import org.springframework.util.FileCopyUtils;

  public byte[] downloadFile(String fileName) {
    byte[] res = new byte[0];
    try {
      File file = new File(BACKUP_FILE_PATH, fileName);
      if (file.exists() && !file.isDirectory()) {
        res = FileCopyUtils.copyToByteArray(file);
      }
    } catch (IOException e) {
      logger.error(e.getMessage());
    }
    return res;
  }

 protected ResponseEntity<byte[]> downloadResponse(byte[] body, String fileName) {
    HttpServletRequest request = ((ServletRequestAttributes) RequestContextHolder
        .getRequestAttributes()).getRequest();
    String header = request.getHeader("User-Agent").toUpperCase();
    HttpStatus status = HttpStatus.CREATED;
    try {
      if (header.contains("MSIE") || header.contains("TRIDENT") || header.contains("EDGE")) {
        fileName = URLEncoder.encode(fileName, "UTF-8");
        fileName = fileName.replace("+", "%20");  // IE下载文件名空格变+号问题
        status = HttpStatus.OK;
      } else {
        fileName = new String(fileName.getBytes("UTF-8"), "ISO8859-1");
      }
    } catch (UnsupportedEncodingException e) {}

    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
    headers.setContentDispositionFormData("attachment", fileName);
    headers.setContentLength(body.length);

    return new ResponseEntity<byte[]>(body, headers, status);
  }

@RequestMapping(value = "/download-backup", method = RequestMethod.GET)
  @ResponseBody
  public ResponseEntity<byte[]> downloadBackupFile(@RequestParam String fileName) {
    byte[] body = backupService.downloadFile(fileName);
    return downloadResponse(body, fileName);
  }