DATAMONGO-1992 - Add mutation support for immutable objects through ReactiveMongoTemplate.

Persisting methods of ReactiveMongoTemplate now return potentially new object instances of immutable objects. New instances are created using wither methods/Kotlin copy(…) methods if an immutable object requires association with an Id or the version number needs to be incremented.

Author: mp911de

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

@@ -927,7 +927,7 @@ <S, T> Mono<T> findAndReplace(Query query, S replacement, FindAndReplaceOptions
 	 * 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);
 
@@ -941,7 +941,7 @@ <S, T> Mono<T> findAndReplace(Query query, S replacement, FindAndReplaceOptions
 	 *
 	 * @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);
 
@@ -950,7 +950,7 @@ <S, T> Mono<T> findAndReplace(Query query, S replacement, FindAndReplaceOptions
 	 *
 	 * @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);
 
@@ -959,7 +959,7 @@ <S, T> Mono<T> findAndReplace(Query query, S replacement, FindAndReplaceOptions
 	 *
 	 * @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);
 
@@ -987,7 +987,7 @@ <S, T> Mono<T> findAndReplace(Query query, S replacement, FindAndReplaceOptions
 	 * 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);
 
@@ -996,7 +996,7 @@ <S, T> Mono<T> findAndReplace(Query query, S replacement, FindAndReplaceOptions
 	 *
 	 * @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);
 
@@ -1005,7 +1005,7 @@ <S, T> Mono<T> findAndReplace(Query query, S replacement, FindAndReplaceOptions
 	 *
 	 * @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);
 
@@ -1014,7 +1014,7 @@ <S, T> Mono<T> findAndReplace(Query query, S replacement, FindAndReplaceOptions
 	 * 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);
 

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

@@ -144,6 +144,7 @@
 import com.mongodb.reactivestreams.client.MongoDatabase;
 import com.mongodb.reactivestreams.client.Success;
 import com.mongodb.util.JSONParseException;
+import reactor.util.function.Tuples;
 
 /**
  * Primary implementation of {@link ReactiveMongoOperations}. It simplifies the use of Reactive MongoDB usage and helps
@@ -1252,17 +1253,18 @@ protected <T> Mono<T> doInsert(String collectionName, T objectToSave, MongoWrite
 
 		return Mono.defer(() -> {
 
-			initializeVersionProperty(objectToSave);
-			maybeEmitEvent(new BeforeConvertEvent<>(objectToSave, collectionName));
+			T toSave = (T) initializeVersionProperty(objectToSave);
+			maybeEmitEvent(new BeforeConvertEvent<>(toSave, collectionName));
 
-			Document dbDoc = toDocument(objectToSave, writer);
+			Document dbDoc = toDocument(toSave, writer);
 
-			maybeEmitEvent(new BeforeSaveEvent<>(objectToSave, dbDoc, collectionName));
+			maybeEmitEvent(new BeforeSaveEvent<>(toSave, dbDoc, collectionName));
 
-			Mono<T> afterInsert = insertDBObject(collectionName, dbDoc, objectToSave.getClass()).flatMap(id -> {
-				populateIdIfNecessary(objectToSave, id);
-				maybeEmitEvent(new AfterSaveEvent<>(objectToSave, dbDoc, collectionName));
-				return Mono.just(objectToSave);
+			Mono<T> afterInsert = insertDBObject(collectionName, dbDoc, toSave.getClass()).map(id -> {
+
+				T saved = (T) populateIdIfNecessary(toSave, id);
+				maybeEmitEvent(new AfterSaveEvent<>(saved, dbDoc, collectionName));
+				return saved;
 			});
 
 			return afterInsert;
@@ -1326,18 +1328,15 @@ protected <T> Flux<T> doInsertBatch(final String collectionName, final Collectio
 		Assert.notNull(writer, "MongoWriter must not be null!");
 
 		Mono<List<Tuple2<T, Document>>> prepareDocuments = Flux.fromIterable(batchToSave)
-				.flatMap(new Function<T, Flux<Tuple2<T, Document>>>() {
-					@Override
-					public Flux<Tuple2<T, Document>> apply(T o) {
+				.map(o -> {
 
-						initializeVersionProperty(o);
-						maybeEmitEvent(new BeforeConvertEvent<>(o, collectionName));
+					T toSave = (T) initializeVersionProperty(o);
+					maybeEmitEvent(new BeforeConvertEvent<>(toSave, collectionName));
 
-						Document dbDoc = toDocument(o, writer);
+					Document dbDoc = toDocument(toSave, writer);
 
-						maybeEmitEvent(new BeforeSaveEvent<>(o, dbDoc, collectionName));
-						return Flux.zip(Mono.just(o), Mono.just(dbDoc));
-					}
+					maybeEmitEvent(new BeforeSaveEvent<>(toSave, dbDoc, collectionName));
+					return Tuples.of(toSave, dbDoc);
 				}).collectList();
 
 		Flux<Tuple2<T, Document>> insertDocuments = prepareDocuments.flatMapMany(tuples -> {
@@ -1349,9 +1348,9 @@ public Flux<Tuple2<T, Document>> apply(T o) {
 
 		return insertDocuments.map(tuple -> {
 
-			populateIdIfNecessary(tuple.getT1(), tuple.getT2().get(ID_FIELD));
-			maybeEmitEvent(new AfterSaveEvent<>(tuple.getT1(), tuple.getT2(), collectionName));
-			return tuple.getT1();
+			T saved = (T) populateIdIfNecessary(tuple.getT1(), tuple.getT2().get(ID_FIELD));
+			maybeEmitEvent(new AfterSaveEvent<>(saved, tuple.getT2(), collectionName));
+			return saved;
 		});
 	}
 
@@ -1438,17 +1437,19 @@ private <T> Mono<T> doSaveVersioned(T objectToSave, MongoPersistentEntity<?> ent
 			// Bump version number
 			convertingAccessor.setProperty(versionProperty, versionNumber.longValue() + 1);
 
-			ReactiveMongoTemplate.this.maybeEmitEvent(new BeforeConvertEvent<>(objectToSave, collectionName));
+			T toSave = (T) convertingAccessor.getBean();
 
-			Document document = ReactiveMongoTemplate.this.toDocument(objectToSave, mongoConverter);
+			ReactiveMongoTemplate.this.maybeEmitEvent(new BeforeConvertEvent<T>(toSave, collectionName));
 
-			ReactiveMongoTemplate.this.maybeEmitEvent(new BeforeSaveEvent<>(objectToSave, document, collectionName));
+			Document document = ReactiveMongoTemplate.this.toDocument(toSave, mongoConverter);
+
+			ReactiveMongoTemplate.this.maybeEmitEvent(new BeforeSaveEvent<>(toSave, document, collectionName));
 			Update update = Update.fromDocument(document, ID_FIELD);
 
-			return doUpdate(collectionName, query, update, objectToSave.getClass(), false, false).map(updateResult -> {
+			return doUpdate(collectionName, query, update, toSave.getClass(), false, false).map(updateResult -> {
 
-				maybeEmitEvent(new AfterSaveEvent<>(objectToSave, document, collectionName));
-				return objectToSave;
+				maybeEmitEvent(new AfterSaveEvent<>(toSave, document, collectionName));
+				return toSave;
 			});
 		});
 	}
@@ -1465,9 +1466,9 @@ protected <T> Mono<T> doSave(String collectionName, T objectToSave, MongoWriter<
 
 			return saveDocument(collectionName, dbDoc, objectToSave.getClass()).map(id -> {
 
-				populateIdIfNecessary(objectToSave, id);
-				maybeEmitEvent(new AfterSaveEvent<>(objectToSave, dbDoc, collectionName));
-				return objectToSave;
+				T saved = (T) populateIdIfNecessary(objectToSave, id);
+				maybeEmitEvent(new AfterSaveEvent<>(saved, dbDoc, collectionName));
+				return saved;
 			});
 		});
 	}
@@ -2521,35 +2522,37 @@ protected <T> void maybeEmitEvent(MongoMappingEvent<T> event) {
 	 * @param id
 	 */
 	@SuppressWarnings("unchecked")
-	private void populateIdIfNecessary(Object savedObject, @Nullable Object id) {
+	private Object populateIdIfNecessary(Object savedObject, @Nullable Object id) {
 
 		if (id == null) {
-			return;
+			return null;
 		}
 
 		if (savedObject instanceof Map) {
 
 			Map<String, Object> map = (Map<String, Object>) savedObject;
 			map.put(ID_FIELD, id);
 
-			return;
+			return map;
 		}
 
 		MongoPersistentProperty idProp = getIdPropertyFor(savedObject.getClass());
 
 		if (idProp == null) {
-			return;
+			return savedObject;
 		}
 
 		ConversionService conversionService = mongoConverter.getConversionService();
 		MongoPersistentEntity<?> entity = mappingContext.getRequiredPersistentEntity(savedObject.getClass());
 		PersistentPropertyAccessor accessor = entity.getPropertyAccessor(savedObject);
 
 		if (accessor.getProperty(idProp) != null) {
-			return;
+			return accessor.getBean();
 		}
 
 		new ConvertingPropertyAccessor(accessor, conversionService).setProperty(idProp, id);
+
+		return accessor.getBean();
 	}
 
 	private MongoCollection<Document> getAndPrepareCollection(MongoDatabase db, String collectionName) {
@@ -2807,15 +2810,19 @@ private <T> Document toDocument(T objectToSave, MongoWriter<T> writer) {
 		}
 	}
 
-	private void initializeVersionProperty(Object entity) {
+	private Object initializeVersionProperty(Object entity) {
 
 		MongoPersistentEntity<?> mongoPersistentEntity = getPersistentEntity(entity.getClass());
 
 		if (mongoPersistentEntity != null && mongoPersistentEntity.hasVersionProperty()) {
 			ConvertingPropertyAccessor accessor = new ConvertingPropertyAccessor(
 					mongoPersistentEntity.getPropertyAccessor(entity), mongoConverter.getConversionService());
 			accessor.setProperty(mongoPersistentEntity.getRequiredVersionProperty(), 0);
+
+			return accessor.getBean();
 		}
+
+		return entity;
 	}
 
 	// Callback implementations