kafka CopyOnWriteMap 源码
kafka CopyOnWriteMap 代码
文件路径:/clients/src/main/java/org/apache/kafka/common/utils/CopyOnWriteMap.java
/*
* 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.kafka.common.utils;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentMap;
/**
* A simple read-optimized map implementation that synchronizes only writes and does a full copy on each modification
*/
public class CopyOnWriteMap<K, V> implements ConcurrentMap<K, V> {
private volatile Map<K, V> map;
public CopyOnWriteMap() {
this.map = Collections.emptyMap();
}
public CopyOnWriteMap(Map<K, V> map) {
this.map = Collections.unmodifiableMap(map);
}
@Override
public boolean containsKey(Object k) {
return map.containsKey(k);
}
@Override
public boolean containsValue(Object v) {
return map.containsValue(v);
}
@Override
public Set<java.util.Map.Entry<K, V>> entrySet() {
return map.entrySet();
}
@Override
public V get(Object k) {
return map.get(k);
}
@Override
public boolean isEmpty() {
return map.isEmpty();
}
@Override
public Set<K> keySet() {
return map.keySet();
}
@Override
public int size() {
return map.size();
}
@Override
public Collection<V> values() {
return map.values();
}
@Override
public synchronized void clear() {
this.map = Collections.emptyMap();
}
@Override
public synchronized V put(K k, V v) {
Map<K, V> copy = new HashMap<K, V>(this.map);
V prev = copy.put(k, v);
this.map = Collections.unmodifiableMap(copy);
return prev;
}
@Override
public synchronized void putAll(Map<? extends K, ? extends V> entries) {
Map<K, V> copy = new HashMap<K, V>(this.map);
copy.putAll(entries);
this.map = Collections.unmodifiableMap(copy);
}
@Override
public synchronized V remove(Object key) {
Map<K, V> copy = new HashMap<K, V>(this.map);
V prev = copy.remove(key);
this.map = Collections.unmodifiableMap(copy);
return prev;
}
@Override
public synchronized V putIfAbsent(K k, V v) {
if (!containsKey(k))
return put(k, v);
else
return get(k);
}
@Override
public synchronized boolean remove(Object k, Object v) {
if (containsKey(k) && get(k).equals(v)) {
remove(k);
return true;
} else {
return false;
}
}
@Override
public synchronized boolean replace(K k, V original, V replacement) {
if (containsKey(k) && get(k).equals(original)) {
put(k, replacement);
return true;
} else {
return false;
}
}
@Override
public synchronized V replace(K k, V v) {
if (containsKey(k)) {
return put(k, v);
} else {
return null;
}
}
}
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