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Java > Open Source Codes > net > sf > retrotranslator > transformer > JarClassLoader


1 /***
2  * Retrotranslator: a Java bytecode transformer that translates Java classes
3  * compiled with JDK 5.0 into classes that can be run on JVM 1.4.
4  *
5  * Copyright (c) 2005 - 2007 Taras Puchko
6  * 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  * 1. Redistributions of source code must retain the above copyright
12  * notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  * notice, this list of conditions and the following disclaimer in the
15  * documentation and/or other materials provided with the distribution.
16  * 3. Neither the name of the copyright holders nor the names of its
17  * contributors may be used to endorse or promote products derived from
18  * this software without specific prior written permission.
19  *
20  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
21  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
24  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
25  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
26  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
27  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
28  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
29  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
30  * THE POSSIBILITY OF SUCH DAMAGE.
31  */
32 package net.sf.retrotranslator.transformer;
33
34 import java.io.*;
35 import java.net.*;
36 import java.util.*;
37 import java.util.jar.*;
38
39 /**
40  * @author Taras Puchko
41  */
42 class JarClassLoader extends URLClassLoader {
43
44     private File file;
45
46     public JarClassLoader(File file, ClassLoader JavaDoc parent) throws IOException {
47         super(getClassPath(file), parent);
48         this.file = file;
49     }
50
51     public String JavaDoc getMainClass() throws IOException {
52         return getAttribute(file, Attributes.Name.MAIN_CLASS);
53     }
54
55     private static URL[] getClassPath(File file) throws IOException {
56         Set<URL> urls = new LinkedHashSet<URL>();
57         addToPath(urls, file);
58         return urls.toArray(new URL[urls.size()]);
59     }
60
61     private static void addToPath(Set<URL> classPath, File file) throws IOException {
62         file = file.getCanonicalFile();
63         if (!file.exists()) return;
64         URL url = file.toURI().toURL();
65         if (classPath.contains(url)) return;
66         classPath.add(url);
67         String JavaDoc attribute = getAttribute(file, Attributes.Name.CLASS_PATH);
68         if (attribute != null) {
69             StringTokenizer tokenizer = new StringTokenizer(attribute);
70             while (tokenizer.hasMoreTokens()) {
71                 addToPath(classPath, new File(file.getParent(), tokenizer.nextToken()));
72             }
73         }
74     }
75
76     private static String JavaDoc getAttribute(File file, Attributes.Name name) {
77         Attributes attributes = getAttributes(file);
78         return attributes == null ? null : attributes.getValue(name);
79     }
80
81     private static Attributes getAttributes(File file) {
82         if (!file.isFile()) return null;
83         try {
84             JarFile jarFile = new JarFile(file);
85             try {
86                 return jarFile.getManifest().getMainAttributes();
87             } finally {
88                 jarFile.close();
89             }
90         } catch (IOException e) {
91             return null;
92         }
93     }
94 }
95
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