SPRING IN ACTION 第4版笔记-第四章ASPECT-ORIENTED SPRING-005-定义切面使用@Aspect、@EnableAspectJAutoProxy、<aop:aspectj-autoproxy>

一、

假设有如下情况，有一个演凑者和一批观众，要实现在演凑者的演凑方法前织入观众的"坐下"、"关手机方法"，在演凑结束后，如果成功，则织入观众"鼓掌"，演凑出错则观众要求"回水"

基本的类如下：

package com.springinaction.springidol;

public interface Instrument {

  public void play();

}

 package com.springinaction.springidol;

 public class Guitar implements Instrument {

   public void play() {

     System.out.println("Strum strum strum");

   }

 }

package com.springinaction.springidol;

public interface Performer {

  void perform() throws PerformanceException;

}

 package com.springinaction.springidol;

 public class Instrumentalist implements Performer {

   public void perform() throws PerformanceException {

     instrument.play();

   }

   private Instrument instrument;

   public void setInstrument(Instrument instrument) {

     this.instrument = instrument;

   }

   public Instrument getInstrument() {

     return instrument;

   }

 }

二、

可以定义的advice

Spring的切面是一个pojo

1.使用@Aspect定义切面类

(1)不同的方法可以用不同的pointcut

 package concert;

 import org.aspectj.lang.annotation.AfterReturning;

 import org.aspectj.lang.annotation.AfterThrowing;

 import org.aspectj.lang.annotation.Aspect;

 import org.aspectj.lang.annotation.Before;

 @Aspect

 public class Audience {

     @Before("execution(** concert.Performance.perform(..))")

     public void silenceCellPhones() {

         System.out.println("Silencing cell phones");

     }

     @Before("execution(** concert.Performance.perform(..))")

     public void takeSeats() {

         System.out.println("Taking seats");

     }

     @AfterReturning("execution(** concert.Performance.perform(..))")

     public void applause() {

         System.out.println("CLAP CLAP CLAP!!!");

     }

     @AfterThrowing("execution(** concert.Performance.perform(..))")

     public void demandRefund() {

         System.out.println("Demanding a refund");

     }

 }

(2)定义一个公共的pointcut，其对应的方法名就是id

 package com.springinaction.springidol;

 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.Pointcut;

 @Aspect

 public class Audience {

   @Pointcut(

         "execution(* com.springinaction.springidol.Performer.perform(..))")

   public void performance() { //<co id="co_definePointcut"/>

   }

   @Before("performance()")

   public void takeSeats() { //<co id="co_takeSeatsBefore"/>

     System.out.println("The audience is taking their seats.");

   }

   @Before("performance()")

   public void turnOffCellPhones() { //<co id="co_turnOffCellPhonesBefore"/>

     System.out.println("The audience is turning off their cellphones");

   }

   @AfterReturning("performance()")

   public void applaud() { //<co id="co_applaudAfter"/>

     System.out.println("CLAP CLAP CLAP CLAP CLAP");

   }

   @AfterThrowing("performance()")

   public void demandRefund() { //<co id="co_demandRefundAfterException"/>

     System.out.println("Boo! We want our money back!");

   }

 }

2.把切面交给Spring容器

(1)在java配置文件中，使用@EnableAspectJAutoProxy

 package concert;

 import org.springframework.context.annotation.Bean;

 import org.springframework.context.annotation.ComponentScan;

 import org.springframework.context.annotation.Configuration;

 import org.springframework.context.annotation.EnableAspectJAutoProxy;

 @Configuration

 @EnableAspectJAutoProxy

 @ComponentScan

 public class ConcertConfig {

     @Bean

     public Audience audience() {

         return new Audience();

     }

 }

(2)在xml使用<aop:aspectj-autoproxy>

 <?xml version="1.0" encoding="UTF-8"?>

 <!--<start id="preamble" />-->

 <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.xsd

      http://www.springframework.org/schema/aop

      http://www.springframework.org/schema/aop/spring-aop.xsd">

 <!--<end id="preamble" />-->

   <bean id="eddie"

       class="com.springinaction.springidol.Instrumentalist">

     <property name="instrument">

       <bean class="com.springinaction.springidol.Guitar" />

     </property>

   </bean>

   <!--<start id="audience_bean" />-->

   <bean id="audience"

       class="com.springinaction.springidol.Audience" />

   <!--<end id="audience_bean" />-->

   <!--<start id="contestant_introducer" />-->

   <bean class="com.springinaction.springidol.ContestantIntroducer" />

   <!--<end id="contestant_introducer" />-->

   <!--<start id="aspectj_autoproxy" />-->

     <aop:aspectj-autoproxy />

   <!--<end id="aspectj_autoproxy" />-->

 </beans>

3.测试

package com.springinaction.springidol;

import org.junit.Test;

import org.junit.runner.RunWith;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.context.ApplicationContext;

import org.springframework.test.context.ContextConfiguration;

import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)

@ContextConfiguration("spring-idol.xml")

public class AspectTest {

  @Autowired

  ApplicationContext context;

  @Test

  public void audienceShouldApplaud() throws Exception {

    Performer eddie = (Performer) context.getBean("eddie");

    eddie.perform();

  }

  @Test

  public void eddieShouldBeAContestant() {

    Contestant eddie = (Contestant) context.getBean("eddie");

    eddie.receiveAward();

  }

}

audienceShouldApplaud的测试结果：

The audience is taking their seats.

The audience is turning off their cellphones

Strum strum strum

CLAP CLAP CLAP CLAP CLAP

巴特西

SPRING IN ACTION 第4版笔记-第四章ASPECT-ORIENTED SPRING-005-定义切面使用@Aspect、@EnableAspectJAutoProxy、<aop:aspectj-autoproxy>

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