关于增强的类

<!--配置的目标类-->
<bean name="studentDao" class="com.imooc.aspectJ.demo2.StudentDaoImp"></bean>

为什么测试用例中的对象是UserDao而不是UserDaoImp，

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

import javax.annotation.Resource;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:applicationContext2.xml")
public class SpringDemo2 {
   @Resource(name = "studentDao")
   private StudentDao studentDao;//这里不能使用 private StudentDaoImp studentDaoImp的原因是什么？
   @Test
   public void demo(){
       studentDao.save();
       studentDao.search();
       studentDao.update();
       studentDao.delete();

   }
}