在使用Feign做服務間呼叫的時候,當下載大的檔案會出現堆疊溢位的情況。另外，檔案管理服務（服務提供者）檔案下載介面無返回值，是通過HttpServletRespoonse傳輸的流資料來響應，那麼服務消費者該如何接受下載的資料呢？

一. 示例介紹

我們呼叫feign_upload_second的下載檔案介面下載檔案，feign_upload_second內部使用feign呼叫feign_upload_first實現檔案下載。

二、feign_upload_first服務提供者

• 服務提供者下載檔案介面

@RequestMapping(value = "/downloadFile",method = RequestMethod.GET,consumes = MediaType.APPLICATION_JSON_UTF8_VALUE)
    public void downloadFile(HttpServletResponse response){
      String filePath = "D://1.txt";
      File file = new File(filePath);
      InputStream in = null
 
;
      if(file.exists()){
        try {
          OutputStream out = response.getOutputStream();
          in = new FileInputStream(file);
          byte buffer[] = new byte[1024];
          int length = 0;
          while ((length = in.read(buffer)) >= 0){
            out.write(buffer,0,length);
          }
        } catch
 
 (IOException e) {
          e.printStackTrace();
        } finally {
          if(in != null){
            try {
              in.close();
            } catch (IOException e) {
              e.printStackTrace();
            }
          }
        }
      }
    }

三、feign_upload_second服務消費者

• 服務提供者遠端呼叫介面

@RequestMapping(value = "/downloadFile",method = RequestMethod.GET,consumes = MediaType.APPLICATION_JSON_UTF8_VALUE)
  Response downloadFile();

用feign.Response來接收

• 服務提供者下載檔案介面

@RequestMapping(value = "/download",method = RequestMethod.GET)
  public ResponseEntity<byte[]> downFile(){
    ResponseEntity<byte[]> result=null ;
    InputStream inputStream = null;
    try {
      // feign檔案下載
      Response response = uploadService.downloadFile();
      Response.Body body = response.body();
      inputStream = body.asInputStream();
      byte[] b = new byte[inputStream.available()];
      inputStream.read(b);
      HttpHeaders heads = new HttpHeaders();
      heads.add(HttpHeaders.CONTENT_DISPOSITION, "attachment;filename=123.txt");
      heads.add(HttpHeaders.CONTENT_TYPE,MediaType.APPLICATION_JSON_VALUE);

      result = new ResponseEntity <byte[]>(b,heads, HttpStatus.OK);
    } catch (IOException e) {
      e.printStackTrace();
    } finally {
      if(inputStream != null){
        try {
          inputStream.close();
        } catch (IOException e) {
          e.printStackTrace();
        }
      }
    }
    return result;
  }