@ResponseBody
    @RequestMapping(value = "/f")
    public void getUser(Model model, HttpServletRequest request,
                          HttpServletResponse response) throws IOException {
        PrintWriter print;
        /*
         * 规则描述:
         *1. 将token、timestamp、nonce三个参数进行字典序排序
         *2. 将三个参数字符串拼接成一个字符串进行sha1加密
         *3. 开发者获得加密后的字符串可与signature对比，标识该请求来源于微信
         */
	    String signature = request.getParameter("signature");
	    String timestamp = request.getParameter("timestamp");
	    String nonce = request.getParameter("nonce");
	    String echostr = request.getParameter("echostr");

	    String token = "beokwithanything";

        List<String> a = new ArrayList<String>();
        a.add(token);
        a.add(timestamp);
        a.add(nonce);
        Collections.sort(a);

        String hashcode = DigestUtils.shaHex(a.get(0)+a.get(1)+a.get(2));
        System.out.println(signature);
        System.out.println(hashcode);

        // 通过检验signature对请求进行校验:
        // 若校验成功则原样返回 echostr，表示接入成功，否则接入失败
        if (hashcode.equals(signature)){
            print = response.getWriter();
            print.write(echostr);
            print.flush();
        }
    }