// 共用的实体类和Mapper
@Data
public class UserFoot {
    ...
}

public interface UserFootMapper extends BaseMapper<UserFoot> {
}

// 方式1：直接继承IService方式
public interface UserFootService extends IService<UserFoot> {
    // 自定义业务方法
    List<UserFoot> getUserFootprints(Long userId);
}

@Service
public class UserFootServiceImpl extends ServiceImpl<UserFootMapper, UserFoot> 
        implements UserFootService {
    
    // 可以注入其他Mapper或Service
    @Autowired
    private UserMapper userMapper;
    
    @Override
    public List<UserFoot> getUserFootprints(Long userId) {
        // 直接使用继承的方法
        return this.list(new LambdaQueryWrapper<UserFoot>()
                .eq(UserFoot::getUserId, userId)
                .orderByDesc(UserFoot::getCreateTime));
    }
}

// 方式2：组合Dao方式
public class UserFootDao extends ServiceImpl<UserFootMapper, UserFoot> {
    // 在Dao层封装数据库操作
    public List<UserFoot> findByUserId(Long userId) {
        return list(new LambdaQueryWrapper<UserFoot>()
                .eq(UserFoot::getUserId, userId)
                .orderByDesc(UserFoot::getCreateTime));
    }
}

public interface UserFootService {
    // 定义业务方法
    List<UserFoot> getUserFootprints(Long userId);
}

@Service
public class UserFootServiceImpl implements UserFootService {
    private final UserFootDao userFootDao;
    private final UserMapper userMapper;  // 同样可以注入其他依赖
    
    @Autowired
    public UserFootServiceImpl(UserFootDao userFootDao, UserMapper userMapper) {
        this.userFootDao = userFootDao;
        this.userMapper = userMapper;
    }
    
    @Override
    public List<UserFoot> getUserFootprints(Long userId) {
        // 通过dao进行数据操作
        return userFootDao.findByUserId(userId);
    }
}