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

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)@Documentedpublic @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 */@Componentpublic 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@Componentpublic 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@Componentpublic 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;@Componentpublic 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 */@Aspectpublic 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 hierarchy2017-09-05 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 ExecutionC1 method executed****AtTargetAspect.crossCuttingCode() : methodName: After Method Execution****AtTargetAspect.crossCuttingCode() : methodName: Before Method ExecutionC2 method executed****AtTargetAspect.crossCuttingCode() : methodName: After Method ExecutionC3 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)@Documentedpublic @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 */@Componentpublic 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@Componentpublic 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;@Componentpublic 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;@Componentpublic 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 */@Aspectpublic 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 hierarchy2017-09-05 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 ExecutionA1 method executed****AtWithinAspect.crossCuttingCode() : methodName: After Method Execution A2 method executedA3 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 hierarchy2017-09-05 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