验证码和异步刷新

异步刷新：
controller

  @PostMapping("/yibu")
    @ResponseBody
    public String yibu(String username){
        JSONObject jsonObject = new JSONObject();
        User user = userService.findByUsername(username);
        if (username!=null){
            if (user!=null){
                jsonObject.put("result","用户存在");
            }else {
                jsonObject.put("result","用户不存在");
            }
        }
        return jsonObject.toString();
    }

页面：

function a1() {
    var username = $("#username").val();
    // alert(username)
    $.ajax({
        url:"/yibu",
        type: "post",
        dataType: "json",
        data: {
            username:username
        },
        success:function (data) {
            if (data.result == "用户存在"){
                $("#tip").css("color","blue");
            }else {
                $("#tip").css("color","red");
            }
            $("#tip").html(data.result);
        },
        error:function () {
            alert(1)
        }
    })
}

验证码：
页面：

var verify = new GVerify("yzm");
    $(function () {
        $("#dlbutton").on("click", function () {
            var username = $("input[name='username']").val();
            var password = $("input[name='password']").val();
            var code = $("input[name='captcha']").val();
            if (username == "") {
                alert("用户名不能为空");
                return;
            }
            if (password == "") {
                alert("密码不能为空");
                return;
            }
            if (code == "") {
                alert("验证码不能为空");
                return;
            }
            if (!verify.validate(code)) {
                alert("验证码错误")
                return;
            }else {
                $.ajax({
                    url:"/doLogin",
                    type:"post",
                    dataType:"json",
                    data:{
                        username:username,
                        password:password
                    },
                    success:function (data) {
                        if (data.result == "0"){
                            window.location.href = "/";
                        }else if (data.result == "1"){
                            alert("密码错误")
                            window.location.href = "/login";
                        }else {
                            alert("用户不存在")
                            window.location.href = "/login";
                        }
                    }
                })
            }
        })
    })

controller：

  @PostMapping("/doLogin")
    @ResponseBody
    public String doLogin(HttpSession session,
                          @RequestParam("username") String username,
                          @RequestParam("password") String password){
        User user = userService.findByUsername(username);
        JSONObject jsonObject = new JSONObject();
        if (user!=null){
            if (user.getPassword().equals(password)){
                jsonObject.put("result","0");
                session.setAttribute("user",user);
                return jsonObject.toString();
            }
            jsonObject.put("result","1");
            return jsonObject.toString();
        }
        jsonObject.put("result","2");
        return jsonObject.toString();
    }