Java封装分页组件，在JSP中进行分页

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#java #jsp #分页

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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：