登陆验证

当我不输入用户名和密码的时候点击登陆怎么不让他提交ACTION ？就是说当用户名和密码为空或者不符合要求的请款下。怎么不让他提交FORM 表单？用javascript 怎么写？*****************************************************************************************************************<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'login.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">

<script type="text/javascript">
function uname(){
var name= document.getElementById("un").value;
if(name==""){
alert("用户名不能为空~~!");
return false;
}
}
function upass(){
var pass = document.getElementById("up").value;
if(pass ==""){
alert("密码不能为空~~!");
return false;
}

}
function imgclick(){
document.getElementById('uimg').src='/PB_Demo/imageCodeMaker?temp=Math.random()';

}
function valiclick(){
var vali = document.getElementById("vali").value;
if(vali==""){
alert("验证码不能为空!");
return false;
}
}
</script>
<style type="text/css">
a:hover{
color:red;
}
#uname{color:red}
#upass{color:red}
#Prompt p{
float: right;
}
</style>
  </head>

  <body>
   <center>
     <form action = "UserinfoLogin.action"" method = "post">
     <div id="uname">
     用户名:<input id="un" type="text" name="userinfo.username" onblur="uname()"><br/>
     </div>
     <div id="upass">
     密&nbsp码&nbsp:<input id="up" type="text" name="userinfo.userpwd" onblur="upass()"><br/>
     </div>
<div id="Prompt" onclick="imgclick()">
       <h1>验证码:<img id="uimg" src="/PB_Demo/imageCodeMaker" /></h1>
       <p>小提示:点击图片可以刷新验证码哦~~</p>
</div>
<div>
         <input id="vali" type="text" name="userinfo.validateCode" onblur="valiclick()"/>
     <div>
     <input type="submit" value="登陆">
     <input type="reset" value="清空">
     <a href="insert.jsp">注册</a>
     </div>
     </div>
    </form>
    </center>
  </body>
</html>

解决方案 »

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方法有很多种最简单的是把<input type="submit" value="登陆">
换成
<input type="button" onclick="aaa(this.form)" value="登陆">function aaa(myform){
if(myform.xxxx.value===''){
    alert('请输入xxxxxx');
}else if(){
    ................
}.........else{
  myform.submit();
}
}
<input type="submit" value="登陆">
该城：
<input type="button" value="登陆" onClick="inputCheck()">
提交可以在function中设置提交。function inputCheck(){
var userId = document.getElementById("userID").value;
var pwd = document.getElementById("PWD").value;
if (userId == null || userId.length == 0 || pwd == null || userId.length == 0) {
alert("");
return false;
}

document.getElementById("form1").submit();
return true;
}
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
  <base href="<%=basePath%>">

  <title>My JSP 'login.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">

<script type="text/javascript">
function uname(){
var name= document.getElementById("un").value;
if(name==""){
alert("用户名不能为空~~!");
return false;
}
return true;
}
function upass(){
var pass = document.getElementById("up").value;
if(pass ==""){
alert("密码不能为空~~!");
return false;
}
return true;}
function imgclick(){
document.getElementById('uimg').src='/PB_Demo/imageCodeMaker?temp=Math.random()';}
function valiclick(){
var vali = document.getElementById("vali").value;
if(vali==""){
alert("验证码不能为空!");
return false;
}
return true;
}
function validates(){
   return uname() && upass() && valiclick();
}
</script>
<style type="text/css">
a:hover{
color:red;
}
#uname{color:red}
#upass{color:red}
#Prompt p{
float: right;
}
</style>
  </head>

  <body>
  <center>
  <form action = "UserinfoLogin.action"" method = "post" submit="return validates();">
  <div id="uname">
  用户名:<input id="un" type="text" name="userinfo.username" onblur="uname()"><br/>
  </div>
  <div id="upass">
  密&nbsp码&nbsp:<input id="up" type="text" name="userinfo.userpwd" onblur="upass()"><br/>
  </div>
<div id="Prompt" onclick="imgclick()">
<h1>验证码:<img id="uimg" src="/PB_Demo/imageCodeMaker" /></h1>
<p>小提示:点击图片可以刷新验证码哦~~</p>
</div>
<div>
<input id="vali" type="text" name="userinfo.validateCode" onblur="valiclick()"/>
<div>
<input type="submit" value="登陆">
<input type="reset" value="清空">
<a href="insert.jsp">注册</a>
</div>
</div>
  </form>
  </center>
  </body>
</html>
以上是在你自己的代码上小做改动至于那三个控件的onblur方法，可有可无了
把登录的onclick事件改一下
然后在JS中判断用户名或密码的输入框是否为空function a(){var name= document.getElementById("un").value;
var pass = document.getElementById("up").value;
var vali = document.getElementById("vali").value;
if(name!=""&&pass!=""&&vali!=null){
return true;
}else{
return false;
}
//下面这个是登录的触发事件
function b(){
if(a()){
//提交表单
}else{
alert("用户名或密码或验证码为空！请重新填写");
return false;
}
}
}
你自己吧思路跟顺序搞清楚，你点击提交马上调用action方法，你现在就是在进入action之前进行判断，如果为空就不进入action
你没必要用js写得这么复杂啊，直接用token防止表单提交就ok了啊
然后在from 那里加个onsubmit="a()"/> 意思在提交之前先去验证表单内容
可以登录的onsubmit="a();" 也可以登录的onclick="b();"