spring —— AOP（前置通知）

一、pom 中需要增加的依赖

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-aop</artifactId>
    <version>6.0.2</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-aspects</artifactId>
    <version>6.0.2</version>
</dependency>

 二、前置通知

（一）基于 xml 的前置通知

 首先，需要在 xml 文件里做如下配置：

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

    <context:component-scan base-package="com.spring.aop"></context:component-scan>
    <aop:aspectj-autoproxy></aop:aspectj-autoproxy>

</beans>

然后，编写目标类：

package com.spring.aop;

import org.springframework.stereotype.Component;

@Component
public class Calculator{

    public int add(int a, int b) {
        System.out.println(a+b);
        return a+b;
    }
    protected String sub(String a){
        System.out.println(a);
        return a;
    }
}

之后，设置切面类： 

package com.spring.aop;

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

@Aspect
@Component
public class LogAspect {
    @Before(value = "execution(public int com.spring.aop.Calculator.add(..))")
    public void beforeMethod(){
        System.out.println("Before Method");
    }
}

最后，测试： 

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

public class TestAop {
    @Test
    public void testAdd(){
        ApplicationContext context = new ClassPathXmlApplicationContext("bean.xml");
        Calculator calculator = context.getBean(Calculator.class);
        calculator.add(2,3);
        calculator.sub("hello");
    }
}

（二）基于全注解的前置通知

目标类：

package com.spring.aop;

import org.springframework.stereotype.Component;

@Component
public class Calculator{

    public int add(int a, int b) {
        System.out.println(a+b);
        return a+b;
    }
    protected String sub(String a){
        System.out.println(a);
        return a;
    }
}

配置类：

package com.spring.aop;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan("com.spring.aop")
public class SpringConfig {
}

切面类： 

package com.spring.aop;

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.context.annotation.EnableAspectJAutoProxy;
import org.springframework.stereotype.Component;
@EnableAspectJAutoProxy
@Aspect
@Component
public class LogAspect {
    @Before(value = "execution(public int com.spring.aop.Calculator.add(..))")
    public void beforeMethod(){
        System.out.println("Before Method");
    }
}

测试类：

package com.spring.aop;

import org.junit.jupiter.api.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class TestAop {
    @Test
    public void testAdd(){
        ApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);
        Calculator calculator = context.getBean(Calculator.class);
        calculator.add(2,3);
        calculator.sub("hello");
    }
}

 比较结果：

基于全注解的前置通知，等同于将 

<context:component-scan base-package="com.spring.aop"></context:component-scan>

配置在配置类的 @ComponentScan 注解中；将

<aop:aspectj-autoproxy></aop:aspectj-autoproxy>

配置在切面类的 @EnableAspectJAutoProxy 注解中。

原文地址：https://blog.csdn.net/firstgrass/article/details/140638160

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