前端开发避坑-form表单action和submit提交与ajax异步提交冲突引起的故障解决！
近期在开发网站前端的时候，始终出现2次请求。困扰了很久。查询了网上的解决办法。发现，根源是因为，我的form表单里增加了一个action。虽然里面是空的，但是依然会在点击submit格式的按钮时，触发一次请求。这就引起了一种怪异的现象。
虽然ajax执行了成功！数据库执行了追加数据操作。但是页面始终停留在当前地址。
非常怪异，实际上，大家去掉form表单内的action，改一下submit,改成button模式，就可以恢复正常了。
<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head><meta charset="UTF-8"><title>用户注册-积德寺-菩提佛堂app-网页版</title><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="keywords" content="许愿祈福,祈福网站"/><meta name="description" content="欢迎注册菩提佛堂app账号信息，可以参加线上共修活动！"/><link th:href="@{/static/css/mycommon.css}" rel="stylesheet" type="text/css"><link th:href="@{/static/css/login.css}" rel="stylesheet" type="text/css"><script th:src="@{/static/js/jquery.js}"></script><style>.qifu_main {margin:10px auto;padding:14px;border: 1px solid #99CC00;border-radius: 8px;background: rgba(235, 179, 22, 0.8);text-align: center;font-size: 1.0em;width: 80%;height:auto;}.qifu_main .form_register {width: auto;height: auto;}.qifu_main p img{width: 80%;}.qifu_main .form_register .item {margin: 8px auto;padding-bottom: 12px;text-align: left;width: auto;height: auto;}.qifu_main .form_register button {display: block;width: 100px;height: 30px;border-radius: 10px;background-color: #ffb100;font-size: 1.0em;color: #FFFFFF;margin: 5px auto;}.qifu_main .form_register .item select{width: 30%;height: 26px;}.qifu_main .form_register .item input{width: 100%;height: 26px;}.qifu_main .form_register .item .icon-input{display: inline-block;height: 30px;line-height: 30px;}.qifu_main .form_register .item label img{width: 30px;height: auto;}</style>
</head>
<body>
<div th:replace="header :: top"></div>
<!--开始注册-->
<div class="qifu_main"><p>欢迎注册会员</p><form id="form_register" class="form_register"><div class="item"><label for="uname"><img th:src="@{/static/images/icon-lianhua.png}">名字:</label><input type="text" required id="uname" name="username" minlength="2" maxlength="10" placeholder="您的名字不超过10个字"><span class="msg-default hidden" id="namespan">用户名长度最小为2,最大为10</span></div><div class="item"><label for="upassword"><img th:src="@{/static/images/icon-lianhua.png}">密码:</label><input type="password" required id="upassword" minlength="6" maxlength="10" name="password" placeholder="请设置您的密码"><span class="msg-default hidden">密码长度在6到10位之间</span></div><div class="item"><label for="upwdconfirm"><img th:src="@{/static/images/icon-lianhua.png}">验证密码:</label><input type="password" required id="upwdconfirm" name="upwdconfirm" minlength="6" maxlength="10" placeholder="请再次输入密码"><span class="msg-default hidden">密码长度在6到10位之间</span></div><div class="item"><label for="phone"><img th:src="@{/static/images/icon-lianhua.png}">手机:</label><input type="phone" required id="phone" name="phone" maxlength="11" pattern="(\d{11})|^((\d{7,8})|(\d{4}|\d{3})-(\d{7,8})|(\d{4}|\d{3})-(\d{7,8})-(\d{4}|\d{3}|\d{2}|\d{1})|(\d{7,8})-(\d{4}|\d{3}|\d{2}|\d{1}))$" placeholder="请输入手机号码"><span class="msg-default hidden" id="phonespan">手机长度最大50位</span></div><div class="item"><label for="email"><img th:src="@{/static/images/icon-lianhua.png}">邮箱:</label><input type="email" required id="email" name="email" maxlength="100" placeholder="请输入邮箱"><span class="msg-default hidden" id="emailspan">邮箱长度最大100位</span></div><div class="item"><button type="button" id="btnRegister" >提交</button> <button type="reset" >重置</button></div></form>
</div>
<!--结束注册-->
<div th:replace="footer :: footer"></div>
<script>/*1.对用户名进行验证*///当对象失去焦点触发验证流程uname.onblur = function(){if(this.validity.valueMissing){this.nextElementSibling.innerHTML = '用户名不能为空';this.nextElementSibling.className = 'msg-error';this.setCustomValidity('用户名不能为空');}else if(this.validity.tooShort){this.nextElementSibling.innerHTML = '用户名不能少于2位';this.nextElementSibling.className = 'msg-error';this.setCustomValidity('用户名不能少于2位');}else {this.nextElementSibling.innerHTML = '用户名格式正确';this.nextElementSibling.className = 'msg-success';this.setCustomValidity('');var data =$("#uname").val();if(!data){ //用户没有输入任何内容return;}/**发起异步GET请求，询问服务器用户名是否已经存在**/$.ajax({url:"../user/checkName",data:"username="+$("#uname").val(),type:"get",dataType:"json",success:function(obj){$("#namespan").html(obj.message);//显示服务器的响应信息if(obj.state==0){$("#namespan").attr("class","msg-error");}else{$("#namespan").attr("class","msg-success");}}});}}uname.onfocus = function(){this.nextElementSibling.innerHTML = '用户名长度在2到10位之间';this.nextElementSibling.className = 'msg-default';}upassword.onfocus = function(){this.nextElementSibling.innerHTML = '密码长度在6到10位之间';this.nextElementSibling.className = 'msg-default';}upassword.onblur = function(){if(this.validity.valueMissing){this.nextElementSibling.innerHTML = '密码不能为空';this.nextElementSibling.className = 'msg-error';this.setCustomValidity('密码不能为空');}else if(this.validity.tooShort){this.nextElementSibling.innerHTML = '密码长度在尽量别少于6位';this.nextElementSibling.className = 'msg-error';this.setCustomValidity('密码长度在尽量别少于6位');}else {this.nextElementSibling.innerHTML = '密码格式正确';this.nextElementSibling.className = 'msg-success';this.setCustomValidity('');}}upwdconfirm.onfocus = function(){this.nextElementSibling.innerHTML = '密码长度在6到10位之间';this.nextElementSibling.className = 'msg-default';}//当确认密码输入框失去焦点时触发验证。upwdconfirm.onblur = function(){if(this.validity.valueMissing){this.nextElementSibling.innerHTML = '密码不能为空';this.nextElementSibling.className = 'msg-error';this.setCustomValidity('密码不能为空');}else if(this.validity.tooShort){this.nextElementSibling.innerHTML = '密码长度在尽量别少于6位';this.nextElementSibling.className = 'msg-error';this.setCustomValidity('密码长度在尽量别少于6位');}else {this.nextElementSibling.innerHTML = '密码格式正确';this.nextElementSibling.className = 'msg-success';this.setCustomValidity('');var pwd1 =$("#upassword").val();var pwd2 =$("#upwdconfirm").val();if(pwd1!=pwd2){this.nextElementSibling.innerHTML = '两次输入密码不一致';this.nextElementSibling.className = 'msg-error';this.setCustomValidity('密码长度在尽量别少于6位');}else{this.nextElementSibling.innerHTML = '两次输入密码一致';this.nextElementSibling.className = 'msg-success';this.setCustomValidity('');}}}/*3.对邮箱地址进行验证*/email.onblur = function(){if(this.validity.valueMissing){this.nextElementSibling.innerHTML = '邮箱不能为空';this.nextElementSibling.className = 'msg-error';this.setCustomValidity('邮箱不能为空');}else if(this.validity.typeMismatch){this.nextElementSibling.innerHTML = '邮箱格式不正确';this.nextElementSibling.className = 'msg-error';this.setCustomValidity('邮箱格式不正确');}else {this.nextElementSibling.innerHTML = '邮箱格式正确';this.nextElementSibling.className = 'msg-success';this.setCustomValidity('');var data =document.getElementById("email").value;if(!data){ //用户没有输入任何内容return;}/**发起异步GET请求，询问服务器邮箱是否已经存在**/$.ajax({url:"../user/checkEmail",data:"email="+$("#email").val(),type:"get",dataType:"json",success:function(obj){$("#emailspan").html(obj.message);if(obj.state==0){$("#emailspan").attr("class","msg-error");}else{$("#emailspan").attr("class","msg-success");}}});}}email.onfocus = function(){this.nextElementSibling.innerHTML = '请输入合法的邮箱地址';this.nextElementSibling.className = 'msg-default';}/*3.对手机号进行验证*/phone.onblur = function(){if(this.validity.valueMissing){this.nextElementSibling.innerHTML = '手机号不能为空';this.nextElementSibling.className = 'msg-error';this.setCustomValidity('手机号不能为空');}else if(this.validity.patternMismatch){this.nextElementSibling.innerHTML = '手机号格式不正确';this.nextElementSibling.className = 'msg-error';this.setCustomValidity('手机号格式不正确');}else {this.nextElementSibling.innerHTML = '手机号格式正确';this.nextElementSibling.className = 'msg-success';this.setCustomValidity('');var data =document.getElementById("phone").value;if(!data){ //用户没有输入任何内容return;}/**发起异步GET请求，询问服务器用户名是否已经存在**/$.ajax({url:"../user/checkPhone",data:"phone="+$("#phone").val(),type:"get",dataType:"json",success:function(obj){$("#phonespan").html(obj.message);if(obj.state==0){$("#phonespan").attr("class","msg-error");}else{$("#phonespan").attr("class","msg-success");}}});}}phone.onfocus = function(){this.nextElementSibling.innerHTML = '请输入合法的手机号';this.nextElementSibling.className = 'msg-default';}
</script>
<script>$('#btnRegister').click(function(){var lengths=0;$('.item').each(function(){if($(this).find('span').hasClass('msg-success')){lengths++;}});//异步注册提交if(lengths==5){$.ajax({url:"../user/register",data:$("#form_register").serialize(),//相当于表单内的提交表单值集合。必须使用到nametype:"post",dataType:"json",success:function(obj){if(obj.state==0){console.log(obj.state)$("#namespan").html(obj.message)$("#namespan").attr("class","msg-error")}else if(obj.state==1){console.log(obj.state)window.location = "../user/showLogin"}},error:function (obj){$("#namespan").html(obj.message)$("#namespan").attr("class","msg-error")}});}})
</script>
</body>
</html>如图所示，这个就是，我修改后的代码，里面button，之前是submit.form的内容页删掉了action.
)
![spring boot的返回值里面含有net.sf.json.JSONObject 报错net.sf.json.JSONNull[“empty“])]](http://pic.xiahunao.cn/spring boot的返回值里面含有net.sf.json.JSONObject 报错net.sf.json.JSONNull[“empty“])])
