在JSP页面中实现检索数据的分页显示

下面将通过一些例程来说明实现JSP页面翻页技术的实现。

首先，在JSP中，通过JAVA servlet 来检索数据，而用JSP来调用结果来显示。

因而，此技术可分为两个部分（依赖关系）：

1. 在服务器端的servlet 中的实现

要点：
& 将查询条件保存到session中，取session中的查询条件

& 设置Statement对象的MaxRows（确定一页显示多少行数据）

& 顺序地通过执行SQL语句查询数据，按maxRows 来检索一个maxRows的数据，

下一页再检索下一maxRows的数据，以此类推。

2. 在JSP中的显示实现

要点：

& 显示maxRows条数据

& 通过“下一页”按钮或超链再次调用刚才的servlet查询下一maxRows的数据

流程如图所示：

下面通过一个例程来说明（一个servlet程序和一个JSP程序）：
l querymedicine. java (Medicine. querymedicine)
package Medicine;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.sql.*;
import Medicine.medicinelist;
import Medicine.searchData;
////////////////////////////////////////////////////
// 接---mutiquery.jsp页面，并从request中得到5条查询条件 ///
// 按条件查询药品，并将结果存进session的“medicinelist”中。 ///
// 张乾 2000年3月15日 ///
////////////////////////////////////////////////////
public class querymedicine extends HttpServlet {
private DBConnectionManager connMgr;
//Initialize global variables
public void init(ServletConfig config) throws ServletException {
super.init(config);
connMgr = DBConnectionManager.getInstance();
}

//========================处理 HTTP Get 请求============================
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Statement stmt=null;
Connection con = connMgr.getConnection("medicine"

;
if (con == null) {
response.sendRedirect("/medicine/con_error.html"

;
return;
}

// ==================== 创建数据库Statement =============================
try {
stmt=con.createStatement();
}
catch (Exception e)
{
connMgr.freeConnection("medicine",con);
response.sendRedirect("/medicine/stmt_error.html"

;
return;
}

//-------------------------------------------------------------
long all_count=0; //存满足条件的药品总数

//===================从request中得到session======================
try{
HttpSession session = request.getSession(false);
if (session == null) {
connMgr.freeConnection("medicine",con);
response.sendRedirect("/medicine/session_error.html"

;
return;
}
//-----------------------------------------------------------

//======从“下一页”提交来的参数取得前页最后一条数据的药品编码=======
String ll_pos=request.getParameter("pos"

;
//如果pos=-1则表示要从头开始查
//----------------------------------------------------------
//=====================查询用的SQL语句串==========================
String sqlstatment="SELECT medicines.ypbm, medsmalltypes.zlmc, medsupertypes.clmc,
medtypes.dlmc, medicines.ypm, medicines.zyyx, medicines.ypzy FROM medicines,
medsmalltypes,medsupertypes,medtypes WHERE medicines.ypbm>"+ll_pos+"
and (( medsmalltypes.zlbm = medicines.zlbm

and ( medsupertypes.clbm = medicines.clbm


and ( medtypes.dlbm = medicines.dlbm

and ( ( medicines.del_flag = 0

";
//-----------------------------------------------------
String zlbm;
String dlbm;
String clbm;
String zyyx;
String ypm;
searchData slist=new searchData();
synchronized (session) {
slist=(searchData)session.getAttribute("searchList"

;
}
if(ll_pos.equals("-1"

){

//===表示不是由“下一页”过来要从头开始查数据==========
if(slist!=null){
synchronized (session) {
session.removeAttribute("searchList"

;
}
}
slist=new searchData();

//=============从设置查询条件页面取得查询条件的参数===================
zlbm=request.getParameter("zlbm"

;
dlbm=request.getParameter("dlbm"

;
clbm=request.getParameter("clbm"

;
zyyx=request.getParameter("zyyx"

;
ypm=request.getParameter("ypm"

;
//------------------------------------------------------
//=================将查询条件参数通过Vector存到session中==========
slist.setZlbm (zlbm);
slist.setDlbm (dlbm);
slist.setClbm (clbm);
slist.setZyyx (zyyx);
slist.setYpm (ypm);
synchronized (session) {
session.setAttribute ("searchList",slist);
}
//---------------------------------------------------------
}
//--------------------------------------------------------
else
{
//============================取出查询条件参数====================
if(slist!=null){
zlbm=slist.getZlbm();
dlbm=slist.getDlbm();
clbm=slist.getClbm();
zyyx=slist.getZyyx();
ypm=slist.getYpm();
}
else{
if(stmt!=null) stmt.close();
stmt.setMaxRows(0);
connMgr.freeConnection("medicine",con);
response.sendRedirect("/medicine/session_error.html"

;
return;
}
//-------------------------------------------------
}
String sql2="select count(*) from medicines where del_flag=0";

//=====================根据条件参数设置SQL语句=======================

if(!(zlbm.trim().equals("0"

)) {
sqlstatment+=(" and ( medicines.zlbm="+zlbm.trim()+"

"

;
sql2+=(" and zlbm="+zlbm.trim()+""

;
}
if(!(dlbm.trim().equals("0"

)) {
sqlstatment+=(" and ( medicines.dlbm="+dlbm.trim()+"

"

;
sql2+=(" and dlbm="+dlbm.trim()+""

;
}
if(!(clbm.trim().equals("0"

)) {
sqlstatment+=(" and ( medicines.clbm="+clbm.trim()+"

"

;
sql2+=(" and clbm="+clbm.trim()+""

;
}
if(!(zyyx.trim().length ()==0)) {
sqlstatment+=(" and ( medicines.zyyx like %"+zyyx.trim()+"%

"

;
sql2+=(" and zyyx like %"+zyyx.trim()+"%"

;
}
if(!(ypm.trim().length ()==0)) {
sqlstatment+=(" and ( medicines.ypm like %"+ypm.trim()+"%

"

;
sql2+=(" and ypm like %"+ypm.trim()+"%"

;
}
sqlstatment+="

) ORDER BY medicines.ypbm ASC ";
//-------------------------------------------------------------
Vector list = new Vector();
//================= 设置一页显示的数据条数（一次检索出的数据条数）===========
stmt.setMaxRows(25);
//----------------------------------------------------------------------
//===================执行查询将结果放到ResultSet中================
ResultSet rs = stmt.executeQuery(sqlstatment);
ResultSet rs2 = stmt.executeQuery(sql2);
//------------------------------------------------
if(rs==null){ //如果没有查询结果数据
if(stmt!=null) stmt.close();
stmt.setMaxRows(0);
connMgr.freeConnection("medicine",con);
response.sendRedirect("/medicine/no_medicine.html"

; //定向到一个页面
return;
}
//====================将药品信息填入数据对象并存入Vector中================
if(rs2.next()){
all_count=rs2.getLong(1); //取得总条数
}
if(rs2!=null)rs2.close();
while(rs.next()){
medicinelist m = new medicinelist();
m.setYpbm(rs.getInt("ypbm"

);
m.setZlmc(rs.getString("zlmc"

);
m.setClmc(rs.getString("clmc"

);
m.setDlmc(rs.getString("dlmc"

);
m.setYpm(rs.getString("ypm"

);
m.setZyyx(rs.getString("zyyx"

);
m.setYpzy(rs.getString("ypzy"

);
m.setClbm(clbm);
m.setDlbm(dlbm);
m.setZlbm(zlbm);
list.addElement(m);
}
//----------------------------------------------------------
if(rs!=null)rs.close();
stmt.setMaxRows(0);
if(stmt!=null)stmt.close();
connMgr.freeConnection("medicine",con);
//========================存入session中===========================
synchronized (session) {
session.setAttribute("medicinelist",list);
}
//-----------------------------------------------
}catch (SQLException e){
connMgr.freeConnection("medicine",con);
response.sendRedirect("/Medicine/sql_error.html"

;
return;}

//=======================重定向到一个JSP页面==========================
String url="/medicine/querymedicine.jsp?all_count="+all_count;
ServletContext sc = getServletContext();
RequestDispatcher rd = sc.getRequestDispatcher(url);
rd.forward(request, response);
//-------------------------------------------------------
}
public void destroy() {
// =================== 在Servlet退出时终止数据库连接,取消Statement对象
if(connMgr!=null) connMgr.release();
//------------------------------------------------------------------------
}
//========================处理HTTP Post 请求 ============================
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request,response);
}

//==========================取得 Servlet 信息 ============================
public String getServletInfo() {
return "medicine.querymedicine Information";
}
}
l querymedicine.jsp

<%@ page language="java" session="true" import="java.util.*,
Medicine.method, Medicine.medicinelist"contentType="text/html;charset=gbk" %>
<script language="javascript">
function next(){
var ls_pos=document.form2.maxpos.value;
document.location="/servlet/Medicine.querymedicine?pos="+ls_pos;
}
function detail(ypbm){
document.location="/servlet/Medicine.Detail?ypbm="+ypbm;
}

<!--add head-->
<div align="center">
<body topmargin="0" leftmargin="10" rightmargin="10” bgcolor="#FFFFFF">
<div align="center">
<center><IFRAME WIDTH=760 height=130 NORESIZE SCROLLING=no FRAMEBORDER=0
MARGINHEIGHT=0 MARGINWIDTH=0 SRC="..medicinetitle.html"></iframe>
</div>
<!--finish-->
<title>商品列表</title>
<%
method md = new method();
Vector sklist;
synchronized (session) {
sklist = (Vector) session.getAttribute("medicinelist"

;
}
%>