Ajax的学习应用

Ajax的常用方式在java web 中的开发的应用代码如下:

<%@ 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 'index.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">
 <!--
 <link rel="stylesheet" type="text/css" href="styles.css">
 -->
 <script type="text/javascript" src="js/Ajax_common.js"></script>
  </head>
 
  <body>
   First Name:<input type="text" id="txt1" />
   <input type="button" name="mybutton" value="Ajax" onclick="showHint(document.getElementById('txt1').value)">
  
</form>

<p>Suggestions: <span id="txtHint"></span></p>

  </body>
</html>

ajax_commons.js的源代码的如下:

 

 var xmlhttp=null;
  //创建xmlhttp对象的
function createHttpObject(){
  try{
    xmlhttp=new XMLHttpRequest();
   
  }catch(e){
    //针对IE创建的xmlhttp对象的信息
   try{
    xmlhttp=ActiveXObject("Msxml2.XMLHTTP");
   }catch(e)
    {
        try{
       xmlhttp=ActiveXObject("Msxml2.XMLHTTP");
    }catch(e)
      {
      }    }
  }
  return xmlhttp;
}

function showHint(username)
{
   xmlhttp=createHttpObject();
   if(xmlhttp==null)
    {
       alert("你的浏览器不支持的Ajax!");
       return ;
    }
    //请求路径的
    var url="./ajaxServlet?username="+username;
    //回调函数的应用
    xmlhttp.onreadystatechange=stateChanged;
    //构建请求信息
    xmlhttp.open("get",url,true);
    //发送请求信息
    xmlhttp.send(null);
}

//状态改变的设置的各种信息
function stateChanged()
{
  if (xmlhttp.readyState==4)
  {
   document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
  }
}

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