ajax交互Struts2的action(1)

1.客户端网页代码

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GB18030">
<title>检测用户名是否唯一</title>
<script language="javascript">
function createRequest(url) {
  http_request = false;
  if (window.XMLHttpRequest) { // 非IE浏览器
   http_request = new XMLHttpRequest(); //创建XMLHttpRequest对象
  } else if (window.ActiveXObject) { // IE浏览器
   try {
    http_request = new ActiveXObject("Msxml2.XMLHTTP"); //创建XMLHttpRequest对象
   } catch (e) {
    try {
     http_request = new ActiveXObject("Microsoft.XMLHTTP"); //创建XMLHttpRequest对象
    } catch (e) {
    }
   }
  }
  if (!http_request) {
   alert("不能创建XMLHttpRequest对象实例！");
   return false;
  }
  http_request.onreadystatechange = getResult; //调用返回结果处理函数
  http_request.open('GET', url, true); //创建与服务器的连接
  http_request.send(null); //向服务器发送请求
}
function getResult() {
  if (http_request.readyState == 4) { // 判断请求状态
   if (http_request.status == 200) { // 请求成功，开始处理返回结果
    document.getElementById("toolTip").innerHTML = http_request.responseText; //设置提示内容
    document.getElementById("toolTip").style.display = "block"; //显示提示框
   } else { // 请求页面有错误
    alert("您所请求的页面有错误！");
   }
  }
}
function checkUser(userName) {
  if (userName.value == "") {
   alert("请输入用户名！");
   userName.focus();
   return;
  } else {
   //createRequest('http://10.65.9.181:8090/ajax/checkUser.jsp?user='+userName.value);
   createRequest('http://10.65.9.181:8090/ajax/checkUser.action?user='
     + userName.value);
  }
}
</script>
<style type="text/css">

</style>
</head>
<body style="margin: 0px;">
<form method="post" action="" name="form1">

      <table width="100%" height="250" border="0" cellpadding="0"
       cellspacing="0">
       <tr>
        <td width="18%" height="54" align="right" style="color: #8e6723"><b>用户名：</b></td>
        <td width="49%"><input name="username" type="text"
         id="username" size="32"></td>
        <td width="33%"><img src="images/checkBt.jpg" width="104"
         height="23" style="cursor: hand;"
         onClick="checkUser(form1.username);"></td>
       </tr>
       <tr>
        <td height="51" align="right" style="color: #8e6723"><b>密码：</b></td>
        <td><input name="pwd1" type="password" id="pwd1" size="35"></td>
        <td rowspan="2">
         <div id="toolTip"></div>
        </td>
       </tr>
       <tr>
        <td height="56" align="right" style="color: #8e6723"><b>确认密码：</b></td>
        <td><input name="pwd2" type="password" id="pwd2" size="35"></td>
       </tr>
       <tr>
        <td height="55" align="right" style="color: #8e6723"><b>E-mail：</b></td>
        <td colspan="2"><input name="email" type="text" id="email"
         size="45"></td>
       </tr>
       <tr>
        <td> </td>
        <td colspan="2"><input type="image" name="imageField"
         src="images/registerBt.jpg"></td>
       </tr>
      </table>
     </div>
    </td>
   </tr>
   <tr>
    <td> </td>
   </tr>
  </table>
</form>
</body>
</html>值得注意的是此处核心代码：

//createRequest('http://10.65.9.181:8090/ajax/checkUser.jsp?user='+userName.valu

补充：web前端 , JavaScript ,