Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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.apache.jackrabbit.oak.plugins.document; import java.util.Collections; import java.util.Map; import java.util.Map.Entry; import java.util.NavigableMap; import java.util.Set; import java.util.concurrent.atomic.AtomicBoolean; import javax.annotation.CheckForNull; import javax.annotation.Nonnull; import javax.annotation.Nullable; import org.apache.jackrabbit.oak.cache.CacheValue; import org.apache.jackrabbit.oak.plugins.document.util.Utils; import com.google.common.collect.Maps; /** * A document corresponds to a node stored in the DocumentNodeStore. A document * contains all the revisions of a node stored in the {@link DocumentStore}. */ public class Document implements CacheValue { /** * The name of the field that contains the document id (the primary key / * the key). The id uniquely identifies a document within a collection. The * requirements and limits of the id are documented in the * {@link DocumentStore} class. * * For nodes, the document id contains the depth of the path (0 for root, 1 * for children of the root), and then the path. */ public static final String ID = "_id"; /** * The modification count on the document. This field is optional and a * {@link DocumentStore} implementation may use it to keep track of how many * times a document is modified. See also {@link #getModCount()}. */ public static final String MOD_COUNT = "_modCount"; /** * The data of this document. */ protected Map<String, Object> data = Maps.newHashMap(); /** * Whether this document is sealed (immutable data). */ private AtomicBoolean sealed = new AtomicBoolean(false); /** * Get the id (the primary key) of this document. * * @return the id or <code>null</code> if none is set. */ @CheckForNull public String getId() { return (String) get(ID); } /** * Get the modification count of this document. * * @return the count or <code>null</code> if * none is set. */ @CheckForNull public Long getModCount() { return Utils.asLong((Number) get(MOD_COUNT)); } /** * Gets the data for the given <code>key</code>. * * @param key the key. * @return the data or <code>null</code>. */ @CheckForNull public Object get(String key) { return data.get(key); } /** * Sets the data for the given <code>key</code>. * * @param key the key. * @param value the value to set. * @return the previous value or <code>null</code> if there was none. */ @CheckForNull public Object put(String key, Object value) { return data.put(key, value); } /** * @return a Set view of the keys contained in this document. */ public Set<String> keySet() { return data.keySet(); } /** * @return a Set view of the entries contained in this document. */ public Set<Entry<String, Object>> entrySet() { return data.entrySet(); } /** * Seals this document and turns it into an immutable object. Any attempt * to modify this document afterwards will result in an * {@link UnsupportedOperationException}. */ public void seal() { if (!sealed.getAndSet(true)) { for (Map.Entry<String, Object> entry : data.entrySet()) { if (entry.getValue() instanceof Map) { @SuppressWarnings("unchecked") Map<Object, Object> map = (Map<Object, Object>) entry.getValue(); entry.setValue(transformAndSeal(map, entry.getKey(), 1)); } } data = Collections.unmodifiableMap(data); } } /** * Determines if this document is sealed or not * @return true if document is sealed. */ public boolean isSealed() { return sealed.get(); } /** * Performs a deep copy of the data within this document to the given target. * * @param target the target document. */ public void deepCopy(Document target) { Utils.deepCopyMap(data, target.data); } /** * Formats this document for use in a log message. * * @return the formatted string */ public String format() { return data.toString().replaceAll(", _", ",\n_").replaceAll("}, ", "},\n"); } //-----------------------------< CacheValue >------------------------------- @Override public int getMemory() { return Utils.estimateMemoryUsage(this.data); } /** * Transform and seal the data of this document. That is, the data becomes * immutable and transformation may be performed on the data. * * @param map the map to transform. * @param key the key for the given map or <code>null</code> if the map * is the top level data map. * @param level the level. Zero for the top level map, one for an entry in * the top level map, etc. * @return the transformed and sealed map. */ @Nonnull protected Map<?, ?> transformAndSeal(@Nonnull Map<Object, Object> map, @Nullable String key, int level) { for (Map.Entry<Object, Object> entry : map.entrySet()) { Object value = entry.getValue(); if (value instanceof Map) { @SuppressWarnings("unchecked") Map<Object, Object> childMap = (Map<Object, Object>) value; entry.setValue(transformAndSeal(childMap, entry.getKey().toString(), level + 1)); } } if (map instanceof NavigableMap) { return Maps.unmodifiableNavigableMap((NavigableMap<Object, Object>) map); } else { return Collections.unmodifiableMap(map); } } @Override public String toString() { return getId(); } }