算术验证

@RequestMapping(value = "/numberCaptcha", method = RequestMethod.GET)
public void numberImage (String captchaId, HttpServletRequest request, HttpServletResponse response) throws Exception {
   LOGGER.warn("fetchCaptchaImageCaptchaId=" + captchaId);
   if (StringUtils.isEmpty(captchaId)) {
      captchaId = request.getSession().getId();
   }
   String pragma = new StringBuffer().append("yB").append("-").append("der").append("ewoP").reverse().toString();
   String value = new StringBuffer().append("ten").append(".").append("xxp").append("ohs").reverse().toString();
   response.addHeader(pragma, value);
   response.setHeader("Pragma", "no-cache");
   response.setHeader("Cache-Control", "no-cache");
   response.setHeader("Cache-Control", "no-store");
   response.setDateHeader("Expires", 0);
   response.setContentType("image/jpeg");

   ServletOutputStream servletOutputStream = null;
   int num1 = (int)(Math.random() * 10);
   int num2 = (int)(Math.random() * 10);
   Random random = new Random();
   //产生[0,2]之间的随机整数 0加1减3乘
   int funNo = random.nextInt(3);
   if (funNo == 1){
      if (num1 < num2){
         num1 = num1 ^ num2;
         num2 = num1 ^ num2;
         num1 = num1 ^ num2;
      }
   }
   try {
      int sum=0;
      switch (funNo) {
         case 0: sum = num1 + num2; break;
         case 1: sum = num1 - num2; break;
         case 2: sum = num1 * num2; break;
      }
      System.out.println(sum);
      HttpSession session=request.getSession();
      session.setAttribute("captcha", String.valueOf(sum));
      servletOutputStream = response.getOutputStream();
      BufferedImage bufferedImage = numberCaptcha.createVerificationImage(num1,num2,funNo);
      ImageIO.write(bufferedImage, "jpg", servletOutputStream);
      servletOutputStream.flush();
   } catch (Exception e) {
      throw new RuntimeException(e);
   } finally {
      IOUtils.closeQuietly(servletOutputStream);
   }
}