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Java > Open Source Codes > asm2 > MarkerClassLoader


1 /*
2  * Manage Java 5 annotations using ASM toolkit
3  * Copyright (c) 2004, Eugene Kuleshov
4  *
5  * This library is free software; you can redistribute it and/or
6  * modify it under the terms of the GNU Lesser General Public
7  * License as published by the Free Software Foundation; either
8  * version 2.1 of the License, or (at your option) any later version.
9  *
10  * This library is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13  * Lesser General Public License for more details.
14  *
15  * You should have received a copy of the GNU Lesser General Public
16  * License along with this library; if not, write to the Free Software
17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18  */
19
20 package asm2;
21
22 import java.io.PrintWriter JavaDoc;
23 import java.net.URL JavaDoc;
24
25 import org.objectweb.asm.ClassAdapter;
26 import org.objectweb.asm.ClassReader;
27 import org.objectweb.asm.ClassVisitor;
28 import org.objectweb.asm.ClassWriter;
29 import org.objectweb.asm.Constants;
30 import org.objectweb.asm.Type;
31 import org.objectweb.asm.attrs.Annotation;
32 import org.objectweb.asm.attrs.Attributes;
33 import org.objectweb.asm.attrs.RuntimeVisibleAnnotations;
34 import org.objectweb.asm.util.TraceClassVisitor;
35
36
37 public class MarkerClassLoader
38     extends ClassLoader JavaDoc {
39
40   private Class JavaDoc c;
41
42   public MarkerClassLoader( Class JavaDoc c) {
43     this.c = c;
44   }
45   
46   public Class JavaDoc loadClass( String JavaDoc name)
47         throws ClassNotFoundException JavaDoc {
48     String JavaDoc resourceName =
49         "/"+name.replace( '.', '/')+".class";
50     URL JavaDoc url = c.getResource( resourceName);
51     if( name.startsWith( "java") ||
52         name.equals(Marker.class.getName()) ||
53         url==null) {
54       return c.getClassLoader().loadClass( name);
55     }
56
57     ClassWriter cw = new ClassWriter(false);
58     try {
59       ClassReader cr =
60         new ClassReader(url.openStream());
61       cr.accept(new MarkerClassVisitor(cw),
62         Attributes.getDefaultAttributes(), false);
63       
64       byte[] b = cw.toByteArray();
65       return defineClass( name, b, 0, b.length);
66       
67     } catch( Exception JavaDoc ex) {
68       throw new ClassNotFoundException JavaDoc(
69           "Unable to load class "+name);
70     
71     }
72   }
73   
74   
75   public static class MarkerClassVisitor extends ClassAdapter {
76
77     public MarkerClassVisitor(ClassVisitor cv) {
78       super(cv);
79     }
80     
81     public void visit( int version, int access,
82         String JavaDoc name, String JavaDoc superName,
83         String JavaDoc[] interfaces, String JavaDoc sourceFile) {
84       super.visit( Constants.V1_5, access, name,
85           superName, interfaces, sourceFile);
86     }
87     
88     public void visitEnd() {
89       String JavaDoc t = Type.getDescriptor(Marker.class);
90       Annotation ann = new Annotation(t);
91       ann.add("value", "Class");
92
93       RuntimeVisibleAnnotations attr =
94         new RuntimeVisibleAnnotations();
95       attr.annotations.add(ann);
96       cv.visitAttribute(attr);
97       
98       super.visitEnd();
99     }
100
101   }
102   
103 }
104
105
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