请求页面request.jsp
代码如下：

%@ 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"
titleInsert 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"
pRocarsId:/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
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
titleresponse the ccrn/title
/head
body
%
    String q = request.getParameter("q");
    System.out.println("message:" + q);
    RocarsBean rocars = RocarsEntity.getRocarsListById(q);
%
table
tr
tdRocarsId/td
tdRocarsCcrn/td/tr
tr
td%=rocars.getRocarsId() %/td
td%=rocars.getCcrn() %/td
/tr
/table
/body
/html

注意这里与自学练习一不同的是，request.jsp页面用一个div来显示信息，response.jsp从数据库里面查询出来的内容放在table标签里，其它的html标签不会在div里面显示。