首先我們先來(lái)一個(gè)簡(jiǎn)單到不能簡(jiǎn)單的服務(wù)接口:

HelloService.java

package com.jd.www.jpl.service;
 
public interface HelloService {
        public void sayHello();
}

以及實(shí)現(xiàn)類

HelloServiceImpl.java

package com.jd.www.jpl.service.impl;
 
import com.jd.www.jpl.service.HelloService;
 
public class HelloServiceImpl implements HelloService {
 
    @Override
    public void sayHello() {
        System.out.println("hello world!!");
    }
}

接著創(chuàng)建一個(gè)攔截器接口

Interceptor.java

package com.jd.www.jpl.common.aop.proxy;
 
public interface Interceptor {
    // 前置通知
    void before();
 
    // 是否采用環(huán)繞通知
    boolean useAround();
 
    // 環(huán)繞通知
    Object around(Object target, Method method, Object[] args)
            throws IllegalAccessException, IllegalArgumentException, InvocationTargetException;
 
    // 事后方法
    void after();
 
    // 異常返回方法
    void afterThrowing();
 
    // 正常返回方法
    void afterReturning();
 
}

依據(jù)這個(gè)接口乳绕，可以給出一個(gè)很簡(jiǎn)單的實(shí)現(xiàn)

MyInterceptor.java

package com.jd.www.jpl.common.aop.proxy.impl;

import com.jd.www.jpl.common.aop.proxy.Interceptor;

public class MyInterceptor implements Interceptor {
    @Override
    public void before() {
        System.out.println("事前通知");
    }

    @Override
    public boolean useAround() {
        return true;
    }

    @Override
    public Object around(Object target, Method method, Object[] args) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException {
        System.out.println("環(huán)繞通知before");
        Object o = method.invoke(target,args);
        System.out.println("環(huán)繞通知after");
        return o;
    }

    @Override
    public void after() {
        System.out.println("事后通知");
    }

    @Override
    public void afterThrowing() {
        System.out.println("異常返回通知"); 
    }

    @Override
    public void afterReturning() {
        System.out.println("正常返回通知");
    }
}

如果用proxy去調(diào)用方法借杰，約定如下：

1播演、首先調(diào)用攔截器的before方法翔怎；

2缨伊、如果攔截器的useAround方法，返回為true辣卒，則執(zhí)行攔截器的around方法拧晕，不執(zhí)行target對(duì)象原有的sayHello方法紊扬；

3、無(wú)論結(jié)果如何都會(huì)執(zhí)行攔截器的after方法唉擂；

4餐屎、如果around方法有異常或者原有的target對(duì)象的sayHello方法有異常楔敌，則執(zhí)行攔截器的afterThrowing方法啤挎，否則執(zhí)行afterReturning方法。

好了卵凑，為了更好的說(shuō)明庆聘，我們來(lái)個(gè)流程圖。

流程圖

對(duì)應(yīng)的ProxyBean

package com.jd.www.jpl.common.aop.proxy.impl;

public class ProxyBean implements InvocationHandler {

    private Object target;
    private Interceptor interceptor;

    public static Object getProxyBean(Object target, Interceptor interceptor){
        ProxyBean proxyBean = new ProxyBean();
        proxyBean.target = target;
        proxyBean.interceptor = interceptor;
        return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(),proxyBean);
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        boolean e = false;
        Object ret = null;
        MyInterceptor myInterceptor = new MyInterceptor();
        myInterceptor.before();
        try {
            if(interceptor.useAround()){
                ret = myInterceptor.around(target,method,args);
            }else {
                ret = method.invoke(target,args);
            }
        } catch (InvocationTargetException | IllegalAccessException | IllegalArgumentException ex) {
            e = true;
        }
        myInterceptor.after();
        if(e){
            myInterceptor.afterThrowing();
        }else{
            myInterceptor.afterReturning();
            return ret;
        }
        return null;
    }
}

創(chuàng)建測(cè)試用例

SpringAopTest.java

package com.jd.jmq.consumer;

import com.jd.www.jpl.common.aop.proxy.impl.MyInterceptor;
import com.jd.www.jpl.common.aop.proxy.impl.ProxyBean;
import com.jd.www.jpl.service.HelloService;
import com.jd.www.jpl.service.impl.HelloServiceImpl;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = {"classpath*:spring/spring-consumer.xml"})
public class SpringAopTest {
    @Test
    public void testAop(){
        HelloService helloService = new HelloServiceImpl();
        HelloService proxy = (HelloService) ProxyBean.getProxyBean(helloService,new MyInterceptor());
        proxy.sayHello();
    }
}

運(yùn)行結(jié)果：

結(jié)果