文件上传，这里以图片上传为例（这里上传到服务器）

@RequestMapping("/upload.do")
    public ModelAndView toUpload(MultipartFile photo, HttpSession session) throws IOException {
        if(!photo.isEmpty()){
            String path=session.getServletContext().getRealPath("\\img");
            String filename=photo.getOriginalFilename();
            if(filename.endsWith(".png")||filename.endsWith(".jpg")){
                File file=new File(path,filename);
                photo.transferTo(file);
                ModelAndView modelAndView=new ModelAndView();
                modelAndView.addObject("filename",filename);
                modelAndView.setViewName("forward:/success.jsp");
                return modelAndView;
            }
        }
        return new ModelAndView("forward:/fail.jsp");
    }

文件下载

@RequestMapping("/download.do")
    public ResponseEntity<byte[]> filedownload(String filename,
                                               HttpServletRequest request)throws IOException{
        String path = request.getServletContext().getRealPath("\\img");
        File file = new File(path,filename);
        HttpHeaders header = new HttpHeaders();
        header.setContentDispositionFormData("attachment",filename);
        header.setContentType(MediaType.APPLICATION_OCTET_STREAM);
        return new ResponseEntity<byte[]>
                (FileUtils.readFileToByteArray(file),header,
                        HttpStatus.OK);
    }