比如，原來的手機只能打電話，發簡訊。
現在，手機可以做為pad（掌上電腦），可以上網，看電影，打遊戲。
但是，我不想去繼承實現，我就要用AOP。
這次Aspect可就不同了

首先出場，基礎類

package com.xbz.learn.spring.aspect.exspandMethod;

public interface Mobile {
    /**
     * 打電話
     */
    public  void doCall();
}

package com.xbz.learn.spring.aspect.exspandMethod;

public interface
 
 Pad {
    /**
     * 做為電腦，可以看電影
     */
    public void watchMovie();
}

package com.xbz.learn.spring.aspect.exspandMethod;

public class SampleMobile implements Mobile{

    public void doCall() {
        System.out.println("可以打電話");
    }

}

package com.xbz.learn.spring.aspect.exspandMethod;

public
 
 class SamplePad implements Pad{

    public void watchMovie() {
        System.out.println("可以看電影");
    }

}

閃亮登場，我們的主角：Aspect類

package com.xbz.learn.spring.aspect.exspandMethod;

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.DeclareParents;

@Aspect
public class
 
 MobileAspect {
    /**
     * value指定了要為哪些類引入該介面
     * <br/>
     * com.xbz.learn.spring.aspect.exspandMethod.Mobile+表示所有的子類，不包括Mobile
     * <br/>
     * 
     */
    @DeclareParents(value="com.xbz.learn.spring.aspect.exspandMethod.Mobile+",
            defaultImpl=SamplePad.class)
    public static Pad pad;
}

JavaConfig類
注意：@EnableAspectJAutoProxy，不然一切都是浮雲

package com.xbz.learn.spring.aspect.exspandMethod;

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

@Configuration
@EnableAspectJAutoProxy
public class JavaConfig {
    @Bean
    public MobileAspect mobileAspect(){
        return new MobileAspect();
    }
    @Bean
    public Mobile mobile(){
        return new SampleMobile();
    }

}

接下來，見證奇蹟的時刻：手機變電腦
測試類

package com.xbz.learn.spring.aspect.exspandMethod;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes={JavaConfig.class})
public class JavaConfigTest {
    @Autowired
    private Mobile mobile;
    @Test
    public void testMobileAspect(){
        System.out.println(mobile.getClass().getName());
        System.out.println("This mobile is a pad?"+(mobile instanceof Pad));
        Pad pad=(Pad) mobile;
        pad.watchMovie();
    }
}

<?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:p="http://www.springframework.org/schema/p"
    xmlns:c="http://www.springframework.org/schema/c"

    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:mvc="http://www.springframework.org/schema/mvc"

    xsi:schemaLocation=
        "http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd 

        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd

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

        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd
">
    <!-- 使用CGLIB代理建立代理物件，預設使用JDK代理 -->
    <aop:aspectj-autoproxy proxy-target-class="false"></aop:aspectj-autoproxy>  
    <aop:config>
        <aop:aspect >
            <aop:declare-parents 
                types-matching="com.xbz.learn.spring.aspect.exspandMethod.Mobile+" 
                implement-interface="com.xbz.learn.spring.aspect.exspandMethod.Pad"
                default-impl="com.xbz.learn.spring.aspect.exspandMethod.SamplePad"
                />
        </aop:aspect>
    </aop:config>
    <!-- 目標類 -->
    <bean id="mobile" class="com.xbz.learn.spring.aspect.exspandMethod.SampleMobile"></bean>
</beans>