1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.commons.proxy.factory.util;
19
20 import java.lang.ref.WeakReference;
21 import java.util.HashMap;
22 import java.util.Map;
23 import java.util.WeakHashMap;
24
25 /**
26 * A cache for storing implementation classes for proxies based on a specific type of {@link ProxyClassGenerator}. A
27 * proxy class cache ensures that there is only one class for every
28 * {@link ProxyClassGenerator}/{@link ClassLoader}/proxy class array combination.
29 *
30 * @author James Carman
31 * @since 1.0
32 */
33 public class ProxyClassCache
34 {
35 //----------------------------------------------------------------------------------------------------------------------
36 // Fields
37 //----------------------------------------------------------------------------------------------------------------------
38
39 private final Map loaderToClassCache = new WeakHashMap();
40 private final ProxyClassGenerator proxyClassGenerator;
41
42 //----------------------------------------------------------------------------------------------------------------------
43 // Constructors
44 //----------------------------------------------------------------------------------------------------------------------
45
46 public ProxyClassCache( ProxyClassGenerator proxyClassGenerator )
47 {
48 this.proxyClassGenerator = proxyClassGenerator;
49 }
50
51 //----------------------------------------------------------------------------------------------------------------------
52 // Other Methods
53 //----------------------------------------------------------------------------------------------------------------------
54
55 /**
56 * Returns the proxy class generated by the {@link ProxyClassGenerator} using the specified {@link ClassLoader} and
57 * array of proxy classes.
58 *
59 * @param classLoader the classloader
60 * @param proxyClasses the proxy classes
61 * @return the proxy class generated by the {@link ProxyClassGenerator} using the specified {@link ClassLoader} and
62 * array of proxy classes
63 */
64 public synchronized Class getProxyClass( ClassLoader classLoader, Class[] proxyClasses )
65 {
66 final Map classCache = getClassCache( classLoader );
67 final String key = toClassCacheKey( proxyClasses );
68 Class proxyClass;
69 WeakReference proxyClassReference = ( WeakReference )classCache.get( key );
70 if( proxyClassReference == null )
71 {
72 proxyClass = proxyClassGenerator.generateProxyClass( classLoader, proxyClasses );
73 classCache.put( key, new WeakReference( proxyClass ) );
74 }
75 else
76 {
77 synchronized( proxyClassReference )
78 {
79 proxyClass = ( Class )proxyClassReference.get();
80 if( proxyClass == null )
81 {
82 proxyClass = proxyClassGenerator.generateProxyClass( classLoader, proxyClasses );
83 classCache.put( key, new WeakReference( proxyClass ) );
84 }
85 }
86 }
87 return proxyClass;
88 }
89
90 private Map getClassCache( ClassLoader classLoader )
91 {
92 Map cache = ( Map )loaderToClassCache.get( classLoader );
93 if( cache == null )
94 {
95 cache = new HashMap();
96 loaderToClassCache.put( classLoader, cache );
97 }
98 return cache;
99 }
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