java web手写实现分页功能

Select * from product limit 0 ,5
Select * from product limit 5 ,5
Select * from product limit 10 ,5
Select * from product limit 15 ,5

package cn.itcast.store.domain;
import java.util.List;
/**
 * 存放分页相关的数据
 *
 * @author yechengchao
 */
public class PageModel {
 //基本属性
 /**当前页数，由用户指定 */
 private int currentPageNum;
 /**每页显示的条数，可以由用户指定每页显示多少 */
 private int pageSize =5;
 /**总记录条数，数据库查出来的 */
 private int totalRecords;
 /**总页数，计算出来的 */
 private int totalPageNum;
 /**每页开始记录的索引，计算出来的 （当前页-1）*（每页数量）=起始值 */
 private int startIndex;
 /**上一页 */
 private int prePageNum;
 /**下一页 */
 private int nextPageNum;
 /**已经分好页的结果集,存放我们查出来的结果集*/
 private List list;
 
 /**扩展属性
 一共每页显示9个页码按钮*/
 /**开始页码*/
 private int startPage;
 /**结束页码*/
 private int endPage;
 
 /**完善属性*/
 private String url;
 

 /**要想使用我的分页，必须给我两个参数。一个是要看哪一页，另一个是总记录条数*/
 public PageModel(int currentPageNum,int totalRecords,int pageSize){
 this.currentPageNum = currentPageNum;
 this.totalRecords = totalRecords;
 this.pageSize=pageSize;
 
 //计算查询记录的开始索引
 startIndex = (currentPageNum-1)*pageSize;
 //计算总页数
 totalPageNum = totalRecords%pageSize==0?(totalRecords/pageSize):(totalRecords/pageSize+1);
 
 //5
 startPage = currentPageNum - 4;
 //结束页码
 endPage = currentPageNum + 4;
 //看看总页数够不够9页
 if(totalPageNum>9){
 //超过了9页
 if(startPage < 1){
 startPage = 1;
 endPage = startPage+8;
 }
 if(endPage>totalPageNum){
 endPage = totalPageNum;
 startPage = endPage-8;
 }
 }else{
 //不够9页
 startPage = 1;
 endPage = totalPageNum;
 }
 }

 public String getUrl() {
 return url;
 }

 public void setUrl(String url) {
 this.url = url;
 }
 
 public int getStartPage() {
 return startPage;
 }

 public void setStartPage(int startPage) {
 this.startPage = startPage;
 }

 public int getEndPage() {
 return endPage;
 }
 public void setEndPage(int endPage) {
 this.endPage = endPage;
 }
 public int getPrePageNum() {
 prePageNum = currentPageNum-1;
 if(prePageNum<1){
 prePageNum = 1;
 }
 return prePageNum;
 }
 public int getNextPageNum() {
 nextPageNum = currentPageNum+1;
 if(nextPageNum>totalPageNum){
 nextPageNum = totalPageNum;
 }
 return nextPageNum;
 }
 public int getCurrentPageNum() {
 return currentPageNum;
 }
 public void setCurrentPageNum(int currentPageNum) {
 this.currentPageNum = currentPageNum;
 }
 public int getPageSize() {
 return pageSize;
 }
 public void setPageSize(int pageSize) {
 this.pageSize = pageSize;
 }
 public int getTotalRecords() {
 return totalRecords;
 }
 public void setTotalRecords(int totalRecords) {
 this.totalRecords = totalRecords;
 }
 public int getTotalPageNum() {
 return totalPageNum;
 }
 public void setTotalPageNum(int totalPageNum) {
 this.totalPageNum = totalPageNum;
 }
 public int getStartIndex() {
 return startIndex;
 }
 public void setStartIndex(int startIndex) {
 this.startIndex = startIndex;
 }
 public void setPrePageNum(int prePageNum) {
 this.prePageNum = prePageNum;
 }
 public void setNextPageNum(int nextPageNum) {
 this.nextPageNum = nextPageNum;
 }
 public List getList() {
 return list;
 }
 public void setList(List list) {
 this.list = list;
 }
}

public String findProductByCidWithPage(HttpServletRequest request, HttpServletResponse response) throws Exception {
 //获取cid,num
 String cid=request.getParameter("cid");
 int curNum=Integer.parseInt(request.getParameter("num"));
 //调用业务层的功能：以分页的形式查询当前页类别下商品信息
 //返回PageModel对象（1当前页商品信息2分页3 url）
 ProductService productService=new ProductServiceImp();
 PageModel pm=productService.findProductByCidWithPage(cid,curNum);
 //将PageModel对象放入request
 request.setAttribute("page", pm);
 //转发到/jsp/product_list.jsp
 return "/jsp/product_list.jsp";
 }

public PageModel findProductByCidWithPage(String cid, int curNum) throws Exception {
 //1 创建pageModel对象 目的：计算分页参数
 
 //统计当前分类下商品的个数 select count(*) from product where cid=?
 int totalRecords=productDao.findtotalRecords(cid);
 PageModel pageModel=new PageModel(curNum, totalRecords, 12);
 //2.关联集合 select * form product where cid=? limit ?,?
 List list=productDao.findProductByCidWithPage(cid,pageModel.getStartIndex(),pageModel.getPageSize());
 pageModel.setList(list);
 //3.关联url
 pageModel.setUrl("ProductServlet?method=findProductByCidWithPage&cid="+cid);
 return pageModel;
 }

public List findProductByCidWithPage(String cid, int startIndex, int pageSize) throws Exception {
 String sql="select * from product where cid=? limit ?,?";
 QueryRunner qr=new QueryRunner(JDBCUtils.getDataSource());
 return qr.query(sql, new BeanListHandler<Product>(Product.class),cid,startIndex,pageSize);
 }

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
 <%--分页显示的开始 --%>
 <div style="text-align:center">
 共${page.totalPageNum}页/第${page.currentPageNum}页
 
 <a href="${pageContext.request.contextPath}/${page.url}&num=1" rel="external nofollow" >首页</a>
 <a href="${pageContext.request.contextPath}/${page.url}&num=${page.prePageNum}" rel="external nofollow" >上一页</a>
 <%--显示的页码，使用forEach遍历显示的页面 --%>
 <c:forEach begin="${page.startPage}" end="${page.endPage}" var="pagenum">
 <a href="${pageContext.request.contextPath}/${page.url}&num=${pagenum}" rel="external nofollow" >${pagenum}</a>
 </c:forEach>
 
 <a href="${pageContext.request.contextPath}/${page.url}&num=${page.nextPageNum}" rel="external nofollow" >下一页</a>
 <a href="${pageContext.request.contextPath}/${page.url}&num=${page.totalPageNum}" rel="external nofollow" >末页</a>
 <input type="text" id="pagenum" name="pagenum" size="1"/><input type="button" value="前往" onclick="jump()" />
 <script type="text/javascript">
 function jump(){
 var totalpage = ${page.totalPageNum};
 var pagenum = document.getElementById("pagenum").value;
 //判断输入的是一个数字
 var reg =/^[1-9][0-9]{0,1}$/;
 if(!reg.test(pagenum)){
 //不是一个有效数字
 alert("请输入符合规定的数字");
 return ;
 }
 //判断输入的数字不能大于总页数
 if(parseInt(pagenum)>parseInt(totalpage)){
 //超过了总页数
 alert("不能大于总页数");
 return;
 }
 //转向分页显示的Servlet
 window.location.href="${pageContext.request.contextPath}/${page.url}&num=" rel="external nofollow" +pagenum;
 }
 </script>
 </div>
 <%--分页显示的结束--%>