@RequestMapping(value = "/files", method = RequestMethod.GET)
    public void getFile(
            HttpServletResponse response) {
        try {
            Book book = bookRepo.getOne(18l);
             response.getOutputStream().write(book.getPdf());
            response.setDateHeader("Expires", -1);
            response.setContentType("application/pdf");
            response.setContentLength(book.getPdf().length);


        } catch (IOException ex) {
            throw new RuntimeException("IOError writing file to output stream");
        }

    }

<embed src="http://localhost:8080/book/files" width="850" height="900" type="application/pdf">