如题，代码如下：
<%@ page language="java" import="java.util.*" pageEncoding="gb2312"%>
<%@page import="DBO.selectDBO"%>
<%@page import="DBO.jingdian"%>
<%@page import="DBO.message"%>
<%
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 'jutijingdian_right_1.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">
-->
</head>
<!--
<script>
function docheck(){
var message=document.getElementById("message");
Object obj=session.getAtribute("Name");
if(message.value==null || message.value==""){
alert("评论内容不能为空")； return false;
}
return true;
}
</script>
-->
<%
int pageNum=1;
request.setCharacterEncoding("GB2312");
String g=request.getParameter("pageNum");
if(g!=null){
pageNum=Integer.parseInt(g);
out.print(pageNum);
}
String s = request.getParameter("id");
selectDBO dbo=new selectDBO();
String bk=dbo.book(s);
String e_ie=dbo.area__introduce(s);
LinkedList jingdianList=dbo.selectjingdian(s);
LinkedList messageList=dbo.selectmessage(s,pageNum);
%>
<body>
<table width="100%" border="1" align="center" height="700">
<tr height="150">
<td width="70%" valign="top" align="left">
<table>
<tr height="20">
<td><b>景区简介：</b></td>
</tr>
<tr>
<td>
<textarea rows="8" cols="99"><%=e_ie %>
</textarea>
</td>
</tr>
</table>
</td>
<td rowspan="4" height="698" align="center">
<table align="center" width="100%" border="1" >
<tr height="25">
<td align="left"><b>美图欣赏：</b></td>
</tr>
<tr>
<td>
<marquee direction="up" ><img src="1440love006.jpg" usemap="#move">
<img src="1440love006.jpg" usemap="#move">
<img src="1440love006.jpg" usemap="#move">
<img src="1440love006.jpg" usemap="#move">
</marquee>
</td>
</tr>
</table>
</td>
</tr>
<tr height="150">
<td >
<table>
<tr>
<td><b>游玩手册：</b></td>
</tr>
<tr>
<td>
<textarea rows="7" cols="99"><%=bk %>
</textarea>
</td>
</tr>
</table>
</td>
</tr>
<tr height="150">
<td>
<table align="center" width="100%">
<%for(int i=0;i<jingdianList.size()/5;i++){ %>
<tr height="28">
<%for(int j=0;j<5;j++){
jingdian jd=(jingdian)jingdianList.get(i*5+j);
%>
<td align="center"><a href="Mustgo1.jsp?id=<%=jd.getJingdian_id()%>" target="right"><%=jd.getJingdian_name() %></a></td>
<%} %>
</tr>
<%} %>
<tr height="28%">
<%for(int i=0;i<jingdianList.size()-((jingdianList.size()/5)*5);i++){
jingdian jd=(jingdian)jingdianList.get(jingdianList.size()-jingdianList.size()%5+i);
%>
<td align="center"><a href="Mustgo1.jsp?id=<%=jd.getJingdian_id()%>" target="right"><%=jd.getJingdian_name() %></a></td>
<%} %>
</tr>
</table>
</td>
</tr>
<tr>
<td>
<table align="center" width="100%" border="1">
<tr height="40">
<td width="56%" align="center" ><b>大家对这个地方的印象</b></td>
<td width="18%" align="center"><b>作者</b></td>
<td width="24%" align="center"><b>发表时间</b></td>
</tr>
<%for(int i=0;i<messageList.size();i++){
message ms=(message)messageList.get(i);
%>
<tr height="40">
<td width="56%"><a href="#"><%=ms.getMessage_text() %></a></td>
<td width="18%">作者</td>
<td width="24%" align="center"><b><%=ms.getMessage_time() %></b></td>
</tr>
<%} %>
<tr height="40">
<td colspan="3" align="center">
<a href="jutijingdian_right_1.jsp?pageNum=<%=pageNum-1 %>">上一页</a>
第1页
<a href="jutijingdian_right_1.jsp?pageNum=<%=pageNum+1 %>">下一页</a>
</td>
</tr>
</table>
<table width="100%">
<tr>
<td>
<textarea name="message" cols="100" rows="50"></textarea>
</td>
</tr>
<tr>
<td>
<input type="submit" value="发表" >
</td>
</tr>
</table>
</td>
</tr>
</table>
</body>
</html>
我想知道在点击下一页或者是上一页之后，再次进入这个页面，如何获得S的值？急需！！！！！