https://github.com/eclipse-ee4j/orb-gmbal-pfl/pfl-asm: GMBAL- Java EE Primative Function Library (Eclipse Foundation)
  • Russell Gold 
ASM: a very small and fast Java bytecode manipulation framework
Copyright (c) 2000-2007 INRIA, France Telecom
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.
3. Neither the name of the copyright holders nor the names of its
   contributors may be used to endorse or promote products derived from
   this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
THE POSSIBILITY OF SUCH DAMAGE.

/***
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2007 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of its
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.glassfish.pfl.objectweb.asm.util;

import java.io.FileInputStream;
import java.io.PrintWriter;

import org.glassfish.pfl.objectweb.asm.AnnotationVisitor;
import org.glassfish.pfl.objectweb.asm.ClassReader;
import org.glassfish.pfl.objectweb.asm.ClassVisitor;
import org.glassfish.pfl.objectweb.asm.FieldVisitor;
import org.glassfish.pfl.objectweb.asm.MethodVisitor;
import org.glassfish.pfl.objectweb.asm.Opcodes;


A ClassVisitor that prints the ASM code that generates the classes it visits. This class visitor can be used to quickly write ASM code to generate some given bytecode: 
     
  • write the Java source code equivalent to the
bytecode you want to generate;
    •  
  • compile it with javac;
    • 

  • make a ASMifierClassVisitor visit this compiled class (see the main method);
    •  
  • edit the generated source code, if
necessary.
    •  
 The source code printed when visiting the
Hello class is the following: 
 


import org.objectweb.asm.*;
public class HelloDump implements Opcodes {
    public static byte[] dump() throws Exception {
        ClassWriter cw = new ClassWriter(0);
        FieldVisitor fv;
        MethodVisitor mv;
        AnnotationVisitor av0;
        cw.visit(49,
                ACC_PUBLIC + ACC_SUPER,
                "Hello",
                null,
                "java/lang/Object",
                null);
        cw.visitSource("Hello.java", null);
        {
            mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
            mv.visitVarInsn(ALOAD, 0);
            mv.visitMethodInsn(INVOKESPECIAL,
                    "java/lang/Object",
                    "<init>",
                    "()V");
            mv.visitInsn(RETURN);
            mv.visitMaxs(1, 1);
            mv.visitEnd();
        }
        {
            mv = cw.visitMethod(ACC_PUBLIC + ACC_STATIC,
                    "main",
                    "([Ljava/lang/String;)V",
                    null,
                    null);
            mv.visitFieldInsn(GETSTATIC,
                    "java/lang/System",
                    "out",
                    "Ljava/io/PrintStream;");
            mv.visitLdcInsn("hello");
            mv.visitMethodInsn(INVOKEVIRTUAL,
                    "java/io/PrintStream",
                    "println",
                    "(Ljava/lang/String;)V");
            mv.visitInsn(RETURN);
            mv.visitMaxs(2, 1);
            mv.visitEnd();
        }
        cw.visitEnd();
        return cw.toByteArray();
    }
}



 where Hello is defined by: 
 


public class Hello {
    public static void main(String[] args) {
        System.out.println("hello");
    }
}





Author:Eric Bruneton, Eugene Kuleshov
/**
 * A {@link ClassVisitor} that prints the ASM code that generates the classes it
 * visits. This class visitor can be used to quickly write ASM code to generate
 * some given bytecode: <ul> <li>write the Java source code equivalent to the
 * bytecode you want to generate;</li> <li>compile it with <tt>javac</tt>;</li>
 * <li>make a {@link ASMifierClassVisitor} visit this compiled class (see the
 * {@link #main main} method);</li> <li>edit the generated source code, if
 * necessary.</li> </ul> The source code printed when visiting the
 * <tt>Hello</tt> class is the following: <p> <blockquote>
 * 
 * <pre>
 * import org.objectweb.asm.*;
 *
 * public class HelloDump implements Opcodes {
 *
 *     public static byte[] dump() throws Exception {
 *
 *         ClassWriter cw = new ClassWriter(0);
 *         FieldVisitor fv;
 *         MethodVisitor mv;
 *         AnnotationVisitor av0;
 *
 *         cw.visit(49,
 *                 ACC_PUBLIC + ACC_SUPER,
 *                 &quot;Hello&quot;,
 *                 null,
 *                 &quot;java/lang/Object&quot;,
 *                 null);
 *
 *         cw.visitSource(&quot;Hello.java&quot;, null);
 *
 *         {
 *             mv = cw.visitMethod(ACC_PUBLIC, &quot;&lt;init&gt;&quot;, &quot;()V&quot;, null, null);
 *             mv.visitVarInsn(ALOAD, 0);
 *             mv.visitMethodInsn(INVOKESPECIAL,
 *                     &quot;java/lang/Object&quot;,
 *                     &quot;&lt;init&gt;&quot;,
 *                     &quot;()V&quot;);
 *             mv.visitInsn(RETURN);
 *             mv.visitMaxs(1, 1);
 *             mv.visitEnd();
 *         }
 *         {
 *             mv = cw.visitMethod(ACC_PUBLIC + ACC_STATIC,
 *                     &quot;main&quot;,
 *                     &quot;([Ljava/lang/String;)V&quot;,
 *                     null,
 *                     null);
 *             mv.visitFieldInsn(GETSTATIC,
 *                     &quot;java/lang/System&quot;,
 *                     &quot;out&quot;,
 *                     &quot;Ljava/io/PrintStream;&quot;);
 *             mv.visitLdcInsn(&quot;hello&quot;);
 *             mv.visitMethodInsn(INVOKEVIRTUAL,
 *                     &quot;java/io/PrintStream&quot;,
 *                     &quot;println&quot;,
 *                     &quot;(Ljava/lang/String;)V&quot;);
 *             mv.visitInsn(RETURN);
 *             mv.visitMaxs(2, 1);
 *             mv.visitEnd();
 *         }
 *         cw.visitEnd();
 *
 *         return cw.toByteArray();
 *     }
 * }
 *
 * </pre>
 * 
 * </blockquote> where <tt>Hello</tt> is defined by: <p> <blockquote>
 * 
 * <pre>
 * public class Hello {
 *
 *     public static void main(String[] args) {
 *         System.out.println(&quot;hello&quot;);
 *     }
 * }
 * </pre>
 * 
 * </blockquote>
 * 
 * @author Eric Bruneton
 * @author Eugene Kuleshov
 */
public class ASMifierClassVisitor extends ASMifierAbstractVisitor implements
        ClassVisitor
{

    
Pseudo access flag used to distinguish class access flags.

/**
     * Pseudo access flag used to distinguish class access flags.
     */
    private static final int ACCESS_CLASS = 262144;

    
Pseudo access flag used to distinguish field access flags.

/**
     * Pseudo access flag used to distinguish field access flags.
     */
    private static final int ACCESS_FIELD = 524288;

    
Pseudo access flag used to distinguish inner class flags.

/**
     * Pseudo access flag used to distinguish inner class flags.
     */
    private static final int ACCESS_INNER = 1048576;

    
The print writer to be used to print the class.

/**
     * The print writer to be used to print the class.
     */
    protected final PrintWriter pw;

    
Prints the ASM source code to generate the given class to the standard
output. 
 Usage: ASMifierClassVisitor [-debug] <fully qualified
class name or class file name>

Params:
  • args – the command line arguments.
Throws:
  • Exception – if the class cannot be found, or if an IO exception
        occurs.
/**
     * Prints the ASM source code to generate the given class to the standard
     * output. <p> Usage: ASMifierClassVisitor [-debug] &lt;fully qualified
     * class name or class file name&gt;
     * 
     * @param args the command line arguments.
     * 
     * @throws Exception if the class cannot be found, or if an IO exception
     *         occurs.
     */
    public static void main(final String[] args) throws Exception {
        int i = 0;
        int flags = ClassReader.SKIP_DEBUG;

        boolean ok = true;
        if (args.length < 1 || args.length > 2) {
            ok = false;
        }
        if (ok && "-debug".equals(args[0])) {
            i = 1;
            flags = 0;
            if (args.length != 2) {
                ok = false;
            }
        }
        if (!ok) {
            System.err.println("Prints the ASM code to generate the given class.");
            System.err.println("Usage: ASMifierClassVisitor [-debug] "
                    + "<fully qualified class name or class file name>");
            return;
        }
        ClassReader cr;
        if (args[i].endsWith(".class") || args[i].indexOf('\\') > -1
                || args[i].indexOf('/') > -1)
        {
            cr = new ClassReader(new FileInputStream(args[i]));
        } else {
            cr = new ClassReader(args[i]);
        }
        cr.accept(new ASMifierClassVisitor(new PrintWriter(System.out)),
                getDefaultAttributes(),
                flags);
    }

    
Constructs a new ASMifierClassVisitor object. 
Params:
  • pw – the print writer to be used to print the class.
/**
     * Constructs a new {@link ASMifierClassVisitor} object.
     * 
     * @param pw the print writer to be used to print the class.
     */
    public ASMifierClassVisitor(final PrintWriter pw) {
        super("cw");
        this.pw = pw;
    }

    // ------------------------------------------------------------------------
    // Implementation of the ClassVisitor interface
    // ------------------------------------------------------------------------

    public void visit(
        final int version,
        final int access,
        final String name,
        final String signature,
        final String superName,
        final String[] interfaces)
    {
        String simpleName;
        int n = name.lastIndexOf('/');
        if (n == -1) {
            simpleName = name;
        } else {
            text.add("package asm." + name.substring(0, n).replace('/', '.')
                    + ";\n");
            simpleName = name.substring(n + 1);
        }
        text.add("import java.util.*;\n");
        text.add("import org.objectweb.asm.*;\n");
        text.add("import org.objectweb.asm.attrs.*;\n");
        text.add("public class " + simpleName + "Dump implements Opcodes {\n\n");
        text.add("public static byte[] dump () throws Exception {\n\n");
        text.add("ClassWriter cw = new ClassWriter(0);\n");
        text.add("FieldVisitor fv;\n");
        text.add("MethodVisitor mv;\n");
        text.add("AnnotationVisitor av0;\n\n");

        buf.setLength(0);
        buf.append("cw.visit(");
        switch (version) {
            case Opcodes.V1_1:
                buf.append("V1_1");
                break;
            case Opcodes.V1_2:
                buf.append("V1_2");
                break;
            case Opcodes.V1_3:
                buf.append("V1_3");
                break;
            case Opcodes.V1_4:
                buf.append("V1_4");
                break;
            case Opcodes.V1_5:
                buf.append("V1_5");
                break;
            case Opcodes.V1_6:
                buf.append("V1_6");
                break;
            default:
                buf.append(version);
                break;
        }
        buf.append(", ");
        appendAccess(access | ACCESS_CLASS);
        buf.append(", ");
        appendConstant(name);
        buf.append(", ");
        appendConstant(signature);
        buf.append(", ");
        appendConstant(superName);
        buf.append(", ");
        if (interfaces != null && interfaces.length > 0) {
            buf.append("new String[] {");
            for (int i = 0; i < interfaces.length; ++i) {
                buf.append(i == 0 ? " " : ", ");
                appendConstant(interfaces[i]);
            }
            buf.append(" }");
        } else {
            buf.append("null");
        }
        buf.append(");\n\n");
        text.add(buf.toString());
    }

    public void visitSource(final String file, final String debug) {
        buf.setLength(0);
        buf.append("cw.visitSource(");
        appendConstant(file);
        buf.append(", ");
        appendConstant(debug);
        buf.append(");\n\n");
        text.add(buf.toString());
    }

    public void visitOuterClass(
        final String owner,
        final String name,
        final String desc)
    {
        buf.setLength(0);
        buf.append("cw.visitOuterClass(");
        appendConstant(owner);
        buf.append(", ");
        appendConstant(name);
        buf.append(", ");
        appendConstant(desc);
        buf.append(");\n\n");
        text.add(buf.toString());
    }

    public void visitInnerClass(
        final String name,
        final String outerName,
        final String innerName,
        final int access)
    {
        buf.setLength(0);
        buf.append("cw.visitInnerClass(");
        appendConstant(name);
        buf.append(", ");
        appendConstant(outerName);
        buf.append(", ");
        appendConstant(innerName);
        buf.append(", ");
        appendAccess(access | ACCESS_INNER);
        buf.append(");\n\n");
        text.add(buf.toString());
    }

    public FieldVisitor visitField(
        final int access,
        final String name,
        final String desc,
        final String signature,
        final Object value)
    {
        buf.setLength(0);
        buf.append("{\n");
        buf.append("fv = cw.visitField(");
        appendAccess(access | ACCESS_FIELD);
        buf.append(", ");
        appendConstant(name);
        buf.append(", ");
        appendConstant(desc);
        buf.append(", ");
        appendConstant(signature);
        buf.append(", ");
        appendConstant(value);
        buf.append(");\n");
        text.add(buf.toString());
        ASMifierFieldVisitor aav = new ASMifierFieldVisitor();
        text.add(aav.getText());
        text.add("}\n");
        return aav;
    }

    public MethodVisitor visitMethod(
        final int access,
        final String name,
        final String desc,
        final String signature,
        final String[] exceptions)
    {
        buf.setLength(0);
        buf.append("{\n");
        buf.append("mv = cw.visitMethod(");
        appendAccess(access);
        buf.append(", ");
        appendConstant(name);
        buf.append(", ");
        appendConstant(desc);
        buf.append(", ");
        appendConstant(signature);
        buf.append(", ");
        if (exceptions != null && exceptions.length > 0) {
            buf.append("new String[] {");
            for (int i = 0; i < exceptions.length; ++i) {
                buf.append(i == 0 ? " " : ", ");
                appendConstant(exceptions[i]);
            }
            buf.append(" }");
        } else {
            buf.append("null");
        }
        buf.append(");\n");
        text.add(buf.toString());
        ASMifierMethodVisitor acv = createASMifierMethodVisitor();
        text.add(acv.getText());
        text.add("}\n");
        return acv;
    }

    protected ASMifierMethodVisitor createASMifierMethodVisitor() {
        return new ASMifierMethodVisitor();
    }

    public AnnotationVisitor visitAnnotation(
        final String desc,
        final boolean visible)
    {
        buf.setLength(0);
        buf.append("{\n");
        buf.append("av0 = cw.visitAnnotation(");
        appendConstant(desc);
        buf.append(", ");
        buf.append(visible);
        buf.append(");\n");
        text.add(buf.toString());
        ASMifierAnnotationVisitor av = new ASMifierAnnotationVisitor(0);
        text.add(av.getText());
        text.add("}\n");
        return av;
    }

    public void visitEnd() {
        text.add("cw.visitEnd();\n\n");
        text.add("return cw.toByteArray();\n");
        text.add("}\n");
        text.add("}\n");
        printList(pw, text);
        pw.flush();
    }

    // ------------------------------------------------------------------------
    // Utility methods
    // ------------------------------------------------------------------------

    
Appends a string representation of the given access modifiers to buf. 
Params:
  • access – some access modifiers.
/**
     * Appends a string representation of the given access modifiers to {@link
     * #buf buf}.
     * 
     * @param access some access modifiers.
     */
    void appendAccess(final int access) {
        boolean first = true;
        if ((access & Opcodes.ACC_PUBLIC) != 0) {
            buf.append("ACC_PUBLIC");
            first = false;
        }
        if ((access & Opcodes.ACC_PRIVATE) != 0) {
            buf.append("ACC_PRIVATE");
            first = false;
        }
        if ((access & Opcodes.ACC_PROTECTED) != 0) {
            buf.append("ACC_PROTECTED");
            first = false;
        }
        if ((access & Opcodes.ACC_FINAL) != 0) {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_FINAL");
            first = false;
        }
        if ((access & Opcodes.ACC_STATIC) != 0) {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_STATIC");
            first = false;
        }
        if ((access & Opcodes.ACC_SYNCHRONIZED) != 0) {
            if (!first) {
                buf.append(" + ");
            }
            if ((access & ACCESS_CLASS) == 0) {
                buf.append("ACC_SYNCHRONIZED");
            } else {
                buf.append("ACC_SUPER");
            }
            first = false;
        }
        if ((access & Opcodes.ACC_VOLATILE) != 0
                && (access & ACCESS_FIELD) != 0)
        {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_VOLATILE");
            first = false;
        }
        if ((access & Opcodes.ACC_BRIDGE) != 0 && (access & ACCESS_CLASS) == 0
                && (access & ACCESS_FIELD) == 0)
        {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_BRIDGE");
            first = false;
        }
        if ((access & Opcodes.ACC_VARARGS) != 0 && (access & ACCESS_CLASS) == 0
                && (access & ACCESS_FIELD) == 0)
        {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_VARARGS");
            first = false;
        }
        if ((access & Opcodes.ACC_TRANSIENT) != 0
                && (access & ACCESS_FIELD) != 0)
        {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_TRANSIENT");
            first = false;
        }
        if ((access & Opcodes.ACC_NATIVE) != 0 && (access & ACCESS_CLASS) == 0
                && (access & ACCESS_FIELD) == 0)
        {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_NATIVE");
            first = false;
        }
        if ((access & Opcodes.ACC_ENUM) != 0
                && ((access & ACCESS_CLASS) != 0
                        || (access & ACCESS_FIELD) != 0 || (access & ACCESS_INNER) != 0))
        {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_ENUM");
            first = false;
        }
        if ((access & Opcodes.ACC_ANNOTATION) != 0
                && (access & ACCESS_CLASS) != 0)
        {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_ANNOTATION");
            first = false;
        }
        if ((access & Opcodes.ACC_ABSTRACT) != 0) {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_ABSTRACT");
            first = false;
        }
        if ((access & Opcodes.ACC_INTERFACE) != 0) {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_INTERFACE");
            first = false;
        }
        if ((access & Opcodes.ACC_STRICT) != 0) {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_STRICT");
            first = false;
        }
        if ((access & Opcodes.ACC_SYNTHETIC) != 0) {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_SYNTHETIC");
            first = false;
        }
        if ((access & Opcodes.ACC_DEPRECATED) != 0) {
            if (!first) {
                buf.append(" + ");
            }
            buf.append("ACC_DEPRECATED");
            first = false;
        }
        if (first) {
            buf.append('0');
        }
    }
}