基于注解的AOP开发

1、快速入门

①、创建目标接口和目标类（内部有切点）
创建一个itheima_spring_aop的项目，创建com.itheima.anno包，然后在里面创建目标类Target和目标接口TargetInterface

package com.itheima.anno;

public class Target implements TargetInterface {

    public void save() {
        System.out.println("save running...");
    }
}

package com.itheima.anno;

public interface TargetInterface {
    public void save();
}

②、创建切面类（内部有增强方法）
创建切面MyAspect类，里面有增强的方法

package com.itheima.anno;

import org.aspectj.lang.ProceedingJoinPoint;

public class MyAspect {
    public void before(){
        System.out.println("前置增强....");
    }

    public void afterReturning(){
        System.out.println("后置增强....");
    }

    //ProceedingJoinPoint：正在执行的连接点 ==> 切点
    public Object around(ProceedingJoinPoint pjp) throws Throwable {
        System.out.println("环绕前增强....");
        Object proceed = pjp.proceed();//切点方法
        System.out.println("环绕后增强....");
        return proceed;
    }

    public void afterThrowing(){
        System.out.println("异常抛出增强....");
    }

    public void after(){
        System.out.println("最终增强....");
    }
}

③、将目标类和切面类的对象创建权交给 spring

import org.springframework.stereotype.Component;

@Component("target")
public class Target implements TargetInterface {
	//代码省略
}

import org.aspectj.lang.ProceedingJoinPoint;
import org.springframework.stereotype.Component;

@Component("myAspect")
public class MyAspect {
    //代码省略
}

④、在切面类中使用注解配置织入关系
在src\main\resource里面创建创建applicationContext-anno.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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

</beans>

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.*;
import org.springframework.stereotype.Component;

@Component("myAspect")
@Aspect//标注当前MyAspect是一个切面类

public class MyAspect {

    //配置前置通知
    @Before("execution(* com.itheima.anno.*.*(..))")
    public void before(){
        System.out.println("前置增强....");
    }
    @AfterReturning("execution(* com.itheima.anno.*.*(..))")
    public void afterReturning(){
        System.out.println("后置增强....");
    }

    //ProceedingJoinPoint：正在执行的连接点 ==> 切点
    @Around("execution(* com.itheima.anno.*.*(..))")
    public Object around(ProceedingJoinPoint pjp) throws Throwable {
        System.out.println("环绕前增强....");
        Object proceed = pjp.proceed();//切点方法
        System.out.println("环绕后增强....");
        return proceed;
    }

    @AfterThrowing("execution(* com.itheima.anno.*.*(..))")
    public void afterThrowing(){
        System.out.println("异常抛出增强....");
    }

    @After("execution(* com.itheima.anno.*.*(..))")
    public void after(){
        System.out.println("最终增强....");
    }
}

⑤、在配置文件中开启组件扫描和 AOP 的自动代理

<?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/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">

    <!--组件扫描-->
    <context:component-scan base-package="com.itheima.anno"/>

    <!--aop自动代理-->
    <aop:aspectj-autoproxy/>

</beans>

⑥、测试
在src\test\java里面创建com.itheima.test包，然后创建测试AnnoTest文件

import com.itheima.anno.TargetInterface;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:applicationContext-anno.xml")
public class AnnoTest {

    @Autowired
    private TargetInterface target;

    @Test
    public void test1(){
        target.save();
    }
}
运行结果：
环绕前增强....
前置增强....
save running...
环绕后增强....
最终增强....
后置增强....

2、注解配置AOP详解

（1）注解通知的类型

• 通知的配置语法：@通知注解("切点表达式")
  
  

（2）切点表达式的抽取

• 同xml配置aop一样，我们可以将切点表达式抽取。抽取方式是在切面内定义方法，在该方法上使用@Pointcut注解定义切点表达式，然后在在增强注解中进行引用。具体如下：

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.*;
import org.springframework.stereotype.Component;

@Component("myAspect")
@Aspect//标注当前MyAspect是一个切面类

public class MyAspect {

    //配置前置通知
    @Before("pointcut()")
    public void before(){
        System.out.println("前置增强....");
    }
    @AfterReturning("pointcut()")
    public void afterReturning(){
        System.out.println("后置增强....");
    }

    //ProceedingJoinPoint：正在执行的连接点 ==> 切点
    @Around("pointcut()")
    public Object around(ProceedingJoinPoint pjp) throws Throwable {
        System.out.println("环绕前增强....");
        Object proceed = pjp.proceed();//切点方法
        System.out.println("环绕后增强....");
        return proceed;
    }

    @AfterThrowing("MyAspect.pointcut()")
    public void afterThrowing(){
        System.out.println("异常抛出增强....");
    }

    @After("MyAspect.pointcut()")
    public void after(){
        System.out.println("最终增强....");
    }

    //定义切点表达式
    @Pointcut("execution(* com.itheima.anno.*.*(..))")
    public void pointcut(){}
}