http://hi.baidu.com/a393060727/blog/item/19dc08d5f2408acd51da4b3b.html
jsp頁面顯示新聞.公告之類的上一篇下一篇(轉載)
2009-07-14 23:23
此方法有二種：
1 在jsp前台頁面判斷并輸出，（适合初學，易了解）
2 在servlet裡判斷并輸出（符合mvc架構）
我們先說第一種方法：
先說dao層，主要是取比目前id小的隻一條，取比目前id大的隻一條，注意排序！下面是在查詢時的最基本語句，這是最基本的：
//string max="select max(id) from news where id< "+id+" order by id desc limit 0,1;";
//string min="select min(id) from news where id> "+id+" order by id asc limit 0,1;";
public news max(long id)throws exception{
/**
* 取下一條
*/
news maxnews=null;
try {
conn=dbinit.getconn();
pstmt=conn.preparestatement("select * from news where id>? order by id asc limit 0,1 ;");
pstmt.setlong(1, id);
rs=pstmt.executequery();
if(rs!=null && rs.next()){
maxnews=new news();
maxnews.setid(rs.getlong("id"));
maxnews.settitle(rs.getstring("title"));
maxnews.setzuozhe(rs.getstring("zuozhe"));
maxnews.setlaiyuan(rs.getstring("laiyuan"));
maxnews.setcontent(rs.getstring("content"));
maxnews.setfabutime(rs.getstring("fabutime"));
}
} catch (runtimeexception e) {
// todo auto-generated catch block
e.printstacktrace();
return null;
}finally{
dbinit.close(rs, pstmt, conn);
}
return maxnews;
}
public news min(long id)throws exception{
* 取上一條
news minnews=null;
pstmt=conn.preparestatement("select * from news where id<? order by id desc limit 0,1 ;");
minnews=new news();
minnews.setid(rs.getlong("id"));
minnews.settitle(rs.getstring("title"));
minnews.setzuozhe(rs.getstring("zuozhe"));
minnews.setlaiyuan(rs.getstring("laiyuan"));
minnews.setcontent(rs.getstring("content"));
minnews.setfabutime(rs.getstring("fabutime"));
return minnews;
二 再說servlet層
在我們顯示詳細新聞的頁面show.jsp所用的servlet方法show()中調用上面兩個dao方法
public void maxmin(httpservletrequest request,httpservletresponse response)throws exception{
/**
* 專用來供前台show.jsp調用的方法（先經show()調用）
*/
newsdao newsdao = new newsdao();
news maxnews=null;
news minnews =null;
//stringbuffer out=new stringbuffer();
//long maxid=0l;
//long minid=0l;
long currentid=long.parselong(request.getparameter("id"));
maxnews=newsdao.max(currentid);
minnews=newsdao.min(currentid);
request.setattribute("currentid",currentid);
request.setattribute("maxnews", maxnews);
request.setattribute("minnews", minnews);
//return out.tostring();
public void show(httpservletrequest request,httpservletresponse response)throws exception{
* 背景檢視新聞詳細資訊
long id= long.parselong(request.getparameter("id"));
news news = null;
if (id!= 0) {
try {
news = newsdao.show(id);
} catch (exception e) {
// todo auto-generated catch block
e.printstacktrace();
this.maxmin(request, response);//調用
request.setattribute("viewnews", news);
request.getrequestdispatcher("shownews.jsp").forward(request,response);
第三：前台show.jsp頁面
<%@ page language="java" import="java.util.*,bean.*" 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>${viewnews.title }</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<link rel="stylesheet" type="text/css" href="css/styles.css">
</head>
<body>
<fieldset>
<legend>新聞詳細資訊</legend>
<div id="news">
<div id="title">${viewnews.title }</div>
<div id="come">新聞來源：${viewnews.laiyuan } &nbsp;&nbsp;編輯：${viewnews.zuozhe } &nbsp;&nbsp;釋出時間：${viewnews.fabutime}</div>
<div id="content">${viewnews.content }</div>
</div>
<div style="text-align:center;">[<a href="#" onclick="window.close();"><font color="#ff0000">關閉本頁面</font></a>] </div>
<!-- 上一篇 下一篇 -->
<%
news maxnews=null;
news minnews=null;
long maxid=0l;
long minid=0l;
long currentid=(long)request.getattribute("currentid");
maxnews=(news)request.getattribute("maxnews");
minnews=(news)request.getattribute("minnews");
if(maxnews!=null && minnews!=null){
maxid=maxnews.getid();
minid=minnews.getid();
if(currentid<=minid){
%>
<div id="prenext">
<span>上一篇: 沒有上一篇</span>
<span>下一篇: <a href="admin/news.do?method=show&id=${maxnews.id}">${maxnews.title }</a></span>
</div>
<%
}
if(minid<currentid && currentid<maxid){
<div id="prenext">
<span>上一篇: <a href="admin/news.do?method=show&id=${minnews.id}">${minnews.title }</a></span>
<%
if(currentid>=maxid){
%>
<div id="prenext">
<span>下一篇: 沒有下一篇</span></div>
}
if(maxnews==null && minnews!=null){
<div id="prenext">
<span>下一篇: <font color="red">沒有下一篇</font></span></div>
if(maxnews!=null && minnews==null){
<span>上一篇: <font color="red">沒有上一篇</font></span>
</fieldset>
</body>
</html>
=============================================================
==============================================================
下面開始說第二種方法：2 在servlet裡判斷并輸出（符合mvc架構）
先說dao層，和上面的方法中一模一樣：
主要是取比目前id小的隻一條，取比目前id大的隻一條，注意排序！下面是在查詢時的最基本語句，這是最基本的：
再說servlet層
public string updown(httpservletrequest request,httpservletresponse response)throws exception{
stringbuffer out=new stringbuffer();
long maxid=0l;
if (maxnews != null && minnews != null) {
maxid = maxnews.getid();
minid = minnews.getid();
string maxstr = "admin/news.do?method=show&id=" + maxid;
string minstr = "admin/news.do?method=show&id=" + minid;
out.append("<div id='prenext'>");
if (minid < currentid && currentid < maxid) {
out.append("<span>上一篇:<a href=" + minstr + ">"+ minnews.gettitle() + "</a></span>");
out.append("<span>下一篇:<a href=" + maxstr + ">"+ maxnews.gettitle() + "</a></span>");
}
if(maxnews != null && minnews == null){
maxid = maxnews.getid();
string maxstr = "admin/news.do?method=show&id=" + maxid;
out.append("<span>上一篇:沒有上一篇</span>");
out.append("<span>下一篇:<a href="+maxstr+">"+ maxnews.gettitle() + "</a></span>");
}
if(maxnews == null && minnews != null){
system.out.println(minid+"@@@@@@@@@@@@@@@");
out.append("<span>上一篇:<a href=" + minstr + ">"+ minnews.gettitle() + "</a></span>");
out.append("<span>下一篇:沒有下一篇</span>");
out.append("</div>");
return out.tostring();
public void show(httpservletrequest request,httpservletresponse response)throws exception{
string updown=this.updown(request, response);
request.setattribute("updown", updown);
最後，在前台調用就友善多了
一句話：${updown}
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