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