Add support to create views via reactive/template API.

This commit introduces support to create MongoDB Views directly via the Reactive-/MongoOperations API.

Closes: #2594
Original pull request: #4142.

Author: christophstrobl

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

@@ -26,7 +26,9 @@
 import org.springframework.data.geo.GeoResults;
 import org.springframework.data.mongodb.core.BulkOperations.BulkMode;
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
+import org.springframework.data.mongodb.core.aggregation.AggregationOperation;
 import org.springframework.data.mongodb.core.aggregation.AggregationOptions;
+import org.springframework.data.mongodb.core.aggregation.AggregationPipeline;
 import org.springframework.data.mongodb.core.aggregation.AggregationResults;
 import org.springframework.data.mongodb.core.aggregation.AggregationUpdate;
 import org.springframework.data.mongodb.core.aggregation.TypedAggregation;
@@ -280,6 +282,56 @@ public <T> T execute(SessionCallback<T> action, Consumer<ClientSession> onComple
 	 */
 	MongoCollection<Document> createCollection(String collectionName, @Nullable CollectionOptions collectionOptions);
 
+	/**
+	 * Create a view with the the provided name whose contents are defined by the {@link AggregationOperation pipeline
+	 * stages} on another collection or view identified by the given {@link #getCollectionName(Class) source type}.
+	 * 
+	 * @param name the name of the view to create.
+	 * @param source the type defining the views source collection.
+	 * @param stages the {@link AggregationOperation aggregation pipeline stages} defining the view content.
+	 * @since 4.0
+	 */
+	default MongoCollection<Document> createView(String name, Class<?> source, AggregationOperation... stages) {
+		return createView(name, source, AggregationPipeline.of(stages));
+	}
+
+	/**
+	 * Create a view with the the provided name whose contents are defined by the  {@link AggregationPipeline pipeline} on
+	 * another collection or view identified by the given {@link #getCollectionName(Class) source type}.
+	 *
+	 * @param name the name of the view to create.
+	 * @param source the type defining the views source collection.
+	 * @param pipeline the {@link AggregationPipeline} defining the view content.
+	 * @since 4.0
+	 */
+	default MongoCollection<Document> createView(String name, Class<?> source, AggregationPipeline pipeline) {
+		return createView(name, source, pipeline, null);
+	}
+
+	/**
+	 * Create a view with the the provided name whose contents are defined by the {@link AggregationPipeline pipeline} on
+	 * another collection or view identified by the given {@link #getCollectionName(Class) source type}.
+	 *
+	 * @param name the name of the view to create.
+	 * @param source the type defining the views source collection.
+	 * @param pipeline the {@link AggregationPipeline} defining the view content.
+	 * @param options additional settings to apply when creating the view. Can be {@literal null}.
+	 * @since 4.0
+	 */
+	MongoCollection<Document> createView(String name, Class<?> source, AggregationPipeline pipeline, @Nullable ViewOptions options);
+
+	/**
+	 * Create a view with the the provided name whose contents are defined by the {@link AggregationPipeline pipeline} on
+	 * another collection or view identified by the given source.
+	 *
+	 * @param name the name of the view to create.
+	 * @param source the name of the collection or view defining the to be created views source.
+	 * @param pipeline the {@link AggregationPipeline} defining the view content.
+	 * @param options additional settings to apply when creating the view. Can be {@literal null}.
+	 * @since 4.0
+	 */
+	MongoCollection<Document> createView(String name, String source, AggregationPipeline pipeline, @Nullable ViewOptions options);
+
 	/**
 	 * A set of collection names.
 	 *

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

@@ -67,6 +67,7 @@
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
 import org.springframework.data.mongodb.core.aggregation.AggregationOperationContext;
 import org.springframework.data.mongodb.core.aggregation.AggregationOptions;
+import org.springframework.data.mongodb.core.aggregation.AggregationPipeline;
 import org.springframework.data.mongodb.core.aggregation.AggregationResults;
 import org.springframework.data.mongodb.core.aggregation.TypedAggregation;
 import org.springframework.data.mongodb.core.convert.DbRefResolver;
@@ -632,6 +633,40 @@ public MongoCollection<Document> createCollection(String collectionName,
 				operations.convertToCreateCollectionOptions(collectionOptions, Object.class));
 	}
 
+	@Override
+	public MongoCollection<Document> createView(String name, Class<?> source, AggregationPipeline pipeline, @Nullable ViewOptions options) {
+
+		return createView(name, getCollectionName(source),
+				queryOperations.createAggregation(Aggregation.newAggregation(source, pipeline.getOperations()), source),
+				options);
+	}
+
+	@Override
+	public MongoCollection<Document> createView(String name, String source, AggregationPipeline pipeline, @Nullable ViewOptions options) {
+
+		return createView(name, source,
+				queryOperations.createAggregation(Aggregation.newAggregation(pipeline.getOperations()), (Class<?>) null),
+				options);
+	}
+
+	private MongoCollection<Document> createView(String name, String source, AggregationDefinition aggregation,
+			@Nullable ViewOptions options) {
+		return doCreateView(name, source, aggregation.getAggregationPipeline(), options);
+	}
+
+	protected MongoCollection<Document> doCreateView(String name, String source, List<Document> pipeline, @Nullable ViewOptions options) {
+
+		CreateViewOptions viewOptions = new CreateViewOptions();
+		if (options != null) {
+			options.getCollation().map(Collation::toMongoCollation).ifPresent(viewOptions::collation);
+		}
+
+		return execute(db -> {
+			db.createView(name, source, pipeline, viewOptions);
+			return db.getCollection(name);
+		});
+	}
+
 	@Override
 	@SuppressWarnings("ConstantConditions")
 	public MongoCollection<Document> getCollection(String collectionName) {

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

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.mongodb.core;
 
+import org.springframework.data.mongodb.core.aggregation.AggregationOperation;
+import org.springframework.data.mongodb.core.aggregation.AggregationPipeline;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
@@ -240,6 +242,56 @@ <T> Mono<MongoCollection<Document>> createCollection(Class<T> entityClass,
 	 */
 	Mono<MongoCollection<Document>> createCollection(String collectionName, CollectionOptions collectionOptions);
 
+	/**
+	 * Create a view with the the provided name whose contents are defined by the {@link AggregationOperation pipeline
+	 * stages} on another collection or view identified by the given {@link #getCollectionName(Class) source type}.
+	 *
+	 * @param name the name of the view to create.
+	 * @param source the type defining the views source collection.
+	 * @param stages the {@link AggregationOperation aggregation pipeline stages} defining the view content.
+	 * @since 4.0
+	 */
+	default Mono<MongoCollection<Document>> createView(String name, Class<?> source, AggregationOperation... stages) {
+		return createView(name, source, AggregationPipeline.of(stages));
+	}
+
+	/**
+	 * Create a view with the the provided name whose contents are defined by the  {@link AggregationPipeline pipeline} on
+	 * another collection or view identified by the given {@link #getCollectionName(Class) source type}.
+	 *
+	 * @param name the name of the view to create.
+	 * @param source the type defining the views source collection.
+	 * @param pipeline the {@link AggregationPipeline} defining the view content.
+	 * @since 4.0
+	 */
+	default Mono<MongoCollection<Document>> createView(String name, Class<?> source, AggregationPipeline pipeline) {
+		return createView(name, source, pipeline, null);
+	}
+
+	/**
+	 * Create a view with the the provided name whose contents are defined by the {@link AggregationPipeline pipeline} on
+	 * another collection or view identified by the given {@link #getCollectionName(Class) source type}.
+	 *
+	 * @param name the name of the view to create.
+	 * @param source the type defining the views source collection.
+	 * @param pipeline the {@link AggregationPipeline} defining the view content.
+	 * @param options additional settings to apply when creating the view. Can be {@literal null}.
+	 * @since 4.0
+	 */
+	Mono<MongoCollection<Document>> createView(String name, Class<?> source, AggregationPipeline pipeline, @Nullable ViewOptions options);
+
+	/**
+	 * Create a view with the the provided name whose contents are defined by the {@link AggregationPipeline pipeline} on
+	 * another collection or view identified by the given source.
+	 *
+	 * @param name the name of the view to create.
+	 * @param source the name of the collection or view defining the to be created views source.
+	 * @param pipeline the {@link AggregationPipeline} defining the view content.
+	 * @param options additional settings to apply when creating the view. Can be {@literal null}.
+	 * @since 4.0
+	 */
+	Mono<MongoCollection<Document>> createView(String name, String source, AggregationPipeline pipeline, @Nullable ViewOptions options);
+
 	/**
 	 * A set of collection names.
 	 *

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

@@ -46,7 +46,6 @@
 import org.bson.types.ObjectId;
 import org.reactivestreams.Publisher;
 import org.reactivestreams.Subscriber;
-
 import org.springframework.beans.BeansException;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
@@ -81,6 +80,7 @@
 import org.springframework.data.mongodb.core.aggregation.Aggregation;
 import org.springframework.data.mongodb.core.aggregation.AggregationOperationContext;
 import org.springframework.data.mongodb.core.aggregation.AggregationOptions;
+import org.springframework.data.mongodb.core.aggregation.AggregationPipeline;
 import org.springframework.data.mongodb.core.aggregation.PrefixingDelegatingAggregationOperationContext;
 import org.springframework.data.mongodb.core.aggregation.RelaxedTypeBasedAggregationOperationContext;
 import org.springframework.data.mongodb.core.aggregation.TypeBasedAggregationOperationContext;
@@ -127,16 +127,7 @@
 import com.mongodb.MongoException;
 import com.mongodb.ReadPreference;
 import com.mongodb.WriteConcern;
-import com.mongodb.client.model.CountOptions;
-import com.mongodb.client.model.CreateCollectionOptions;
-import com.mongodb.client.model.DeleteOptions;
-import com.mongodb.client.model.EstimatedDocumentCountOptions;
-import com.mongodb.client.model.FindOneAndDeleteOptions;
-import com.mongodb.client.model.FindOneAndReplaceOptions;
-import com.mongodb.client.model.FindOneAndUpdateOptions;
-import com.mongodb.client.model.ReplaceOptions;
-import com.mongodb.client.model.ReturnDocument;
-import com.mongodb.client.model.UpdateOptions;
+import com.mongodb.client.model.*;
 import com.mongodb.client.model.changestream.FullDocument;
 import com.mongodb.client.result.DeleteResult;
 import com.mongodb.client.result.InsertOneResult;
@@ -671,6 +662,42 @@ public Mono<MongoCollection<Document>> createCollection(String collectionName,
 		return doCreateCollection(collectionName, convertToCreateCollectionOptions(collectionOptions));
 	}
 
+	@Override
+	public Mono<MongoCollection<Document>> createView(String name, Class<?> source, AggregationPipeline pipeline, @Nullable ViewOptions options) {
+
+		return createView(name, getCollectionName(source),
+				queryOperations.createAggregation(Aggregation.newAggregation(source, pipeline.getOperations()), source),
+				options);
+	}
+
+	@Override
+	public Mono<MongoCollection<Document>> createView(String name, String source, AggregationPipeline pipeline,
+			@Nullable ViewOptions options) {
+
+		return createView(name, source,
+				queryOperations.createAggregation(Aggregation.newAggregation(pipeline.getOperations()), (Class<?>) null),
+				options);
+	}
+
+	private Mono<MongoCollection<Document>> createView(String name, String source, AggregationDefinition aggregation,
+			@Nullable ViewOptions options) {
+		return doCreateView(name, source, aggregation.getAggregationPipeline(), options);
+	}
+
+	protected Mono<MongoCollection<Document>> doCreateView(String name, String source, List<Document> pipeline,
+			@Nullable ViewOptions options) {
+
+		CreateViewOptions viewOptions = new CreateViewOptions();
+		if (options != null) {
+			options.getCollation().map(Collation::toMongoCollation).ifPresent(viewOptions::collation);
+		}
+
+		return execute(db -> {
+			return Flux.from(db.createView(name, source, pipeline, viewOptions))
+					.then(Mono.fromSupplier(() -> db.getCollection(name)));
+		}).next();
+	}
+
 	@Override
 	public Mono<MongoCollection<Document>> getCollection(String collectionName) {
 

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

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.mongodb.core;
+
+import java.util.Optional;
+
+import org.springframework.data.mongodb.core.query.Collation;
+import org.springframework.lang.Nullable;
+
+/**
+ * Immutable object holding additional options to be applied when creating a MongoDB
+ * <a href="https://www.mongodb.com/docs/manual/core/views/">views</a>.
+ * 
+ * @author Christoph Strobl
+ * @since 4.0
+ */
+public class ViewOptions {
+
+	@Nullable private Collation collation;
+
+	static ViewOptions none() {
+		return new ViewOptions();
+	}
+
+	/**
+	 * Creates new instance of {@link ViewOptions}.
+	 */
+	public ViewOptions() {
+		this(null);
+	}
+
+	private ViewOptions(@Nullable Collation collation) {
+		this.collation = collation;
+	}
+
+	/**
+	 * Get the {@link Collation} to be set.
+	 *
+	 * @return {@link Optional#empty()} if not set.
+	 */
+	public Optional<Collation> getCollation() {
+		return Optional.ofNullable(collation);
+	}
+
+	/**
+	 * @param collation the {@link Collation} to use for language-specific string comparison.
+	 * @return new instance of {@link ViewOptions}.
+	 */
+	public ViewOptions collation(Collation collation) {
+		return new ViewOptions(collation);
+	}
+}

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

@@ -16,6 +16,7 @@
 package org.springframework.data.mongodb.core.aggregation;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.function.Predicate;
@@ -34,6 +35,10 @@ public class AggregationPipeline {
 
 	private final List<AggregationOperation> pipeline;
 
+	public static AggregationPipeline of(AggregationOperation... stages) {
+		return new AggregationPipeline(Arrays.asList(stages));
+	}
+
 	/**
 	 * Create an empty pipeline
 	 */