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.lang.Nullable; import org.bson.LazyBSONCallback; import org.bson.types.ObjectId; import java.util.Iterator; import java.util.List; /** * A {@code BSONCallback} for the creation of {@code LazyDBObject} and {@code LazyDBList} instances. */ public class LazyDBCallback extends LazyBSONCallback implements DBCallback { /** * Construct an instance. * * @param collection the {@code DBCollection} containing the document. This parameter is no longer used. */ public LazyDBCallback(@Nullable final DBCollection collection) { } @Override public Object createObject(final byte[] bytes, final int offset) { LazyDBObject document = new LazyDBObject(bytes, offset, this); Iterator<String> iterator = document.keySet().iterator(); if (iterator.hasNext() && iterator.next().equals("$ref") && iterator.hasNext() && iterator.next().equals("$id")) { return new DBRef((String) document.get("$db"), (String) document.get("$ref"), document.get("$id")); } return document; } @Override @SuppressWarnings("rawtypes") public List createArray(final byte[] bytes, final int offset) { return new LazyDBList(bytes, offset, this); } @Override public Object createDBRef(final String ns, final ObjectId id) { return new DBRef(ns, id); } }