字节码

1 动态生成新的类

• 动态改变类的结构

2 字节码操作库

• BCEL
• ASM
• CGLIB
• Javassist 使用简单

3 简单使用

   public class Demo01{
      public static void main(String[] args){
           ClassPool pool = ClassPook,getDefault();
          CtClass cc  =       pool.makeClass("com.bjsxt.bean.Emp");
          CtField  f1 = CtField.make("private int empno;", cc);
          CtField  f2 = CtField.make("private int enameo;", cc);
          cc.addField(f1);
          cc.addField(f2);

          CtConstructor constructor = new Ctconstructor(new CtClass []{});
          constructor.setBody("{}");
cc.addConstructor(constructor);
        cc.writeFiled("c:/myjava");

}

4 处理类的基本用法

   public class Demo02{
      public static void main(String[] args){
           ClassPool pool = ClassPook,getDefault();
          CtClass cc  =       pool.get("com.bjsxt.bean.Emp");
         byte[] bytes = cc.toBytecode();
        System.out.printn(cc.getName);
        System.out.printn(cc.getSimpleName);
        System.out.printn(cc.getSuperClass);
        System.out.printn(cc.getInterface);
}

4 处理方法的基本用法

   public class Demo03{
      public static void main(String[] args){
           ClassPool pool = ClassPook,getDefault();
          CtClass cc  =       pool.get("com.bjsxt.bean.Emp");
         CtMethod m = CtNewMethod.make()
          CtMethod m = newCtMethod(CtClass.intType,"add",new CtClass[] {Ctclass.intType,CtClass.intType},cc);
        m.setModifiers(Modifier.PUBLIC;
      m.setBody("{return $1 + $2} ");

)
)
}