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ASMifierClassVisitor.javaAPI DocGlassfish v2 API17333Thu Mar 02 11:51:18 GMT 2006oracle.toplink.libraries.asm.util

ASMifierClassVisitor

public class ASMifierClassVisitor extends PrintClassVisitor
A {@link PrintClassVisitor PrintClassVisitor} 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 {@link ASMifierClassVisitor} visit this compiled class (see the {@link #main main} method);
  • edit the generated source code, if necessary.
The source code printed when visiting the Hello class is the following: 

import oracle.toplink.libraries.asm.*;
import java.io.FileOutputStream;

public class Dump implements Constants {

public static void main (String[] args) throws Exception {

ClassWriter cw = new ClassWriter(false);
CodeVisitor cv;

cw.visit(ACC_PUBLIC + ACC_SUPER, "Hello", "java/lang/Object", null, "Hello.java");

{
cv = cw.visitMethod(ACC_PUBLIC + ACC_STATIC, "main", "([Ljava/lang/String;)V", null, null);
cv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
cv.visitLdcInsn("hello");
cv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V");
cv.visitInsn(RETURN);
cv.visitMaxs(2, 1);
}
{
cv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
cv.visitVarInsn(ALOAD, 0);
cv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V");
cv.visitInsn(RETURN);
cv.visitMaxs(1, 1);
}
cw.visitEnd();

FileOutputStream os = new FileOutputStream("Dumped.class");
os.write(cw.toByteArray());
os.close();
}
}
where Hello is defined by: 

public class Hello {

public static void main (String[] args) {
System.out.println("hello");
}
}
author
Eric Bruneton, Eugene Kuleshov

Fields Summary
private static final int
ACCESS_CLASS
private static final int
ACCESS_FIELD
private static final int
ACCESS_INNER
Constructors Summary
public ASMifierClassVisitor(PrintWriter pw)
Constructs a new {@link ASMifierClassVisitor} object.

param
pw the print writer to be used to print the class.

    super(pw);
Methods Summary
voidappendAccess(int access)
Appends a string representation of the given access modifiers to {@link #buf buf}.

param
access some access modifiers.

    boolean first = true;
    if ((access & Constants.ACC_PUBLIC) != 0) {
      buf.append("ACC_PUBLIC");
      first = false;
    }
    if ((access & Constants.ACC_PRIVATE) != 0) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_PRIVATE");
      first = false;
    }
    if ((access & Constants.ACC_PROTECTED) != 0) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_PROTECTED");
      first = false;
    }
    if ((access & Constants.ACC_FINAL) != 0) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_FINAL");
      first = false;
    }
    if ((access & Constants.ACC_STATIC) != 0) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_STATIC");
      first = false;
    }
    if ((access & Constants.ACC_SYNCHRONIZED) != 0) {
      if (!first) {
        buf.append(" + ");
      }
      if ((access & ACCESS_CLASS) != 0) {
        buf.append("ACC_SUPER");
      } else {
        buf.append("ACC_SYNCHRONIZED");
      }
      first = false;
    }
    if ((access & Constants.ACC_VOLATILE) != 0 && (access & ACCESS_FIELD) != 0 ) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_VOLATILE");
      first = false;
    }
    if ((access & Constants.ACC_BRIDGE) != 0 &&
        (access & ACCESS_CLASS) == 0 && (access & ACCESS_FIELD) == 0) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_BRIDGE");
      first = false;
    }
    if ((access & Constants.ACC_VARARGS) != 0 &&
        (access & ACCESS_CLASS) == 0 && (access & ACCESS_FIELD) == 0) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_VARARGS");
      first = false;
    }
    if ((access & Constants.ACC_TRANSIENT) != 0 &&
        (access & ACCESS_FIELD) != 0) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_TRANSIENT");
      first = false;
    }
    if ((access & Constants.ACC_NATIVE) != 0 &&
        (access & ACCESS_CLASS) == 0 &&
        (access & ACCESS_FIELD) == 0) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_NATIVE");
      first = false;
    }
    if ((access & Constants.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 & Constants.ACC_ANNOTATION) != 0 &&
        ((access & ACCESS_CLASS) != 0)) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_ANNOTATION");
      first = false;
    }
    if ((access & Constants.ACC_ABSTRACT) != 0) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_ABSTRACT");
      first = false;
    }
    if ((access & Constants.ACC_INTERFACE) != 0) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_INTERFACE");
      first = false;
    }
    if ((access & Constants.ACC_STRICT) != 0) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_STRICT");
      first = false;
    }
    if ((access & Constants.ACC_SYNTHETIC) != 0) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_SYNTHETIC");
      first = false;
    }
    if ((access & Constants.ACC_DEPRECATED) != 0) {
      if (!first) {
        buf.append(" + ");
      }
      buf.append("ACC_DEPRECATED");
      first = false;
    }
    if (first) {
      buf.append("0");
    }
static voidappendConstant(java.lang.StringBuffer buf, java.lang.Object cst)
Appends a string representation of the given constant to the given buffer.

param
buf a string buffer.
param
cst an {@link java.lang.Integer Integer}, {@link java.lang.Float Float}, {@link java.lang.Long Long}, {@link java.lang.Double Double} or {@link String String} object. May be null.

    if (cst == null) {
      buf.append("null");
    } else if (cst instanceof String) {
      String s = (String)cst;
      buf.append("\"");
      for (int i = 0; i < s.length(); ++i) {
        char c = s.charAt(i);
        if (c == '\n") {
          buf.append("\\n");
        } else if (c == '\r") {
            buf.append("\\r");
        } else if (c == '\\") {
          buf.append("\\\\");
        } else if (c == '"") {
          buf.append("\\\"");
        } else if( c<0x20 || c>0x7f) {
          buf.append( "\\u");
          if( c<0x10) {
            buf.append( "000");
          } else if( c<0x100) {
            buf.append( "00");
          } else if( c<0x1000) {
            buf.append( "0");
          }
          buf.append( Integer.toString( c, 16));
        } else {
          buf.append(c);
        }
      }
      buf.append("\"");
    } else if (cst instanceof Type) {
      buf.append("Type.getType(\"");
      buf.append(((Type)cst).getDescriptor());
      buf.append("\")");
    } else if (cst instanceof Integer) {
      buf.append("new Integer(")
        .append(cst)
        .append(")");
    } else if (cst instanceof Float) {
      buf.append("new Float(\"")
        .append(cst).append("\")");
    } else if (cst instanceof Long) {
      buf.append("new Long(")
        .append(cst)
        .append("L)");
    } else if (cst instanceof Double) {
      buf.append("new Double(\"")
        .append(cst).append("\")");
    }
public static voidmain(java.lang.String[] args)
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>

param
args the command line arguments.
throws
Exception if the class cannot be found, or if an IO exception occurs.


                                                        

           
    if (args.length < 1 || args.length > 2) {
      printUsage();
    }
    int i = 0;
    boolean skipDebug = true;
    if (args[0].equals("-debug")) {
      i = 1;
      skipDebug = false;
      if (args.length != 2) {
        printUsage();
      }
    }
    ClassReader cr;
    if (args[i].endsWith(".class")) {
      cr = new ClassReader(new FileInputStream(args[i]));
    } else {
      cr = new ClassReader(args[i]);
    }
    cr.accept(new ASMifierClassVisitor(
      new PrintWriter(System.out)), getDefaultAttributes(), skipDebug);
private static voidprintUsage()

    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>");
    System.exit(-1);
public voidvisit(int version, int access, java.lang.String name, java.lang.String superName, java.lang.String[] interfaces, java.lang.String sourceFile)

    int n = name.lastIndexOf( "/");
    if( n>-1) {
      text.add("package asm."+name.substring( 0, n).replace( '/", '.")+";\n");
    }
    
    text.add("import oracle.toplink.libraries.asm.*;\n");
    text.add("import oracle.toplink.libraries.asm.attrs.*;\n");
    text.add("import java.util.*;\n\n");
    text.add("public class "+(n==-1 ? name : name.substring( n+1))+"Dump implements Constants {\n\n");
    text.add("public static byte[] dump () throws Exception {\n\n");
    text.add("ClassWriter cw = new ClassWriter(false);\n");
    text.add("CodeVisitor cv;\n\n");

    buf.setLength(0);
    buf.append("cw.visit(");    
    switch(version) {
      case Constants.V1_1:
        buf.append("V1_1");
        break;
      
      case Constants.V1_2:
        buf.append("V1_2");
        break;
      
      case Constants.V1_3:
        buf.append("V1_3");
        break;
      
      case Constants.V1_4:
        buf.append("V1_4");
        break;
      
      case Constants.V1_5:
        buf.append("V1_5");
        break;
  
      default:
        buf.append(version);
        break;
    }
    buf.append(", ");
    appendAccess(access | ACCESS_CLASS);
    buf.append(", ");
    appendConstant(buf, name);
    buf.append(", ");
    appendConstant(buf, 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(buf, interfaces[i]);
      }
      buf.append(" }");
    } else {
      buf.append("null");
    }
    buf.append(", ");
    appendConstant(buf, sourceFile);
    buf.append(");\n\n");
    text.add(buf.toString());
public voidvisitAttribute(oracle.toplink.libraries.asm.Attribute attr)

    buf.setLength(0);
    if (attr instanceof ASMifiable) {
      buf.append("{\n");
      buf.append("// CLASS ATRIBUTE\n");
      ((ASMifiable)attr).asmify(buf, "attr", null);
      buf.append("cw.visitAttribute(attr);\n");
      buf.append("}\n");
    } else {
      buf.append("// WARNING! skipped a non standard class attribute of type \"");
      buf.append(attr.type).append("\"\n");
    }
    text.add(buf.toString());
public voidvisitEnd()

    text.add("cw.visitEnd();\n\n");
    // text.add("FileOutputStream os = new FileOutputStream(\"Dumped.class\");\n");
    // text.add("os.write(cw.toByteArray());\n");
    // text.add("os.close();\n");
    text.add("return cw.toByteArray();\n");
    text.add("}\n");
    text.add("}\n");
    super.visitEnd();
public voidvisitField(int access, java.lang.String name, java.lang.String desc, java.lang.Object value, oracle.toplink.libraries.asm.Attribute attrs)

    buf.setLength(0);

    int n = 1;
    if (attrs != null) {
      buf.append("{\n");
      buf.append("// FIELD ATTRIBUTES\n");
      Attribute a = attrs;
      while (a != null) {
        if (a instanceof ASMifiable) {
          ((ASMifiable)a).asmify(buf, "fieldAttrs" + n, null);
          if (n > 1) {
            buf.append("fieldAttrs" + (n - 1) + " = fieldAttrs" + n + ";\n");
          }
	      n++;
        } else {
          buf.append("// WARNING! skipped non standard field attribute of type ");
          buf.append(a.type).append("\n");
        }
        a = a.next;
      }
    }

    buf.append("cw.visitField(");
    appendAccess(access | ACCESS_FIELD);
    buf.append(", ");
    appendConstant(buf, name);
    buf.append(", ");
    appendConstant(buf, desc);
    buf.append(", ");
    appendConstant(buf, value);

    if (n==1) {
      buf.append(", null);\n\n");
    } else {
      buf.append(", fieldAttrs1);\n");
      buf.append("}\n\n");
    }

    text.add(buf.toString());
public voidvisitInnerClass(java.lang.String name, java.lang.String outerName, java.lang.String innerName, int access)

    buf.setLength(0);
    buf.append("cw.visitInnerClass(");
    appendConstant(buf, name);
    buf.append(", ");
    appendConstant(buf, outerName);
    buf.append(", ");
    appendConstant(buf, innerName);
    buf.append(", ");
    appendAccess(access | ACCESS_INNER);
    buf.append(");\n\n");
    text.add(buf.toString());
public oracle.toplink.libraries.asm.CodeVisitorvisitMethod(int access, java.lang.String name, java.lang.String desc, java.lang.String[] exceptions, oracle.toplink.libraries.asm.Attribute attrs)

    buf.setLength(0);

    buf.append("{\n");

    int n = 1;
    if (attrs != null) {
      buf.append("// METHOD ATTRIBUTES\n");
      Attribute a = attrs;
      while (a != null) {
        if (a instanceof ASMifiable) {
          ((ASMifiable)a).asmify(buf, "methodAttrs" + n, null);
          if (n > 1) {
            buf.append("methodAttrs" + (n - 1) + ".next = methodAttrs" + n + ";\n");
          }
          n++;
        } else {
          buf.append("// WARNING! skipped non standard method attribute of type ");
          buf.append(a.type).append("\n");
        }
        a = a.next;
      }
    }

    buf.append("cv = cw.visitMethod(");
    appendAccess(access);
    buf.append(", ");
    appendConstant(buf, name);
    buf.append(", ");
    appendConstant(buf, desc);
    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(buf, exceptions[i]);
      }
      buf.append(" }");
    } else {
      buf.append("null");
    }
    if (n==1) {
      buf.append(", null);\n");
    } else {
      buf.append(", methodAttrs1);\n");
    }

    text.add(buf.toString());
    PrintCodeVisitor pcv = new ASMifierCodeVisitor();
    text.add(pcv.getText());
    text.add("}\n");
    return pcv;