Spring-AOP @AspectJ切點函數之@annotation()用法

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@annotation()概述

@annotation表示標註瞭某個註解的所有方法。

下面通過一個實例說明@annotation()的用法。 AnnotationTestAspect定義瞭一個後置切面增強，該增強將應用到標註瞭NeedTest的目標方法中。

實例

代碼已托管到Github—> https://github.com/yangshangwei/SpringMaster

這裡寫圖片描述

首先我們先自定義一個註解@NeedTest。

如何自定義註解請參考Java-Java5.0註解解讀

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: 自定義註解@NeedTest
 * 
 * @author: Mr.Yang
 * 
 * @date: 2017年8月26日 下午11:19:12
 */
// 聲明註解的保留期限
@Retention(RetentionPolicy.RUNTIME)
// 聲明可以使用該註解的目標類型
@Target(ElementType.METHOD)
@Documented
public @interface NeedTest {
	// 聲明註解成員
	boolean value() default false;
}

下面我們定義接口 Waiter

package com.xgj.aop.spring.advisor.aspectJ.function;
public interface Waiter {
 public void greetTo(String clientName);
 public void serverTo(String clientName);
}

接口實現類 兩個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);
	}
}

我們可以看到 NaiveWaiter#greetTo()方法標註瞭@NeedTest， NaughtWaiter#serverTo()也標註瞭@NeedTest，我們的目標就是將後置增強織入到這兩個標註瞭@NeedTest的方法中。

接下來編寫切面的橫切邏輯

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 、 後置增強 ,@annotation表示標註瞭某個註解的所有方法
 * 
 * @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");
	}
}

接下來通過Spring自動應用切面，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">
<!-- 使用基於Schema的aop命名空間進行配置 -->
 
<!-- 基於@AspectJ切面的驅動器 -->
<aop:aspectj-autoproxy/>
 
<!-- 目標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"/>
<!-- 使用瞭@AspectJ註解的切面類 -->
<bean class="com.xgj.aop.spring.advisor.aspectJ.function.annotationFun.AnnotationTestAspect"/>
</beans>

最後編寫測試代碼：

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");
  // 必須是接口類型,否則拋類型轉換異常
  Waiter waiter = (Waiter) ctx.getBean("naiveWaiter");
  // 因為greetTo標註瞭@NeedTest,因此會被後置增強
  waiter.greetTo("XiaoGongJiang");
  waiter.serverTo("XiaoGongJiang");
  Waiter naughtWaiter = (Waiter) ctx.getBean("naughtWaiter");
  // serverTo標註瞭@NeedTest,因此會被後置增強
  naughtWaiter.serverTo("XiaoGongJiang");
 }
}

運行結果：

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

從輸出結果中可以看出，切面被正確的織入到瞭標註有@NeedTest註解的方法中。

以上為個人經驗，希望能給大傢一個參考，也希望大傢多多支持WalkonNet。

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