实践案例包括两个项目，服务提供者项目名：upload-service，调用服务项目名：upload-client，主要给出两个服务之间的调用过程，文件上传功能不提供

项目框架：spring-boot 2.0.1.RELEASE、spring-cloud Finchley.RELEASE

依赖：

        <dependency>
            <groupId>io.github.openfeign.form</groupId>
            <artifactId>feign-form</artifactId>
            <version>3.0.3</version>
        </dependency>
        <dependency>
            <groupId>io.github.openfeign.form</groupId>
            <artifactId>feign-form-spring</artifactId>
            <version>3.0.3</version>
        </dependency>
        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.3.3</version>
        </dependency>

一.文件上传服务upload-service
1.控制层

@Slf4j
@CrossOrigin
@RestController
@RequestMapping("/ftp")
@Api(description = "文件上传控制")
public class FtpFileController {

    @Autowired
    private FtpFileService ftpFileService;

    /**
     * FTP文件上传
     *
     * @return
     */
    @PostMapping(value = "/uploadFile", consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    public FtpApiResponse<FtpUploadResDTO> uploadFileFTP(@RequestPart(value = "file") MultipartFile file,
                                                         @RequestParam("logId") String logId) {
        FtpApiResponse<FtpUploadResDTO> result = new FtpApiResponse<>();
        LogUtil.updateLogId(logId);
        try {
            log.info("文件上传开始!}");
            Long startTime = System.currentTimeMillis();
            FtpUploadResDTO resDTO = ftpFileService.uploadFile(file);
            result.setData(resDTO);
            result.setSuccess(true);
            result.setTimeInMillis(System.currentTimeMillis() - startTime);
            log.info("文件上传结束 resDTO：{}，耗时:{}", resDTO, (System.currentTimeMillis() - startTime));
        } catch (ServiceException e){
            result.setSuccess(false);
            result.setErrorCode(ErrorMsgEnum.FILE_UPLOAD_EXCEPTION.getCode());
            result.setErrorMsg(ErrorMsgEnum.FILE_UPLOAD_EXCEPTION.getMsg());
        } catch (Exception e) {
            result.setSuccess(false);
            result.setErrorCode(ErrorMsgEnum.SYSTEM_ERROR.getCode());
            result.setErrorMsg(ErrorMsgEnum.SYSTEM_ERROR.getMsg());
            log.info("文件上传失败 Exception：{}", Throwables.getStackTraceAsString(e));
        }
        return result;
    }
}

2.业务层

@Service
@Slf4j
public class FtpFileService {

    @Autowired
    private FtpFileManager ftpFileManager;

    /**
     * 上传文件
     *
     * @param file
     * @return
     */
    public FtpUploadResDTO uploadFile(MultipartFile file) {
        try {
            //判断上传文件是否为空
            if (null == file || file.isEmpty() || file.getSize() == 0) {
                log.info("传入的文件为空,file:{}", file);
                throw new ServiceException(ErrorMsgEnum.EMPTY_FILE);
            }
            //文件上传至ftp服务目录
            FtpFileRecordDO ftpFileRecordDO = ftpFileManager.fileUploadToFtp(file);
            if (null == ftpFileRecordDO) {
                log.info("文件上传至ftp服务目录异常");
                throw new ServiceException(ErrorMsgEnum.FILE_UPLOAD_TO_FTP_EXCEPTION);
            }
            return ftpFileManager.addFileRecord(ftpFileRecordDO);
        } catch (Exception e) {
            log.error("业务异常,case", e);
            throw new ServiceException(ErrorMsgEnum.SYSTEM_ERROR);
        }
    }
}

3.服务写好后，需要把远程接口暴露出去

@FeignClient(value  = "upload-service", configuration = UpDownFtpFacade.MultipartSupportConfig.class)
public interface UpDownFtpFacade {

    /**
     * FTP上传文件
     *
     * @param file 文件
     * @param logId 日志id
     * @return
     */
    @PostMapping(value = "/ftp/uploadFile",consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
    FtpApiResponse<FtpUploadResDTO> uploadFileFTP(@RequestPart(value = "file") MultipartFile file,
                                                  @RequestParam("logId") String logId);

    /**
     * 引用配置类MultipartSupportConfig.并且实例化
     */
    @Configuration
    class MultipartSupportConfig {
        @Bean
        public Encoder feignFormEncoder() {
            return new SpringFormEncoder();
        }
    }

}

二.文件上传客户端upload-client

@Slf4j
@Component
public class FileManager {
     @Autowired
     private UpDownFtpFacade upDownFtpFacade;
     
     /**
     * 调用远程上传文件接口
     *
     * @param file 待上传的文件
     * @return 下载路径
     **/
    public FtpApiResponse<FtpUploadResDTO> requestFtpFacade(MultipartFile file) {
        try {
            DiskFileItem fileItem = (DiskFileItem) new DiskFileItemFactory().createItem("file",
                    MediaType.ALL_VALUE, true, file.getOriginalFilename());
            InputStream input = file.getInputStream();
            OutputStream os = fileItem.getOutputStream();
            IOUtils.copy(input, os);
            MultipartFile multi = new CommonsMultipartFile(fileItem);
            FtpApiResponse<FtpUploadResDTO> response = upDownFtpFacade.uploadFileFTP(multi, LogUtil.getLogId());
            if (null == response || !response.getSuccess() || null == response.getData()) {
                throw new ManagerException(ErrorMsgEnum.FIlE_UPLOAD_FAILED);
            }
            return response;
        } catch (Exception e) {
            throw new ManagerException(ErrorMsgEnum.FIlE_UPLOAD_FAILED);
        }
     }
}