@The reason why the Autowired annotation is empty

Used recently springboot There is a problem in rewriting the dark horse travel website , Namely @Autowired The comment is empty
Pay attention to the use of
@Autowired public userDao userDao;
For this class, you must give spring management

    @Service
public class UserServiceImpl extends ServiceImpl<userDao, User> implements UserService {

In the original project, direct new The way
UserService userService = new UserServiceImpl();