1 package org.apache.maven.shared.runtime;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 import java.io.IOException;
23 import java.net.URL;
24 import java.net.URLClassLoader;
25 import java.util.Enumeration;
26
27 /**
28 * A parent- or child-delegating class loader for use by tests.
29 *
30 * @author <a href="mailto:markh@apache.org">Mark Hobson</a>
31 * @version $Id: DelegatingClassLoader.java 831910 2009-11-02 15:05:33Z markh $
32 */
33 public class DelegatingClassLoader extends URLClassLoader
34 {
35 // fields -----------------------------------------------------------------
36
37 private final boolean childDelegating;
38
39 // constructors -----------------------------------------------------------
40
41 public DelegatingClassLoader( URL[] urls )
42 {
43 super( urls );
44
45 childDelegating = false;
46 }
47
48 public DelegatingClassLoader( URL[] urls, ClassLoader parent )
49 {
50 this( urls, parent, false );
51 }
52
53 public DelegatingClassLoader( URL[] urls, ClassLoader parent, boolean childDelegating )
54 {
55 super( urls, parent );
56
57 this.childDelegating = childDelegating;
58 }
59
60 // ClassLoader methods ----------------------------------------------------
61
62 /**
63 * {@inheritDoc}
64 */
65 @Override
66 public Class<?> loadClass( String name ) throws ClassNotFoundException
67 {
68 Class<?> klass;
69
70 if ( childDelegating )
71 {
72 klass = findLoadedClass( name );
73
74 if ( klass == null )
75 {
76 try
77 {
78 klass = findClass( name );
79 }
80 catch ( ClassNotFoundException exception )
81 {
82 if ( getParent() != null )
83 {
84 klass = getParent().loadClass( name );
85 }
86 }
87 }
88 }
89 else
90 {
91 klass = super.loadClass( name );
92 }
93
94 return klass;
95 }
96
97 /**
98 * {@inheritDoc}
99 */
100 @Override
101 public URL getResource( String name )
102 {
103 URL url;
104
105 if ( childDelegating )
106 {
107 url = findResource( name );
108
109 if ( url == null && getParent() != null )
110 {
111 url = getParent().getResource( name );
112 }
113 }
114 else
115 {
116 url = super.getResource( name );
117 }
118
119 return url;
120 }
121
122 /**
123 * {@inheritDoc}
124 */
125 @Override
126 public Enumeration<URL> getResources( String name ) throws IOException
127 {
128 Enumeration<URL> urls;
129
130 if ( childDelegating )
131 {
132 urls = findResources( name );
133
134 if ( getParent() != null )
135 {
136 Enumeration<URL> parentURLs = getParent().getResources( name );
137
138 urls = new CompositeEnumeration<URL>( urls, parentURLs );
139 }
140 }
141 else
142 {
143 urls = super.getResources( name );
144 }
145
146 return urls;
147 }
148 }