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 private Map getClassCache( ClassLoader classLoader )
56 {
57 Map cache = ( Map ) loaderToClassCache.get(classLoader);
58 if( cache == null )
59 {
60 cache = new HashMap();
61 loaderToClassCache.put(classLoader, cache);
62 }
63 return cache;
64 }
65
66 private String toClassCacheKey( Class[] proxyClasses )
67 {
68 final StringBuffer sb = new StringBuffer();
69 for( int i = 0; i < proxyClasses.length; i++ )
70 {
71 Class proxyInterface = proxyClasses[i];
72 sb.append(proxyInterface.getName());
73 if( i != proxyClasses.length - 1 )
74 {
75 sb.append(",");
76 }
77 }
78 return sb.toString();
79 }
80
81 /**
82 * Returns the proxy class generated by the {@link ProxyClassGenerator} using the specified {@link ClassLoader} and
83 * array of proxy classes.
84 *
85 * @param classLoader the classloader
86 * @param proxyClasses the proxy classes
87 * @return the proxy class generated by the {@link ProxyClassGenerator} using the specified {@link ClassLoader} and
88 * array of proxy classes
89 */
90 public synchronized Class getProxyClass( ClassLoader classLoader, Class[] proxyClasses )
91 {
92 final Map classCache = getClassCache(classLoader);
93 final String key = toClassCacheKey(proxyClasses);
94 Class proxyClass;
95 WeakReference proxyClassReference = ( WeakReference ) classCache.get(key);
96 if( proxyClassReference == null )
97 {
98 proxyClass = proxyClassGenerator.generateProxyClass(classLoader, proxyClasses);
99 classCache.put(key, new WeakReference(proxyClass));
100 }
101 else
102 {
103 synchronized( proxyClassReference )
104 {
105 proxyClass = ( Class ) proxyClassReference.get();
106 if( proxyClass == null )
107 {
108 proxyClass = proxyClassGenerator.generateProxyClass(classLoader, proxyClasses);
109 classCache.put(key, new WeakReference(proxyClass));
110 }
111 }
112 }
113 return proxyClass;
114 }
115 }
116