@annotation()概述

@annotation表示标注了某个注解的所有方法。

下面通过一个实例说明@annotation()的用法。AnnotationTestAspect定义了一个后置切面增强，该增强将应用到标注了NeedTest的目标方法中。

实例

代码已托管到Github—> https://github.com/yangshangwei/SpringMaster

这里写图片描述

首先我们先自定义一个注解@NeedTest。

如何自定义注解请参考Java-Java5.0注解解读

package com.xgj.aop.spring.advisor.aspectJ.function;import java.lang.annotation.Documented;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;/**
 * 
 * 
 * @ClassName: NeedTest
 * 
 * @Description: 自定义注解@NeedTest
 * 
 * @author: Mr.Yang
 * 
 * @date: 2017年8月26日 下午11:19:12
 */// 声明注解的保留期限@Retention(RetentionPolicy.RUNTIME)// 声明可以使用该注解的目标类型@Target(ElementType.METHOD)@Documentedpublic @interfaceNeedTest{// 声明注解成员booleanvalue()defaultfalse;}

下面我们定义接口 Waiter

package com.xgj.aop.spring.advisor.aspectJ.function;publicinterfaceWaiter{publicvoidgreetTo(String clientName);publicvoidserverTo(String clientName);}

接口实现类两个NaiveWaiter 和 NaughtWaiter

package com.xgj.aop.spring.advisor.aspectJ.function;publicclassNaiveWaiterimplementsWaiter{@NeedTest(true)@OverridepublicvoidgreetTo(String clientName){
		System.out.println("NaiveWaiter:greet to "+ clientName);}@OverridepublicvoidserverTo(String clientName){
		System.out.println("NaiveWaiter:server to "+ clientName);}publicvoidsmile(String clientName,int times){
		System.out.println("NaiveWaiter:smile to  "+ clientName+" "+ times+" times");}}

package com.xgj.aop.spring.advisor.aspectJ.function;publicclassNaughtWaiterimplementsWaiter{@OverridepublicvoidgreetTo(String clientName){
		System.out.println("NaughtWaiter:greet to "+ clientName);}@NeedTest(true)@OverridepublicvoidserverTo(String clientName){
		System.out.println("NaughtWaiter:server to "+ clientName);}publicvoidjoke(String clientName,int times){
		System.out.println("NaughtyWaiter:play "+ times+" jokes to "+ clientName);}}

我们可以看到 NaiveWaiter#greetTo()方法标注了@NeedTest， NaughtWaiter#serverTo()也标注了@NeedTest，我们的目标就是将后置增强织入到这两个标注了@NeedTest的方法中。

接下来编写切面的横切逻辑

package com.xgj.aop.spring.advisor.aspectJ.function.annotationFun;import org.aspectj.lang.annotation.AfterReturning;import org.aspectj.lang.annotation.Aspect;/**
 * 
 * 
 * @ClassName: AnnotationTestAspect
 * 
 * @Description: 切面 、 后置增强 ,@annotation表示标注了某个注解的所有方法
 * 
 * @author: Mr.Yang
 * 
 * @date: 2017年8月26日 下午11:23:53
 */@AspectpublicclassAnnotationTestAspect{@AfterReturning("@annotation(com.xgj.aop.spring.advisor.aspectJ.function.NeedTest)")publicvoidneedTest(){
		System.out.println("needTest() executed,some logic is here");}}

接下来通过Spring自动应用切面，配置文件如下

<?xml version="1.0" encoding="UTF-8"?><beansxmlns="http://www.springframework.org/schema/beans"xmlns:aop="http://www.springframework.org/schema/aop"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
		http://www.springframework.org/schema/aop
		http://www.springframework.org/schema/aop/spring-aop.xsd"><!-- 使用基于Schema的aop命名空间进行配置 --><!-- 基于@AspectJ切面的驱动器 --><aop:aspectj-autoproxy/><!-- 目标Bean --><beanid="naiveWaiter"class="com.xgj.aop.spring.advisor.aspectJ.function.NaiveWaiter"/><beanid="naughtWaiter"class="com.xgj.aop.spring.advisor.aspectJ.function.NaughtWaiter"/><!-- 使用了@AspectJ注解的切面类 --><beanclass="com.xgj.aop.spring.advisor.aspectJ.function.annotationFun.AnnotationTestAspect"/></beans>

最后编写测试代码：

package com.xgj.aop.spring.advisor.aspectJ.function.annotationFun;import org.junit.Test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import com.xgj.aop.spring.advisor.aspectJ.function.Waiter;publicclassAnnotationTestAspcetTest{@Testpublicvoidtest(){
		ApplicationContext ctx=newClassPathXmlApplicationContext("com/xgj/aop/spring/advisor/aspectJ/function/annotationFun/conf-annotation.xml");// 必须是接口类型,否则抛类型转换异常
		Waiter waiter=(Waiter) ctx.getBean("naiveWaiter");// 因为greetTo标注了@NeedTest,因此会被后置增强
		waiter.greetTo("XiaoGongJiang");
		waiter.serverTo("XiaoGongJiang");

		Waiter naughtWaiter=(Waiter) ctx.getBean("naughtWaiter");// serverTo标注了@NeedTest,因此会被后置增强
		naughtWaiter.serverTo("XiaoGongJiang");}}

运行结果：

2017-08-2701:24:22,551  INFO[main](AbstractApplicationContext.java:583)- Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@6ac604: startup date[Sun Aug2701:24:22 BOT2017]; root of context hierarchy2017-08-2701:24:22,647  INFO[main](XmlBeanDefinitionReader.java:317)- Loading XML bean definitions fromclasspath resource[com/xgj/aop/spring/advisor/aspectJ/function/annotationFun/conf-annotation.xml]
NaiveWaiter:greet to XiaoGongJiangneedTest() executed,some logic is here
NaiveWaiter:server to XiaoGongJiang
NaughtWaiter:server to XiaoGongJiangneedTest() executed,some logic is here

从输出结果中可以看出，切面被正确的织入到了标注有@NeedTest注解的方法中。