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formform.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;@Overridepublic 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：