KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > com > go > trove > util > DelegateClassLoader


1 /* ====================================================================
2  * Trove - Copyright (c) 1997-2000 Walt Disney Internet Group
3  * ====================================================================
4  * The Tea Software License, Version 1.1
5  *
6  * Copyright (c) 2000 Walt Disney Internet Group. All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  *
12  * 1. Redistributions of source code must retain the above copyright
13  * notice, this list of conditions and the following disclaimer.
14  *
15  * 2. Redistributions in binary form must reproduce the above copyright
16  * notice, this list of conditions and the following disclaimer in
17  * the documentation and/or other materials provided with the
18  * distribution.
19  *
20  * 3. The end-user documentation included with the redistribution,
21  * if any, must include the following acknowledgment:
22  * "This product includes software developed by the
23  * Walt Disney Internet Group (http://opensource.go.com/)."
24  * Alternately, this acknowledgment may appear in the software itself,
25  * if and wherever such third-party acknowledgments normally appear.
26  *
27  * 4. The names "Tea", "TeaServlet", "Kettle", "Trove" and "BeanDoc" must
28  * not be used to endorse or promote products derived from this
29  * software without prior written permission. For written
30  * permission, please contact opensource@dig.com.
31  *
32  * 5. Products derived from this software may not be called "Tea",
33  * "TeaServlet", "Kettle" or "Trove", nor may "Tea", "TeaServlet",
34  * "Kettle", "Trove" or "BeanDoc" appear in their name, without prior
35  * written permission of the Walt Disney Internet Group.
36  *
37  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
38  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
39  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
40  * DISCLAIMED. IN NO EVENT SHALL THE WALT DISNEY INTERNET GROUP OR ITS
41  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
42  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
43  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
44  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
45  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
46  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
47  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
48  * ====================================================================
49  *
50  * For more information about Tea, please see http://opensource.go.com/.
51  */
52
53 package com.go.trove.util;
54 import java.io.InputStream JavaDoc;
55 import java.net.URL JavaDoc;
56
57 /******************************************************************************
58  * ClassLoader that delegates class loading requests if the parent ClassLoader
59  * (and its ancestors) can't fulfill the request. Class loading requests are
60  * handed off to scouts, which are called upon in sequence to find the class,
61  * until the class is found. If neither the parent or scouts can find a
62  * requested class, a normal ClassNotFoundException is thrown.
63  *
64  * @author Brian S O'Neill
65  * @version
66  * <!--$$Revision:--> 14 <!-- $-->, <!--$$JustDate:--> 7/27/01 <!-- $-->
67  */
68 public class DelegateClassLoader extends ClassLoader JavaDoc {
69     private ClassLoader JavaDoc[] mScouts;
70
71     /**
72      * @param parent ClassLoader that gets first chance to load a class
73      * @param scouts ClassLoaders that get next chances to load a class, if the
74      * parent couldn't find it.
75      */
76     public DelegateClassLoader(ClassLoader JavaDoc parent, ClassLoader JavaDoc[] scouts) {
77         super(parent);
78         mScouts = (ClassLoader JavaDoc[])scouts.clone();
79    }
80
81     /**
82      * @param scouts ClassLoaders that get next chances to load a class, if the
83      * parent couldn't find it.
84      * @deprecated Actual parent ClassLoader must always be provided to prevent
85      * unexpected behavior.
86      */
87     public DelegateClassLoader(ClassLoader JavaDoc[] scouts) {
88         super();
89         mScouts = (ClassLoader JavaDoc[])scouts.clone();
90     }
91
92     protected synchronized Class JavaDoc findClass(String JavaDoc name)
93         throws ClassNotFoundException JavaDoc
94     {
95         for (int i=0; i<mScouts.length; i++) {
96             try {
97                 return mScouts[i].loadClass(name);
98             }
99             catch (ClassNotFoundException JavaDoc e) {
100             }
101         }
102         throw new ClassNotFoundException JavaDoc(name);
103     }
104     
105     protected URL JavaDoc findResource(String JavaDoc name) {
106         URL JavaDoc resource = null;
107
108         try {
109             for (int i=0; i<mScouts.length; i++) {
110                 resource = mScouts[i].getResource(name);
111                 if (resource != null) {
112                     return resource;
113                 }
114             }
115         }
116         catch (Exception JavaDoc e) {
117             e.printStackTrace();
118         }
119         return resource;
120     }
121 }
122
Popular Tags