xmlhttp中的疑惑

在与客户端与服务器端的通信中一般用到两种方法，iframe隐藏和xmlhttp,用iframe隐藏我明白服务器端怎么写，可是使用xmlhttp时我不太明白服务器端的代码要怎么写，求指点。。现在我想实现的是在客户端的用户名是否可用的验证。。客户端代码如下：<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>无标题页</title>
    <script type="text/javascript">
    var request;
    function createXMLHTTP()
    {
         if(window.XMLHttpRequest)
         {
            return new XMLHttpRequest();
         }
         else if(window.ActiveXObject)
         {
             try
             {
                return new ActiveXObject("MSXML2.XMLHTTP");
             }
             catch(oException)
             {
                return new ActiveXObject("Microsoft.XMLHTTP");
             }
         }
         else
         {
            throw new Error("not exists");
         }
    }
      function checkUsername()
      {
         var userValue=document.getElementById("username").value;
         {
            if(userValue="")
            {
                alert("Please enter a user name to check!")
                return;
            }
            var url="bb.aspx?username="+userValue;
            request=createXMLHTTP();
            request.open("get","bb.aspx","true");
            request.onreadystatechange=checkUsername_callBack;
            request.send(null);
         }
      }
      function checkUsername_callBack(sResponseText)
      {
         if(request.readystate==4)
         {
            if(request.status==200)
            {
                var userValue=document.getElementById("username").value;
                if(sResponseText=="available")
                {
                    alert("username:"+userValue+"is  available!");
                }
                else
                {
                    alert("username:"+userValue+"is not available!");
                }
             }
         }
      }
    </script>
</head>
<body>
<form>
<table>
<tr>
<td>UserName</td>
<td><input type="text" id="username" /></td>
<td><input type="button" value="验证" onclick="checkUsername()"/></td>
</tr>
</table>
</form>
</body>
</html>服务器端要怎么对它进行验证呢

解决方案 »

  1.   

    他其实就是一个请求
    所以可以当做平常的页面请求来处理
    session也是可以用的
      

  2.   

    那要怎么返回这个处理完的数据呢比如说我在服务器端验证的用户名可用，然后我就要向它返回一个available,将它传到客户端定义的这个变量sResponseText中
      

  3.   

      function checkUsername()
          {
             var userValue=document.getElementById("username").value;
             {
                if(userValue="")
                {
                    alert("Please enter a user name to check!")
                    return;
                }
                var url="bb.aspx?username="+userValue;
                request=createXMLHTTP();
                request.open("get","bb.aspx","true");
                 xmlHttp.onreadystatechange =function(){
                        
                          
                                 if(request.readyState==4 && request.status == 200)
                                {
                                   checkUsername_callBack(request.responseText);
                                }
                            
                         };
                request.send(null);
             }
          }
          function checkUsername_callBack(sResponseText)
          {
            
              
                    var userValue=document.getElementById("username").value;
                    if(sResponseText=="available")
                    {
                        alert("username:"+userValue+"is  available!");
                    }
                    else
                    {
                        alert("username:"+userValue+"is not available!");
                    }
          
          }
      

  4.   

    后台用out.write()把你想返回到前台的给输出去
    比如说是avaliable或者error