org.objectweb.asm.util
Class ASMifierClassVisitor

java.lang.Object
  extended by org.objectweb.asm.util.AbstractVisitor
      extended by org.objectweb.asm.util.ASMifierAbstractVisitor
          extended by org.objectweb.asm.util.ASMifierClassVisitor
All Implemented Interfaces:
ClassVisitor

public class ASMifierClassVisitor
extends ASMifierAbstractVisitor
implements ClassVisitor

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:

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

Field Summary
protected  PrintWriter pw
          The print writer to be used to print the class.
 
Fields inherited from class org.objectweb.asm.util.ASMifierAbstractVisitor
name
 
Fields inherited from class org.objectweb.asm.util.AbstractVisitor
buf, OPCODES, text, TYPES
 
Constructor Summary
ASMifierClassVisitor(PrintWriter pw)
          Constructs a new ASMifierClassVisitor object.
 
Method Summary
protected  ASMifierMethodVisitor createASMifierMethodVisitor()
           
static void main(String[] args)
          Prints the ASM source code to generate the given class to the standard output.
 void visit(int version, int access, String name, String signature, String superName, String[] interfaces)
          Visits the header of the class.
 AnnotationVisitor visitAnnotation(String desc, boolean visible)
          Prints the ASM code that generates the given annotation.
 void visitEnd()
          Prints the ASM code to end the visit.
 FieldVisitor visitField(int access, String name, String desc, String signature, Object value)
          Visits a field of the class.
 void visitInnerClass(String name, String outerName, String innerName, int access)
          Visits information about an inner class.
 MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions)
          Visits a method of the class.
 void visitOuterClass(String owner, String name, String desc)
          Visits the enclosing class of the class.
 void visitSource(String file, String debug)
          Visits the source of the class.
 
Methods inherited from class org.objectweb.asm.util.ASMifierAbstractVisitor
visitAttribute
 
Methods inherited from class org.objectweb.asm.util.AbstractVisitor
appendString, getDefaultAttributes, getText, print
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 
Methods inherited from interface org.objectweb.asm.ClassVisitor
visitAttribute
 

Field Detail

pw

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

Constructor Detail

ASMifierClassVisitor

public ASMifierClassVisitor(PrintWriter pw)
Constructs a new ASMifierClassVisitor object.

Parameters:
pw - the print writer to be used to print the class.
Method Detail

main

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

Parameters:
args - the command line arguments.
Throws:
Exception - if the class cannot be found, or if an IO exception occurs.

visit

public void visit(int version,
                  int access,
                  String name,
                  String signature,
                  String superName,
                  String[] interfaces)
Description copied from interface: ClassVisitor
Visits the header of the class.

Specified by:
visit in interface ClassVisitor
Parameters:
version - the class version.
access - the class's access flags (see Opcodes). This parameter also indicates if the class is deprecated.
name - the internal name of the class (see getInternalName).
signature - the signature of this class. May be null if the class is not a generic one, and does not extend or implement generic classes or interfaces.
superName - the internal of name of the super class (see getInternalName). For interfaces, the super class is Object. May be null, but only for the Object class.
interfaces - the internal names of the class's interfaces (see getInternalName). May be null.

visitSource

public void visitSource(String file,
                        String debug)
Description copied from interface: ClassVisitor
Visits the source of the class.

Specified by:
visitSource in interface ClassVisitor
Parameters:
file - the name of the source file from which the class was compiled. May be null.
debug - additional debug information to compute the correspondance between source and compiled elements of the class. May be null.

visitOuterClass

public void visitOuterClass(String owner,
                            String name,
                            String desc)
Description copied from interface: ClassVisitor
Visits the enclosing class of the class. This method must be called only if the class has an enclosing class.

Specified by:
visitOuterClass in interface ClassVisitor
Parameters:
owner - internal name of the enclosing class of the class.
name - the name of the method that contains the class, or null if the class is not enclosed in a method of its enclosing class.
desc - the descriptor of the method that contains the class, or null if the class is not enclosed in a method of its enclosing class.

visitInnerClass

public void visitInnerClass(String name,
                            String outerName,
                            String innerName,
                            int access)
Description copied from interface: ClassVisitor
Visits information about an inner class. This inner class is not necessarily a member of the class being visited.

Specified by:
visitInnerClass in interface ClassVisitor
Parameters:
name - the internal name of an inner class (see getInternalName).
outerName - the internal name of the class to which the inner class belongs (see getInternalName). May be null for not member classes.
innerName - the (simple) name of the inner class inside its enclosing class. May be null for anonymous inner classes.
access - the access flags of the inner class as originally declared in the enclosing class.

visitField

public FieldVisitor visitField(int access,
                               String name,
                               String desc,
                               String signature,
                               Object value)
Description copied from interface: ClassVisitor
Visits a field of the class.

Specified by:
visitField in interface ClassVisitor
Parameters:
access - the field's access flags (see Opcodes). This parameter also indicates if the field is synthetic and/or deprecated.
name - the field's name.
desc - the field's descriptor (see Type).
signature - the field's signature. May be null if the field's type does not use generic types.
value - the field's initial value. This parameter, which may be null if the field does not have an initial value, must be an Integer, a Float, a Long, a Double or a String (for int, float, long or String fields respectively). This parameter is only used for static fields. Its value is ignored for non static fields, which must be initialized through bytecode instructions in constructors or methods.
Returns:
a visitor to visit field annotations and attributes, or null if this class visitor is not interested in visiting these annotations and attributes.

visitMethod

public MethodVisitor visitMethod(int access,
                                 String name,
                                 String desc,
                                 String signature,
                                 String[] exceptions)
Description copied from interface: ClassVisitor
Visits a method of the class. This method must return a new MethodVisitor instance (or null) each time it is called, i.e., it should not return a previously returned visitor.

Specified by:
visitMethod in interface ClassVisitor
Parameters:
access - the method's access flags (see Opcodes). This parameter also indicates if the method is synthetic and/or deprecated.
name - the method's name.
desc - the method's descriptor (see Type).
signature - the method's signature. May be null if the method parameters, return type and exceptions do not use generic types.
exceptions - the internal names of the method's exception classes (see getInternalName). May be null.
Returns:
an object to visit the byte code of the method, or null if this class visitor is not interested in visiting the code of this method.

createASMifierMethodVisitor

protected ASMifierMethodVisitor createASMifierMethodVisitor()

visitAnnotation

public AnnotationVisitor visitAnnotation(String desc,
                                         boolean visible)
Description copied from class: ASMifierAbstractVisitor
Prints the ASM code that generates the given annotation.

Specified by:
visitAnnotation in interface ClassVisitor
Overrides:
visitAnnotation in class ASMifierAbstractVisitor
Parameters:
desc - the class descriptor of the annotation class.
visible - true if the annotation is visible at runtime.
Returns:
a visitor to visit the annotation values.

visitEnd

public void visitEnd()
Description copied from class: ASMifierAbstractVisitor
Prints the ASM code to end the visit.

Specified by:
visitEnd in interface ClassVisitor
Overrides:
visitEnd in class ASMifierAbstractVisitor