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.proxy2.impl;
19
20 import java.lang.ref.Reference;
21 import java.lang.ref.WeakReference;
22 import java.util.Arrays;
23 import java.util.HashMap;
24 import java.util.HashSet;
25 import java.util.Map;
26 import java.util.Set;
27 import java.util.WeakHashMap;
28
29 /**
30 * A cache for storing implementation classes for proxies based on a specific type of {@link ProxyClassGenerator}. A
31 * proxy class cache ensures that there is only one class for every {@link ProxyClassGenerator}/{@link ClassLoader}
32 * /proxy class array combination.
33 *
34 * @since 1.0
35 */
36 public class ProxyClassCache
37 {
38
39 //******************************************************************************************************************
40 // Fields
41 //******************************************************************************************************************
42
43 private final Map<ClassLoader, Map<Set<Class<?>>, WeakReference<Class<?>>>> loaderToClassCache
44 = new WeakHashMap<ClassLoader, Map<Set<Class<?>>, WeakReference<Class<?>>>>();
45 private final ProxyClassGenerator proxyClassGenerator;
46
47 //******************************************************************************************************************
48 // Constructors
49 //******************************************************************************************************************
50
51 /**
52 * Create a new ProxyClassCache instance.
53 *
54 * @param proxyClassGenerator
55 */
56 public ProxyClassCache(ProxyClassGenerator proxyClassGenerator)
57 {
58 this.proxyClassGenerator = proxyClassGenerator;
59 }
60
61 //******************************************************************************************************************
62 // Other Methods
63 //******************************************************************************************************************
64
65 private Map<Set<Class<?>>, WeakReference<Class<?>>> getClassCache(ClassLoader classLoader)
66 {
67 Map<Set<Class<?>>, WeakReference<Class<?>>> cache = loaderToClassCache.get(classLoader);
68 if (cache == null)
69 {
70 cache = new HashMap<Set<Class<?>>, WeakReference<Class<?>>>();
71 loaderToClassCache.put(classLoader, cache);
72 }
73 return cache;
74 }
75
76 private Set<Class<?>> toClassCacheKey(Class<?>[] proxyClasses)
77 {
78 return new HashSet<Class<?>>(Arrays.asList(proxyClasses));
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
86 * the classloader
87 * @param proxyClasses
88 * the proxy classes
89 * @return the proxy class generated by the {@link ProxyClassGenerator} using the specified {@link ClassLoader} and
90 * array of proxy classes
91 */
92 public synchronized Class<?> getProxyClass(ClassLoader classLoader, Class<?>[] proxyClasses)
93 {
94 final Map<Set<Class<?>>, WeakReference<Class<?>>> classCache = getClassCache(classLoader);
95 final Set<Class<?>> key = toClassCacheKey(proxyClasses);
96 Class<?> proxyClass;
97 Reference<Class<?>> proxyClassReference = classCache.get(key);
98 if (proxyClassReference == null)
99 {
100 proxyClass = proxyClassGenerator.generateProxyClass(classLoader, proxyClasses);
101 classCache.put(key, new WeakReference<Class<?>>(proxyClass));
102 }
103 else
104 {
105 synchronized (proxyClassReference)
106 {
107 proxyClass = proxyClassReference.get();
108 if (proxyClass == null)
109 {
110 proxyClass = proxyClassGenerator.generateProxyClass(classLoader, proxyClasses);
111 classCache.put(key, new WeakReference<Class<?>>(proxyClass));
112 }
113 }
114 }
115 return proxyClass;
116 }
117 }