@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

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)
- @Documented
- public @interface NeedTest {
- // 声明注解成员
- boolean value() default false;
- }
下面我们定义接口 Waiter
- package com.xgj.aop.spring.advisor.aspectJ.function;
- public interface Waiter {
- public void greetTo(String clientName);
- public void serverTo(String clientName);
- }
接口实现类 两个NaiveWaiter 和 NaughtWaiter
- package com.xgj.aop.spring.advisor.aspectJ.function;
- public class NaiveWaiter implements Waiter {
- @NeedTest(true)
- @Override
- public void greetTo(String clientName) {
- System.out.println("NaiveWaiter:greet to " + clientName);
- }
- @Override
- public void serverTo(String clientName) {
- System.out.println("NaiveWaiter:server to " + clientName);
- }
- public void smile(String clientName, int times) {
- System.out.println("NaiveWaiter:smile to " + clientName + " " + times
- + " times");
- }
- }
- package com.xgj.aop.spring.advisor.aspectJ.function;
- public class NaughtWaiter implements Waiter {
- @Override
- public void greetTo(String clientName) {
- System.out.println("NaughtWaiter:greet to " + clientName);
- }
- @NeedTest(true)
- @Override
- public void serverTo(String clientName) {
- System.out.println("NaughtWaiter:server to " + clientName);
- }
- public void joke(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
- */
- @Aspect
- public class AnnotationTestAspect {
- @AfterReturning("@annotation(com.xgj.aop.spring.advisor.aspectJ.function.NeedTest)")
- public void needTest() {
- 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"?>
- <beans xmlns="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 -->
- <bean id="naiveWaiter" class="com.xgj.aop.spring.advisor.aspectJ.function.NaiveWaiter"/>
- <bean id="naughtWaiter" class="com.xgj.aop.spring.advisor.aspectJ.function.NaughtWaiter"/>
- <!-- 使用了@AspectJ注解的切面类 -->
- <bean class="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;
- public class AnnotationTestAspcetTest {
- @Test
- public void test() {
- ApplicationContext ctx = new ClassPathXmlApplicationContext(
- "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:
2017-08-27 01:24:22,551 INFO [main] (AbstractApplicationContext.java:583) - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@6ac604: startup date [Sun Aug 27 01:24:22 BOT 2017]; root of context hierarchy
2017-08-27 01:24:22,647 INFO [main] (XmlBeanDefinitionReader.java:317) - Loading XML bean definitions from class path resource [com/xgj/aop/spring/advisor/aspectJ/function/annotationFun/conf-annotation.xml]
NaiveWaiter:greet to XiaoGongJiang
needTest() executed,some logic is here
NaiveWaiter:server to XiaoGongJiang
NaughtWaiter:server to XiaoGongJiang
needTest() 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。
以上为个人经验,希望能给大家一个参考,也希望大家多多支持w3xue。