接口
public interface UserService {
    List<User> getUserList();
    User getUser(int id);
}
接口实现类
@Service("userService")
public class UserServiceImpl implements UserService{
    @Autowired
    private UserDao userDao;
    public List<User> getUserList() {
        List<User> userList = userDao.getUserList();
        return userList;
    }
    public User getUser(int id) {
        User user = userDao.getUser(id);
        return user;
    }
}
原文:https://www.cnblogs.com/6ovo6/p/13730779.html