文件 - 03 下载文件：根据文件id获取下载链接

系列文章：

文件 - 01 上传附件到服务器并保存信息到MySQL

文件 - 02 上传临时文件到服务器

整体思路：

1. 根据文件id获取下载链接

@RestController
@ResponseBody
@ResponseResult
@Slf4j
@RequestMapping("/ngsoc/PORTAL/api/v1")
@Api(tags = "File")
public class FileController {
    
    
    @ApiOperation(value = "根据文件id获取下载链接", httpMethod = "GET")
    @RequestMapping(value = "/files/downloadLink/{fileId}", method = RequestMethod.GET)
    public DownloadLinkResponse getDownloadLink(
            @ApiParam(value = "文件id", required = true) @PathVariable("fileId") String fileId
    ) throws UploadDownloadFileException {
    
        FileInfo fileInfo = fileDao.existFileId(fileId);
        fileIdAuthorityServiceImpl.assertThisUserHaveAuthority(fileInfo);
        if (ObjectUtils.isEmpty(fileInfo)) {
    
            throw new UploadDownloadFileException(I18nUtils.i18n("exception.file.input.id"));
        }
        String downloadLink = fileService.getDownloadLink(fileId);
        DownloadLinkResponse downloadLinkResponse = new DownloadLinkResponse();
        downloadLinkResponse.setDownloadLink(downloadLink);
        return downloadLinkResponse;
    }
}

@Data
public class DownloadLinkResponse {
    

    private String downloadLink;
}

2. 判断文件id是否存在

FileInfo fileInfo = fileDao.existFileId(fileId);

@Mapper
@Repository
public interface IFileMapper {
    
    
    /** * 判断文件id是否存在 * * @param fileId * @return */
    FileInfo existFileId(@Param("fileId") String fileId);
}

<select id="existFileId" parameterType="String" resultType="portal.model.entity.FileInfo">
    SELECT fileId FROM t_upload_file
    where fileId = #{fileId} and <include refid="unexpiredFilter"/>
</select>

<!-- 大于号 &gt;-->
<!-- 永不过期 neverExpire = 1，或者未过期的，即过期时间 >= 当前时间 -->
<sql id="unexpiredFilter">
    (neverExpire = 1 or expireTime &gt;= current_timestamp())
</sql>

3. 确定用户拥有操作这个fileId的权限

fileIdAuthorityServiceImpl.assertThisUserHaveAuthority(fileInfo);

public interface FileIdAuthorityService {
    
    /** * 确定用户拥有操作这个fileId的权限 * <p> * 否则报错 * * @param fileInfo fileInfo * @return FileInfo * @throws FileIdAuthorityException 当用户无权限操作该文件时 */
    @Nullable
    FileInfo assertThisUserHaveAuthority(@Nullable FileInfo fileInfo);
}

@Slf4j
@Service
public class FileIdAuthorityServiceImpl implements FileIdAuthorityService {
    
    
    @Nullable
    @Override
    public FileInfo assertThisUserHaveAuthority(@Nullable FileInfo fileInfo) {
    
        if (fileInfo == null) {
    
            return null;
        }
        String userName = SpringSecurityUtil.getCurrentUserNameFromSpringSecurity();
        return this.assertThisUserHaveAuthority(fileInfo, userName);
    }

    @Nullable
    @Override
    public FileInfo assertThisUserHaveAuthority(@Nullable FileInfo fileInfo, @Nullable String userName) {
    
        log.debug("assertThisUserHaveAuthority : fileInfo : {} , userName : {}", fileInfo, userName);
        if (fileInfo == null) {
    
            return null;
        }
        if (fileInfo.getShare() == null || fileInfo.getShare() == FileInfoShareEnum.SHARE_TO_ALL.getValue()) {
    
            return fileInfo;
        }
        if (StringUtils.equalsAny(
                userName,
                "transfer",
                fileInfo.getFileUploader()
        )) {
    
            // 按照当前云soc权限设计，凡是API调用都是transfer账户
            return fileInfo;
        }
        throw new FileIdAuthorityException(
                fileInfo.getFileId(),
                userName
        );
    }
}

4. 根据文件Id获取含token 的文件下载连接

public interface IFileService {
    

    /** * 根据文件Id获取含token 的文件下载连接 * * @param fileId 文件Id * @return */
    String getDownloadLink(String fileId);
    
   /** * redis保存文件token、id的键值对 * * @param token * @param id * @throws DataAccessException */
    void saveDownloadLinkTokenId(String token, String id) throws DataAccessException;
}

@Controller
@Slf4j
public class FileServiceImpl implements IFileService {
    

    @Autowired
    private FileConfig fileConfig;
    
    @Autowired
    private RedisTemplate<String, String> stringRedisTemplate;

    @Override
    public String getDownloadLink(String fileId) throws DataAccessException {
    
        // 生成token
        String downloadLinkToken = UuidUtils.uuidWithoutMinus();
        // 文件的下载链接：/ngsoc/PORTAL/api/v1/files/fetch/downloadLinkToken
        String downloadLink = fileConfig.getDownloadLinkBase().concat(downloadLinkToken);
        // 将token 和 fileId进行绑定并设置过期时间
        saveDownloadLinkTokenId(downloadLinkToken, fileId);
        return downloadLink;
    }
    
    // 将token和fileId绑定并设置过期时间
    @Override
    public void saveDownloadLinkTokenId(String token, String id) throws DataAccessException {
    
        Boolean flag = stringRedisTemplate.opsForValue()
                .setIfAbsent(token, id, fileConfig.getTokenExpireTime(), TimeUnit.MINUTES);
        if (BooleanUtils.isNotTrue(flag)) {
    
            log.error("save downloadLinkToken-fileId failed.");
            throw new RedisDataAccessException("exception.file.redis.save");
        }
    }
}

5. 读取配置文件信息

ngsoc:
  file:
    savePath: /opt/ngsoc/data/local/upload/
    tokenExpireTime: 10
    downloadLinkBase: /ngsoc/PORTAL/api/v1/files/fetch/
    content-type:
      - image
    white-suffix: [ pdf, doc, xml, html, doc, docx, txt, wps, xls, xlsx, png, jpg, jpeg, gif, rtf, bmp, icon, mpg, zip, rar, 7z, ppt, pptx ]
    white-urls:
      - /api/v1/files/fetch/*
    folderSize: 8
    folderSizeUnit: G
    # 临时文件的过期时间，默认半天 12h
    expireTimeForTempFile: 12h
    # 清理过期文件任务的冷静期，暂定为 30min
    calmingPeriodOfClearTask: 30min

@Data
@Configuration
@ConfigurationProperties(prefix = "ngsoc.file")
public class FileConfig {
    

    /** * 临时文件的默认过期时间 */
    public static final String DEFAULT_EXPIRE_TIME_FOR_TEMP_FILE = "12h";

    /** * 冷静期的默认时间 */
    public static final String DEFAULT_CALMING_PERIOD_OF_CLEAR_TASK = "30min";

    /** * 附件的保存路径 * */
    private String savePath;

    /** * token的失效时间 * */
    private Integer tokenExpireTime;

    /** * 附件下载的路径 * */
    private String downloadLinkBase;

    /** * 文件类型 * */
    private List<String> contentType;

    /** * 附件白名单后缀 * */
    private List<String> whiteSuffix;

    /** * 白名单 */
    private List<String> whiteUrls;

    /** * 文件最小尺寸 * */
    private Integer minFileSize;

    /** * 文件大小 * */
    private Integer folderSize;

    /** * 文件大小的单位 * */
    private String folderSizeUnit;

    /** * 临时文件的失效时间 * */
    private String expireTimeForTempFile;

    /** * 任务清理的周期 * */
    private String calmingPeriodOfClearTask;
}