@GetMapping("/download/file")
    public void download( HttpServletResponse response) {
        
        String fileName = "다운로드 했을떄 표시되는 파일명";
        String saveFilePath = "불러올 파일의 저장 경로 ";

        File downloadFile = new File(saveFilePath);

        byte fileByte[] = new byte[0];
        try {
            fileByte = FileUtils.readFileToByteArray(downloadFile);

            response.setContentType("application/octet-stream");
            response.setContentLength(fileByte.length);
            response.setHeader("Content-Disposition", "attachment; fileName=\"" + URLEncoder.encode(fileName, "UTF-8") + "\";");
            response.setHeader("Content-Transfer-Encoding", "binary");

            response.getOutputStream().write(fileByte);
            response.getOutputStream().flush();
            response.getOutputStream().close();

        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }