java字节码框架ASM操作字节码的方法浅析

long f (int n, String s, int[] arr);

f (ILjava/lang/String;[I)J

private void hi(double a, List<String> b);

hi (DLjava/util/List;)V

public class Test {

 public static void main(String[] args) throws Exception {
 ClassPrinter printer = new ClassPrinter();
 //读取静态内部类Bazhang
 ClassReader cr = new ClassReader("Test$Bazhang");
 cr.accept(printer, 0);

 }

 //静态内部类
 static class Bazhang {

 public Bazhang(int a) {
 }

 private long f (int n, String s, int[] arr){
  return 0;
 }

 private void hi(double a, List<String> b){

 }
 }

 static class ClassPrinter extends ClassVisitor {

 public ClassPrinter() {
  super(Opcodes.ASM5);
 }

 @Override
 public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
  super.visit(version, access, name, signature, superName, interfaces);
  //打印出父类name和本类name
  System.out.println(superName + " " + name);
 }

 @Override
 public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
  //打印出方法名和类型签名
  System.out.println(name + " " + desc);
  return super.visitMethod(access, name, desc, signature, exceptions);
 }
 }

}

java/lang/Object Test$Bazhang
<init> ()V
f (ILjava/lang/String;[I)J
hi (DLjava/util/List;)V

public void newFunc(String str){
 
}

public static void main(String[] args) throws Exception {
 ClassReader cr = new ClassReader(Bazhang.class.getName());
 ClassWriter cw = new ClassWriter(cr, ClassWriter.COMPUTE_MAXS);

 cr.accept(cw, Opcodes.ASM5);

 MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "newFunc", "(Ljava/lang/String;)V", null, null);

 mv.visitInsn(Opcodes.RETURN);
 mv.visitEnd();

 // 获取生成的class文件对应的二进制流
 byte[] code = cw.toByteArray();
 
 //将二进制流写到out/下
 FileOutputStream fos = new FileOutputStream("out/Bazhang222.class");
 fos.write(code);
 fos.close();

}

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

import java.util.List;

class Test$Bazhang {
 Test$Bazhang() {
 }

 private long f(int n, String s, int[] arr) {
 return 0L;
 }

 private void hi(double a, List<String> b) {
 }

 public void newFunc(String var1) {
 }
}