SpringAOP的引入通过@DeclareParents实现，其目标是对于一个已有的类引入新的接口。

//业务接口类
package com.codestd.springstudy.aop.introductions;

public interface Animal {

    public void sleep();

    public void shout();
}

//-----------------------------------------
//实现类
package com.codestd.springstudy.aop.introductions;
import org.springframework.stereotype.Component;

@Component
public class Cock implements Animal {

    @Override
    public void sleep() {
        System.out.println("Cock sleep");
    }

    @Override
    public void shout() {
        System.out.println("Cock shout");
    }

}

//-----------------------------------------
//要引入的接口
package com.codestd.springstudy.aop.introductions;

public interface Flyable {
    public void fly();
}

//-----------------------------------------
//引入接口的实现类
package com.codestd.springstudy.aop.introductions;

public class DefaultFlyable implements Flyable {

    @Override
    public void fly() {
        System.out.println("fly");
    }

}

//-----------------------------------------
//声明引入
package com.codestd.springstudy.aop.introductions;

import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.DeclareParents;
import org.springframework.stereotype.Component;

@Component
@Aspect
public class AnimalIntroduction {

    @DeclareParents(value="com.codestd.springstudy.aop.introductions.Animal+", defaultImpl=DefaultFlyable.class)
    public static Flyable flyable;


}

现在就可以认为Animal的实现类同时也实现了Flyable接口。然后可以直接从Spring容器中获取Bean，然后调用接口内的方法。接口的方法是defaultImpl中指定的实现类中方法的实现。

//-----------------------------------------
//测试，现在可以直接通过Spring获取到实现
package com.codestd.springstudy.aop.introductions;

import javax.annotation.Resource;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations={"classpath:aop/applicationContext.xml"})
public class AnimalTest {

    @Resource(name="cock")
    private Flyable flyable;

    @Test
    public void test() {
        this.flyable.fly();
    }

}