@RequestMapping("/updateAvatar.html")

    public String updateHeadUrl(MultipartFile avatar, Model model, HttpSession session) throws IOException {

        // 文件类型限制

        String[] allowedType = {"image/bmp", "image/gif", "image/jpeg", "image/png"};

        boolean allowed = Arrays.asList(allowedType).contains(avatar.getContentType());

        if (!allowed) {

            model.addAttribute("error3","图片格式仅限bmp，jpg，png，gif~");

            return "editProfile";

        }

        // 图片大小限制

        if (avatar.getSize() > 3 * 1024 * 1024) {

            model.addAttribute("error3","图片大小限制在3M以下哦~");

            return "editProfile";

        }

        // 包含原始文件名的字符串

        String filename = avatar.getOriginalFilename();

        // 提取文件拓展名

        String extension = filename.substring(filename.indexOf(".") +1);

        String dir = context.getRealPath("/upload/avatar/");

        //如果目录不存在,级联创建

        //.normalize()方法用于标准化路径,替换/\等问题

        if(!Files.exists(Paths.get(dir)))

        {

            Files.createDirectories(Paths.get(dir).normalize());

        }

        String uuid = UUID.randomUUID().toString();

        String webUrl = String.format("/upload/avatar/%s.%s",uuid,extension);

        String target = String.format("%s/%s.%s",dir,uuid,extension);

        //写入文件

        Files.write(Paths.get(target).normalize(),avatar.getBytes());

        //更新数据库中头像URL

        int uid = (int) session.getAttribute("uid");

        userService.updateHeadUrl(uid,webUrl);

        return "redirect:profile.html";

    }