Spring-AOP @AspectJ进阶之命名切点

概述

在前面所举的例子中，比如

@Before("within(com.xgj.aop.spring.advisor.aspectJAdvance.pointcutComplex.*)"            + " && execution(* greetTo(..))")    public void matchGreetTo() {        System.out.println("matchGreetTo executed,some logic is here ");    }

切点直接声明在增强方法处，这种切点声明方式称为匿名切点，匿名切点只能在声明处使用。

如果希望在其它地方重用一个切点，我们可以通过@Pointcut注解以及切面类方法对切点进行命名

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示例

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

package com.xgj.aop.spring.advisor.aspectJAdvance.namePoint;import org.aspectj.lang.annotation.Pointcut;/** *  *  * @ClassName: NamePoint *  * @Description: 如果希望在其它地方重用一个切点，我们可以通过@Pointcut注解以及切面类方法对切点进行命名 *  * @author: Mr.Yang *  * @date: 2017年9月10日 下午11:13:45 */public class NamePoint{    /**     *      *      * @Title: inPackage     *      * @Description: 通过注解方法inPackage()对该切点进行命名，方法可视域     *               修饰符为private,表明该命名切点只能在本切面类中使用。     *      *      * @return: void     */    @Pointcut("within(com.xgj.aop.spring.advisor.aspectJAdvance.namePoint)")    private void inPackage() {    };    /**     *      *      * @Title: greetTo     *      * @Description: 通过注解方法greetTo()对该切点进行命名，方法可视域     *               修饰符为protected,表明该命名切点可以在当前包中的切面 类、子切面类中中使用。     *      *      * @return: void     */    @Pointcut("execution(* greetTo(..))")    protected void greetTo() {    }    /**     *      *      * @Title: inPkgGreetTo     *      * @Description: 引用命名切点定义的切点，本切点也是命名切点， 它对应的可视域为public     *      *      * @return: void     */    @Pointcut("inPackage() and greetTo()")    public void inPkgGreetTo() {    }}

上面上述示例中定义了3个命名切点，命名切点的使用类方法作为切点的名称，此外方法的访问修饰符还控制了切点的可引用性，这种可引用性和类方法的可访问性相同，如private的切点只能在本类中引用，public的切点可以在任何类中引用。

命名切点仅利用方法名及访问修饰符的信息，所以习惯上，方法的返回类型为void，并且方法体为空。

我们可以通过下图更直观地了解命名切点的结构：

inPkgGreetTo()的切点引用了同类中的greetTo()切点，而inPkgGreetTo()切点可以被任何类引用。

你还可以扩展NamePoint类，通过类的继承关系定义更多的切点。 命名切点定义好后，就可以在定义切面时通过名称引用切点.

来看个示例

假设有两个业务类

package com.xgj.aop.spring.advisor.aspectJAdvance.namePoint;import org.springframework.stereotype.Component;/** *  *  * @ClassName: NaiveWaiter *  * @Description: @Component注解标注的bean *  * @author: Mr.Yang *  * @date: 2017年9月10日 下午11:55:00 */@Componentpublic class NaiveWaiter {    public void greetTo(String clientName) {        System.out.println("NaiveWaiter greetTo " + clientName);    }    public void serverTo(String clientName) {        System.out.println("NaiveWaiter serverTo " + clientName);    }}

package com.xgj.aop.spring.advisor.aspectJAdvance.namePoint;import org.springframework.stereotype.Component;@Componentpublic class CuteWaiter {    public void greetTo(String clientName) {        System.out.println("CuteWaiter greetTo " + clientName);    }    public void serverTo(String clientName) {        System.out.println("CuteWaiter serverTo " + clientName);    }}

切点命名复用上面那个切点，然后编写切面NamePointAspect

package com.xgj.aop.spring.advisor.aspectJAdvance.namePoint;import org.aspectj.lang.annotation.AfterReturning;import org.aspectj.lang.annotation.Aspect;/** *  *  * @ClassName: NamePointTest *  * @Description: 使用@Aspect注解标注的切面，演示命名切点的使用 *  * @author: Mr.Yang *  * @date: 2017年9月10日 下午11:42:39 */@Aspectpublic class NamePointAspect {    /**     *      *      * @Title: pkgGreetTo     *      * @Description: 引用了NamePoint.inPkgGreetTo()切点     *      *      * @return: void     */    @AfterReturning("NamePoint.inPkgGreetTo()")    public void pkgGreetTo() {        System.out.println("pkgGreetTo exectued ,some logic is here ");    }    /**     *      *      * @Title: pkgGreetToNotNaiveWaiter     *      * @Description: 在复合运算中使用了命名切点     *      *      * @return: void     */    @AfterReturning("!target(com.xgj.aop.spring.advisor.aspectJAdvance.namePoint.NaiveWaiter) && NamePoint.inPkgGreetTo()")    public void pkgGreetToNotNaiveWaiter() {        System.out                .println("pkgGreetToNotNaiveWaiter() executed,some logic is here");    }}

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"    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.aspectJAdvance.namePoint"/><!-- 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.aspectJAdvance.namePoint.NamePointAspect"/></beans>

测试类

package com.xgj.aop.spring.advisor.aspectJAdvance.namePoint;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;/** *  *  * @ClassName: NamePointAspectTest *  * @Description: 命名切点测试类 *  * @author: Mr.Yang *  * @date: 2017年9月10日 下午11:56:50 */public class NamePointAspectTest {    public static void main(String[] args) {        ApplicationContext ctx = new ClassPathXmlApplicationContext(                "classpath:com/xgj/aop/spring/advisor/aspectJAdvance/namePoint/conf-namePoint.xml");        CuteWaiter cuteWaiter = ctx.getBean("cuteWaiter", CuteWaiter.class);        NaiveWaiter naiveWaiter = ctx.getBean("naiveWaiter", NaiveWaiter.class);        naiveWaiter.greetTo("XiaoGongJiang");        System.out.println("================");        cuteWaiter.greetTo("XiaoGongJiang");        System.out.println("================");        naiveWaiter.serverTo("XiaoGongJiang");        System.out.println("================");        cuteWaiter.serverTo("XiaoGongJiang");    }}

运行结果

2017-09-11 00:58:34,752  INFO [main] (AbstractApplicationContext.java:583) - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@4888884e: startup date [Mon Sep 11 00:58:34 BOT 2017]; root of context hierarchy2017-09-11 00:58:34,821  INFO [main] (XmlBeanDefinitionReader.java:317) - Loading XML bean definitions from class path resource [com/xgj/aop/spring/advisor/aspectJAdvance/namePoint/conf-namePoint.xml]NaiveWaiter greetTo XiaoGongJiangpkgGreetTo exectued ,some logic is here ================CuteWaiter greetTo XiaoGongJiangpkgGreetTo exectued ,some logic is here pkgGreetToNotNaiveWaiter() executed,some logic is here================NaiveWaiter serverTo XiaoGongJiangpkgGreetTo exectued ,some logic is here ================CuteWaiter serverTo XiaoGongJiangpkgGreetTo exectued ,some logic is here pkgGreetToNotNaiveWaiter() executed,some logic is here

可以看到NaiveWaiter greetTo 方法 没有织入第二个增强。