Springboot编写CRUD时访问对应数据函数返回null的问题及解决方法

public class Bot {
    @TableId(type = IdType.AUTO )
    private Integer id ;
    private  Integer user_id ;
    private String name ;
    private String description ;
    private String content ;
    private Integer rating ;
    @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    private Date create_time ;
    @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    private Date modify_time ;
}

@Service
public class RemoveServiceImpl implements RemoveService {
    @Autowired
    BotMapper botMapper ;
    @Override
    public Map<String, String> remove(Map<String, String> data) {
        UsernamePasswordAuthenticationToken authenticationToken =
                (UsernamePasswordAuthenticationToken) SecurityContextHolder.getContext().getAuthentication() ;
        UserDetailsImpl loginUser = (UserDetailsImpl) authenticationToken.getPrincipal() ;
        User user = loginUser.getUser() ;
        Map<String,String> map = new HashMap<>();
        int bot_id = Integer.parseInt(data.get("bot_id")) ;
        Bot bot = botMapper.selectById(bot_id) ;
        if(bot == null) {
            map.put("error_message", "Bot不存在") ;
            return map ;
        }
        System.out.println("new BOT_ID" + bot.getId());
        System.out.println(bot.getName());
        System.out.println(bot.getUser_id());
        System.out.println(user.getId());
        if(!bot.getUser_id().equals(user.getId())) {
            map.put("error_message", "你没有权限") ;
            return map ;
        }
        botMapper.deleteById(bot_id) ;
        map.put("error_message", "success") ;
        return map ;
    }
}

public class Bot {
    @TableId(type = IdType.AUTO )
    private Integer id ;
    private Integer userId ;
    private String name ;
    private String description ;
    private String content ;
    private Integer rating ;
    @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    private Date create_time ;
    @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
    private Date modify_time ;
}

bot.getUser_id()

bot.getUserId()