Spring -- aop, 用Aspectj进行AOP开发

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1. 概要

添加类库:aspectjrt.jar和aspectjweaver.jar

添加aop schema.

定义xml元素:<aop:aspectj-autoproxy>

编写java类,并用@Aspect注解成通知

AspectJ 支持 5 种类型的通知注解:

@Before: 前置通知,在方法执行之前执行

@After: 后置通知,在方法执行之后执行

@AfterRunning: 返回通知,在方法返回结果之后执行

@AfterThrowing: 异常通知,在方法抛出异常之后

@Around: 环绕通知,围绕着方法执行

配置成普通bean元素即可.

前置通知:@Before

@Aspect

public class AudienceAdvice {

@Before("execution(* WelcomeService.*(..))")

public void takeSeats(){..}

@Before("execution(* WelcomeService.*(..))")

public void turnOffCellphone(JoinPoint jp){..}

JoinPoint参数可访问连接点细节,入方法名和参数等.

jp.getTarget()//目标对象

jp.getThis()//当前的代理对象

jp.getArgs();//方法调用参数

jp.getSignature().getName()//方法签名

后置通知:@After

@After("execution(* *..WelcomeService.*(..))")

public void applaud(){..}

后置通知在目标方法执行完成之后执行.一个切面aspect包含很多通知.

@After

后置通知表明目标方法执行完之后,不论是否抛异常,都会织入该通知.

@AfterReturning

方法返回后通知只在目标方法返回以后执行,若抛异常不执行.

@AfterReturning(pointcut="",returning="res")

public void xxx(Joinput jp,Object res)

在后置通知中可接收到返回值.res即是用来接收返回值的对象.

环绕通知:@Around

@Around("execution(* *..WelcomeService.*(..))")

public void around(ProceedingPointCut jp){..}

注意:可以控制目标方法是否调用,以及返回完全不同的对象,要慎用.

指定优先级:

@Aspect

@Order(0)

public class xxx{...}

加上@Order注解可以指定加入切面的优先级(先后顺序,值越小,优先级越高)

引入通知:

@Aspect

public class MyAspectjIntroduction {

@DeclareParents(value="*..*Service*",

defaultImpl=ModifyDateImpl.class)

private ModifyDate md ;

}

value:指定哪些类可以应用该属性

defaultImpl:指定接口的实现类

典型Aspectj切入点表达式定义:

execution(* cn.itcast.WelcomeServiceImpl.*(..))

execution(public * *..WelcomeServiceImpl.*(..))

execution(public void *..WelcomeServiceImpl.*(..))

execution(public void *..*Service.*(double,double))..

切入点表达式运算(&& || !)

@Pointcut("execution(..) || execution(..)")

2. 示例代码：

Performer.java 演员接口

public interface Performer {public void show();}

Singer.java 接口实现

public class Singer implements Performer {public void show() {System.out.println("其实我是个演员!");//String str = null ;//str.toString();}}

Audience.java 观众类，即通知类

package cn.itcast.spring.aop.aspectj;import org.aspectj.lang.JoinPoint;import org.aspectj.lang.annotation.After;import org.aspectj.lang.annotation.AfterReturning;import org.aspectj.lang.annotation.AfterThrowing;import org.aspectj.lang.annotation.Aspect;import org.aspectj.lang.annotation.Before;import org.aspectj.lang.annotation.DeclareParents;import org.aspectj.lang.annotation.Pointcut;/** * 观众， 需要添加 @Aspect */@Aspectpublic class Audience {/** * 引入通知, */@DeclareParents(value="cn.itcast.spring.aop.aspectj.Singer",defaultImpl=ModifyDateImpl.class)private ModifyDate md ;/** * 定义在切入点， 切入点表达式 *///任意返回值  Performer中 任意方法 任意参数 @Pointcut("execution(* cn.itcast.spring.aop.aspectj.Performer.*(..))")public void perform(){}/** * 坐好 */@Before(value="perform()")public void takeSeat(){System.out.println("takeSeat");}/** * 关机 */@Before(value="perform()")public void turnOffCellphone(JoinPoint jp){System.out.println(jp.getSignature().getName());System.out.println(jp.getArgs());System.out.println(jp.getTarget());System.out.println(jp.getThis());System.out.println("turnOffCellphone");}/** * returning:指定哪个参数接受方法的返回值 */@AfterReturning(pointcut="perform()",returning="ret")public void applaud(Object ret){System.out.println("applaud");System.out.println("ret = " + ret);}/** * 退票 * throwing:指定哪个参数接受异常信息 */@AfterThrowing(pointcut="perform()",throwing="e")public void demandMoney(Exception e){System.out.println("demandMoney");System.out.println("出事了 " + e.getMessage());}@After("perform()")public void goHome(){System.out.println("goHome");}/** 环绕通知*/@Around(value="perform()")public Object watch(ProceedingJoinPoint pjp){try {System.out.println("takeSeat");System.out.println("turnOffCellphone");Object o = pjp.proceed();System.out.println("applaud");return o;} catch (Throwable e) {System.out.println("demandMoney");}finally{System.out.println("goHome");}return null ;}}

ModifyDate.java 引入通知接口

/** * 修改日期 */public interface ModifyDate {public void setModifyDate(Date date);public Date getModifyDate();}

ModifyDateImpl.java 引入通知实现

public class ModifyDateImpl implements ModifyDate {private Date date ;public Date getModifyDate() {return date;}public void setModifyDate(Date date) {this.date = date ;}}

aspectj.xml 配置文件

<?xml version="1.0"?><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/beans                         http://www.springframework.org/schema/beans/spring-beans-2.5.xsd                         http://www.springframework.org/schema/aop                         http://www.springframework.org/schema/aop/spring-aop-2.5.xsd ">    <!-- 观众通知 -->    <bean id="audience" class="cn.itcast.spring.aop.aspectj.Audience" />        <!-- 歌手 -->    <bean id="singer" class="cn.itcast.spring.aop.aspectj.Singer" />        <!-- 使用aspectj自动产生代理 -->    <aop:aspectj-autoproxy /></beans>

App.java 测试代码

public class App {public static void main(String[] args) {ApplicationContext ac = new ClassPathXmlApplicationContext("cn/itcast/spring/aop/aspectj/aspectj.xml");Performer p = (Performer) ac.getBean("singer");p.show();//测试引入通知((ModifyDate)p).setModifyDate(new Date());System.out.println(((ModifyDate)p).getModifyDate());}}

3. 使用pojo+xml开发aop

基于注解的aspectj声明优先于xml配置.基于xml的配置是spring专有的.aspectj得到越来越多的支持,具备更好的重用性.

其他bean 和通知类都不会改变，只会不再需要用注解，改用xml文件

pojo.xml 引入通知，前置后置异常通知

<?xml version="1.0"?><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/beans                         http://www.springframework.org/schema/beans/spring-beans-2.5.xsd                         http://www.springframework.org/schema/aop                         http://www.springframework.org/schema/aop/spring-aop-2.5.xsd ">    <!-- 观众 -->    <bean id="audience" class="cn.itcast.spring.aop.pojo.Audience" />    <!-- 歌手 -->    <bean id="singer" class="cn.itcast.spring.aop.pojo.Singer" />        <!-- aop配置 -->    <aop:config>        <aop:aspect ref="audience">            <!-- 引入通知 -->            <aop:declare-parents types-matching="cn.itcast.spring.aop.pojo.Singer"                                 implement-interface="cn.itcast.spring.aop.pojo.ModifyDate"                                 default-impl="cn.itcast.spring.aop.pojo.ModifyDateImpl"/>            <!-- 单独定义切入点表达式 -->            <aop:pointcut id="audiencePointcut" expression="execution(* cn.itcast.spring.aop.pojo.Performer.*(..))"/>                        <!-- 前置通知 -->            <aop:before method="takeSeat" pointcut-ref="audiencePointcut" />            <aop:before method="turnOffCellphone" pointcut-ref="audiencePointcut"/>                        <!-- 后置通知,ret指定哪个参数接受返回值 -->            <aop:after-returning method="applaud" pointcut-ref="audiencePointcut" returning="ret"/>                        <!-- throwing:指定哪个参数接受异常信息 -->            <aop:after-throwing method="demandMoney" pointcut-ref="audiencePointcut" throwing="ex"/>                        <!--  -->            <aop:after method="goHome" pointcut-ref="audiencePointcut"/>        </aop:aspect>    </aop:config></beans>

pojoAround.xml 环绕通知

<?xml version="1.0"?><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/beans                         http://www.springframework.org/schema/beans/spring-beans-2.5.xsd                         http://www.springframework.org/schema/aop                         http://www.springframework.org/schema/aop/spring-aop-2.5.xsd ">    <!-- 观众 -->    <bean id="audience" class="cn.itcast.spring.aop.pojo.AudienceAround" />    <!-- 歌手 -->    <bean id="singer" class="cn.itcast.spring.aop.pojo.Singer" />        <!-- aop配置 -->    <aop:config>        <aop:aspect ref="audience">            <aop:around method="watch" pointcut="execution(* cn.itcast.spring.aop.pojo.Performer.*(..))"/>        </aop:aspect>    </aop:config></beans>

------------ 不适用注解的另一种配置方法在xml配置文件中加--------------

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