001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 018 package org.apache.commons.proxy.factory.util; 019 020 import java.lang.ref.WeakReference; 021 import java.util.HashMap; 022 import java.util.Map; 023 import java.util.WeakHashMap; 024 025 /** 026 * A cache for storing implementation classes for proxies based on a specific type of {@link ProxyClassGenerator}. A 027 * proxy class cache ensures that there is only one class for every 028 * {@link ProxyClassGenerator}/{@link ClassLoader}/proxy class array combination. 029 * 030 * @author James Carman 031 * @since 1.0 032 */ 033 public class ProxyClassCache 034 { 035 //---------------------------------------------------------------------------------------------------------------------- 036 // Fields 037 //---------------------------------------------------------------------------------------------------------------------- 038 039 private final Map loaderToClassCache = new WeakHashMap(); 040 private final ProxyClassGenerator proxyClassGenerator; 041 042 //---------------------------------------------------------------------------------------------------------------------- 043 // Constructors 044 //---------------------------------------------------------------------------------------------------------------------- 045 046 public ProxyClassCache( ProxyClassGenerator proxyClassGenerator ) 047 { 048 this.proxyClassGenerator = proxyClassGenerator; 049 } 050 051 //---------------------------------------------------------------------------------------------------------------------- 052 // Other Methods 053 //---------------------------------------------------------------------------------------------------------------------- 054 055 /** 056 * Returns the proxy class generated by the {@link ProxyClassGenerator} using the specified {@link ClassLoader} and 057 * array of proxy classes. 058 * 059 * @param classLoader the classloader 060 * @param proxyClasses the proxy classes 061 * @return the proxy class generated by the {@link ProxyClassGenerator} using the specified {@link ClassLoader} and 062 * array of proxy classes 063 */ 064 public synchronized Class getProxyClass( ClassLoader classLoader, Class[] proxyClasses ) 065 { 066 final Map classCache = getClassCache( classLoader ); 067 final String key = toClassCacheKey( proxyClasses ); 068 Class proxyClass; 069 WeakReference proxyClassReference = ( WeakReference )classCache.get( key ); 070 if( proxyClassReference == null ) 071 { 072 proxyClass = proxyClassGenerator.generateProxyClass( classLoader, proxyClasses ); 073 classCache.put( key, new WeakReference( proxyClass ) ); 074 } 075 else 076 { 077 synchronized( proxyClassReference ) 078 { 079 proxyClass = ( Class )proxyClassReference.get(); 080 if( proxyClass == null ) 081 { 082 proxyClass = proxyClassGenerator.generateProxyClass( classLoader, proxyClasses ); 083 classCache.put( key, new WeakReference( proxyClass ) ); 084 } 085 } 086 } 087 return proxyClass; 088 } 089 090 private Map getClassCache( ClassLoader classLoader ) 091 { 092 Map cache = ( Map )loaderToClassCache.get( classLoader ); 093 if( cache == null ) 094 { 095 cache = new HashMap(); 096 loaderToClassCache.put( classLoader, cache ); 097 } 098 return cache; 099 } 100 101 private String toClassCacheKey( Class[] proxyClasses ) 102 { 103 final StringBuffer sb = new StringBuffer(); 104 for( int i = 0; i < proxyClasses.length; i++ ) 105 { 106 Class proxyInterface = proxyClasses[i]; 107 sb.append( proxyInterface.getName() ); 108 if( i != proxyClasses.length - 1 ) 109 { 110 sb.append( "," ); 111 } 112 } 113 return sb.toString(); 114 } 115 } 116