数据的分页处理

当页面中要显示的内容过多需要分多页显示、或是数据量过大内存吃不消时，需要分页处理。

原理：每次从数据库中取出一定量的数据，通过jsp页面显示

实现：

①写一个类封装分页的页面

②从数据库中取出一个页面的数据，将信息封装到分页页面对象中

③根据情况，将分页的页面对象设置到request对象、session对象或servletContext对象属性中，供jsp页面调用

④在jsp页面中显示分页数据、分页页码、上一页下一页、跳转页面等

下面看具体代码:

分页页面Page类：

  1 package cn.wzbrilliant.domain;
  2
  3 import java.util.List;
  4
  5 //界面上所有与分页有关的都找此类要
  6 public class Page {
  7     private List records;
  8     private int pagesize = 10;//每页显示的记录条数
  9     private int pagenum;//用户要看的页码即当前页码
 10     private int totalpage;//总页数
 11     private int startIndex;//每页开始记录的索引
 12     private int totalrecords;//总记录条数
 13
 14     //显示的页码
 15     private int startPage;
 16     private int endPage;
 17
 18     public Page(int pagenum,int totalrecords){
 19         this.pagenum = pagenum;
 20         this.totalrecords = totalrecords;
 21
 22         //计算每页开始记录的索引
 23         startIndex = (pagenum-1)*pagesize;
 24         //计算总页数
 25         totalpage = totalrecords%pagesize==0?totalrecords/pagesize:(totalrecords/pagesize+1);
 26
 27         //显示的页码
 28         if(totalpage<=9){
 29             startPage = 1;
 30             endPage = totalpage;
 31         }else{
 32             startPage = pagenum-4;
 33             endPage = pagenum+4;
 34             if(startPage<1){
 35                 startPage = 1;
 36                 endPage = 9;
 37             }
 38             if(endPage>totalpage){
 39                 endPage = totalpage;
 40                 startPage = totalpage-8;
 41             }
 42         }
 43     }
 44
 45     public List getRecords() {
 46         return records;
 47     }
 48
 49     public void setRecords(List records) {
 50         this.records = records;
 51     }
 52
 53     public int getPagesize() {
 54         return pagesize;
 55     }
 56
 57     public void setPagesize(int pagesize) {
 58         this.pagesize = pagesize;
 59     }
 60     public int getPagenum() {
 61         return pagenum;
 62     }
 63
 64     public void setPagenum(int pagenum) {
 65         this.pagenum = pagenum;
 66     }
 67
 68     public int getTotalpage() {
 69         return totalpage;
 70     }
 71
 72     public void setTotalpage(int totalpage) {
 73         this.totalpage = totalpage;
 74     }
 75
 76     public int getStartIndex() {
 77         return startIndex;
 78     }
 79     public void setStartIndex(int startIndex) {
 80         this.startIndex = startIndex;
 81     }
 82
 83     public int getTotalrecords() {
 84         return totalrecords;
 85     }
 86
 87     public void setTotalrecords(int totalrecords) {
 88         this.totalrecords = totalrecords;
 89     }
 90
 91     public int getStartPage() {
 92         return startPage;
 93     }
 94
 95     public void setStartPage(int startPage) {
 96         this.startPage = startPage;
 97     }
 98
 99     public int getEndPage() {
100         return endPage;
101     }
102
103     public void setEndPage(int endPage) {
104         this.endPage = endPage;
105     }
106
107 }

从数据库中取出一定条数的记录，此处以mysql为例，sql语句为select * from 表名 limit ?,?   两个问号分别为起始位置和结束位置

在jsp页面中显示分页页码、上一页下一页、跳转页面等的实现代码：

 1 <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
 2 <!-- 分页的部分 -->
 3  第${page.pagenum}页/共${page.totalpage}页&nbsp;&nbsp;
 4  <a href="${pageContext.request.contextPath}/servlet/ShowAllMessageServlet">首页</a>&nbsp;&nbsp;
 5  <a href="${pageContext.request.contextPath}/servlet/ShowAllMessageServlet?pagenum=${page.pagenum-1==0?1:page.pagenum-1}">上一页</a>&nbsp;&nbsp;
 6       <c:forEach begin="${page.startPage}" end="${page.endPage}" var="num">
 7             <a href="${pageContext.request.contextPath}/servlet/ShowAllMessageServlet?pagenum=${num}">${num }</a>
 8       </c:forEach>
 9                   &nbsp;&nbsp;
10     <a href="${pageContext.request.contextPath}/servlet/ShowAllMessageServlet?pagenum=${page.pagenum+1>page.totalpage?page.totalpage:page.pagenum+1}">下一页</a>&nbsp;&nbsp;
11     <a href="${pageContext.request.contextPath}/servlet/ShowAllMessageServlet?pagenum=${page.totalpage}">尾页</a>
12     <select id="s1">
13           <c:forEach begin="1" end="${page.totalpage}" var="num">
14                  <option value="${num}" ${page.pagenum==num?‘selected="selected"‘:‘‘}>${num}</option>
15           </c:forEach>
16      </select>
17      <a href="javascript:jump()">跳转</a>
18
19 <script type="text/javascript">
20       function jump(){
21             var num = document.getElementById("s1").value;
22             window.location.href="${pageContext.request.contextPath}/servlet/ShowAllCustomersServlet?pagenum="+num;
23       }
24 </script>