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SPRING IN ACTION 第4版笔记-第四章ASPECT-ORIENTED SPRING-010-Introduction为类增加新方法

时间:2016-03-03 23:03:09      阅读:547      评论:0      收藏:0      [点我收藏+]

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一、

1.Introduction的作用是给类动态的增加方法

When Spring discovers a bean annotated with @Aspect , it will automatically create a proxy that delegates calls to either the proxied bean or to the introduction implementation, depending on whether the method called belongs to the proxied bean or to the introduced interface.

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二、例子

要为演出者增加encore功能

1.

package concert;

public interface Performance {
  void performance();
}

2.

 1 package concert;
 2 
 3 import org.springframework.stereotype.Component;
 4 
 5 @Component
 6 public class Eminem implements Performance{
 7 
 8     @Override
 9     public void performance() {
10         System.out.println("you can do anything set to your mind");
11     }
12 
13 }

3.

package concert;

public interface Encoreable {
    void performEncore();
}

4.

 1 package concert;
 2 
 3 public class DefaultEncoreable implements Encoreable{
 4 
 5     @Override
 6     public void performEncore() {
 7         System.out.println("DefaultEncoreable---> performEncore()");
 8     }
 9 
10 }

5.

 1 package concert;
 2 
 3 import org.aspectj.lang.annotation.Aspect;
 4 import org.aspectj.lang.annotation.DeclareParents;
 5 import org.springframework.stereotype.Component;
 6 
 7 @Aspect
 8 @Component
 9 public class EncoreableIntroducer {
10     @DeclareParents(value = "concert.Performance+", defaultImpl = DefaultEncoreable.class)
11     public static Encoreable encoreable;
12 }

解析:

 @DeclareParents的作用是把"Encoreable"介绍给"Performance",它由三部分组成

(1)value:要增加新功能的bean的接口类型

(2)defaultImpl:要增加的功能接口的实现

(3)增加的功能接口的静态变量

6.配置文件

package concert;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.EnableAspectJAutoProxy;

@Configuration
@ComponentScan
@EnableAspectJAutoProxy
public class Config {

}

 

7.测试

 1 import org.junit.Test;
 2 import org.junit.runner.RunWith;
 3 import org.springframework.beans.factory.annotation.Autowired;
 4 import org.springframework.context.ApplicationContext;
 5 import org.springframework.test.context.ContextConfiguration;
 6 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 7 
 8 import concert.Config;
 9 import concert.Encoreable;
10 
11 @RunWith(SpringJUnit4ClassRunner.class)
12 @ContextConfiguration(classes=Config.class)
13 public class IntroductionTest {
14   @Autowired
15   ApplicationContext context;
16 
17   @Test
18   public void eddieShouldBeAContestant() {
19     Encoreable eminem = (Encoreable) context.getBean("eminem");
20     eminem.performEncore();
21 //      Performance eminem = (Performance) context.getBean("eminem");
22 //      eminem.performance();
23   }
24 }

 

另外:xml的配置方法:

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <beans xmlns="http://www.springframework.org/schema/beans"
 3  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4  xmlns:aop="http://www.springframework.org/schema/aop"
 5  xsi:schemaLocation="http://www.springframework.org/schema/beans 
 6      http://www.springframework.org/schema/beans/spring-beans.xsd
 7      http://www.springframework.org/schema/aop
 8      http://www.springframework.org/schema/aop/spring-aop.xsd">
 9 
10   <bean id="eddie"
11       class="com.springinaction.springidol.Instrumentalist">
12     <property name="instrument">
13       <bean class="com.springinaction.springidol.Guitar" />
14     </property>
15   </bean>
16 
17   <!--<start id="audience_bean"/>--> 
18   <bean id="audience" 
19       class="com.springinaction.springidol.Audience" />
20   <!--<end id="audience_bean"/>-->
21 
22   <!--<start id="audience_aspect"/>--> 
23   <aop:config>
24     <aop:aspect ref="audience">
25       <aop:pointcut id="performance" expression=
26         "execution(* com.springinaction.springidol.Performer.perform(..))" 
27       /> 
28       <aop:before 
29           pointcut-ref="performance"
30           method="takeSeats()" />
31       <aop:before 
32           pointcut-ref="performance"
33           method="turnOffCellPhones" />
34       <aop:after-returning
35           pointcut-ref="performance"
36           method="applaud" />
37       <aop:after-throwing 
38           pointcut-ref="performance"
39           method="demandRefund" />
40     </aop:aspect>
41     
42     <!--<start id="contestant_introduction"/>--> 
43 <aop:aspect>
44   <aop:declare-parents 
45     types-matching="com.springinaction.springidol.Performer+" 
46     implement-interface="com.springinaction.springidol.Contestant"
47     default-impl="com.springinaction.springidol.GraciousContestant"
48     />
49 </aop:aspect>
50     <!--<end id="contestant_introduction"/>-->
51 
52     <!--
53 <start id="delegate_ref"/>    
54 <aop:declare-parents 
55   types-matching="com.springinaction.springidol.Performer+" 
56   implement-interface="com.springinaction.springidol.Contestant"
57   delegate-ref="contestantDelegate"
58   />
59     <end id="delegate_ref"/>   
60 
61 <start id="contestant_delegate"/>    
62 <bean id="contestantDelegate"
63     class="com.springinaction.springidol.GraciousContestant" />
64     <end id="contestant_delegate"/>   
65 
66      -->
67     
68   </aop:config>
69   <!--<end id="audience_aspect" />-->
70 
71 </beans>

 

SPRING IN ACTION 第4版笔记-第四章ASPECT-ORIENTED SPRING-010-Introduction为类增加新方法

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原文地址:http://www.cnblogs.com/shamgod/p/5240348.html

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