ajax局部刷新，，在线等啊，，，

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!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=ISO-8859-1">
<title>Insert title here</title>
<script type="text/javascript">
    function createXmlHttp(){
        var xmlhttp;
        if(window.XMLHttpRequest){
            xmlhttp=new XMLHttpRequest();
        }
        else{
            xmlhttp=new ActiveObject("Microsoft.XMLHTTP");
        }
    }
    
    function submit(){
        //创建xmlhttp对象
        createXmlHttp();
        if(xmlhttp!=null){
            window.alert("bu kong");
        }
        xmlhttp.onreadyStatechange=function(){
            if(xmlhttp.readyState==4&&xmlhttp.status==200){
                document.getElementById("txt").innerHTML=xmlhttp.responseText;
            }
        }
        xmlhttp.open("GET","select.jsp",true);
        xmlhttp.send(null);
    }
</script>
</head>
<body>
<input type="button" onClick=submit() value="chakan">
&nbsp
<div id="txt"></div>
</body>
</html>
Java code<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8" import="java.sql.*" import="javax.servlet.http.HttpServletResponse"%>
    <%@ page import="com.mysql.jdbc.Driver" %>
<!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=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
<%
    Connection con;
    Statement sta;
    ResultSet rs;        Class.forName("com.mysql.jdbc.Driver");            con=DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","");
            String sql="select * from user";    sta=con.createStatement();    rs=sta.executeQuery(sql);
    while(rs.next()){
        
        out.print(rs.getString(2));
    }
%>
</body>
</html>求助高手，帮小弟解惑，在线等