Web层
public class test01 {
    public static void main(String[] args) {
        ApplicationContext app =
                new ClassPathXmlApplicationContext("applicationContext.xml");
//        UserDao userDao = (UserDao) applicationContext.getBean("userDao");
//        userDao.save();
       UserService userService = (UserService) app.getBean("userService");
       userService.serv();


    }
}

Service层
@Component("userService")
public class UserServiceImpl implements UserService {
    @Autowired
    @Qualifier("userDao")
    private UserDao userDao;

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }

    public void serv() {
      userDao.save();
    }
}
Daon层
@Component("userDao")
public class UserDaoImpl implements UserDao {



    public void save() {

     System.out.println("你好世界");
    }
}

Web层
public class test01 {
    public static void main(String[] args) {
        ApplicationContext app =
                new ClassPathXmlApplicationContext("applicationContext.xml");
//        UserDao userDao = (UserDao) applicationContext.getBean("userDao");
//        userDao.save();
       UserService userService = (UserService) app.getBean("userService");
       userService.serv();


    }
}

Service层
@Component("userService")
public class UserServiceImpl implements UserService {
    @Autowired
    @Qualifier("userDao")
    private UserDao userDao;

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }

    public void serv() {
      userDao.save();
    }
}
Daon层
@Component("userDao")
public class UserDaoImpl implements UserDao {



    public void save() {

     System.out.println("你好世界");
    }
}