Java封装分页组件，在JSP中进行分页

分页离不开两个必须的量①当前页②每页显示几条记录，有了这两个量，就可以构建分页所需的各种量了，如总页数，页面页码的开始索引，结束索引等。

一、分页组件

package edu.njcit.action;

import java.util.List;
/**
* 分页组件
* @author Administrator
* @param <T>
*/
public class PageView<T> {
/** 分页数据 **/
private List<T> records;
/** 页码开始索引和结束索引 **/
private PageIndex pageindex;
/** 总页数 **/
private long totalpage = 1;
/** 每页显示记录数，默认12 **/
private int recordPerPage=12;
/** 当前页 **/
private int currentpage = 1;
/** 总记录数 **/
private long totalrecord;
/** 页码数量，默认10 **/
private int pagecode = 10;
/** 获取记录的开始索引 **/
public int getStartRecordIndex() {
return (this.currentpage-1)*this.recordPerPage;
}
public int getPagecode() {
return pagecode;
}

public void setPagecode(int pagecode) {
this.pagecode = pagecode;
}
/**
* 构造函数
* @param recordPerPage 每页显示的记录数
* @param currentpage 当前页
*/
public PageView(int recordPerPage, int currentpage) {
this.recordPerPage = recordPerPage;
this.currentpage = currentpage;
}
/**
* 构造函数
* @param recordPerPage 每页显示的记录数
* @param currentpage 当前页
* @param pagecode 页码数量
*/
public PageView(int recordPerPage, int currentpage,int pagecode) {
this.recordPerPage = recordPerPage;
this.currentpage = currentpage;
this.pagecode=pagecode;
}

public void setQueryResult(QueryResult<T> qr){
setTotalrecord(qr.getTotalrecord());
setRecords(qr.getResultlist());
}

public long getTotalrecord() {
return totalrecord;
}
public void setTotalrecord(long totalrecord) {
this.totalrecord = totalrecord;
//总记录数变化时，要重新计算总页码和页码开始，结束索引
setTotalpage(this.totalrecord%this.recordPerPage==0? this.totalrecord/this.recordPerPage : this.totalrecord/this.recordPerPage+1);
}
public List<T> getRecords() {
return records;
}
public void setRecords(List<T> records) {
this.records = records;
}
public PageIndex getPageindex() {
return pageindex;
}
public long getTotalpage() {
return totalpage;
}
public void setTotalpage(long totalpage) {
this.totalpage = totalpage;
this.pageindex = PageIndex.getPageIndex(pagecode, currentpage, totalpage);
}
public int getRecordPerPage() {
return recordPerPage;
}
public int getCurrentpage() {
return currentpage;
}
}

其中，页码索引类如下：

package edu.njcit.action;
/**
* 页面页码类
* @author Administrator
*/
public class PageIndex {
private long startindex;//开始页码
private long endindex;//结束页码

public PageIndex(long startindex, long endindex) {
this.startindex = startindex;
this.endindex = endindex;
}
public long getStartindex() {
return startindex;
}
public void setStartindex(long startindex) {
this.startindex = startindex;
}
public long getEndindex() {
return endindex;
}
public void setEndindex(long endindex) {
this.endindex = endindex;
}
/**
* 根据页码数量，当前页，总页数构建页码索引
* @param pagecode 页码数量
* @param currentPage 当前页
* @param totalpage 总页数
* @return
*/
public static PageIndex getPageIndex(long pagecode, int currentPage, long totalpage){
long startpage = currentPage-(pagecode%2==0? pagecode/2-1 : pagecode/2);
long endpage = currentPage+pagecode/2;
if(startpage<1){
startpage = 1;
if(totalpage>=pagecode) endpage = pagecode;
else endpage = totalpage;
}
if(endpage>totalpage){
endpage = totalpage;
if((endpage-pagecode)>0) startpage = endpage-pagecode+1;
else startpage = 1;
}
return new PageIndex(startpage, endpage);
}
}

QueryResult是查询结果类，是对到DB中检索出来的数据的封装，可以直接放进PageView中

package edu.njcit.action;

import java.util.List;
/**
* 查询结果
* @author Administrator
* @param <T>
*/
public class QueryResult<T> {
private List<T> resultlist;
/**
* 页面看到的总记录数
* 默认情况下=resultlist.size(),也可自行指定
*/
private long totalrecord;//

public List<T> getResultlist() {
return resultlist;
}
public void setResultlist(List<T> resultlist) {
this.resultlist = resultlist;
}
public long getTotalrecord() {
return totalrecord;
}
public void setTotalrecord(long totalrecord) {
this.totalrecord = totalrecord;
}
public QueryResult(List<T> resultlist, long totalrecord) {
super();
this.resultlist = resultlist;
this.totalrecord = totalrecord;
}

}

二、下面可以把分页单独抽出为一个JSP，需要分页时，直接include即可

<%@ page language="java" pageEncoding="UTF-8"%>
<font color="black">
当前页:第${pageView.currentpage}页 | 总记录数:${pageView.totalrecord}条 | 每页显示:${pageView.recordPerPage}条 | 总页数:${pageView.totalpage}页
</font>
<br/>
<c:forEach begin="${pageView.pageindex.startindex}" end="${pageView.pageindex.endindex}" var="wp">
<c:if test="${pageView.currentpage==wp}"><b><font color="gray">第${wp}页</font></b></c:if>
<c:if test="${pageView.currentpage!=wp}"><a href="javascript:topage('${wp}')" class="a03">第${wp}页</a></c:if>
</c:forEach>

这里需要一段JS代码，用于当点击第几页时更改currentPage和提交表单：

//到指定的分页页面
function topage(page){
var form = document.forms[0];//包含currentPage hidden框的form
form.currentPage.value=page;
form.submit();
}

三、现在就可以应用封装好的分页组件了

package edu.njcit.action.paging;

import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import com.opensymphony.xwork2.ActionSupport;
import edu.njcit.action.ActionSupportBase;
import edu.njcit.action.PageView;
import edu.njcit.action.QueryResult;
import edu.njcit.entity.Student;

public class PagingAction extends ActionSupportBase {

private static final long serialVersionUID = 1L;
@Override
public String execute() throws Exception {

List<Student> list=new ArrayList<Student>();
//模拟数据
for (int i = 1; i <= 300; i++) {
Student student=new Student();
student.setId(String.valueOf(i));
student.setBirth(new Date());
student.setAge(i);
student.setName((i)+""+i);
list.add(student);
}

PageView<Student> pageView=new PageView<Student>(12,getCurrentPage());
int start=pageView.getStartRecordIndex();
int lenght=pageView.getRecordPerPage();
QueryResult<Student> qr=new QueryResult<Student>(list.subList(start, start+lenght),list.size());
pageView.setQueryResult(qr);
request.setAttribute("pageView", pageView);
return ActionSupport.SUCCESS;
}
}

结果页面如下：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ include file="/taglib.jsp" %>
<%
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>My JSP 'index.jsp' starting page</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/style.css">
<script language="javascript" src="/js/topage.js"></script>
</head>
<body>
学生如下：<br/>
<s:form action="paging" method="post">
<s:hidden name="currentPage"></s:hidden>
<table style="border:solid 1px green;">
<tr><td>学号</td><td>姓名</td><td>年龄</td><td>生日</td></tr>
<c:forEach items="${pageView.records}" var="entry">
<tr>
<td>${entry.id}</td>
<td>${entry.name}</td>
<td>${entry.age}</td>
<td><fmt:formatDate value="${entry.birth}" type="both" pattern="yyyy-MM-dd" /></td>
</tr>
</c:forEach>
</table>
</s:form>
<!-- 将分页JSP包含进来 -->
<%@ include file="/fenye.jsp" %>
</body>
</html>

最终效果如下：