util.function.Function;
 import java.util.function.Supplier;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -205,6 +208,7 @@ class ExpressionEvaluatingParameterBinder {
 	 * @param binding must not be {@literal null}.
 	 * @return
 	 */
+	@SuppressWarnings("unchecked")
 	private String getParameterValueForBinding(MongoParameterAccessor accessor, MongoParameters parameters,
 			ParameterBinding binding) {
 
@@ -221,37 +225,7 @@ class ExpressionEvaluatingParameterBinder {
 			return binding.isExpression() ? JSON.serialize(value) : QuotedString.unquote(JSON.serialize(value));
 		}
 
-		if (value instanceof byte[]) {
-
-			if (binding.isQuoted()) {
-				return DatatypeConverter.printBase64Binary((byte[]) value);
-			}
-
-			return encode(new Binary((byte[]) value), BinaryCodec::new);
-		}
-
-		if (value instanceof UUID) {
-
-			if (binding.isQuoted()) {
-				return value.toString();
-			}
-
-			return encode((UUID) value, UuidCodec::new);
-		}
-
-		return JSON.serialize(value);
-	}
-
-	private <T> String encode(T value, Supplier<Codec<T>> defaultCodec) {
-
-		Codec<T> codec = codecRegistryProvider.getCodecFor((Class<T>) value.getClass()).orElseGet(defaultCodec);
-
-		StringWriter writer = new StringWriter();
-
-		codec.encode(new JsonWriter(writer), value, null);
-		writer.flush();
-
-		return writer.toString();
+		return EncodableValue.create(value).encode(codecRegistryProvider, binding.isQuoted());
 	}
 
 	/**
@@ -473,4 +447,221 @@ class ExpressionEvaluatingParameterBinder {
 			return quoted.substring(1, quoted.length() - 1);
 		}
 	}
+
+	/**
+	 * Value object encapsulating a bindable value, that can be encoded to be represented as JSON (BSON).
+	 *
+	 * @author Mark Paluch
+	 */
+	abstract static class EncodableValue {
+
+		/**
+		 * Obtain a {@link EncodableValue} given {@code value}.
+		 *
+		 * @param value the value to encode, may be {@literal null}.
+		 * @return the {@link EncodableValue} for {@code value}.
+		 */
+		@SuppressWarnings("unchecked")
+		public static EncodableValue create(@Nullable Object value) {
+
+			if (value instanceof byte[]) {
+				return new BinaryValue((byte[]) value);
+			}
+
+			if (value instanceof UUID) {
+				return new UuidValue((UUID) value);
+			}
+
+			if (value instanceof Collection) {
+
+				Collection<?> collection = (Collection<?>) value;
+				Class<?> commonElement = CollectionUtils.findCommonElementType(collection);
+
+				if (commonElement != null) {
+
+					if (UUID.class.isAssignableFrom(commonElement)) {
+						return new UuidCollection((Collection<UUID>) value);
+					}
+
+					if (byte[].class.isAssignableFrom(commonElement)) {
+						return new BinaryCollectionValue((Collection<byte[]>) value);
+					}
+				}
+			}
+
+			return new ObjectValue(value);
+		}
+
+		/**
+		 * Encode the encapsulated value.
+		 *
+		 * @param provider
+		 * @param quoted
+		 * @return
+		 */
+		public abstract String encode(CodecRegistryProvider provider, boolean quoted);
+
+		/**
+		 * Encode a {@code value} to JSON.
+		 *
+		 * @param provider
+		 * @param value
+		 * @param defaultCodec
+		 * @param <V>
+		 * @return
+		 */
+		protected <V> String encode(CodecRegistryProvider provider, V value, Supplier<Codec<V>> defaultCodec) {
+
+			StringWriter writer = new StringWriter();
+
+			doEncode(provider, writer, value, defaultCodec);
+
+			return writer.toString();
+		}
+
+		/**
+		 * Encode a {@link Collection} to JSON and potentially apply a {@link Function mapping function} before encoding.
+		 *
+		 * @param provider
+		 * @param value
+		 * @param mappingFunction
+		 * @param defaultCodec
+		 * @param <I> Input value type.
+		 * @param <V> Target type.
+		 * @return
+		 */
+		protected <I, V> String encodeCollection(CodecRegistryProvider provider, Iterable<I> value,
+				Function<I, V> mappingFunction, Supplier<Codec<V>> defaultCodec) {
+
+			StringWriter writer = new StringWriter();
+
+			writer.append("[");
+			value.forEach(it -> {
+
+				if (writer.getBuffer().length() > 1) {
+					writer.append(", ");
+				}
+
+				doEncode(provider, writer, mappingFunction.apply(it), defaultCodec);
+			});
+
+			writer.append("]");
+			writer.flush();
+
+			return writer.toString();
+		}
+
+		@SuppressWarnings("unchecked")
+		private <V> void doEncode(CodecRegistryProvider provider, StringWriter writer, V value,
+				Supplier<Codec<V>> defaultCodec) {
+
+			Codec<V> codec = provider.getCodecFor((Class<V>) value.getClass()).orElseGet(defaultCodec);
+
+			JsonWriter jsonWriter = new JsonWriter(writer);
+			codec.encode(jsonWriter, value, null);
+			jsonWriter.flush();
+		}
+	}
+
+	/**
+	 * {@link EncodableValue} for {@code byte[]} to render to {@literal $binary}.
+	 */
+	@RequiredArgsConstructor
+	static class BinaryValue extends EncodableValue {
+
+		private final byte[] value;
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.repository.query.ExpressionEvaluatingParameterBinder.EncodableValue#encode(org.springframework.data.mongodb.CodecRegistryProvider, boolean)
+		 */
+		@Override
+		public String encode(CodecRegistryProvider provider, boolean quoted) {
+
+			if (quoted) {
+				return DatatypeConverter.printBase64Binary(this.value);
+			}
+
+			return encode(provider, new Binary(this.value), BinaryCodec::new);
+		}
+	}
+
+	/**
+	 * {@link EncodableValue} for {@link Collection} containing only {@code byte[]} items to render to a BSON list
+	 * containing {@literal $binary}.
+	 */
+	@RequiredArgsConstructor
+	static class BinaryCollectionValue extends EncodableValue {
+
+		private final Collection<byte[]> value;
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.repository.query.ExpressionEvaluatingParameterBinder.EncodableValue#encode(org.springframework.data.mongodb.CodecRegistryProvider, boolean)
+		 */
+		@Override
+		public String encode(CodecRegistryProvider provider, boolean quoted) {
+			return encodeCollection(provider, this.value, Binary::new, BinaryCodec::new);
+		}
+	}
+
+	/**
+	 * {@link EncodableValue} for {@link UUID} to render to {@literal $binary}.
+	 */
+	@RequiredArgsConstructor
+	static class UuidValue extends EncodableValue {
+
+		private final UUID value;
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.repository.query.ExpressionEvaluatingParameterBinder.EncodableValue#encode(org.springframework.data.mongodb.CodecRegistryProvider, boolean)
+		 */
+		@Override
+		public String encode(CodecRegistryProvider provider, boolean quoted) {
+
+			if (quoted) {
+				return this.value.toString();
+			}
+
+			return encode(provider, this.value, UuidCodec::new);
+		}
+	}
+
+	/**
+	 * {@link EncodableValue} for {@link Collection} containing only {@link UUID} items to render to a BSON list
+	 * containing {@literal $binary}.
+	 */
+	@RequiredArgsConstructor
+	static class UuidCollection extends EncodableValue {
+
+		private final Collection<UUID> value;
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.repository.query.ExpressionEvaluatingParameterBinder.EncodableValue#encode(org.springframework.data.mongodb.CodecRegistryProvider, boolean)
+		 */
+		@Override
+		public String encode(CodecRegistryProvider provider, boolean quoted) {
+			return encodeCollection(provider, this.value, Function.identity(), UuidCodec::new);
+		}
+	}
+
+	/**
+	 * Fallback-{@link EncodableValue} for {@link Object}-typed values.
+	 */
+	@RequiredArgsConstructor
+	static class ObjectValue extends EncodableValue {
+
+		private final @Nullable Object value;
+
+		/* 
+		 * (non-Javadoc)
+		 * @see org.springframework.data.mongodb.repository.query.ExpressionEvaluatingParameterBinder.EncodableValue#encode(org.springframework.data.mongodb.CodecRegistryProvider, boolean)
+		 */
+		@Override
+		public String encode(CodecRegistryProvider provider, boolean quoted) {
+			return JSON.serialize(this.value);
+		}
+	}
 }

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

@@ -45,6 +45,7 @@ public interface MongoParameterAccessor extends ParameterAccessor {
 	 *
 	 * @return
 	 */
+	@Nullable
 	Point getGeoNearLocation();
 
 	/**

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

@@ -19,6 +19,7 @@ import java.util.Arrays;
 import java.util.List;
 
 import org.springframework.data.domain.Range;
+import org.springframework.data.domain.Range.Bound;
 import org.springframework.data.geo.Distance;
 import org.springframework.data.geo.Point;
 import org.springframework.data.mongodb.core.query.Term;
@@ -66,9 +67,9 @@ public class MongoParametersParameterAccessor extends ParametersParameterAccesso
 		}
 
 		int maxDistanceIndex = mongoParameters.getMaxDistanceIndex();
-		Distance maxDistance = maxDistanceIndex == -1 ? null : (Distance) getValue(maxDistanceIndex);
+		Bound<Distance> maxDistance = maxDistanceIndex == -1 ? Bound.unbounded() : Bound.inclusive((Distance) getValue(maxDistanceIndex));
 
-		return new Range<Distance>(null, maxDistance);
+		return Range.of(Bound.unbounded(), maxDistance);
 	}
 
 	/*

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

@@ -21,6 +21,7 @@ import java.util.Arrays;
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.Optional;
+import java.util.regex.Pattern;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -113,9 +114,8 @@ class MongoQueryCreator extends AbstractQueryCreator<Query, Criteria> {
 
 		PersistentPropertyPath<MongoPersistentProperty> path = context.getPersistentPropertyPath(part.getProperty());
 		MongoPersistentProperty property = path.getLeafProperty();
-		Criteria criteria = from(part, property, where(path.toDotPath()), (PotentiallyConvertingIterator) iterator);
 
-		return criteria;
+		return from(part, property, where(path.toDotPath()), iterator);
 	}
 
 	/*
@@ -132,7 +132,7 @@ class MongoQueryCreator extends AbstractQueryCreator<Query, Criteria> {
 		PersistentPropertyPath<MongoPersistentProperty> path = context.getPersistentPropertyPath(part.getProperty());
 		MongoPersistentProperty property = path.getLeafProperty();
 
-		return from(part, property, base.and(path.toDotPath()), (PotentiallyConvertingIterator) iterator);
+		return from(part, property, base.and(path.toDotPath()), iterator);
 	}
 
 	/*
@@ -206,7 +206,9 @@ class MongoQueryCreator extends AbstractQueryCreator<Query, Criteria> {
 			case NOT_CONTAINING:
 				return createContainingCriteria(part, property, criteria.not(), parameters);
 			case REGEX:
-				return criteria.regex(parameters.next().toString());
+
+				Object param = parameters.next();
+				return param instanceof Pattern ? criteria.regex((Pattern) param) : criteria.regex(param.toString());
 			case EXISTS:
 				return criteria.exists((Boolean) parameters.next());
 			case TRUE:

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

@@ -16,13 +16,14 @@
 package org.springframework.data.mongodb.repository.query;
 
 import java.io.Serializable;
+import java.lang.annotation.Annotation;
 import java.lang.reflect.Method;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 
 import org.springframework.core.annotation.AnnotatedElementUtils;
-import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.data.geo.GeoPage;
 import org.springframework.data.geo.GeoResult;
 import org.springframework.data.geo.GeoResults;
@@ -40,6 +41,7 @@ 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.ConcurrentReferenceHashMap;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
@@ -57,6 +59,7 @@ public class MongoQueryMethod extends QueryMethod {
 
 	private final Method method;
 	private final MappingContext<? extends MongoPersistentEntity<?>, MongoPersistentProperty> mappingContext;
+	private final Map<Class<? extends Annotation>, Optional<Annotation>> annotationCache;
 
 	private @Nullable MongoEntityMetadata<?> metadata;
 
@@ -77,6 +80,7 @@ public class MongoQueryMethod extends QueryMethod {
 
 		this.method = method;
 		this.mappingContext = mappingContext;
+		this.annotationCache = new ConcurrentReferenceHashMap<>();
 	}
 
 	/*
@@ -110,9 +114,8 @@ public class MongoQueryMethod extends QueryMethod {
 
 	private Optional<String> findAnnotatedQuery() {
 
-		return Optional.ofNullable(getQueryAnnotation()) //
-				.map(AnnotationUtils::getValue) //
-				.map(it -> (String) it) //
+		return lookupQueryAnnotation() //
+				.map(Query::value) //
 				.filter(StringUtils::hasText);
 	}
 
@@ -121,10 +124,11 @@ public class MongoQueryMethod extends QueryMethod {
 	 *
 	 * @return
 	 */
+	@Nullable
 	String getFieldSpecification() {
 
-		return Optional.ofNullable(getQueryAnnotation()) //
-				.map(it -> (String) AnnotationUtils.getValue(it, "fields")) //
+		return lookupQueryAnnotation() //
+				.map(Query::fields) //
 				.filter(StringUtils::hasText) //
 				.orElse(null);
 	}
@@ -156,8 +160,7 @@ public class MongoQueryMethod extends QueryMethod {
 				MongoPersistentEntity<?> collectionEntity = domainClass.isAssignableFrom(returnedObjectType) ? returnedEntity
 						: managedEntity;
 
-				this.metadata = new SimpleMongoEntityMetadata<Object>((Class<Object>) returnedEntity.getType(),
-						collectionEntity);
+				this.metadata = new SimpleMongoEntityMetadata<>((Class<Object>) returnedEntity.getType(), collectionEntity);
 			}
 		}
 
@@ -207,7 +210,11 @@ public class MongoQueryMethod extends QueryMethod {
 	 */
 	@Nullable
 	Query getQueryAnnotation() {
-		return AnnotatedElementUtils.findMergedAnnotation(method, Query.class);
+		return lookupQueryAnnotation().orElse(null);
+	}
+
+	Optional<Query> lookupQueryAnnotation() {
+		return doFindAnnotation(Query.class);
 	}
 
 	TypeInformation<?> getReturnType() {
@@ -230,7 +237,7 @@ public class MongoQueryMethod extends QueryMethod {
 	 */
 	@Nullable
 	Meta getMetaAnnotation() {
-		return AnnotatedElementUtils.findMergedAnnotation(method, Meta.class);
+		return doFindAnnotation(Meta.class).orElse(null);
 	}
 
 	/**
@@ -241,7 +248,7 @@ public class MongoQueryMethod extends QueryMethod {
 	 */
 	@Nullable
 	Tailable getTailableAnnotation() {
-		return AnnotatedElementUtils.findMergedAnnotation(method, Tailable.class);
+		return doFindAnnotation(Tailable.class).orElse(null);
 	}
 
 	/**
@@ -266,6 +273,10 @@ public class MongoQueryMethod extends QueryMethod {
 			metaAttributes.setMaxScan(meta.maxScanDocuments());
 		}
 
+		if (meta.cursorBatchSize() != 0) {
+			metaAttributes.setCursorBatchSize(meta.cursorBatchSize());
+		}
+
 		if (StringUtils.hasText(meta.comment())) {
 			metaAttributes.setComment(meta.comment());
 		}
@@ -283,4 +294,35 @@ public class MongoQueryMethod extends QueryMethod {
 
 		return metaAttributes;
 	}
+
+	/**
+	 * Check if the query method is decorated with an non empty {@link Query#sort()}.
+	 *
+	 * @return true if method annotated with {@link Query} having an non empty sort attribute.
+	 * @since 2.1
+	 */
+	public boolean hasAnnotatedSort() {
+		return lookupQueryAnnotation().map(it -> !it.sort().isEmpty()).orElse(false);
+	}
+
+	/**
+	 * Get the sort value, used as default, extracted from the {@link Query} annotation.
+	 *
+	 * @return the {@link Query#sort()} value.
+	 * @throws IllegalStateException if method not annotated with {@link Query}. Make sure to check
+	 *           {@link #hasAnnotatedQuery()} first.
+	 * @since 2.1
+	 */
+	public String getAnnotatedSort() {
+
+		return lookupQueryAnnotation().map(Query::sort).orElseThrow(() -> new IllegalStateException(
+				"Expected to find @Query annotation but did not. Make sure to check hasAnnotatedSort() before."));
+	}
+
+	@SuppressWarnings("unchecked")
+	private <A extends Annotation> Optional<A> doFindAnnotation(Class<A> annotationType) {
+
+		return (Optional<A>) this.annotationCache.computeIfAbsent(annotationType,
+				it -> Optional.ofNullable(AnnotatedElementUtils.findMergedAnnotation(method, it)));
+	}
 }

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

@@ -0,0 +1,61 @@
+/*
+ * 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.repository.query;
+
+import org.aopalliance.intercept.MethodInterceptor;
+import org.bson.Document;
+import org.springframework.aop.framework.ProxyFactory;
+import org.springframework.data.mongodb.core.query.Query;
+
+/**
+ * Internal utility class to help avoid duplicate code required in both the reactive and the sync {@link Query} support
+ * offered by repositories.
+ *
+ * @author Christoph Strobl
+ * @since 2.1
+ * @currentRead Assassin's Apprentice - Robin Hobb
+ */
+class QueryUtils {
+
+	/**
+	 * Decorate {@link Query} and add a default sort expression to the given {@link Query}. Attributes of the given
+	 * {@code sort} may be overwritten by the sort explicitly defined by the {@link Query} itself.
+	 *
+	 * @param query the {@link Query} to decorate.
+	 * @param defaultSort the default sort expression to apply to the query.
+	 * @return the query having the given {@code sort} applied.
+	 */
+	static Query decorateSort(Query query, Document defaultSort) {
+
+		if (defaultSort.isEmpty()) {
+			return query;
+		}
+
+		ProxyFactory factory = new ProxyFactory(query);
+		factory.addAdvice((MethodInterceptor) invocation -> {
+
+			if (!invocation.getMethod().getName().equals("getSortObject")) {
+				return invocation.proceed();
+			}
+
+			Document combinedSort = new Document(defaultSort);
+			combinedSort.putAll((Document) invocation.proceed());
+			return combinedSort;
+		});
+
+		return (Query) factory.getProxy();
+	}
+}

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

@@ -51,23 +51,6 @@ interface ReactiveMongoQueryExecution {
 
 	Object execute(Query query, Class<?> type, String collection);
 
-	/**
-	 * {@link ReactiveMongoQueryExecution} for collection returning queries using tailable cursors.
-	 *
-	 * @author Mark Paluch
-	 */
-	@RequiredArgsConstructor
-	final class TailExecution implements ReactiveMongoQueryExecution {
-
-		private final @NonNull ReactiveMongoOperations operations;
-		private final Pageable pageable;
-
-		@Override
-		public Object execute(Query query, Class<?> type, String collection) {
-			return operations.tail(query.with(pageable), type, collection);
-		}
-	}
-
 	/**
 	 * {@link MongoQueryExecution} to execute geo-near queries.
 	 *

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

@@ -79,7 +79,7 @@ public class ReactiveMongoQueryMethod extends MongoQueryMethod {
 								ClassUtils.getShortName(method.getDeclaringClass()), method.getName()));
 			}
 
-			if (!multiWrapper && !singleWrapperWithWrappedPageableResult) {
+			if (!multiWrapper) {
 				throw new IllegalStateException(String.format(
 						"Method has to use a either multi-item reactive wrapper return type or a wrapped Page/Slice type. Offending method: %s",
 						method.toString()));

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

@@ -134,6 +134,15 @@ public class ReactivePartTreeMongoQuery extends AbstractReactiveMongoQuery {
 		return tree.isCountProjection();
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.repository.query.AbstractReactiveMongoQuery#isExistsQuery()
+	 */
+	@Override
+	protected boolean isExistsQuery() {
+		return tree.isExistsProjection();
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.repository.query.AbstractReactiveMongoQuery#isDeleteQuery()

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

@@ -28,7 +28,6 @@ import org.springframework.data.mongodb.repository.query.ExpressionEvaluatingPar
 import org.springframework.data.mongodb.repository.query.StringBasedMongoQuery.ParameterBinding;
 import org.springframework.data.mongodb.repository.query.StringBasedMongoQuery.ParameterBindingParser;
 import org.springframework.data.repository.query.QueryMethodEvaluationContextProvider;
-import org.springframework.data.spel.EvaluationContextProvider;
 import org.springframework.expression.spel.standard.SpelExpressionParser;
 import org.springframework.util.Assert;
 
@@ -41,13 +40,14 @@ import org.springframework.util.Assert;
  */
 public class ReactiveStringBasedMongoQuery extends AbstractReactiveMongoQuery {
 
-	private static final String COUND_AND_DELETE = "Manually defined query for %s cannot be both a count and delete query at the same time!";
+	private static final String COUNT_EXISTS_AND_DELETE = "Manually defined query for %s cannot be a count and exists or delete query at the same time!";
 	private static final Logger LOG = LoggerFactory.getLogger(ReactiveStringBasedMongoQuery.class);
 	private static final ParameterBindingParser BINDING_PARSER = ParameterBindingParser.INSTANCE;
 
 	private final String query;
 	private final String fieldSpec;
 	private final boolean isCountQuery;
+	private final boolean isExistsQuery;
 	private final boolean isDeleteQuery;
 	private final List<ParameterBinding> queryParameterBindings;
 	private final List<ParameterBinding> fieldSpecParameterBindings;
@@ -93,11 +93,23 @@ public class ReactiveStringBasedMongoQuery extends AbstractReactiveMongoQuery {
 		this.fieldSpec = BINDING_PARSER.parseAndCollectParameterBindingsFromQueryIntoBindings(
 				method.getFieldSpecification(), this.fieldSpecParameterBindings);
 
-		this.isCountQuery = method.hasAnnotatedQuery() ? method.getQueryAnnotation().count() : false;
-		this.isDeleteQuery = method.hasAnnotatedQuery() ? method.getQueryAnnotation().delete() : false;
+		if (method.hasAnnotatedQuery()) {
 
-		if (isCountQuery && isDeleteQuery) {
-			throw new IllegalArgumentException(String.format(COUND_AND_DELETE, method));
+			org.springframework.data.mongodb.repository.Query queryAnnotation = method.getQueryAnnotation();
+
+			this.isCountQuery = queryAnnotation.count();
+			this.isExistsQuery = queryAnnotation.exists();
+			this.isDeleteQuery = queryAnnotation.delete();
+
+			if (hasAmbiguousProjectionFlags(this.isCountQuery, this.isExistsQuery, this.isDeleteQuery)) {
+				throw new IllegalArgumentException(String.format(COUNT_EXISTS_AND_DELETE, method));
+			}
+
+		} else {
+
+			this.isCountQuery = false;
+			this.isExistsQuery = false;
+			this.isDeleteQuery = false;
 		}
 
 		this.parameterBinder = new ExpressionEvaluatingParameterBinder(expressionParser, evaluationContextProvider);
@@ -133,6 +145,15 @@ public class ReactiveStringBasedMongoQuery extends AbstractReactiveMongoQuery {
 		return isCountQuery;
 	}
 
+	/*
+	 * (non-Javadoc)
+	 * @see org.springframework.data.mongodb.repository.query.AbstractReactiveMongoQuery#isExistsQuery()
+	 */
+	@Override
+	protected boolean isExistsQuery() {
+		return isExistsQuery;
+	}
+
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.repository.query.AbstractReactiveMongoQuery#isDeleteQuery()
@@ -151,4 +172,9 @@ public class ReactiveStringBasedMongoQuery extends AbstractReactiveMongoQuery {
 		return false;
 	}
 
+	private static boolean hasAmbiguousProjectionFlags(boolean isCountQuery, boolean isExistsQuery,
+			boolean isDeleteQuery) {
+		return BooleanUtil.countBooleanTrueValues(isCountQuery, isExistsQuery, isDeleteQuery) > 1;
+	}
+
 }

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

@@ -20,7 +20,9 @@ import java.util.Collections;
 import java.util.List;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
+import java.util.regex.PatternSyntaxException;
 
+import org.bson.BSON;
 import org.bson.Document;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -37,6 +39,7 @@ import org.springframework.util.StringUtils;
 import com.mongodb.DBObject;
 import com.mongodb.DBRef;
 import com.mongodb.util.JSON;
+import com.mongodb.util.JSONCallback;
 
 /**
  * Query to use a plain JSON String to create the {@link Query} to actually execute.
@@ -170,11 +173,6 @@ public class StringBasedMongoQuery extends AbstractMongoQuery {
 		return this.isDeleteQuery;
 	}
 
-	private static boolean hasAmbiguousProjectionFlags(boolean isCountQuery, boolean isExistsQuery,
-			boolean isDeleteQuery) {
-		return countBooleanValues(isCountQuery, isExistsQuery, isDeleteQuery) > 1;
-	}
-
 	/*
 	 * (non-Javadoc)
 	 * @see org.springframework.data.mongodb.repository.query.AbstractMongoQuery#isLimiting()
@@ -184,18 +182,9 @@ public class StringBasedMongoQuery extends AbstractMongoQuery {
 		return false;
 	}
 
-	private static int countBooleanValues(boolean... values) {
-
-		int count = 0;
-
-		for (boolean value : values) {
-
-			if (value) {
-				count++;
-			}
-		}
-
-		return count;
+	private static boolean hasAmbiguousProjectionFlags(boolean isCountQuery, boolean isExistsQuery,
+			boolean isDeleteQuery) {
+		return BooleanUtil.countBooleanTrueValues(isCountQuery, isExistsQuery, isDeleteQuery) > 1;
 	}
 
 	/**
@@ -239,7 +228,8 @@ public class StringBasedMongoQuery extends AbstractMongoQuery {
 			String transformedInput = transformQueryAndCollectExpressionParametersIntoBindings(input, bindings);
 			String parseableInput = makeParameterReferencesParseable(transformedInput);
 
-			collectParameterReferencesIntoBindings(bindings, JSON.parse(parseableInput));
+			collectParameterReferencesIntoBindings(bindings,
+					JSON.parse(parseableInput, new LenientPatternDecodingCallback()));
 
 			return transformedInput;
 		}
@@ -374,6 +364,43 @@ public class StringBasedMongoQuery extends AbstractMongoQuery {
 		}
 	}
 
+	/**
+	 * {@link JSONCallback} with lenient handling for {@link PatternSyntaxException} falling back to a placeholder
+	 * {@link Pattern} for intermediate query document rendering.
+	 */
+	private static class LenientPatternDecodingCallback extends JSONCallback {
+
+		private static final Pattern EMPTY_MARKER = Pattern.compile("__Spring_Data_MongoDB_Bind_Marker__");
+
+		/*
+		 * (non-Javadoc)
+		 * @see com.mongodb.util.JSONCallback#objectDone()
+		 */
+		@Override
+		public Object objectDone() {
+			return exceptionSwallowingStackReducingObjectDone();
+		}
+
+		private Object exceptionSwallowingStackReducingObjectDone/*CauseWeJustNeedTheStructureNotTheActualValue*/() {
+
+			Object value;
+
+			try {
+				return super.objectDone();
+			} catch (PatternSyntaxException e) {
+				value = EMPTY_MARKER;
+			}
+
+			if (!isStackEmpty()) {
+				_put(curName(), value);
+			} else {
+				value = !BSON.hasDecodeHooks() ? value : BSON.applyDecodingHooks(value);
+				setRoot(value);
+			}
+			return value;
+		}
+	}
+
 	/**
 	 * A generic parameter binding with name or position information.
 	 *

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

@@ -15,12 +15,10 @@
  */
 package org.springframework.data.mongodb.repository.support;
 
-import org.springframework.data.domain.Persistable;
 import org.springframework.data.mongodb.core.mapping.MongoPersistentEntity;
 import org.springframework.data.mongodb.repository.query.MongoEntityInformation;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
-import org.springframework.util.ClassUtils;
 
 /**
  * Support class responsible for creating {@link MongoEntityInformation} instances for a given
@@ -47,10 +45,6 @@ final class MongoEntityInformationSupport {
 
 		Assert.notNull(entity, "Entity must not be null!");
 
-		MappingMongoEntityInformation<T, ID> entityInformation = new MappingMongoEntityInformation<T, ID>(
-				(MongoPersistentEntity<T>) entity, (Class<ID>) idType);
-
-		return ClassUtils.isAssignable(Persistable.class, entity.getType())
-				? new PersistableMongoEntityInformation<T, ID>(entityInformation) : entityInformation;
+		return new MappingMongoEntityInformation<>((MongoPersistentEntity<T>) entity, (Class<ID>) idType);
 	}
 }

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

@@ -0,0 +1,437 @@
+/*
+ * 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.repository.support;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.regex.Pattern;
+
+import org.bson.BsonJavaScript;
+import org.bson.BsonRegularExpression;
+import org.bson.Document;
+import org.bson.types.ObjectId;
+import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
+
+import com.mongodb.DBRef;
+import com.querydsl.core.types.*;
+import com.querydsl.mongodb.MongodbOps;
+
+/**
+ * <p>
+ * Serializes the given Querydsl query to a Document query for MongoDB.
+ * </p>
+ * <p>
+ * Original implementation source {@link com.querydsl.mongodb.MongodbSerializer} by {@literal The Querydsl Team}
+ * (<a href="http://www.querydsl.com/team">http://www.querydsl.com/team</a>) licensed under the Apache License, Version
+ * 2.0.
+ * </p>
+ * Modified to use {@link Document} instead of {@link com.mongodb.DBObject}, updated nullable types and code format. Use
+ * Bson specific types and add {@link QuerydslMongoOps#NO_MATCH}.
+ *
+ * @author laimw
+ * @author Mark Paluch
+ * @author Christoph Strobl
+ * @since 2.1
+ */
+abstract class MongodbDocumentSerializer implements Visitor<Object, Void> {
+
+	@Nullable
+	Object handle(Expression<?> expression) {
+		return expression.accept(this, null);
+	}
+
+	/**
+	 * Create the MongoDB specific query document.
+	 *
+	 * @param predicate must not be {@literal null}.
+	 * @return empty {@link Document} by default.
+	 */
+	Document toQuery(Predicate predicate) {
+
+		Object value = handle(predicate);
+
+		if (value == null) {
+			return new Document();
+		}
+
+		Assert.isInstanceOf(Document.class, value,
+				() -> String.format("Invalid type. Expected Document but found %s", value.getClass()));
+
+		return (Document) value;
+	}
+
+	/**
+	 * Create the MongoDB specific sort document.
+	 *
+	 * @param orderBys must not be {@literal null}.
+	 * @return empty {@link Document} by default.
+	 */
+	Document toSort(List<OrderSpecifier<?>> orderBys) {
+
+		Document sort = new Document();
+
+		orderBys.forEach(orderSpecifier -> {
+
+			Object key = orderSpecifier.getTarget().accept(this, null);
+
+			Assert.notNull(key, () -> String.format("Mapped sort key for %s must not be null!", orderSpecifier));
+			sort.append(key.toString(), orderSpecifier.getOrder() == Order.ASC ? 1 : -1);
+		});
+
+		return sort;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see com.querydsl.core.types.Visitor#visit(com.querydsl.core.types.Constant, java.lang.Void)
+	 */
+	@Override
+	public Object visit(Constant<?> expr, Void context) {
+
+		if (!Enum.class.isAssignableFrom(expr.getType())) {
+			return expr.getConstant();
+		}
+
+		@SuppressWarnings("unchecked") // Guarded by previous check
+		Constant<? extends Enum<?>> expectedExpr = (Constant<? extends Enum<?>>) expr;
+		return expectedExpr.getConstant().name();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see com.querydsl.core.types.Visitor#visit(com.querydsl.core.types.TemplateExpression, java.lang.Void)
+	 */
+	@Override
+	public Object visit(TemplateExpression<?> expr, Void context) {
+		throw new UnsupportedOperationException();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see com.querydsl.core.types.Visitor#visit(com.querydsl.core.types.FactoryExpression, java.lang.Void)
+	 */
+	@Override
+	public Object visit(FactoryExpression<?> expr, Void context) {
+		throw new UnsupportedOperationException();
+	}
+
+	protected String asDBKey(Operation<?> expr, int index) {
+
+		String key = (String) asDBValue(expr, index);
+
+		Assert.hasText(key, () -> String.format("Mapped key must not be null nor empty for expression %s.", expr));
+		return key;
+	}
+
+	@Nullable
+	protected Object asDBValue(Operation<?> expr, int index) {
+		return expr.getArg(index).accept(this, null);
+	}
+
+	private String regexValue(Operation<?> expr, int index) {
+
+		Object value = expr.getArg(index).accept(this, null);
+
+		Assert.notNull(value, () -> String.format("Regex for %s must not be null.", expr));
+		return Pattern.quote(value.toString());
+	}
+
+	protected Document asDocument(String key, @Nullable Object value) {
+		return new Document(key, value);
+	}
+
+	@SuppressWarnings("unchecked")
+	@Override
+	public Object visit(Operation<?> expr, Void context) {
+
+		Operator op = expr.getOperator();
+		if (op == Ops.EQ) {
+
+			if (expr.getArg(0) instanceof Operation) {
+				Operation<?> lhs = (Operation<?>) expr.getArg(0);
+				if (lhs.getOperator() == Ops.COL_SIZE || lhs.getOperator() == Ops.ARRAY_SIZE) {
+					return asDocument(asDBKey(lhs, 0), asDocument("$size", asDBValue(expr, 1)));
+				} else {
+					throw new UnsupportedOperationException("Illegal operation " + expr);
+				}
+			} else if (expr.getArg(0) instanceof Path) {
+				Path<?> path = (Path<?>) expr.getArg(0);
+				Constant<?> constant = (Constant<?>) expr.getArg(1);
+				return asDocument(asDBKey(expr, 0), convert(path, constant));
+			}
+		} else if (op == Ops.STRING_IS_EMPTY) {
+			return asDocument(asDBKey(expr, 0), "");
+		} else if (op == Ops.AND) {
+
+			Map<Object, Object> lhs = (Map<Object, Object>) handle(expr.getArg(0));
+			Map<Object, Object> rhs = (Map<Object, Object>) handle(expr.getArg(1));
+
+			LinkedHashSet<Entry<Object, Object>> lhs2 = new LinkedHashSet<>(lhs.entrySet());
+			lhs2.retainAll(rhs.entrySet());
+
+			if (lhs2.isEmpty()) {
+				lhs.putAll(rhs);
+				return lhs;
+			} else {
+				List<Object> list = new ArrayList<>(2);
+				list.add(handle(expr.getArg(0)));
+				list.add(handle(expr.getArg(1)));
+				return asDocument("$and", list);
+			}
+
+		} else if (op == Ops.NOT) {
+			// Handle the not's child
+			Operation<?> subOperation = (Operation<?>) expr.getArg(0);
+			Operator subOp = subOperation.getOperator();
+			if (subOp == Ops.IN) {
+				return visit(
+						ExpressionUtils.operation(Boolean.class, Ops.NOT_IN, subOperation.getArg(0), subOperation.getArg(1)),
+						context);
+			} else {
+				Document arg = (Document) handle(expr.getArg(0));
+				return negate(arg);
+			}
+
+		} else if (op == Ops.OR) {
+
+			List<Object> list = new ArrayList<>(2);
+			list.add(handle(expr.getArg(0)));
+			list.add(handle(expr.getArg(1)));
+			return asDocument("$or", list);
+
+		} else if (op == Ops.NE) {
+
+			Path<?> path = (Path<?>) expr.getArg(0);
+			Constant<?> constant = (Constant<?>) expr.getArg(1);
+			return asDocument(asDBKey(expr, 0), asDocument("$ne", convert(path, constant)));
+
+		} else if (op == Ops.STARTS_WITH) {
+			return asDocument(asDBKey(expr, 0), new BsonRegularExpression("^" + regexValue(expr, 1)));
+		} else if (op == Ops.STARTS_WITH_IC) {
+			return asDocument(asDBKey(expr, 0), new BsonRegularExpression("^" + regexValue(expr, 1), "i"));
+		} else if (op == Ops.ENDS_WITH) {
+			return asDocument(asDBKey(expr, 0), new BsonRegularExpression(regexValue(expr, 1) + "$"));
+		} else if (op == Ops.ENDS_WITH_IC) {
+			return asDocument(asDBKey(expr, 0), new BsonRegularExpression(regexValue(expr, 1) + "$", "i"));
+		} else if (op == Ops.EQ_IGNORE_CASE) {
+			return asDocument(asDBKey(expr, 0), new BsonRegularExpression("^" + regexValue(expr, 1) + "$", "i"));
+		} else if (op == Ops.STRING_CONTAINS) {
+			return asDocument(asDBKey(expr, 0), new BsonRegularExpression(".*" + regexValue(expr, 1) + ".*"));
+		} else if (op == Ops.STRING_CONTAINS_IC) {
+			return asDocument(asDBKey(expr, 0), new BsonRegularExpression(".*" + regexValue(expr, 1) + ".*", "i"));
+		} else if (op == Ops.MATCHES) {
+			return asDocument(asDBKey(expr, 0), new BsonRegularExpression(asDBValue(expr, 1).toString()));
+		} else if (op == Ops.MATCHES_IC) {
+			return asDocument(asDBKey(expr, 0), new BsonRegularExpression(asDBValue(expr, 1).toString(), "i"));
+		} else if (op == Ops.LIKE) {
+
+			String regex = ExpressionUtils.likeToRegex((Expression) expr.getArg(1)).toString();
+			return asDocument(asDBKey(expr, 0), new BsonRegularExpression(regex));
+		} else if (op == Ops.BETWEEN) {
+
+			Document value = new Document("$gte", asDBValue(expr, 1));
+			value.append("$lte", asDBValue(expr, 2));
+			return asDocument(asDBKey(expr, 0), value);
+		} else if (op == Ops.IN) {
+
+			int constIndex = 0;
+			int exprIndex = 1;
+			if (expr.getArg(1) instanceof Constant<?>) {
+				constIndex = 1;
+				exprIndex = 0;
+			}
+			if (Collection.class.isAssignableFrom(expr.getArg(constIndex).getType())) {
+				@SuppressWarnings("unchecked") // guarded by previous check
+				Collection<?> values = ((Constant<? extends Collection<?>>) expr.getArg(constIndex)).getConstant();
+				return asDocument(asDBKey(expr, exprIndex), asDocument("$in", values));
+			} else {
+				Path<?> path = (Path<?>) expr.getArg(exprIndex);
+				Constant<?> constant = (Constant<?>) expr.getArg(constIndex);
+				return asDocument(asDBKey(expr, exprIndex), convert(path, constant));
+			}
+		} else if (op == Ops.NOT_IN) {
+
+			int constIndex = 0;
+			int exprIndex = 1;
+			if (expr.getArg(1) instanceof Constant<?>) {
+
+				constIndex = 1;
+				exprIndex = 0;
+			}
+			if (Collection.class.isAssignableFrom(expr.getArg(constIndex).getType())) {
+
+				@SuppressWarnings("unchecked") // guarded by previous check
+				Collection<?> values = ((Constant<? extends Collection<?>>) expr.getArg(constIndex)).getConstant();
+				return asDocument(asDBKey(expr, exprIndex), asDocument("$nin", values));
+			} else {
+
+				Path<?> path = (Path<?>) expr.getArg(exprIndex);
+				Constant<?> constant = (Constant<?>) expr.getArg(constIndex);
+				return asDocument(asDBKey(expr, exprIndex), asDocument("$ne", convert(path, constant)));
+			}
+		} else if (op == Ops.COL_IS_EMPTY) {
+
+			List<Object> list = new ArrayList<>(2);
+			list.add(asDocument(asDBKey(expr, 0), new ArrayList<Object>()));
+			list.add(asDocument(asDBKey(expr, 0), asDocument("$exists", false)));
+			return asDocument("$or", list);
+		} else if (op == Ops.LT) {
+			return asDocument(asDBKey(expr, 0), asDocument("$lt", asDBValue(expr, 1)));
+		} else if (op == Ops.GT) {
+			return asDocument(asDBKey(expr, 0), asDocument("$gt", asDBValue(expr, 1)));
+		} else if (op == Ops.LOE) {
+			return asDocument(asDBKey(expr, 0), asDocument("$lte", asDBValue(expr, 1)));
+		} else if (op == Ops.GOE) {
+			return asDocument(asDBKey(expr, 0), asDocument("$gte", asDBValue(expr, 1)));
+		} else if (op == Ops.IS_NULL) {
+			return asDocument(asDBKey(expr, 0), asDocument("$exists", false));
+		} else if (op == Ops.IS_NOT_NULL) {
+			return asDocument(asDBKey(expr, 0), asDocument("$exists", true));
+		} else if (op == Ops.CONTAINS_KEY) {
+
+			Path<?> path = (Path<?>) expr.getArg(0);
+			Expression<?> key = expr.getArg(1);
+			return asDocument(visit(path, context) + "." + key.toString(), asDocument("$exists", true));
+		} else if (op == MongodbOps.NEAR) {
+			return asDocument(asDBKey(expr, 0), asDocument("$near", asDBValue(expr, 1)));
+		} else if (op == MongodbOps.NEAR_SPHERE) {
+			return asDocument(asDBKey(expr, 0), asDocument("$nearSphere", asDBValue(expr, 1)));
+		} else if (op == MongodbOps.ELEM_MATCH) {
+			return asDocument(asDBKey(expr, 0), asDocument("$elemMatch", asDBValue(expr, 1)));
+		} else if (op == QuerydslMongoOps.NO_MATCH) {
+			return new Document("$where", new BsonJavaScript("function() { return false }"));
+		}
+
+		throw new UnsupportedOperationException("Illegal operation " + expr);
+	}
+
+	private Object negate(Document arg) {
+
+		List<Object> list = new ArrayList<>();
+		for (Map.Entry<String, Object> entry : arg.entrySet()) {
+
+			if (entry.getKey().equals("$or")) {
+				list.add(asDocument("$nor", entry.getValue()));
+			} else if (entry.getKey().equals("$and")) {
+
+				List<Object> list2 = new ArrayList<>();
+				for (Object o : ((Collection) entry.getValue())) {
+					list2.add(negate((Document) o));
+				}
+				list.add(asDocument("$or", list2));
+			} else if (entry.getValue() instanceof Pattern || entry.getValue() instanceof BsonRegularExpression) {
+				list.add(asDocument(entry.getKey(), asDocument("$not", entry.getValue())));
+			} else if (entry.getValue() instanceof Document) {
+				list.add(negate(entry.getKey(), (Document) entry.getValue()));
+			} else {
+				list.add(asDocument(entry.getKey(), asDocument("$ne", entry.getValue())));
+			}
+		}
+		return list.size() == 1 ? list.get(0) : asDocument("$or", list);
+	}
+
+	private Object negate(String key, Document value) {
+
+		if (value.size() == 1) {
+			return asDocument(key, asDocument("$not", value));
+		} else {
+
+			List<Object> list2 = new ArrayList<>();
+			for (Map.Entry<String, Object> entry2 : value.entrySet()) {
+				list2.add(asDocument(key, asDocument("$not", asDocument(entry2.getKey(), entry2.getValue()))));
+			}
+
+			return asDocument("$or", list2);
+		}
+	}
+
+	protected Object convert(Path<?> property, Constant<?> constant) {
+
+		if (isReference(property)) {
+			return asReference(constant.getConstant());
+		} else if (isId(property)) {
+
+			if (isReference(property.getMetadata().getParent())) {
+				return asReferenceKey(property.getMetadata().getParent().getType(), constant.getConstant());
+			} else if (constant.getType().equals(String.class) && isImplicitObjectIdConversion()) {
+
+				String id = (String) constant.getConstant();
+				return ObjectId.isValid(id) ? new ObjectId(id) : id;
+			}
+		}
+		return visit(constant, null);
+	}
+
+	protected boolean isImplicitObjectIdConversion() {
+		return true;
+	}
+
+	protected DBRef asReferenceKey(Class<?> entity, Object id) {
+		// TODO override in subclass
+		throw new UnsupportedOperationException();
+	}
+
+	protected abstract DBRef asReference(Object constant);
+
+	protected abstract boolean isReference(@Nullable Path<?> arg);
+
+	protected boolean isId(Path<?> arg) {
+		// TODO override in subclass
+		return false;
+	}
+
+	@Override
+	public String visit(Path<?> expr, Void context) {
+
+		PathMetadata metadata = expr.getMetadata();
+
+		if (metadata.getParent() != null) {
+
+			Path<?> parent = metadata.getParent();
+			if (parent.getMetadata().getPathType() == PathType.DELEGATE) {
+				parent = parent.getMetadata().getParent();
+			}
+			if (metadata.getPathType() == PathType.COLLECTION_ANY) {
+				return visit(parent, context);
+			} else if (parent.getMetadata().getPathType() != PathType.VARIABLE) {
+
+				String rv = getKeyForPath(expr, metadata);
+				String parentStr = visit(parent, context);
+				return rv != null ? parentStr + "." + rv : parentStr;
+			}
+		}
+		return getKeyForPath(expr, metadata);
+	}
+
+	protected String getKeyForPath(Path<?> expr, PathMetadata metadata) {
+		return metadata.getElement().toString();
+	}
+
+	@Override
+	public Object visit(SubQueryExpression<?> expr, Void context) {
+		throw new UnsupportedOperationException();
+	}
+
+	@Override
+	public Object visit(ParamExpression<?> expr, Void context) {
+		throw new UnsupportedOperationException();
+	}
+}

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

@@ -1,103 +0,0 @@
-/*
- * Copyright 2017-2018 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.repository.support;
-
-import lombok.NonNull;
-import lombok.RequiredArgsConstructor;
-
-import org.springframework.data.domain.Persistable;
-import org.springframework.data.mongodb.repository.query.MongoEntityInformation;
-
-/**
- * {@link MongoEntityInformation} implementation wrapping an existing {@link MongoEntityInformation} considering
- * {@link Persistable} types by delegating {@link #isNew(Object)} and {@link #getId(Object)} to the corresponding
- * {@link Persistable#isNew()} and {@link Persistable#getId()} implementations.
- *
- * @author Christoph Strobl
- * @author Oliver Gierke
- * @since 1.10
- */
-@RequiredArgsConstructor
-class PersistableMongoEntityInformation<T, ID> implements MongoEntityInformation<T, ID> {
-
-	private final @NonNull MongoEntityInformation<T, ID> delegate;
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.repository.MongoEntityInformation#getCollectionName()
-	 */
-	@Override
-	public String getCollectionName() {
-		return delegate.getCollectionName();
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.mongodb.repository.MongoEntityInformation#getIdAttribute()
-	 */
-	@Override
-	public String getIdAttribute() {
-		return delegate.getIdAttribute();
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.repository.core.EntityInformation#isNew(java.lang.Object)
-	 */
-	@Override
-	@SuppressWarnings("unchecked")
-	public boolean isNew(T t) {
-
-		if (t instanceof Persistable) {
-			return ((Persistable<ID>) t).isNew();
-		}
-
-		return delegate.isNew(t);
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.repository.core.EntityInformation#getId(java.lang.Object)
-	 */
-	@Override
-	@SuppressWarnings("unchecked")
-	public ID getId(T t) {
-
-		if (t instanceof Persistable) {
-			return ((Persistable<ID>) t).getId();
-		}
-
-		return delegate.getId(t);
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.repository.core.support.PersistentEntityInformation#getIdType()
-	 */
-	@Override
-	public Class<ID> getIdType() {
-		return delegate.getIdType();
-	}
-
-	/*
-	 * (non-Javadoc)
-	 * @see org.springframework.data.repository.core.support.EntityMetadata#getJavaType()
-	 */
-	@Override
-	public Class<T> getJavaType() {
-		return delegate.getJavaType();
-	}
-}

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

@@ -0,0 +1,202 @@
+/*
+ * 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.repository.support;
+
+import java.util.List;
+
+import org.bson.Document;
+import org.springframework.lang.Nullable;
+
+import com.querydsl.core.DefaultQueryMetadata;
+import com.querydsl.core.QueryModifiers;
+import com.querydsl.core.SimpleQuery;
+import com.querydsl.core.support.QueryMixin;
+import com.querydsl.core.types.Expression;
+import com.querydsl.core.types.FactoryExpression;
+import com.querydsl.core.types.OrderSpecifier;
+import com.querydsl.core.types.ParamExpression;
+import com.querydsl.core.types.Predicate;
+
+/**
+ * {@code QuerydslAbstractMongodbQuery} provides a base class for general Querydsl query implementation.
+ * <p>
+ * Original implementation source {@link com.querydsl.mongodb.AbstractMongodbQuery} by {@literal The Querydsl Team}
+ * (<a href="http://www.querydsl.com/team">http://www.querydsl.com/team</a>) licensed under the Apache License, Version
+ * 2.0.
+ * </p>
+ * Modified for usage with {@link MongodbDocumentSerializer}.
+ * 
+ * @param <Q> concrete subtype
+ * @author laimw
+ * @author Mark Paluch
+ * @author Christoph Strobl
+ * @since 2.1
+ */
+public abstract class QuerydslAbstractMongodbQuery<K, Q extends QuerydslAbstractMongodbQuery<K, Q>>
+		implements SimpleQuery<Q> {
+
+	private final MongodbDocumentSerializer serializer;
+	private final QueryMixin<Q> queryMixin;
+
+	/**
+	 * Create a new MongodbQuery instance
+	 *
+	 * @param serializer serializer
+	 */
+	@SuppressWarnings("unchecked")
+	QuerydslAbstractMongodbQuery(MongodbDocumentSerializer serializer) {
+
+		this.queryMixin = new QueryMixin<>((Q) this, new DefaultQueryMetadata(), false);
+		this.serializer = serializer;
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see com.querydsl.core.SimpleQuery#distinct()
+	 */
+	@Override
+	public Q distinct() {
+		return queryMixin.distinct();
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see com.querydsl.core.FilteredClause#where(com.querydsl.core.types.Predicate[])
+	 */
+	@Override
+	public Q where(Predicate... e) {
+		return queryMixin.where(e);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see com.querydsl.core.SimpleQuery#limit(long)
+	 */
+	@Override
+	public Q limit(long limit) {
+		return queryMixin.limit(limit);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see com.querydsl.core.SimpleQuery#offset()
+	 */
+	@Override
+	public Q offset(long offset) {
+		return queryMixin.offset(offset);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see com.querydsl.core.SimpleQuery#restrict(com.querydsl.core.QueryModifiers)
+	 */
+	@Override
+	public Q restrict(QueryModifiers modifiers) {
+		return queryMixin.restrict(modifiers);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see com.querydsl.core.SimpleQuery#orderBy(com.querydsl.core.types.OrderSpecifier)
+	 */
+	@Override
+	public Q orderBy(OrderSpecifier<?>... o) {
+		return queryMixin.orderBy(o);
+	}
+
+	/*
+	 * (non-Javadoc)
+	 * @see com.querydsl.core.SimpleQuery#set(com.querydsl.core.types.ParamExpression, Object)
+	 */
+	@Override
+	public <T> Q set(ParamExpression<T> param, T value) {
+		return queryMixin.set(param, value);
+	}
+
+	/**
+	 * Compute the actual projection {@link Document} from a given projectionExpression by serializing the contained
+	 * {@link Expression expressions} individually.
+	 *
+	 * @param projectionExpression the computed projection {@link Document}.
+	 * @return never {@literal null}. An empty {@link Document} by default.
+	 * @see MongodbDocumentSerializer#handle(Expression)
+	 */
+	protected Document createProjection(@Nullable Expression<?> projectionExpression) {
+
+		if (!(projectionExpression instanceof FactoryExpression)) {
+			return new Document();
+		}
+
+		Document projection = new Document();
+		((FactoryExpression<?>) projectionExpression).getArgs().stream() //
+				.filter(Expression.class::isInstance) //
+				.map(Expression.class::cast) //
+				.map(serializer::handle) //
+				.forEach(it -> projection.append(it.toString(), 1));
+
+		return projection;
+	}
+
+	/**
+	 * Compute the filer {@link Document} from the given {@link Predicate}.
+	 *
+	 * @param predicate can be {@literal null}.
+	 * @return an empty {@link Document} if predicate is {@literal null}.
+	 * @see MongodbDocumentSerializer#toQuery(Predicate)
+	 */
+	protected Document createQuery(@Nullable Predicate predicate) {
+
+		if (predicate == null) {
+			return new Document();
+		}
+
+		return serializer.toQuery(predicate);
+	}
+
+	/**
+	 * Compute the sort {@link Document} from the given list of {@link OrderSpecifier order specifiers}.
+	 *
+	 * @param orderSpecifiers can be {@literal null}.
+	 * @return an empty {@link Document} if predicate is {@literal null}.
+	 * @see MongodbDocumentSerializer#toSort(List)
+	 */
+	protected Document createSort(List<OrderSpecifier<?>> orderSpecifiers) {
+		return serializer.toSort(orderSpecifiers);
+	}
+
+	/**
+	 * Get the actual {@link QueryMixin} delegate.
+	 * 
+	 * @return
+	 */
+	QueryMixin<Q> getQueryMixin() {
+		return queryMixin;
+	}
+
+	/**
+	 * Get the where definition as a Document instance
+	 *
+	 * @return
+	 */
+	Document asDocument() {
+		return createQuery(queryMixin.getMetadata().getWhere());
+	}
+
+	@Override
+	public String toString() {
+		return asDocument().toString();
+	}
+}