org.springframework.util.CachingMapDecorator Maven / Gradle / Ivy
/*
* Copyright 2002-2009 the original author or authors.
*
* 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 org.springframework.util;
import java.io.Serializable;
import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.Map;
import java.util.Set;
import java.util.WeakHashMap;
/**
* A simple decorator for a Map, encapsulating the workflow for caching
* expensive values in a target Map. Supports caching weak or strong keys.
*
* This class is an abstract template. Caching Map implementations
* should subclass and override the create(key)
method which
* encapsulates expensive creation of a new object.
*
* @author Keith Donald
* @author Juergen Hoeller
* @since 1.2.2
*/
public abstract class CachingMapDecorator implements Map, Serializable {
private static Object NULL_VALUE = new Object();
private final Map targetMap;
private final boolean synchronize;
private final boolean weak;
/**
* Create a CachingMapDecorator with strong keys,
* using an underlying synchronized Map.
*/
public CachingMapDecorator() {
this(false);
}
/**
* Create a CachingMapDecorator,
* using an underlying synchronized Map.
* @param weak whether to use weak references for keys and values
*/
public CachingMapDecorator(boolean weak) {
Map internalMap = (weak ? new WeakHashMap() : new HashMap());
this.targetMap = Collections.synchronizedMap(internalMap);
this.synchronize = true;
this.weak = weak;
}
/**
* Create a CachingMapDecorator with initial size,
* using an underlying synchronized Map.
* @param weak whether to use weak references for keys and values
* @param size the initial cache size
*/
public CachingMapDecorator(boolean weak, int size) {
Map internalMap = weak ? new WeakHashMap (size) : new HashMap(size);
this.targetMap = Collections.synchronizedMap(internalMap);
this.synchronize = true;
this.weak = weak;
}
/**
* Create a CachingMapDecorator for the given Map.
* The passed-in Map won't get synchronized explicitly,
* so make sure to pass in a properly synchronized Map, if desired.
* @param targetMap the Map to decorate
*/
public CachingMapDecorator(Map targetMap) {
this(targetMap, false, false);
}
/**
* Create a CachingMapDecorator for the given Map.
* The passed-in Map won't get synchronized explicitly unless
* you specify "synchronize" as "true".
* @param targetMap the Map to decorate
* @param synchronize whether to synchronize on the given Map
* @param weak whether to use weak references for values
*/
@SuppressWarnings("unchecked")
public CachingMapDecorator(Map targetMap, boolean synchronize, boolean weak) {
Assert.notNull(targetMap, "'targetMap' must not be null");
this.targetMap = (Map) (synchronize ? Collections.synchronizedMap(targetMap) : targetMap);
this.synchronize = synchronize;
this.weak = weak;
}
public int size() {
return this.targetMap.size();
}
public boolean isEmpty() {
return this.targetMap.isEmpty();
}
public boolean containsKey(Object key) {
return this.targetMap.containsKey(key);
}
public boolean containsValue(Object value) {
Object valueToCheck = (value != null ? value : NULL_VALUE);
if (this.synchronize) {
synchronized (this.targetMap) {
return containsValueOrReference(valueToCheck);
}
}
else {
return containsValueOrReference(valueToCheck);
}
}
private boolean containsValueOrReference(Object value) {
if (this.targetMap.containsValue(value)) {
return true;
}
for (Object mapVal : this.targetMap.values()) {
if (mapVal instanceof Reference && value.equals(((Reference) mapVal).get())) {
return true;
}
}
return false;
}
public V remove(Object key) {
return unwrapReturnValue(this.targetMap.remove(key));
}
@SuppressWarnings("unchecked")
private V unwrapReturnValue(Object value) {
Object returnValue = value;
if (returnValue instanceof Reference) {
returnValue = ((Reference) returnValue).get();
}
return (returnValue == NULL_VALUE ? null : (V) returnValue);
}
public void putAll(Map map) {
this.targetMap.putAll(map);
}
public void clear() {
this.targetMap.clear();
}
public Set keySet() {
if (this.synchronize) {
synchronized (this.targetMap) {
return new LinkedHashSet(this.targetMap.keySet());
}
}
else {
return new LinkedHashSet(this.targetMap.keySet());
}
}
public Collection values() {
if (this.synchronize) {
synchronized (this.targetMap) {
return valuesCopy();
}
}
else {
return valuesCopy();
}
}
@SuppressWarnings("unchecked")
private Collection valuesCopy() {
LinkedList values = new LinkedList();
for (Iterator