Spring的AOP实现(7)

使用BeanPostProcessor方式实现Spring的AOP

IUserService.java

package com.qfedu.aop07;

import java.util.List;

public interface IUserService {

    /**
     * 获取所有的用户对象列表
     * @return
     */
    List<Object> getAllUser();

    /**
     * 保存用户
     * @param user
     * @return
     */
    boolean saveUser(Object user);

    /**
     * 根据用户uid删除该uid对应的用户信息
     * @param uid
     * @return
     */
    boolean deleteUser(int uid);

    /**
     * 更新指定用户信息
     * @param obj
     * @return
     */
    boolean updateUser(Object obj);


    void getUserByUid();
}

UserServiceImpl.java

package com.qfedu.aop07;

import org.springframework.stereotype.Component;

import java.util.ArrayList;
import java.util.List;

@Component("us")
public class UserServiceImpl implements IUserService {

    @Override
    public List<Object> getAllUser() {
        System.out.println("--------getAllUser----------");
        return new ArrayList<>();
    }

    @Override
    public boolean saveUser(Object user) {
        System.out.println("--------saveUser----------");
        return true;
    }

    @Override
    public boolean deleteUser(int uid) {
        System.out.println("--------deleteUser----------");
        return false;
    }

    @Override
    public boolean updateUser(Object obj) {
        System.out.println("--------updateUser----------");
        return true;
    }

    @Override
    public void getUserByUid() {
        System.out.println("--------getUserByUid----------");
        System.out.println(1 / 0);
        String str = null;
        System.out.println(str.length());
    }
}

MyAspect.java

package com.qfedu.aop07;

/**
 * 自定义切面类，分别有前置方法和后置方法
 */
public class MyAspect {

    public void before(){
        System.out.println("this is my aspect before");
    }

    public void after(){
        System.out.println("this is my aspect after");
    }
}

beans.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">

    <!--<bean id="us" class="com.qfedu.aop07.UserServiceImpl" />-->

    <!--
        context:component-scan上下文的组件扫描
            base-package指定要扫描的包为com.qfedu.aop07
    -->
    <context:component-scan base-package="com.qfedu.aop07" />

    <!--
       指定BeanPostProcessor的Factory hook，让每个bean对象初始化是自动回调该对象中的回调方法
    -->
    <bean class="com.qfedu.aop07.MyBeanPostProcessor" />
</beans>

MyBeanPostProcessor.java

package com.qfedu.aop07;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;

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

/**
 * 配置了包扫描之后，该类会初始化两个对象EventListenerMethodProcessor和DefaultEventListenerFactory，再外加我们自己的组件对象
 *
 * 所以会发现有三个before打印
 *
 * 我还专门加了一个UserServiceImpl2，你会发现将有四个before的打印（注意看看该类上的Component注解是否启用）
 *
 */
public class MyBeanPostProcessor implements BeanPostProcessor {
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("this is before " + bean);
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        System.out.println("this is after");

        return Proxy.newProxyInstance(MyBeanPostProcessor.class.getClassLoader(), bean.getClass().getInterfaces(), new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

                MyAspect ma = new MyAspect();

                ma.before();

                Object obj = method.invoke(bean, args);

                ma.after();

                return obj;
            }
        });
    }
}

TestAOP07.java

package com.qfedu.aop07;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TestAOP07 {

    @Test
    public void testAOP07(){

        ApplicationContext ac = new ClassPathXmlApplicationContext("com/qfedu/aop07/beans.xml");

        IUserService us = ac.getBean("us", IUserService.class);

        us.deleteUser(1);
        us.updateUser("zhangsan");
        us.saveUser("lisi");
        us.getAllUser();
        us.getUserByUid();
    }
}

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原文链接：https://blog.youkuaiyun.com/zpz2001/article/details/104559307