Byte Code Engineering Example

package compare;

public class ImplementRunnable1 implements Runnable1{


@Override
public void method() {
System.out.println("Test");

}
void Method1(){
System.out.println("hhhhh");
method() ;


}

}

package compare;

import java.io.DataOutputStream;

import java.io.File;

import java.io.FileOutputStream;

import java.util.*;

import org.objectweb.asm.*;

import org.objectweb.asm.attrs.*;

public class ImplementRunnable1Dump implements Opcodes {

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

//

// }

public static byte[] dump() throws Exception {

ClassWriter cw = new ClassWriter(0);

FieldVisitor fv;

MethodVisitor mv;

AnnotationVisitor av0;

cw.visit(V1_7, ACC_PUBLIC + ACC_SUPER, "compare/NoRunnable",

null, "java/lang/Object", new String[] { "compare/Runnable1" });

cw.visitSource("NoRunnable.java", null);

{

fv = cw.visitField(ACC_PRIVATE, "x", "Ljava/lang/String;", null,

null);

fv.visitEnd();

}

{

mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);

mv.visitCode();

Label l0 = new Label();

mv.visitLabel(l0);

mv.visitVarInsn(ALOAD, 0);

mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>",

"()V");

mv.visitInsn(RETURN);

Label l1 = new Label();

mv.visitLabel(l1);

mv.visitLocalVariable("this", "Lcompare/NoRunnable;", null,

l0, l1, 0);

mv.visitMaxs(1, 1);

mv.visitEnd();

}

{

mv = cw.visitMethod(ACC_PUBLIC, "method", "()V", null, null);

mv.visitCode();

Label l0 = new Label();

mv.visitLabel(l0);

mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out",

"Ljava/io/PrintStream;");

mv.visitLdcInsn("Test");

mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println",

"(Ljava/lang/String;)V");

Label l1 = new Label();

mv.visitLabel(l1);

mv.visitInsn(RETURN);

Label l2 = new Label();

mv.visitLabel(l2);

mv.visitLocalVariable("this", "Lcompare/NoRunnable;", null,

l0, l2, 0);

mv.visitMaxs(2, 1);

mv.visitEnd();

}

{

mv = cw.visitMethod(0, "Method1", "()V", null, null);

mv.visitCode();

Label l0 = new Label();

mv.visitLabel(l0);

mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out",

"Ljava/io/PrintStream;");

mv.visitLdcInsn("hhhhh");

mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println",

"(Ljava/lang/String;)V");

Label l1 = new Label();

mv.visitLabel(l1);

mv.visitVarInsn(ALOAD, 0);

mv.visitMethodInsn(INVOKEVIRTUAL, "compare/NoRunnable",

"method", "()V");

Label l2 = new Label();

mv.visitLabel(l2);

mv.visitInsn(RETURN);

Label l3 = new Label();

mv.visitLabel(l3);

mv.visitLocalVariable("this", "Lcompare/NoRunnable;", null,

l0, l3, 0);

mv.visitMaxs(2, 1);

mv.visitEnd();

}

cw.visitEnd();

return cw.toByteArray();

}

}

package compare;

public class NoRunnable {

void Method1(){

System.out.println("i");

}

}

package compare;

public interface Runnable1 {

void method();

}

package compare;

import java.io.DataOutputStream;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import org.junit.Test;

public class TestP {

@Test

public void  MethodTest() throws IOException, Exception{

ImplementRunnable1Dump d=new ImplementRunnable1Dump();

  File outputDir=new File("bin/compare");

       DataOutputStream dout=new DataOutputStream(new FileOutputStream(new File(outputDir,"NoRunnable.class")));

       dout.write(d.dump());

NoRunnable y=new NoRunnable();

y.Method1();

}

}