@ApiOperation("CaptchaUtil使用：图形验证码")
    @GetMapping("/captchaUtil")
    public void captchaUtil(HttpServletRequest request, HttpServletResponse response)  {
        //生成验证码图片
        CircleCaptcha lineCaptcha = CaptchaUtil.createCircleCaptcha(200, 100);
        try {
            request.getSession().setAttribute("CAPTCHA_KEY", lineCaptcha.getCode());
            response.setContentType("image/png");//告诉浏览器输出内容为图片
            response.setHeader("Pragma", "No-cache");//禁止浏览器缓存
            response.setHeader("Cache-Control", "no-cache");
            response.setDateHeader("Expire", 0);
            lineCaptcha.write(response.getOutputStream());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }