MapWritable.java
上传用户:quxuerui
上传日期:2018-01-08
资源大小:41811k
文件大小:4k
- /**
- * Copyright 2007 The Apache Software Foundation
- *
- * 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.hadoop.io;
- import java.io.DataInput;
- import java.io.DataOutput;
- import java.io.IOException;
- import java.util.Collection;
- import java.util.HashMap;
- import java.util.Map;
- import java.util.Set;
- import org.apache.hadoop.util.ReflectionUtils;
- /**
- * A Writable Map.
- */
- public class MapWritable extends AbstractMapWritable
- implements Map<Writable, Writable> {
- private Map<Writable, Writable> instance;
-
- /** Default constructor. */
- public MapWritable() {
- super();
- this.instance = new HashMap<Writable, Writable>();
- }
-
- /**
- * Copy constructor.
- *
- * @param other the map to copy from
- */
- public MapWritable(MapWritable other) {
- this();
- copy(other);
- }
-
- /** {@inheritDoc} */
- public void clear() {
- instance.clear();
- }
- /** {@inheritDoc} */
- public boolean containsKey(Object key) {
- return instance.containsKey(key);
- }
- /** {@inheritDoc} */
- public boolean containsValue(Object value) {
- return instance.containsValue(value);
- }
- /** {@inheritDoc} */
- public Set<Map.Entry<Writable, Writable>> entrySet() {
- return instance.entrySet();
- }
- /** {@inheritDoc} */
- public Writable get(Object key) {
- return instance.get(key);
- }
-
- /** {@inheritDoc} */
- public boolean isEmpty() {
- return instance.isEmpty();
- }
- /** {@inheritDoc} */
- public Set<Writable> keySet() {
- return instance.keySet();
- }
- /** {@inheritDoc} */
- @SuppressWarnings("unchecked")
- public Writable put(Writable key, Writable value) {
- addToMap(key.getClass());
- addToMap(value.getClass());
- return instance.put(key, value);
- }
- /** {@inheritDoc} */
- public void putAll(Map<? extends Writable, ? extends Writable> t) {
- for (Map.Entry<? extends Writable, ? extends Writable> e: t.entrySet()) {
- put(e.getKey(), e.getValue());
- }
- }
- /** {@inheritDoc} */
- public Writable remove(Object key) {
- return instance.remove(key);
- }
- /** {@inheritDoc} */
- public int size() {
- return instance.size();
- }
- /** {@inheritDoc} */
- public Collection<Writable> values() {
- return instance.values();
- }
-
- // Writable
-
- /** {@inheritDoc} */
- @Override
- public void write(DataOutput out) throws IOException {
- super.write(out);
-
- // Write out the number of entries in the map
-
- out.writeInt(instance.size());
- // Then write out each key/value pair
-
- for (Map.Entry<Writable, Writable> e: instance.entrySet()) {
- out.writeByte(getId(e.getKey().getClass()));
- e.getKey().write(out);
- out.writeByte(getId(e.getValue().getClass()));
- e.getValue().write(out);
- }
- }
- /** {@inheritDoc} */
- @SuppressWarnings("unchecked")
- @Override
- public void readFields(DataInput in) throws IOException {
- super.readFields(in);
-
- // First clear the map. Otherwise we will just accumulate
- // entries every time this method is called.
- this.instance.clear();
-
- // Read the number of entries in the map
-
- int entries = in.readInt();
-
- // Then read each key/value pair
-
- for (int i = 0; i < entries; i++) {
- Writable key = (Writable) ReflectionUtils.newInstance(getClass(
- in.readByte()), getConf());
-
- key.readFields(in);
-
- Writable value = (Writable) ReflectionUtils.newInstance(getClass(
- in.readByte()), getConf());
-
- value.readFields(in);
- instance.put(key, value);
- }
- }
- }