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：

1.

package com.springinaction.springidol;

public interface Instrument {
  public void play();
}

2.

 package com.springinaction.springidol;

 public class Guitar implements Instrument {
   public void play() {
     System.out.println("Strum strum strum");
   }
 }

3.

package com.springinaction.springidol;

public interface Performer {
  void perform() throws PerformanceException;
}

4.

 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