Servlet+JSP分页

以上面的文章列表分页为例，我觉得分页有两点重要的，

一是：分页我们必须首先自己搞清楚，文章总数、每页显示文章数(页大小)、页数

二是：如何做好页脚的分页导航条

 

实际应用中，文章总数这个值我们从数据库可以得到；每页显示的文章数即分页的页大小可以自己定义；页数我们可以通过下面的个表达式简单得出。

 

假设：

  int pageSize = 10; //分页大小
  int totalPosts = PagingDAO.entryList.size(); //总文章数
  int totalPages = totalPosts/pageSize + ((totalPosts%pageSize)>0?1:0); //计算得出的总页数

 

每页的文章怎么取出来？

  知道分页的大小之后，我们生成了页好的选取下拉框，每次选择第几页的时候，都会向Servlet传递当前选择页号的参数，这样Servlet调用后面的DAO相应的方法，取得文章列表信息，再回传到JSP以供显示。

 

看看我们用作显示的index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"  pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

page Size : ${pageSize}
<br />
Total Posts: ${totalPosts}
<br />
Total Pages: ${totalPages}
<br />
Current Page: ${pageNumber}
<hr />

<table>
    <thead>
        <tr align="center">
            <td width="10%">Article IDtd>
            <td width="70%">Article Titletd>
            <td colspan="3">Actionstd>
        tr>
    thead>
    <tbody>
        <c:forEach items="${entryList}" var="entry">
            <tr align="center">
                <td>${entry.entryID}td>
                <td>${entry.title}td>
                <td><a href="viewEntry?entryID=${entry.entryID}">Viewa>td>
                <td><a href="editEntry?entryID=${entry.entryID}">Edita>td>
                <td><a href="deleteEntry?entryID=${entry.entryID}">Deletea>td>
            tr>
        c:forEach>
    tbody>
    <tfoot>
        <tr align="center">
            <td colspan="5">
                <jsp:include page="paging_footer.jsp">jsp:include>
            td>
        tr>
    tfoot>
table>

<hr/>

<%@ page language="java" contentType="text/html; charset=UTF-8"	pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

page Size : ${pageSize}


Total Posts: ${totalPosts}


Total Pages: ${totalPages}


Current Page: ${pageNumber}



			

	

		

			
Article ID
			
Article Title
			
Actions
		
	
	

		

				
${entry.entryID}
				
${entry.title}
				
View
				
Edit
				
Delete
			
		
	
	

		

			

				
			
		
	

 

 

这些流程清晰之后，我们就可以实现分页导航条了，也就是上面的paging_footer.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"  pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>

<script type="text/javascript">
function gotoSelectedPage()
{
    var x = document.getElementById("navigatorForm");
    //alert("Original action: " + x.action)
    x.submit();
}
script>
<form action="Posts" method="get" id="navigatorForm">
    <a href="Posts?pageNumber=1">首页a>
    <c:if test="${pageNumber>1}">
        <a href="Posts?pageNumber=${pageNumber-1}">上一页a>
    c:if>
    跳转到第 <select name="pageNumber" onchange="gotoSelectedPage();">
    <c:forEach begin="1" end="${totalPages}" step="1" var="pageIndex">
        <c:choose>
            <c:when test="${pageIndex eq pageNumber}">
                <option value="${pageIndex}" selected="selected">${pageIndex}option>
            c:when>
            <c:otherwise>
                <option value="${pageIndex}">${pageIndex}option>
            c:otherwise>
        c:choose>
    c:forEach>
    select>页
    <c:if test="${pageNumber>
        <a href="Posts?pageNumber=${pageNumber+1}">下一页a>
    c:if>
    <a href="Posts?pageNumber=${totalPages}">末页a>
form>

<%@ page language="java" contentType="text/html; charset=UTF-8"	pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>



	首页 
	
		上一页
	 
	跳转到第 
	
		
			
				${pageIndex}
			
			
				${pageIndex}
			
		
	
	页 
	
		下一页
	 
	末页

 

 

Posts是我们的Servlet，负责取得相关参数，和DAO打交道，取得一些文章的数据，然后传递到JSP，我们来看一下这个Servlet 的 doGet 方法。

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String pageNumberStr = request.getParameter("pageNumber");
    int pageNumber = 1;
    if(pageNumberStr!=null && !pageNumberStr.isEmpty())
    {
        pageNumber = Integer.parseInt(pageNumberStr);
    }

    int pageSize = 10; //分页大小
    int totalPosts = PagingDAO.entryList.size(); //总文章数
    int totalPages = totalPosts/pageSize + ((totalPosts%pageSize)>0?1:0); //计算得出的总页数

    request.setAttribute("pageSize", pageSize);
    request.setAttribute("totalPosts", totalPosts);
    request.setAttribute("pageNumber", pageNumber);
    request.setAttribute("totalPages", totalPages);

    List entryList = PagingDAO.getEntryList(pageNumber, pageSize);
    System.out.println("entryList:"+ entryList.size());
    request.setAttribute("entryList", entryList);

    request.getRequestDispatcher("index.jsp").forward(request, response);
}

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		String pageNumberStr = request.getParameter("pageNumber");
		int pageNumber = 1;
		if(pageNumberStr!=null && !pageNumberStr.isEmpty())
		{
			pageNumber = Integer.parseInt(pageNumberStr);
		}
		
		int pageSize = 10; //分页大小
		int totalPosts = PagingDAO.entryList.size(); //总文章数
		int totalPages = totalPosts/pageSize + ((totalPosts%pageSize)>0?1:0); //计算得出的总页数
		
		request.setAttribute("pageSize", pageSize);
		request.setAttribute("totalPosts", totalPosts);
		request.setAttribute("pageNumber", pageNumber);
		request.setAttribute("totalPages", totalPages);
		
		List entryList = PagingDAO.getEntryList(pageNumber, pageSize);
		System.out.println("entryList:"+ entryList.size());
		request.setAttribute("entryList", entryList);
		
		request.getRequestDispatcher("index.jsp").forward(request, response);		
	}

 

  分页其实还是很简单的事情，为了方便新手上路，这里提供一下这个eclipse的工程压缩包，直接导入就能用了。

(注意：对于eclipse JEE版本，工程导入后，请自行拷贝jstl.jar 和 standard.jar到WEB-INF/lib目录，如果没有配置Server的话，down个tomcat在eclipse里配置一下，不然怎么run？这个基础的应该都会吧)