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.interceptor;
19
20 import org.apache.commons.proxy.ObjectProvider;
21 import org.apache.commons.proxy.ProxyFactory;
22 import org.apache.commons.proxy.ProxyUtils;
23 import org.apache.commons.proxy.Interceptor;
24
25 /**
26 * An <code>InterceptorChain</code> assists with creating proxies which go through a series of
27 * {@link Interceptor interceptors}.
28 *
29 * <pre>
30 * MyServiceInterface serviceImpl = ...;
31 * ProxyFactory factory = ...;
32 * Interceptor[] interceptors = ...;
33 * InterceptorChain chain = new InterceptorChain(interceptors);
34 * ObjectProvider provider = chain.createProxyProvider(factory, serviceImpl);
35 * MyServiceInterface serviceProxy = ( MyServiceInterface )provider.getObject();
36 * serviceProxy.someServiceMethod(...); // This will go through the interceptors!
37 * </pre>
38 *
39 * @author James Carman
40 * @since 1.0
41 */
42 public class InterceptorChain
43 {
44 //----------------------------------------------------------------------------------------------------------------------
45 // Fields
46 //----------------------------------------------------------------------------------------------------------------------
47 private final Interceptor[] interceptors;
48
49 //----------------------------------------------------------------------------------------------------------------------
50 // Constructors
51 //----------------------------------------------------------------------------------------------------------------------
52
53 public InterceptorChain( Interceptor[] interceptors )
54 {
55 this.interceptors = interceptors;
56 }
57
58 //----------------------------------------------------------------------------------------------------------------------
59 // Other Methods
60 //----------------------------------------------------------------------------------------------------------------------
61
62 private Object createProxy( ProxyFactory proxyFactory, ClassLoader classLoader, Object terminus,
63 Class[] proxyClasses )
64 {
65 Object currentTarget = terminus;
66 for( int i = interceptors.length - 1; i >= 0; --i )
67 {
68 currentTarget = proxyFactory
69 .createInterceptorProxy( classLoader, currentTarget, interceptors[i], proxyClasses );
70 }
71 return currentTarget;
72 }
73
74 /**
75 * Creates an {@link ObjectProvider} which will return a proxy that sends method invocations through this
76 * chain of interceptors and ultimately arrive at the supplied terminus object. The proxy will support all
77 * interfaces implemented by the terminus object. The thread context classloader will be used to generate the
78 * proxy class.
79 *
80 * @param proxyFactory the {@link ProxyFactory} to use to create the proxy
81 * @param terminus the terminus
82 * @return an {@link ObjectProvider} which will return a proxy that sends method invocations through this
83 * chain of interceptors and ultimately arrive at the supplied terminus object
84 */
85 public ObjectProvider createProxyProvider( ProxyFactory proxyFactory, Object terminus )
86 {
87 return createProxyProvider( proxyFactory, terminus, null );
88 }
89
90 /**
91 * Creates an {@link ObjectProvider} which will return a proxy that sends method invocations through this
92 * chain of interceptors and ultimately arrive at the supplied terminus object. The proxy will support only
93 * the specified interfaces/classes. The thread context classloader will be used to generate the
94 * proxy class.
95 *
96 * @param proxyFactory the {@link ProxyFactory} to use to create the proxy
97 * @param terminus the terminus
98 * @param proxyClasses the interfaces to support
99 * @return an {@link ObjectProvider} which will return a proxy that sends method invocations through this
100 * chain of interceptors and ultimately arrive at the supplied terminus object
101 */
102 public ObjectProvider createProxyProvider( ProxyFactory proxyFactory, Object terminus, Class[] proxyClasses )
103 {
104 return createProxyProvider( proxyFactory, Thread.currentThread().getContextClassLoader(), terminus,
105 proxyClasses );
106 }
107
108 /**
109 * Creates an {@link ObjectProvider} which will return a proxy that sends method invocations through this
110 * chain of interceptors and ultimately arrive at the supplied terminus object. The proxy will support only
111 * the specified interfaces/classes. The specified classloader will be used to generate the
112 * proxy class.
113 *
114 * @param proxyFactory the {@link ProxyFactory} to use to create the proxy
115 * @param classLoader the classloader to be used to generate the proxy class
116 * @param terminus the terminus
117 * @param proxyClasses the interfaces to support
118 * @return an {@link ObjectProvider} which will return a proxy that sends method invocations through this
119 * chain of interceptors and ultimately arrive at the supplied terminus object
120 */
121 public ObjectProvider createProxyProvider( ProxyFactory proxyFactory, ClassLoader classLoader, Object terminus,
122 Class[] proxyClasses )
123 {
124 if( proxyClasses == null || proxyClasses.length == 0 )
125 {
126 proxyClasses = ProxyUtils.getAllInterfaces( terminus.getClass() );
127 }
128 return new ProxyObjectProvider( proxyFactory, classLoader, terminus, proxyClasses );
129 }
130
131 //----------------------------------------------------------------------------------------------------------------------
132 // Inner Classes
133 //----------------------------------------------------------------------------------------------------------------------
134
135 private class ProxyObjectProvider implements ObjectProvider
136 {
137 private final ClassLoader classLoader;
138 private final Class[] proxyClasses;
139 private final Object terminus;
140 private final ProxyFactory proxyFactory;
141
142 public ProxyObjectProvider( ProxyFactory proxyFactory, ClassLoader classLoader, Object terminus,
143 Class[] proxyClasses )
144 {
145 this.classLoader = classLoader;
146 this.proxyClasses = proxyClasses;
147 this.terminus = terminus;
148 this.proxyFactory = proxyFactory;
149 }
150
151 public Object getObject()
152 {
153 return createProxy( proxyFactory, classLoader, terminus, proxyClasses );
154 }
155 }
156 }
157