StreamingResponseBody 返回空文件

Question

I'm trying to create a rest service to download files from a repository, using Springboot.

I'm trying to return a ResponseEntity with StreamingResponseBody, to return the file that i get from the repository, as an InputStream.

This is the current code i have:

@GetMapping(path = "/downloadFile")
    public ResponseEntity<StreamingResponseBody> downloadFile(@RequestParam(value = "documentId") String documentId,
            HttpServletRequest request, HttpServletResponse response) throws InterruptedException, IOException {

        InputStream is = downloadService.getDocument(documentId);

        StreamingResponseBody out = outputStream -> {

            outputStream.write(IOUtils.toByteArray(is));
        };

        HttpHeaders headers = new HttpHeaders();
        headers.add("Content-Type", "text/csv");
        headers.add("Content-Disposition", "attachment; filename=" + documentId);
        headers.add("Pragma", "no-cache");
        headers.add("Cache-Control", "no-cache");

        return (new ResponseEntity<>(out, headers, HttpStatus.OK));

    }

When I consume this endpoint, using directly the browser, or postman, the file that is downloaded comes empty. I understand that the OutputStream is written to asynchronously (Async is enabled in the config class).

How can I consume this service and get the file completely written, the way it comes from the repository I'm using ? ( if possible using Postman, just for testing purposes)

Am i building the service correctly?

Answer 1

I have modified the code bit little, in my documentId is the name of the file to be downloaded. I have tested, it is working fine. Check below the code.

@GetMapping(path = "/downloadFile")
public ResponseEntity<StreamingResponseBody> downloadFile(
      @RequestParam(value = "documentId") String documentId,
      HttpServletRequest request,
      HttpServletResponse response)
      throws InterruptedException, IOException {
    String dirPath = "E:/sure-delete/"; //Directory having the files
    InputStream inputStream = new FileInputStream(new File(dirPath + documentId));
    final StreamingResponseBody out =
        outputStream -> {
          int nRead;
          byte[] data = new byte[1024];
          while ((nRead = inputStream.read(data, 0, data.length)) != -1) {
            System.out.println("Writing some bytes of file...");
            outputStream.write(data, 0, nRead);
          }
        };
    HttpHeaders headers = new HttpHeaders();
    headers.add("Content-Type", "text/csv");
    headers.add("Content-Disposition", "attachment; filename=" + documentId);
    headers.add("Pragma", "no-cache");
    headers.add("Cache-Control", "no-cache");
    return ResponseEntity.ok().headers(headers).body(out);
  }