springboot项目中使用了mybatisplus的baseMapper中的?报错

报错信息如下：
Invalid bound statement (not found): cn.itsource.fastgo.mapper.EmployeeMapper.selectOne

这是service层的接口实现类
@Service
@Transactional(readOnly = true,propagation = Propagation.SUPPORTS)
public class EmployeeServiceImpl extends ServiceImpl implements IEmployeeService {

@Override
public Employee login(String username, String password) {
    return baseMapper.selectOne(new QueryWrapper<Employee>()
            .eq("username",username)
            .eq("password",password));
}

}

这是mapper
@Mapper
public interface EmployeeMapper extends BaseMapper {
}

这是controller
@RestController
public class LoginController {

@Autowired
private IEmployeeService employeeService;

@PostMapping("/login")
@ApiOperation(value = "登录接口" + "")
public AjaxResult login(@RequestBody Map<String,Object> params){
    String username = (String) params.get("username");
    String password = (String) params.get("password");
    Employee employee = employeeService.login(username,password);
    if(null!=employee){
        //登录成功
        return AjaxResult.me();
    }
    //登录失败
    return AjaxResult.me().setSuccess(false).setMessage("用户名或密码错误!");
}

}

请问大神们为什么调用的是basemapper的selectOne方法，但是会报错employeeMapper找不到selectOne