Translator


1   /*
2     * JBoss, Home of Professional Open Source
3     * Copyright 2005, JBoss Inc., and individual contributors as indicated
4     * by the @authors tag. See the copyright.txt in the distribution for a
5     * full listing of individual contributors.
6     *
7     * This is free software; you can redistribute it and/or modify it
8     * under the terms of the GNU Lesser General Public License as
9     * published by the Free Software Foundation; either version 2.1 of
10    * the License, or (at your option) any later version.
11    *
12    * This software is distributed in the hope that it will be useful,
13    * but WITHOUT ANY WARRANTY; without even the implied warranty of
14    * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15    * Lesser General Public License for more details.
16    *
17    * You should have received a copy of the GNU Lesser General Public
18    * License along with this software; if not, write to the Free
19    * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20    * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
21    */
22  package org.jboss.util.loading;
23  
24  import java.security.ProtectionDomain  ;
25  
26  /** An interface for transforming byte code before Class creation. This is
27   * compatible with the JDK1.5 java.lang.instrument.ClassFileTransformer
28   * proposal.
29   * 
30   * @author Scott.Stark@jboss.org
31   * @version $Revision: 1958 $
32   */
33  public interface Translator
34  {
35     /** Optionally transform the supplied class file and return a new replacement
36      * class file.
37      *
38      * <P> If a transformer has been registered with the class loading layer,
39      * the transformer will be called for every new class definition.
40      * The request for a new class definition is made with
41      * {@link java.lang.ClassLoader#defineClass ClassLoader.defineClass}.
42      * The transformer is called during the processing of the request, before
43      * the class file bytes have been verified or applied.
44      *
45      * <P>
46      * If the implementing method determines that no transformations are needed,
47      * it should return <code>null</code>. Otherwise, it should create a new
48      * byte[] array and copy the input <code>classfileBuffer</code> into it,
49      * along with all desired transformations. The input <code>classfileBuffer</code>
50      * must not be modified.
51      *
52      * @param loader - the defining loader of the class to be transformed, may
53      *    be <code>null</code> if the bootstrap loader
54      * @param className - the fully-qualified name of the class
55      * @param classBeingRedefined - if this is a redefine, the class being
56      *    redefined, otherwise <code>null</code>
57      * @param protectionDomain - the protection domain of the class being
58      *    defined or redefined
59      * @param classfileBuffer - the input byte buffer in class file format - must
60      *    not be modified
61      *
62      * @throws Exception - if the input does not represent a well-formed class file
63      * @return a well-formed class file buffer (the result of the transform), 
64      * or <code>null</code> if no transform is performed.
65      */
66     public byte[] transform(ClassLoader   loader,
67        String   className,
68        Class   classBeingRedefined,
69        ProtectionDomain   protectionDomain,
70        byte[] classfileBuffer)
71        throws Exception  ;
72  
73     /** Called to indicate that the ClassLoader is being discarded by the server.
74      * 
75      * @param loader - a class loader that has possibly been used previously
76      *    as an argument to transform.
77      */ 
78     public void unregisterClassLoader(ClassLoader   loader);
79  }
80
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