18Spring后置通知

Spring后置通知，和前置通知类似，直接看代码：

package com.cn.spring.aop.impl;
//加减乘除的接口类
public interface ArithmeticCalculator {
    int add(int i, int j);
    int sub(int i, int j);
    int mul(int i, int j);
    int div(int i, int j);
}

package com.cn.spring.aop.impl;

import org.springframework.stereotype.Component;

//实现类
@Component
public class ArithmeticCalculatorImpl implements ArithmeticCalculator {
    @Override
    public int add(int i, int j) {
        int result = i + j;
        return result;
    }

    @Override
    public int sub(int i, int j) {
        int result = i - j;
        return result;
    }

    @Override
    public int mul(int i, int j) {
        int result = i * j;
        return result;
    }

    @Override
    public int div(int i, int j) {
        int result = i / j;
        return result;
    }
}

package com.cn.spring.aop.impl;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.stereotype.Component;

import java.util.Arrays;
import java.util.List;

//把这个类声明为一个切面：首先需要把该类放入到IOC容器中，在声明为一个切面
@Aspect
@Component
public class LoggingAspect {

    //声明该方法是一个前置通知：在目标方法开始之前执行
    @Before("execution(public int ArithmeticCalculator.*(int, int))")
    public void beforeMethod(JoinPoint joinPoint) {
        String methodName = joinPoint.getSignature().getName();
        List<Object> args = Arrays.asList(joinPoint.getArgs());

        System.out.println("The method " +  methodName + " begins with " + args);
    }

    //后置通知：在目标方法执行后（无论是否发生异常），执行的通知
    //在后置通知中还不能访问目标方法执行的结果
    @After("execution(public int ArithmeticCalculator.*(int, int))")
    public void afterMethod(JoinPoint joinPoint) {
        String methodName = joinPoint.getSignature().getName();
        List<Object> args = Arrays.asList(joinPoint.getArgs());

        System.out.println("The method " +  methodName + " ends with " + args);
    }
}

package com.cn.spring.aop.impl;

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

public class Main {
    public static void main(String[] args) {
        //1.创建Spring的IOC容器
        ApplicationContext ctx = new ClassPathXmlApplicationContext("17-1.xml");

        //2.从IOC容器中huo获取bean的实例
        ArithmeticCalculator arithmeticCalculator = ctx.getBean(ArithmeticCalculator.class);

        //3.使用bean
        int result = arithmeticCalculator.add(3, 6);
        System.out.println("result:" + result);
    }
}

<?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:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">
    <context:component-scan base-package="com.cn.spring.aop.impl">
    </context:component-scan>

    <!--使AspjectJ注解起作用：自动为匹配的类生成代理对象-->
    <aop:aspectj-autoproxy></aop:aspectj-autoproxy>
</beans>