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Java > Open Source Codes > javassist > LoaderClassPath


1 /*
2  * Javassist, a Java-bytecode translator toolkit.
3  * Copyright (C) 1999-2005 Shigeru Chiba. All Rights Reserved.
4  *
5  * The contents of this file are subject to the Mozilla Public License Version
6  * 1.1 (the "License"); you may not use this file except in compliance with
7  * the License. Alternatively, the contents of this file may be used under
8  * the terms of the GNU Lesser General Public License Version 2.1 or later.
9  *
10  * Software distributed under the License is distributed on an "AS IS" basis,
11  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
12  * for the specific language governing rights and limitations under the
13  * License.
14  */
15
16 package javassist;
17
18 import java.io.InputStream JavaDoc;
19 import java.net.URL JavaDoc;
20 import java.lang.ref.WeakReference JavaDoc;
21
22 /**
23  * A class search-path representing a class loader.
24  *
25  * <p>It is used for obtaining a class file from the given
26  * class loader by <code>getResourceAsStream()</code>.
27  * The <code>LoaderClassPath</code> refers to the class loader through
28  * <code>WeakReference</code>. If the class loader is garbage collected,
29  * the other search pathes are examined.
30  *
31  * <p>The given class loader must have both <code>getResourceAsStream()</code>
32  * and <code>getResource()</code>.
33  *
34  * @author <a HREF="mailto:bill@jboss.org">Bill Burke</a>
35  * @author Shigeru Chiba
36  *
37  * @see ClassPool#insertClassPath(ClassPath)
38  * @see ClassPool#appendClassPath(ClassPath)
39  * @see ClassClassPath
40  */
41 public class LoaderClassPath implements ClassPath {
42     private WeakReference JavaDoc clref;
43
44     /**
45      * Creates a search path representing a class loader.
46      */
47     public LoaderClassPath(ClassLoader JavaDoc cl) {
48         clref = new WeakReference JavaDoc(cl);
49     }
50
51     public String JavaDoc toString() {
52         Object JavaDoc cl = null;
53         if (clref != null)
54             cl = clref.get();
55
56         return cl == null ? "<null>" : cl.toString();
57     }
58
59     /**
60      * Obtains a class file from the class loader.
61      * This method calls <code>getResourceAsStream(String)</code>
62      * on the class loader.
63      */
64     public InputStream JavaDoc openClassfile(String JavaDoc classname) {
65         String JavaDoc cname = classname.replace('.', '/') + ".class";
66         ClassLoader JavaDoc cl = (ClassLoader JavaDoc)clref.get();
67         if (cl == null)
68             return null; // not found
69 else
70             return cl.getResourceAsStream(cname);
71     }
72
73     /**
74      * Obtains the URL of the specified class file.
75      * This method calls <code>getResource(String)</code>
76      * on the class loader.
77      *
78      * @return null if the class file could not be found.
79      */
80     public URL JavaDoc find(String JavaDoc classname) {
81         String JavaDoc cname = classname.replace('.', '/') + ".class";
82         ClassLoader JavaDoc cl = (ClassLoader JavaDoc)clref.get();
83         if (cl == null)
84             return null; // not found
85 else
86             return cl.getResource(cname);
87     }
88
89     /**
90      * Closes this class path.
91      */
92     public void close() {
93         clref = null;
94     }
95 }
96
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