Java 对接第三方接口返回的文件下载保存 or 上传文件给第三方（服务端-客户端）

提示：文章写完后，目录可以自动生成，如何生成可参考右边的帮助文档

---

前言

最近遇到一个给第三方系统上传和下载的需求，第三方只作为服务方，这里记录一下（非前端调用）。
下载-如需要拿到某业务信息，包括附件也需要下载
上传-审批的结果需要推送给第三方，其中也包括附件

---

一、上传

1.服务方

  /**
     * 上传文件
     * request: {"sign":"B85FB491665FAFBB7C5F3377BDBE986C","fileCount":"2"}
     * requestBody: ["D:\\LZH\\Desktop\\2023年1月28日设计批复通过.xlsx","D:\\LZH\\Desktop\\2023年1月28日设计批复通过2.xlsx"]
     * response:[{"fileName":"2023年1月28日设计批复通过.xlsx","size":57191,"remark":"上传成功","id":"6f8a2755-0c00-4f40-ac94-705cfe8e4d7e","uuid":"6f8a2755-0c00-4f40-ac94-705cfe8e4d7e","url":"http://127.0.0.1/cmsr/6f8a2755-0c00-4f40-ac94-705cfe8e4d7e"},{"errorIndex":1,"remark":"上传失败"}]
     * 
     */
    @RequestMapping(value = "/uploadFile",method = RequestMethod.POST)
    public String uploadFile(HttpServletRequest request) {
        Map<String,Object> result = new HashMap<>();
        
        MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest) request;
        final int fileCount = Integer.parseInt(request.getParameter("fileCount"));
        List<Map<String,Object>> list=new ArrayList<>(fileCount);
        for (int i = 0; i < fileCount; i++) {
            MultipartFile file = multipartRequest.getFile("file"+i);// 获取上传文件对象
            Map<String,Object> map = new HashMap<>();
            try {
                // 上传并返回新文件名称
                String uuid = FileUploadUtils.upload(file, "xcall");
                final Optional<Attachment> attOptional = Attachment.findByUuid(uuid);
                if (attOptional.isEmpty()) {
                    throw new Exception("上传失败");
                }
                Attachment att = attOptional.get();
                String url = serverConfig.getUrl() + "/" + uuid;
                map.put("id", uuid);
                map.put("uuid", uuid);
                map.put("fileName", att.getName());
                map.put("size", att.getLength());
                map.put("url", url);
                map.put("remark", "上传成功");
            } catch (Exception e) {
                map.put("remark", "上传失败");
                map.put("errorIndex", i);
                log.error("XCallController uploadFile e:",e);
            }
            list.add(map);
        }
        result.put("attachment",list);
        return JSON.toJSONString(list);
//        return JSON.toJSONString(result);
    }

2.调用方

            List<SysFile> sysFiles = fileService.listByIds(ids);
            List<File> files = new ArrayList<>(sysFiles.size());
            for (SysFile f : sysFiles) {
                File file = new File(aPath +File.separator+f.getPath());
                files.add(file);
            }
            HashMap<String, String> body = new HashMap<>();
            body.put("fileCount", String.valueOf(files.size()));
            body.put("sign", getMd5(body));
            HashMap<String, Object> headers = new HashMap<>();
            String result = HttpUtils.httpPostByFile(a.getHost()+"/uploadFile", body, headers, files);
            o.setReportFiles(result);
            log.info("uploadFile    result:"+result);

二、下载

1.服务方

代码如下（示例）：

   /**
     * 下载文件
     */
    @RequestMapping(value = "/downloadFile",method = RequestMethod.GET)
    public void downloadFile(@RequestParam("uuid") String uuid, HttpServletResponse response) {
        try {
            Attachment attachment = Attachment.findByUuid(uuid).get();
            String filePath = a.getProfile() + attachment.getPath();
            response.setHeader("fileName", URLEncoder.encode(attachment.getName(), StandardCharsets.UTF_8));
            response.setHeader("uuid",attachment.getUuid()+"");
            FileUtils.writeBytes(filePath, response.getOutputStream());
        } catch (Exception e) {
            log.error("下载文件失败", e);
        }
    }

2.调用方

代码如下（示例）：

 /**
     * 下载附件
     *
     * @return
     */
    public void downloadFile(ReportRecord r) {
        List<Map<String ,String>>files=new ArrayList<>();
        List<SysFile>list=new ArrayList<>();
        for (String uuid : r.getFileIds().split(",")) {
            try {
                HashMap<String, String> params = new HashMap<>();
                params.put("uuid", uuid);
                params.put("sign", getMd5(params));
                HashMap<String, Object> headers = new HashMap<>();
                final Map<String, Object> resultMap = HttpUtils.httpGet(xcall.getHost()+"cmsr/report/downloadFile", params, headers);
                String id = IdUtil.getSuid();
                final String fileName = resultMap.getOrDefault("fileName",id).toString();
                String ext = fileName.substring(fileName.lastIndexOf('.'));

                // 1 先上传文件
                String path = upload((byte[]) resultMap.get("bytes"), id + ext);//以id为文件名保证不重复

                // 2 建立SysFile数据
                SysFile sysFile = new SysFile();
                sysFile.setId(id);
                sysFile.setName(fileName);
                sysFile.setUploader("ordinary");
                sysFile.setPath(path);
                list.add(sysFile);

                Map<String ,String> f=new HashMap<>(2);
                f.put("id",id);
                f.put("name",fileName);
                files.add(f);
            } catch (Exception e) {
                r.putRemark("附件下载失败，uuid："+uuid);
            }
        }
        r.setAccessory(JSON.toJSONString(files));
        fileService.saveBatch(list);
        
    }

    public String upload(byte[] bytes, String name) {
        String path = getPath(name);
        String fullPath = xbpmRootPath + File.separator + path;
//        FileUtil.writeFromStream(is, fullPath);
        FileUtil.writeBytes(bytes,fullPath);
        return path;
    }

---

HttpUtils.java

    private static CloseableHttpClient httpClient;

    static {
        try {
            SSLContext sslContext = SSLContextBuilder.create().useProtocol(SSLConnectionSocketFactory.SSL).loadTrustMaterial((x, y) -> true).build();
            RequestConfig config = RequestConfig.custom().setConnectTimeout(10000).setSocketTimeout(10000).build();
            httpClient = HttpClientBuilder.create().setDefaultRequestConfig(config).setSSLContext(sslContext).setSSLHostnameVerifier((x, y) -> true).build();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

 public static String httpPostByFile(String url, Map<String, String> body, Map<String, Object> headers, List<File> files) {
        String result = "";
        try {
            HttpPost httpPost = new HttpPost(url);
            for (Map.Entry<String, Object> header : headers.entrySet()) {
                httpPost.setHeader(header.getKey(), String.valueOf(header.getValue()));
            }

            MultipartEntityBuilder builder = MultipartEntityBuilder.create().setMode(HttpMultipartMode.RFC6532);
            // 设置请求的编码格式
            builder.setCharset(Consts.UTF_8);
            builder.setContentType(ContentType.MULTIPART_FORM_DATA);
            // 添加文件,也可以添加字节流
//			builder.addBinaryBody("file", files);
            //或者使用字节流也行,根据具体需要使用
            for (int i = 0; i < files.size(); i++) {
                try {
                    builder.addBinaryBody("file"+i, Files.readAllBytes(files.get(i).toPath()), ContentType.APPLICATION_OCTET_STREAM,files.get(i).getName());
                } catch (IOException e) {
                    log.error("httpPostByFile 文件不存在    e:",e);
                }
            }
            // 或者builder.addPart("file",new FileBody(file));
            for (Map.Entry<String, String> map : body.entrySet()) {
                builder.addTextBody(map.getKey(), map.getValue());
            }
            HttpEntity reqEntity = builder.build();
            httpPost.setEntity(reqEntity);
            
            CloseableHttpResponse response = httpClient.execute(httpPost);
            
            HttpEntity entity = response.getEntity();
            if (entity != null) {
                result = EntityUtils.toString(entity, StandardCharsets.UTF_8);
            }
            EntityUtils.consume(entity);
            response.close();
            return result;
        } catch (Exception e) {
            e.printStackTrace();
            log.error("发送http请求异常 e:",e);
            return "";
        }
    }

    public static Map<String, Object> httpGet(String url, Map<String, String> params, Map<String, Object> headers) {
        HttpGet httpGet;
        Map<String,Object> map=new HashMap<>();
        try {
            List<NameValuePair> nameValuePairArrayList = new ArrayList<>();
            if (params != null) {
                for (Map.Entry<String, String> param : params.entrySet()) {
                    nameValuePairArrayList.add(new BasicNameValuePair(param.getKey(), param.getValue()));
                }
            }
            //参数转换为字符串
            String paramsStr = EntityUtils.toString(new UrlEncodedFormEntity(nameValuePairArrayList, StandardCharsets.UTF_8));
            httpGet = new HttpGet(url + "?" + paramsStr);
            for (Map.Entry<String, Object> header : headers.entrySet()) {
                httpGet.setHeader(header.getKey(), String.valueOf(header.getValue()));
            }
            CloseableHttpResponse response = httpClient.execute(httpGet);
            HttpEntity entity = response.getEntity();
            ByteArrayOutputStream outputStream=new ByteArrayOutputStream();
            entity.writeTo(outputStream);
//            final long copy = IoUtil.copy(inputStream, outputStream);
            final byte[] bytes = outputStream.toByteArray();
//            FileUtil.writeBytes(bytes,"D:\\data\run\\dy_admin\\upload\\xcall\\2023\\02\\23\\a.xlsx");
//            FileUtil.writeBytes(bytes,"D:\\LZH\\Desktop\\2023年1月28日设计批复通过4.xlsx");
            map.put("bytes",bytes);
            map.put("fileName", URLDecoder.decode(response.getHeaders("filename")[0].getValue(), StandardCharsets.UTF_8));
            map.put("uuid", response.getHeaders("uuid")[0].getValue());
            EntityUtils.consume(entity);
            response.close();
        } catch (Exception e) {
            log.error("发送http请求异常 e:",e);
        }
        return map;
    }

总结

1.上传是批量进行的，如果文件过大会导致内存问题吧
2.上传下载没有重试机会，一旦因为网络或者其他不可控因素导致中断