Java tutorial
/* * Copyright 2008-present MongoDB, Inc. * * 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 com.mongodb; import com.mongodb.client.model.Collation; import com.mongodb.lang.Nullable; import com.mongodb.operation.GroupOperation; import org.bson.BsonDocumentWrapper; import org.bson.BsonJavaScript; import static com.mongodb.assertions.Assertions.notNull; /** * This class groups the argument for a group operation and can build the underlying command object * * @mongodb.driver.manual reference/command/group/ Group * @deprecated the group command was deprecated in MongoDB 3.4 */ @Deprecated public class GroupCommand { private final String collectionName; private final DBObject keys; private final String keyf; private final DBObject condition; private final DBObject initial; private final String reduce; private final String finalize; private final Collation collation; /** * Creates a new group command. * * @param collection the collection from which to perform the group by operation. * @param keys the field or fields to group. * @param condition optional - a filter to determine which documents in the collection to process. * @param initial the initial state of the aggregation result document. * @param reduce a JavaScript aggregation function that operates on the documents during the grouping operation. * @param finalize optional - a JavaScript function that runs each item in the result set before group returns the final value. */ public GroupCommand(final DBCollection collection, final DBObject keys, final DBObject condition, final DBObject initial, final String reduce, @Nullable final String finalize) { this(collection, keys, condition, initial, reduce, finalize, null); } /** * Creates a new group command. * * @param collection the collection from which to perform the group by operation. * @param keys the field or fields to group. * @param condition optional - a filter to determine which documents in the collection to process. * @param initial the initial state of the aggregation result document. * @param reduce a JavaScript aggregation function that operates on the documents during the grouping operation. * @param finalize optional - a JavaScript function that runs each item in the result set before group returns the final value. * @param collation optional - the collation options * * @since 3.4 */ public GroupCommand(final DBCollection collection, final DBObject keys, final DBObject condition, final DBObject initial, final String reduce, @Nullable final String finalize, @Nullable final Collation collation) { notNull("collection", collection); this.collectionName = collection.getName(); this.keys = keys; this.condition = condition; this.initial = initial; this.reduce = reduce; this.finalize = finalize; this.keyf = null; this.collation = collation; } /** * Creates a new group command. * * @param collection the collection from which to perform the group by operation. * @param keyf the function that creates a "key object" for use as the grouping key * @param condition optional - a filter to determine which documents in the collection to process. * @param initial the initial state of the aggregation result document. * @param reduce a JavaScript aggregation function that operates on the documents during the grouping operation. * @param finalize optional - a JavaScript function that runs each item in the result set before group returns the final value. * * @since 3.1 */ public GroupCommand(final DBCollection collection, final String keyf, final DBObject condition, final DBObject initial, final String reduce, final String finalize) { this(collection, keyf, condition, initial, reduce, finalize, null); } /** * Creates a new group command. * * @param collection the collection from which to perform the group by operation. * @param keyf the function that creates a "key object" for use as the grouping key * @param condition optional - a filter to determine which documents in the collection to process. * @param initial the initial state of the aggregation result document. * @param reduce a JavaScript aggregation function that operates on the documents during the grouping operation. * @param finalize optional - a JavaScript function that runs each item in the result set before group returns the final value. * @param collation optional - the collation options * * @since 3.4 */ public GroupCommand(final DBCollection collection, final String keyf, final DBObject condition, final DBObject initial, final String reduce, @Nullable final String finalize, @Nullable final Collation collation) { notNull("collection", collection); this.collectionName = collection.getName(); this.keyf = notNull("keyf", keyf); this.condition = condition; this.initial = initial; this.reduce = reduce; this.finalize = finalize; this.keys = null; this.collation = collation; } /** * Turns this group command into the DBObject format of the command. * * @return a DBObject containing the group command as a MongoDB document */ public DBObject toDBObject() { DBObject args = new BasicDBObject("ns", collectionName).append("cond", condition).append("$reduce", reduce) .append("initial", initial); if (keys != null) { args.put("key", keys); } if (keyf != null) { args.put("$keyf", keyf); } if (finalize != null) { args.put("finalize", finalize); } return new BasicDBObject("group", args); } GroupOperation<DBObject> toOperation(final MongoNamespace namespace, final DBObjectCodec codec, final boolean retryReads) { if (initial == null) { throw new IllegalArgumentException( "Group command requires an initial document for the aggregate result"); } if (reduce == null) { throw new IllegalArgumentException("Group command requires a reduce function for the aggregate result"); } GroupOperation<DBObject> operation = new GroupOperation<DBObject>(namespace, new BsonJavaScript(reduce), new BsonDocumentWrapper<DBObject>(initial, codec), codec).retryReads(retryReads); if (keys != null) { operation.key(new BsonDocumentWrapper<DBObject>(keys, codec)); } if (keyf != null) { operation.keyFunction(new BsonJavaScript(keyf)); } if (condition != null) { operation.filter(new BsonDocumentWrapper<DBObject>(condition, codec)); } if (finalize != null) { operation.finalizeFunction(new BsonJavaScript(finalize)); } operation.collation(collation); return operation; } }