docs: public HttpEntity<byte[]> downloadDspBill(String fileName, String value) {
  
          HttpHeaders header = new HttpHeaders();
          byte[] res = value.getBytes();
  
          String name = null;
  
          try {
              name = URLEncoder.encode(fileName, "UTF-8");
          } catch (UnsupportedEncodingException e) {
              e.printStackTrace();
          }
  
          header.set("Content-Disposition", "attachment; filename=" + name);
          header.setContentLength(res.length);
          return new HttpEntity<byte[]>(res, header);
      }