001    /***
002     *
003     * Copyright (c) 2007 Paul Hammant
004     * All rights reserved.
005     *
006     * Redistribution and use in source and binary forms, with or without
007     * modification, are permitted provided that the following conditions
008     * are met:
009     * 1. Redistributions of source code must retain the above copyright
010     *    notice, this list of conditions and the following disclaimer.
011     * 2. Redistributions in binary form must reproduce the above copyright
012     *    notice, this list of conditions and the following disclaimer in the
013     *    documentation and/or other materials provided with the distribution.
014     * 3. Neither the name of the copyright holders nor the names of its
015     *    contributors may be used to endorse or promote products derived from
016     *    this software without specific prior written permission.
017     *
018     * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
019     * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
020     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
021     * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
022     * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
023     * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
024     * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
025     * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
026     * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
027     * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
028     * THE POSSIBILITY OF SUCH DAMAGE.
029     */
030    package com.thoughtworks.paranamer.generator;
031    
032    import java.io.File;
033    import java.io.FileInputStream;
034    import java.io.FileOutputStream;
035    import java.io.IOException;
036    import java.io.InputStream;
037    
038    import org.objectweb.asm.ClassReader;
039    import org.objectweb.asm.ClassWriter;
040    import org.objectweb.asm.Opcodes;
041    
042    /**
043     * A bytecode enhancer which adds a new static variable to some specific class.
044     * 
045     * @author Guilherme Silveira
046     */
047    public class Enhancer implements Opcodes {
048    
049            public void enhance(File classFile, String parameterNameData)
050                            throws IOException {
051    
052                    byte[] classBytecode = addExtraStaticField(classFile, parameterNameData);
053                    FileOutputStream os = new FileOutputStream(classFile);
054                    os.write(classBytecode);
055                    os.close();
056            }
057    
058            private byte[] addExtraStaticField(File classFile,
059                            final String parameterNameData) throws IOException {
060    
061                    InputStream inputStream = new FileInputStream(classFile);
062                    ClassReader reader = new ClassReader(inputStream);
063    
064                    ClassWriter writer = new ClassWriter(reader, 0);
065                    // TODO fix problem with inner classes, two classes in one classFile and
066                    // so on...
067                    // TODO doc typo on page 21: recommended
068    
069                    AddFieldAdapter adapter = new AddFieldAdapter(writer, ACC_PUBLIC
070                                    + ACC_FINAL + ACC_STATIC, "__PARANAMER_DATA",
071                                    "Ljava/lang/String;", parameterNameData);
072    
073                    reader.accept(adapter, 0);
074    
075                    inputStream.close();
076                    return writer.toByteArray();
077            }
078    
079    }