一、步骤

jdk动态代理反射机制

package jdkproxy;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

/**
 * 调用处理器实现类
 */
public class JdkProxy implements InvocationHandler {

    //需要增强的类
    private Object target;  //目标代理类

    public JdkProxy(Object target) {
        this.target = target;
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

        //开启事务
        System.out.println("动态代理 开启事务");
        Object result = method.invoke(target, args);
        System.out.println("动态代理 提交事务");

        return result;
    }

    public static void main(String[] args) {

        UserDao userDao = new UserDaoImpl();    //创建目标对象

        JdkProxy jdkProxy = new JdkProxy(userDao);  //创建调用处理器实现类

        ClassLoader classLoader = userDao.getClass().getClassLoader();  //获取目标对象类的加载器

        Class<?>[] interfaces = userDao.getClass().getInterfaces(); //获得userDao对象实现接口的数组。

        /**
         * Proxy动态代理类并返回代理类的一个实例
         * 该方法用于为指定类装载器、一组接口及调用处理器生成动态代理类实例
         */
        UserDao userDao1 =(UserDao) Proxy.newProxyInstance(classLoader, interfaces, jdkProxy);

        userDao1.test();

    }
}

二、Cglib代理

步骤

package cglibProxy;

import jdkproxy.UserDao;
import jdkproxy.UserDaoImpl;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

import java.lang.reflect.Method;
//字节码asm
public class CglibInterceptor<T> implements MethodInterceptor {    //cglib 代理实现

    //需要增强的类
    private T target;  //目标代理类

    public T getInstance(Object target) {
        this.target = target;
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(target.getClass());
        enhancer.setCallback(this);
        return (T)enhancer.create();
    }

    @Override
    public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
        //开启事务
        System.out.println("代理 开启事务");
        Object result = methodProxy.invoke(target, objects);
        System.out.println("代理 提交事务");
        return result;
    }

    public static void main(String[] args) {

        CglibInterceptor cglibInterceptor = new CglibInterceptor();
        UserDao userDao1 = (UserDao)cglibInterceptor.getInstance(new UserDaoImpl());
        userDao1.test();
    }

}