@AspectJ 作為通過 Java 5 注釋注釋的普通的 Java 類，它指的是聲明aspects 的一種風格。通過在基于架構(gòu)的 XML 配置文件中包含以下元素，@AspectJ 支持是可用的。

aop:aspectj-autoproxy/

大致流程如下：

(1) 首先利用注解聲明一個Aspect：

import org.aspectj.lang.annotation.Aspect; @Aspect public class AspectModule { }

該aspect在Beans.xml中需要進行如下配置：

Beans.xml：

<bean id="myAspect" class="org.xyz.AspectModule"><!-- configure properties of aspect here as normal --> </bean>

(2) 聲明一個切入點PointCut. 切入點表達式定義了我們感興趣的哪個方法會真正被執(zhí)行。

一個例子：該切入點將與 com.tutorialspoint 包下的 Student 類中的 getName() 方法相匹配：

import org.aspectj.lang.annotation.Pointcut; @Pointcut("execution(* com.tutorialspoint.Student.getName(..))") private void getname() {}

(3) 聲明Advice：

@Before("businessService()") public void doBeforeTask(){... } @After("businessService()") public void doAfterTask(){... } @AfterReturning(pointcut = "businessService()", returning="retVal") public void doAfterReturnningTask(Object retVal){// you can intercept retVal here.... } @AfterThrowing(pointcut = "businessService()", throwing="ex") public void doAfterThrowingTask(Exception ex){// you can intercept thrown exception here.... } @Around("businessService()") public void doAroundTask(){... }

看個具體的例子。

Logging.java:

import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Pointcut; import org.aspectj.lang.annotation.Before; import org.aspectj.lang.annotation.After; import org.aspectj.lang.annotation.AfterThrowing; import org.aspectj.lang.annotation.AfterReturning; import org.aspectj.lang.annotation.Around; @Aspect public class Logging {/** Following is the definition for a pointcut to select* all the methods available. So advice will be called* for all the methods.*/@Pointcut("execution(* com.sap.*.*(..))")private void selectAll(){}/** * This is the method which I would like to execute* before a selected method execution.*/@Before("selectAll()")public void beforeAdvice(){System.out.println("Going to setup student profile.");}/** * This is the method which I would like to execute* after a selected method execution.*/@After("selectAll()")public void afterAdvice(){System.out.println("Student profile has been setup.");}/** * This is the method which I would like to execute* when any method returns.*/@AfterReturning(pointcut = "selectAll()", returning="retVal")public void afterReturningAdvice(Object retVal){System.out.println("Returning:" + retVal.toString() );}/*** This is the method which I would like to execute* if there is an exception raised by any method.*/@AfterThrowing(pointcut = "selectAll()", throwing = "ex")public void AfterThrowingAdvice(IllegalArgumentException ex){System.out.println("There has been an exception: " + ex.toString()); } }

定義一個名叫selectAll的Pointcut，execution表達式的值為：execution(* com.sap..(…))

意思是選中package com.sap下的所有Java類方法來動態(tài)調(diào)用advice.

Beans.xml的內(nèi)容：

<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd "><aop:aspectj-autoproxy/><!-- Definition for student bean --><bean id="student" class="com.sap.Student"><property name="name" value="Zara" /><property name="age" value="11"/> </bean><!-- Definition for logging aspect --><bean id="logging" class="com.sap.Logging"/> </beans>

如果不使用@AspectJ和@pointcut注解，我們需要在Beans.xml里進行冗長的定義aspect和pointcut定義：

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