package com.bjsxt.test;

@Author(name="gaoqi", year=2014)

public class Emp {

    private int empno;

    private String ename;

    public void sayHello(int a){

        System.out.println("sayHello,"+a);

    }

    public int getEmpno() {

        return empno;

    }

    public void setEmpno(int empno) {

        this.empno = empno;

    }

    public String getEname() {

        return ename;

    }

    public void setEname(String ename) {

        this.ename = ename;

    }

    public Emp(int empno, String ename) {

        super();

        this.empno = empno;

        this.ename = ename;

    }

    public Emp() {

    }

}

package com.bjsxt.test;

import java.lang.reflect.Method;

import java.util.Arrays;

import javassist.ClassPool;

import javassist.CtClass;

import javassist.CtConstructor;

import javassist.CtField;

import javassist.CtMethod;

import javassist.CtNewMethod;

import javassist.Modifier;

import javassist.NotFoundException;

/**

 * 测试javassist的API

 * @author 尚学堂高淇 www.sxt.cn

 *

 */

public class Demo02 {

    /**

     * 处理类的基本用法

     * @throws Exception

     */

    public static void test01() throws Exception{

        ClassPool pool = ClassPool.getDefault();

        CtClass cc = pool.get("com.bjsxt.test.Emp");

        byte[] bytes = cc.toBytecode();

        System.out.println(Arrays.toString(bytes));

        System.out.println(cc.getName()); //获取类名

        System.out.println(cc.getSimpleName()); //获取简要类名

        System.out.println(cc.getSuperclass()); //获得父类

        System.out.println(cc.getInterfaces()); //获得接口

    }

    /**

     * 测试产生新的方法

     * @throws Exception

     */

    public static void test02() throws Exception{

        ClassPool pool = ClassPool.getDefault();

        CtClass cc = pool.get("com.bjsxt.test.Emp");

//        CtMethod m = CtNewMethod.make("public int add(int a,int b){return a+b;}", cc);

        /*

        *CtClass.intType,CtClass.intType是add函数的两个形参的类型这里没有制定形参的名字，这里通过占位符来指定形参名字

        $0表示this对象

        $1表示第一个形参

        $2表示第二个形参

        */

        CtMethod m = new CtMethod(CtClass.intType,"add",

                new CtClass[]{CtClass.intType,CtClass.intType},cc);

        m.setModifiers(Modifier.PUBLIC);

        m.setBody("{System.out.println(\"www.sxt.cn\");return $1+$2;}");

        cc.addMethod(m);

        //通过反射调用新生成的方法

        Class clazz = cc.toClass();

        Object obj = clazz.newInstance();  //通过调用Emp无参构造器，创建新的Emp对象

        Method method = clazz.getDeclaredMethod("add", int.class,int.class);

        Object result = method.invoke(obj, 200,300);

        System.out.println(result);

    }

    /**

     * 修改已有的方法的信息，修改方法体的内容

     * @throws Exception

     */

    public static void test03() throws Exception{

        ClassPool pool = ClassPool.getDefault();

        CtClass cc = pool.get("com.bjsxt.test.Emp");

        CtMethod cm = cc.getDeclaredMethod("sayHello",new CtClass[]{CtClass.intType});

        cm.insertBefore("System.out.println($1);System.out.println(\"start!!!\");");

        /*

        *在每一行前面加入内容

        */

        cm.insertAt(9, "int b=3;System.out.println(\"b=\"+b);");

        cm.insertAfter("System.out.println(\"end!!!\");");

        //通过反射调用新生成的方法

        Class clazz = cc.toClass();

        Object obj = clazz.newInstance();  //通过调用Emp无参构造器，创建新的Emp对象

        Method method = clazz.getDeclaredMethod("sayHello", int.class);

        method.invoke(obj, 300);

    }

    /**

     * 添加新的属性的操作

     * @throws Exception

     */

    public static void test04() throws Exception{

        ClassPool pool = ClassPool.getDefault();

        CtClass cc = pool.get("com.bjsxt.test.Emp");

//        CtField f1 = CtField.make("private int empno;", cc);

        CtField f1 = new CtField(CtClass.intType,"salary",cc);

        f1.setModifiers(Modifier.PRIVATE);

        cc.addField(f1);

//        cc.getDeclaredField("ename");   //获取指定的属性

        //增加相应的set和get方法

        cc.addMethod(CtNewMethod.getter("getSalary", f1));;

        cc.addMethod(CtNewMethod.getter("setSalary", f1));;

    }

    /**

     * 构造方法的操作

     * @throws Exception

     */

    public static void test05() throws Exception {

        ClassPool pool = ClassPool.getDefault();

        CtClass cc = pool.get("com.bjsxt.test.Emp");

        CtConstructor[] cs = cc.getConstructors();

        for (CtConstructor c : cs) {

            System.out.println(c.getLongName());

        }

    }

    public static void test06() throws Exception{

         CtClass cc = ClassPool.getDefault().get("com.bjsxt.test.Emp");

         Object[] all = cc.getAnnotations();

         Author a = (Author)all[0];

         String name = a.name();

         int year = a.year();

         System.out.println("name: " + name + ", year: " + year);

    }

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

        test06();

    }

}

package com.bjsxt.test;

public @interface Author {

          String name();

           int year();

 }