Spring-AOP @AspectJ进阶之增强织入的顺序

概述

一个连接点可以同时匹配多个切点，切点对应的增强在连接点上的织入顺序到底是如何安排呢？这个问题需要分三种情况讨论：

• 如果增强在同一个切面类中声明，则依照增强在切面类中定义的顺序进行织入；

• 如果增强位于不同的切面类中，且这些切面类都实现了org.springframework.core.Ordered接口，则由接口方法的顺序号决定（顺序号小的先织入）；

• 如果增强位于不同的切面类中，且这些切面类没有实现org.springframework.core.Ordered接口，织入的顺序是不确定的。

我们可以通过下图描述这种织入的规则：

切面类A和B都实现为Ordered接口，A切面类对应序号为1，B切面类对应序号为2，A切面类按顺序定义了3个增强，B切面类按顺序定义两个增强，这5个增强对应的切点都匹配某个目标类的连接点，则增强织入的顺序为图中虚线所示。

---

示例

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

业务类

package com.xgj.aop.spring.advisor.aspectJAdvance.pointOrder;

import org.springframework.stereotype.Component;

/**
 * 
 * 
 * @ClassName: Bussiness
 * 
 * @Description: @Component标注的Bean
 * 
 * @author: Mr.Yang
 * 
 * @date: 2017年9月11日 上午1:38:06
 */

@Component
public class Bussiness {

    public void dealBussiness() {
        System.out.println("dealBussiness executed");
    }
}

切面1

package com.xgj.aop.spring.advisor.aspectJAdvance.pointOrder;

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.core.annotation.Order;

/**
 * 
 * 
 * @ClassName: PointOrderOneAspect
 * 
 * @Description: @Aspect标注的切面,实现Ordered接口 重写getOrder方法 后者 使用注解 @Order(value = 1)
 * 
 * @author: Mr.Yang
 * 
 * @date: 2017年9月11日 上午1:35:42
 */

@Aspect
@Order(value = 1)
public class PointOrderOneAspect {

    @Before("execution(* dealBussiness(..))")
    public void method1() {
        System.out.println("method1 executed");
    }

    @Before("execution(* dealBussiness(..))")
    public void method2() {
        System.out.println("method2 executed");
    }

    @Before("execution(* dealBussiness(..))")
    public void method3() {
        System.out.println("method3 executed");
    }

}

切面2

package com.xgj.aop.spring.advisor.aspectJAdvance.pointOrder;

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.springframework.core.annotation.Order;

/**
 * 
 * 
 * @ClassName: PointOrderTwoAspect
 * 
 * @Description: @Aspect标注的切面,实现Ordered接口 重写getOrder方法 后者 使用注解 @Order(value = 2)
 * 
 * @author: Mr.Yang
 * 
 * @date: 2017年9月11日 上午1:36:02
 */

@Aspect
@Order(value = 2)
public class PointOrderTwoAspect {

    @Before("execution(* dealBussiness(..))")
    public void method4() {
        System.out.println("method4 executed");
    }

    @Before("execution(* dealBussiness(..))")
    public void method5() {
        System.out.println("method5 executed");
    }

}

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.aspectJAdvance.pointOrder"/>

<!-- 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.pointOrder.PointOrderOneAspect"/>
<bean class="com.xgj.aop.spring.advisor.aspectJAdvance.pointOrder.PointOrderTwoAspect"/>

</beans>

测试类

package com.xgj.aop.spring.advisor.aspectJAdvance.pointOrder;

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

public class PointOrderAspectTest {

    @Test
    public void test() {
        ApplicationContext ctx = new ClassPathXmlApplicationContext(
                "com/xgj/aop/spring/advisor/aspectJAdvance/pointOrder/conf-pointOrder.xml");

        Bussiness bussiness = ctx.getBean("bussiness", Bussiness.class);

        bussiness.dealBussiness();
    }
}

运行结果

2017-09-11 01:46:32,790  INFO [main] (AbstractApplicationContext.java:583) - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@3695de1a: startup date [Mon Sep 11 01:46:32 BOT 2017]; root of context hierarchy
2017-09-11 01:46:32,869  INFO [main] (XmlBeanDefinitionReader.java:317) - Loading XML bean definitions from class path resource [com/xgj/aop/spring/advisor/aspectJAdvance/pointOrder/conf-pointOrder.xml]
method1 executed
method2 executed
method3 executed
method4 executed
method5 executed
dealBussiness executed