kenshinobiy

1.当输入用户名和密码为空的时候,需要判断。这时候就用到了校验用户名和密码,这个需要在jsp的前端页面写;有两种方法,一种是用submit提交。一种是用button提交。
方法一:

在jsp的前端页面的头部插入一个js方法:

 function checkUser(){
   var result = document.getElementById("userid").value;
   var password = document.getElementById("userpassid").value;
   if(result == ""  ){
     alert("用户名不能为空");
     return false;
   }
   if(password == ""  ){
    alert("密码不能为空");
     return false;
   }else{
   return true;
   }
}

在form表单里写成这样:

<form id="formid"  name= "myform" method = \'post\'  action = \'user_login_submit.action\' onsubmit = "return checkUser();" >
            <table width="100%" border="0">
              <tr>
                <td width="60" height="40" align="right">用户名&nbsp;</td>
                <td><input type="text" value="" class="text2" name = "username" id = "userid"/></td>
              </tr>
              <tr>
                <td width="60" height="40" align="right">密&nbsp;&nbsp;码&nbsp;</td>
                <td><input type="password" value="" class="text2" name = "userpass" id = "userpassid"/></td>
              </tr>
              <tr>
                <td width="60" height="40" align="right">&nbsp;</td>
                <td><div class="c4">
                    <input type="submit" value="" class="btn2"  />

 

方法二:

function checkUser(){
   var result = document.getElementById("userid").value;
   var password = document.getElementById("passid").value;

   if(result == ""  ){
     alert("用户名不能为空");
     return false;
   }
   if(password == ""  ){
    alert("密码不能为空");
     return false;
   }
  document.getElementById("formid").submit();
}

form表格的写法,需要写id
 <form id="formid" method = \'post\'  action = \'user_login_submit.action\'  >

button按钮的写法如下:

<input type="button" value="" class="btn2" onclick = "checkUser();" />

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