/* | |
* 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.commons.proxy.impl; | |
import java.lang.ref.WeakReference; | |
import java.util.HashMap; | |
import java.util.Map; | |
import java.util.WeakHashMap; | |
/** | |
* A cache for storing implementation classes for proxies based on a specific type of {@link ProxyClassGenerator}. A | |
* proxy class cache ensures that there is only one class for every | |
* {@link ProxyClassGenerator}/{@link ClassLoader}/proxy class array combination. | |
* | |
* @author James Carman | |
* @since 1.0 | |
*/ | |
public class ProxyClassCache | |
{ | |
//********************************************************************************************************************** | |
// Fields | |
//********************************************************************************************************************** | |
private final Map loaderToClassCache = new WeakHashMap(); | |
private final ProxyClassGenerator proxyClassGenerator; | |
//********************************************************************************************************************** | |
// Constructors | |
//********************************************************************************************************************** | |
public ProxyClassCache( ProxyClassGenerator proxyClassGenerator ) | |
{ | |
this.proxyClassGenerator = proxyClassGenerator; | |
} | |
//********************************************************************************************************************** | |
// Other Methods | |
//********************************************************************************************************************** | |
private Map getClassCache( ClassLoader classLoader ) | |
{ | |
Map cache = ( Map ) loaderToClassCache.get(classLoader); | |
if( cache == null ) | |
{ | |
cache = new HashMap(); | |
loaderToClassCache.put(classLoader, cache); | |
} | |
return cache; | |
} | |
private String toClassCacheKey( Class[] proxyClasses ) | |
{ | |
final StringBuffer sb = new StringBuffer(); | |
for( int i = 0; i < proxyClasses.length; i++ ) | |
{ | |
Class proxyInterface = proxyClasses[i]; | |
sb.append(proxyInterface.getName()); | |
if( i != proxyClasses.length - 1 ) | |
{ | |
sb.append(","); | |
} | |
} | |
return sb.toString(); | |
} | |
/** | |
* Returns the proxy class generated by the {@link ProxyClassGenerator} using the specified {@link ClassLoader} and | |
* array of proxy classes. | |
* | |
* @param classLoader the classloader | |
* @param proxyClasses the proxy classes | |
* @return the proxy class generated by the {@link ProxyClassGenerator} using the specified {@link ClassLoader} and | |
* array of proxy classes | |
*/ | |
public synchronized Class getProxyClass( ClassLoader classLoader, Class[] proxyClasses ) | |
{ | |
final Map classCache = getClassCache(classLoader); | |
final String key = toClassCacheKey(proxyClasses); | |
Class proxyClass; | |
WeakReference proxyClassReference = ( WeakReference ) classCache.get(key); | |
if( proxyClassReference == null ) | |
{ | |
proxyClass = proxyClassGenerator.generateProxyClass(classLoader, proxyClasses); | |
classCache.put(key, new WeakReference(proxyClass)); | |
} | |
else | |
{ | |
synchronized( proxyClassReference ) | |
{ | |
proxyClass = ( Class ) proxyClassReference.get(); | |
if( proxyClass == null ) | |
{ | |
proxyClass = proxyClassGenerator.generateProxyClass(classLoader, proxyClasses); | |
classCache.put(key, new WeakReference(proxyClass)); | |
} | |
} | |
} | |
return proxyClass; | |
} | |
} |