Mybatis-plus的Service接口

在有了实体类的基础上，创建UserInfoMapper 接口，并继承 BaseMapper 接口
```
public interface UserInfoMapper extends BaseMapper<UserInfo> {}
```
继承 IService 创建 Service 接口，并创建对应的实现类
```
public interface UserInfoService extends IService<UserInfo> {}
```

UserInfoServiceImpl 实现类

@Service
public class UserInfoServiceImpl extends ServiceImpl<UserInfoMapper, UserInfo>
        implements UserInfoService {}

Controller

@RestController
public class HelloController {
 
    @Autowired
    UserInfoService userInfoService;
 
    @RequestMapping("/test")
    public UserInfo test(){
        // 根据id查询数据
        UserInfo user = userInfoService.getById(1);
        return user;
    }
}