Spring-AOP @AspectJ切点函数之@annotation()

@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">




<aop:aspectj-autoproxy/>


<bean id="naiveWaiter" class="com.xgj.aop.spring.advisor.aspectJ.function.NaiveWaiter"/>

<bean id="naughtWaiter" class="com.xgj.aop.spring.advisor.aspectJ.function.NaughtWaiter"/>


<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。