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：

package cn.wzbrilliant.domain;

import java.util.List;

//界面上所有与分页有关的都找此类要
public class Page {
private List records;
private int pagesize = 10;//每页显示的记录条数
private int pagenum;//用户要看的页码即当前页码
private int totalpage;//总页数
private int startIndex;//每页开始记录的索引
private int totalrecords;//总记录条数

//显示的页码
private int startPage;
private int endPage;

public Page(int pagenum,int totalrecords){
this.pagenum = pagenum;
this.totalrecords = totalrecords;

//计算每页开始记录的索引
startIndex = (pagenum-1)*pagesize;
//计算总页数
totalpage = totalrecords%pagesize==0?totalrecords/pagesize:(totalrecords/pagesize+1);

//显示的页码
if(totalpage<=9){
startPage = 1;
endPage = totalpage;
}else{
startPage = pagenum-4;
endPage = pagenum+4;
if(startPage<1){
startPage = 1;
endPage = 9;
}
if(endPage>totalpage){
endPage = totalpage;
startPage = totalpage-8;
}
}
}

public List getRecords() {
return records;
}

public void setRecords(List records) {
this.records = records;
}

public int getPagesize() {
return pagesize;
}

public void setPagesize(int pagesize) {
this.pagesize = pagesize;
}
public int getPagenum() {
return pagenum;
}

public void setPagenum(int pagenum) {
this.pagenum = pagenum;
}

public int getTotalpage() {
return totalpage;
}

public void setTotalpage(int totalpage) {
this.totalpage = totalpage;
}

public int getStartIndex() {
return startIndex;
}
public void setStartIndex(int startIndex) {
this.startIndex = startIndex;
}

public int getTotalrecords() {
return totalrecords;
}

public void setTotalrecords(int totalrecords) {
this.totalrecords = totalrecords;
}

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;
}

}

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：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!-- 分页的部分 -->
第${page.pagenum}页/共${page.totalpage}页  
<a href="${pageContext.request.contextPath}/servlet/ShowAllMessageServlet">首页</a>  
<a href="${pageContext.request.contextPath}/servlet/ShowAllMessageServlet?pagenum=${page.pagenum-1==0?1:page.pagenum-1}">上一页</a>  
<c:forEach begin="${page.startPage}" end="${page.endPage}" var="num">
<a href="${pageContext.request.contextPath}/servlet/ShowAllMessageServlet?pagenum=${num}">${num }</a>
</c:forEach>
  
<a href="${pageContext.request.contextPath}/servlet/ShowAllMessageServlet?pagenum=${page.pagenum+1>page.totalpage?page.totalpage:page.pagenum+1}">下一页</a>  
<a href="${pageContext.request.contextPath}/servlet/ShowAllMessageServlet?pagenum=${page.totalpage}">尾页</a>
<select id="s1">
<c:forEach begin="1" end="${page.totalpage}" var="num">
<option value="${num}" ${page.pagenum==num?'selected="selected"':''}>${num}</option>
</c:forEach>
</select>
<a href="javascript:jump()">跳转</a>

<script type="text/javascript">
function jump(){
var num = document.getElementById("s1").value;
window.location.href="${pageContext.request.contextPath}/servlet/ShowAllCustomersServlet?pagenum="+num;
}
</script>