Spring-AOP @AspectJ切点函数之@within()和@target

Posted 2022-02-07 小小工匠

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文章目录

概述
@target(M)的匹配规则
@within(M)的匹配规则
实例
- @target
- @within
注意事项

概述

除了@annotation和@args外，还有另外两个用于注解的切点函数，分别是@target和@within.

和@annotation @args函数一样，@target和@within也只接受注解类名作为入参。

其中@target(M)匹配任意标注了@M的目标类，而@within(M)匹配标注了@M的类及其子孙类（子类经测试匹配不到，欢迎指正）

@target(M)的匹配规则

@target使用@target(注解类型全限定名)匹配当前目标对象类型的执行方法, 必须是在目标对象上声明注解，在接口上声明不起作用

@within(M)的匹配规则

经验证，目前发现和 @target(M)的匹配规则是一样的。

@within(注解类型全限定名)匹配所有持有指定注解的类里面的方法, 即要把注解加在类上. 在接口上声明不起作用。 子孙类经测试匹配不到，如有错误烦请指出。

实例

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

@target

首先自定义一个注解用于测试用

package com.xgj.aop.spring.advisor.aspectJ.function.attarget;

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: Mark
 * 
 * @Description: 自定义注解
 * 
 * @author: Mr.Yang
 * 
 * @date: 2017年9月5日 下午12:02:46
 */

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
public @interface Mark 

	public String value() default "";

4个注解标注的POJO ，继承关系 C3 -->C2–> C1–> C0

package com.xgj.aop.spring.advisor.aspectJ.function.attarget;

import org.springframework.stereotype.Component;

/**
 * 
 * 
 * @ClassName: C0
 * 
 * @Description: @Component 标注的Bean
 * 
 * @author: Mr.Yang
 * 
 * @date: 2017年9月5日 下午1:36:37
 */

@Component
public class C0 

	public void methodName() 
		System.out.println("C0 method executed");

C1类声明处标注了自定义注解@Mark

package com.xgj.aop.spring.advisor.aspectJ.function.attarget;

import org.springframework.stereotype.Component;

@Mark
@Component
public class C1 extends C0 
	public void methodName() 
		System.out.println("C1 method executed");

C2类声明处标注了自定义注解@Mark

package com.xgj.aop.spring.advisor.aspectJ.function.attarget;

import org.springframework.stereotype.Component;

@Mark
@Component
public class C2 extends C1 
	public void methodName() 
		System.out.println("C2 method executed");

package com.xgj.aop.spring.advisor.aspectJ.function.attarget;

import org.springframework.stereotype.Component;

@Component
public class C3 extends C2 
	public void methodName() 
		System.out.println("C3 method executed");

使用@Aspect标注的环绕增强切面

package com.xgj.aop.spring.advisor.aspectJ.function.attarget;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;

/**
 * 
 * 
 * @ClassName: AtTargetAspect
 * 
 * @Description: 标注了@Aspect的切面 环绕增强切面
 * 
 * @author: Mr.Yang
 * 
 * @date: 2017年9月5日 上午11:59:26
 */

@Aspect
public class AtTargetAspect 

	@Around("@target(com.xgj.aop.spring.advisor.aspectJ.function.attarget.Mark)")
	public void crossCuttingCode(ProceedingJoinPoint joinPoint)
			throws Throwable 
		System.out.println("****AtTargetAspect.crossCuttingCode() : "
				+ joinPoint.getSignature().getName()
				+ ": Before Method Execution");
		try 
			joinPoint.proceed();
		 finally 
			// Do Something useful, If you have
		
		System.out.println("****AtTargetAspect.crossCuttingCode() : "
				+ joinPoint.getSignature().getName()
				+ ": After Method Execution");

配置文件

<?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"
	xmlns:context="http://www.springframework.org/schema/context"
	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
		http://www.springframework.org/schema/context 
       	http://www.springframework.org/schema/context/spring-context.xsd">

<!-- (1)声明Context命名空间以及Schema文件   (2)扫描类包以及应用注解定义的bean -->
<context:component-scan base-package="com.xgj.aop.spring.advisor.aspectJ.function.attarget"/>

<!-- 基于@AspectJ切面的驱动器 -->
<aop:aspectj-autoproxy proxy-target-class="true"/>
 
<!-- 使用了@AspectJ注解的切面类 -->
<bean class="com.xgj.aop.spring.advisor.aspectJ.function.attarget.AtTargetAspect"/>

</beans>

测试代码

package com.xgj.aop.spring.advisor.aspectJ.function.attarget;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class AtTargetAspectTest 

	private ApplicationContext ctx;

	@Test
	public void test() 
		ctx = new ClassPathXmlApplicationContext(
				"classpath:com/xgj/aop/spring/advisor/aspectJ/function/attarget/conf-attarget.xml");

		C0 c0 = ctx.getBean("c0", C0.class);
		C1 c1 = ctx.getBean("c1", C1.class);
		C2 c2 = ctx.getBean("c2", C2.class);
		C3 c3 = ctx.getBean("c3", C3.class);

		// C0没有标注了@Mark，不会被织入增强
		c0.methodName();
		// C1标注了@Mark，会被织入增强
		c1.methodName();
		// C2标注了@Mark，会被织入增强
		c2.methodName();
		// C3没有标注了@Mark，不会被织入增强
		c3.methodName();

运行结果：

2017-09-05 13:40:56,244  INFO [main] (AbstractApplicationContext.java:583) - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@c24cb3: startup date [Tue Sep 05 13:40:56 BOT 2017]; root of context hierarchy
2017-09-05 13:40:56,338  INFO [main] (XmlBeanDefinitionReader.java:317) - Loading XML bean definitions from class path resource [com/xgj/aop/spring/advisor/aspectJ/function/attarget/conf-attarget.xml]
C0 method executed
****AtTargetAspect.crossCuttingCode() : methodName: Before Method Execution
C1 method executed
****AtTargetAspect.crossCuttingCode() : methodName: After Method Execution
****AtTargetAspect.crossCuttingCode() : methodName: Before Method Execution
C2 method executed
****AtTargetAspect.crossCuttingCode() : methodName: After Method Execution
C3 method executed

C1 和 C2标注了@Mark注解，可以看到成功的织入了@Around环绕增强

@within

自定义一个注解

package com.xgj.aop.spring.advisor.aspectJ.function.atwithin;

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: Mark
 * 
 * @Description: 自定义注解
 * 
 * @author: Mr.Yang
 * 
 * @date: 2017年9月5日 下午12:02:46
 */

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
@Documented
public @interface Mark2 

	public String value() default "";

4个注解声明的POJO Bean

package com.xgj.aop.spring.advisor.aspectJ.function.atwithin;

import org.springframework.stereotype.Component;

/**
 * 
 * 
 * @ClassName: C0
 * 
 * @Description: @Component 标注的Bean
 * 
 * @author: Mr.Yang
 * 
 * @date: 2017年9月5日 下午1:36:37
 */

@Component
public class A0 

	public void methodName() 
		System.out.println("A0 method executed \\n");

package com.xgj.aop.spring.advisor.aspectJ.function.atwithin;

import org.springframework.stereotype.Component;

/**
 * 
 * 
 * @ClassName: A1
 * 
 * @Description: 标注了@Mark2，可以被增强
 * 
 * @author: Mr.Yang
 * 
 * @date: 2017年9月5日 下午6:02:21
 */

@Mark2
@Component
public class A1 extends A0 
	public void methodName() 
		System.out.println("A1 method executed");

package com.xgj.aop.spring.advisor.aspectJ.function.atwithin;

import org.springframework.stereotype.Component;

@Component
public class A2 extends A1 

	public void methodName() 
		System.out.println("A2 method executed");

package com.xgj.aop.spring.advisor.aspectJ.function.atwithin;

import org.springframework.stereotype.Component;

@Component
public class A3 extends A2 

	public void methodName() 
		System.out.println("A3 method executed");

切面实现了Ordered接口

package com.xgj.aop.spring.advisor.aspectJ.function.atwithin;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.core.Ordered;

/**
 * 
 * 
 * @ClassName: AtWithinAspect
 * 
 * @Description: 标注了@Aspect 环绕增强切面
 * 
 * @author: Mr.Yang
 * 
 * @date: 2017年9月5日 下午1:53:40
 */

@Aspect
public class AtWithinAspect implements Ordered 

	@Around("@within(com.xgj.aop.spring.advisor.aspectJ.function.atwithin.Mark2)")
	public void crossCuttingCode(ProceedingJoinPoint joinPoint)
			throws Throwable 
		System.out.println("****AtWithinAspect.crossCuttingCode() : "
				+ joinPoint.getSignature().getName()
				+ ": Before Method Execution");
		try 
			joinPoint.proceed();
		 finally 
			// Do Something useful, If you have
		
		System.out.println("****AtWithinAspect.crossCuttingCode() : "
				+ joinPoint.getSignature().getName()
				+ ": After Method Execution \\n");
	

	@Override
	public int getOrder() 
		return 1;

配置文件


<?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"
	xmlns:context="http://www.springframework.org/schema/context"
	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
		http://www.springframework.org/schema/context 
       	http://www.springframework.org/schema/context/spring-context.xsd">

<!-- (1)声明Context命名空间以及Schema文件   (2)扫描类包以及应用注解定义的bean -->
<context:component-scan base-package="com.xgj.aop.spring.advisor.aspectJ.function.atwithin"/>

<!-- 基于@AspectJ切面的驱动器 -->
<aop:aspectj-autoproxy proxy-target-class="true"/>
 
<!-- 使用了@AspectJ注解的切面类 -->
<bean class="com.xgj.aop.spring.advisor.aspectJ.function.atwithin.AtWithinAspect"/>

</beans>

测试类

package com.xgj.aop.spring.advisor.aspectJ.function.atwithin;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class AtWithinAspectTest 

	private ApplicationContext ctx;

	@Test
	public void test() 
		ctx = new ClassPathXmlApplicationContext(
				"classpath:com/xgj/aop/spring/advisor/aspectJ/function/atwithin/conf-atwithin.xml");

		A0 a0 = ctx.getBean("a0", A0.class);
		A1 a1 = ctx.getBean("a1", A1.class);
		A2 a2 = ctx.getBean("a2", A2.class);
		A3 a3 = ctx.getBean("a3", A3.class);

		// A0没有标注@Mark，不会被织入增强
		a0.methodName();
		// A1标注了@Mark，会被织入增强
		a1.methodName();
		// A2没有标注@Mark，不会被织入增强
		a2.methodName();
		// A3没有标注@Mark，不会被织入增强
		a3.methodName();

运行结果：

2017-09-05 18:04:01,685  INFO [main] (AbstractApplicationContext.java:583) - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@c24cb3: startup date [Tue Sep 05 18:04:01 BOT 2017]; root of context hierarchy
2017-09-05 18:04:01,793  INFO [main] (XmlBeanDefinitionReader.java:317) - Loading XML bean definitions from class path resource [com/xgj/aop/spring/advisor/aspectJ/function/atwithin/conf-atwithin.xml]
A0 method executed 

****AtWithinAspect.crossCuttingCode() : methodName: Before Method Execution
A1 method executed
****AtWithinAspect.crossCuttingCode() : methodName: After Method Execution 

A2 method executed
A3 method executed

注意事项

如果标注了@M注解的是一个接口，则所有实现该接口的类并不匹配@within(M) . 假设接口Waiter标注了@Mark注解，但是它的实现类NaiveWaiter、NaughtyWaiter这些接口实现类灭有标注@Mark, 则@within(com.xgj.Mark) 和 @target(com,xgj.Mark)都不匹配NaiveWaiter、NaughtyWaiter。因为@within() @target() @annotation函数都是针对目标类而言的，而非针对运行时的引用类型而言。需要特别注意。

验证过程见github中的 com.xgj.aop.spring.advisor.aspectJ.function.atwithin2

输出结果：

2017-09-05 18:11:18,171  INFO [main] (AbstractApplicationContext.java:583) - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@24b9371e: startup date [Tue Sep 05 18:11:18 BOT 2017]; root of context hierarchy
2017-09-05 18:11:18,285  INFO [main] (XmlBeanDefinitionReader.java:317) - Loading XML bean definitions from class path resource [com/xgj/aop/spring/advisor/aspectJ/function/atwithin2/beans.xml]
NaughtyWaiter:greet to XiaoGong...
NaiveWaiter:greet to Jiang...

标注在接口上的@@Monitorable，使用within ，实现类中的方法并没有匹配

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