@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。
