AJAX自学练习无刷新从数据库后台取数据显示

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请求页面request.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1" 
pageEncoding="ISO-8859-1"%> 
<!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=UTF-8"> 
<title>Insert title here</title> 
<script language="javascript"><!-- 
function GetXmlHttpObject(){ 
    var xmlHttp = null; 
    try{ 
        xmlHttp = new XMLHttpRequest(); 
    }catch(e){ 
        try{ 
            xmlHttp = new ActiveXObject("Msxml2.XMLHTTP"); 
        }catch(e){ 
            xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); 
        } 
    } 
    return xmlHttp; 

} 
function showMsg(str){ 
    xmlHttp = GetXmlHttpObject(); 
    if(xmlHttp == null){ 
        alert ("you browser don't support the ajax"); 
         return; 

    } 
    var url = "response.jsp"; 
    url = url + "?q="+ str; 
    url = url + "&sid ="+ Math.random(); 
    xmlHttp.onreadystatechange = stateChanged; 
    xmlHttp.open("GET", url, true); 
    xmlHttp.send(null); 
} 
function stateChanged() 
{ 
    if(xmlHttp.readyState==4) 
    { 
        document.getElementById("showHint").innerHTML = xmlHttp.responseText; 
    } 
} 
// --></script> 
</head> 
<body> 
<form name="form1" action="" method="post"> 
<p>RocarsId:</p> 
    <select name="select1" onchange="showMsg(document.form1.select1.options[document.form1.select1.selectedIndex].value)" > 
        <option value="140">140</option> 
        <option value="150">150</option> 
    </select> 
    <div id="showHint">Show rocars ccrn messages.</div> 
</form> 
</body> 
</html>

response.jsp

复制代码代码如下:

<%@ page language="java" contentType="text/plain; charset=UTF-8" 
pageEncoding="UTF-8"%> 
<%@ page import="com.lwf.eus.util.*,java.util.*,com.lwf.eus.entity.*,com.lwf.eus.bean.*" %> 
<html> 
<head> 
<title>response the ccrn</title> 
</head> 
<body> 
<% 
    String q = request.getParameter("q"); 
    System.out.println("message:" + q); 
    RocarsBean rocars = RocarsEntity.getRocarsListById(q); 
%> 
<table> 
<tr> 
<td>RocarsId</td> 
<td>RocarsCcrn</td></tr> 
<tr> 
<td><%=rocars.getRocarsId() %></td> 
<td><%=rocars.getCcrn() %></td> 
</tr> 
</table> 
</body> 
</html>