public static void serve(HttpServletResponse response, File file) throws IOException {
                response.setContentType("application/octet-stream");
                // response.setHeader  ("Content-Disposition", "attachment;filename=filename.mp4");
                response.setHeader("Content-Type", "video/mp4");

                int BUFFER_SIZE = 512;
                try (
                        BufferedInputStream input  = new BufferedInputStream(new FileInputStream(file), BUFFER_SIZE);
                        BufferedOutputStream output = new BufferedOutputStream(response.getOutputStream(), BUFFER_SIZE);
                ) {
                        byte[] bytes = new byte[BUFFER_SIZE];
                        int length;
                        while ((length = input.read(bytes)) > 0) {
                                output.write(bytes, 0, length);
                        }
                }
        }