javaee之分页练习

时间：2023-01-31 12:28:35

学习了数据库连接池后，我们发现除了把数据显示出来后，如果数据过大，一次性全部显示，页面会显得很臃肿，所以我们引进了分页技术，来实现分页效果。运用c3p0和dbutil的技术能够把数据用sql的limit语句实现分页

首先，核心的是创建一个分页类，PageBean.class

package example.entity;

import java.util.List;

public class Pagebean {

	private int firstPage =1; //首页
	private int prePage; //上一页
	private int nextPage; //下一页
	private int totalPage; //末页/总页数
	private int curPage; //当前页
	private List datas; //需要显示的数据
	private int curSize =3; //每页显示的数据
	private int totalSize; // 总的记录数
	
	public int getFirstPage() {
		return firstPage;
	}
	public void setFirstPage(int firstPage) {
		this.firstPage = firstPage;
	}
	public int getPrePage() {
		return this.getCurPage()==this.getFirstPage()?this.getFirstPage():this.getCurPage()-1;
	}
	public void setPrePage(int prePage) {
		this.prePage = prePage;
	}
	public int getNextPage() {
		return this.getCurPage()==this.getTotalPage()?this.getTotalPage():this.getCurPage()+1;
	}
	public void setNextPage(int nextPage) {
		this.nextPage = nextPage;
	}
	public int getTotalPage() {
		return this.getTotalSize()%this.getCurSize()==0?this.getTotalSize()/this.getCurSize():this.getTotalSize()/this.getCurSize()+1;
	}
	public void setTotalPage(int totalPage) {
		this.totalPage = totalPage;
	}
	public int getCurPage() {
		return curPage;
	}
	public void setCurPage(int curPage) {
		this.curPage = curPage;
	}
	public List getDatas() {
		return datas;
	}
	public void setDatas(List datas) {
		this.datas = datas;
	}
	public int getCurSize() {
		return curSize;
	}
	public void setCurSize(int curSize) {
		this.curSize = curSize;
	}
	public int getTotalSize() {
		return totalSize;
	}
	public void setTotalSize(int totalSize) {
		this.totalSize = totalSize;
	}
	
}

然后，定义一个数据访问层dao 

package example.dao;

import java.sql.SQLException;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

import example.entity.Student;
import example.util.c3p0util;

public class studentdao {


<span style="white-space:pre">	</span>//查询数据库的总记录数
	public int querycount() throws Exception{
		QueryRunner qr = new QueryRunner(c3p0util.getData());
		
		 Long l = qr.query("select count(*) from student", new ScalarHandler());
		 return l.intValue();
	}
	
	//计算每页显示的数据数
	public List query(int curpage,int cursize) throws Exception{
		QueryRunner qr = new QueryRunner(c3p0util.getData());
		return qr.query("select * from student limit ?,?", new BeanListHandler(Student.class), (curpage-1)*cursize,cursize);
	}
}

定义一个Servlet来接受参数 

package mjf.page.web;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import mjf.page.dao.StudentDao;
import mjf.page.entity.PageBean;

public class QueryServlet extends HttpServlet {

	
	StudentDao dao = new StudentDao();
	
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		PageBean pb = new PageBean();
		
		
		//计算总记录数
				pb.setTotalsize(dao.queryCount());
				
		
		
		//计算当前页
				String curpage = request.getParameter("curpage");
				if(curpage==null || curpage.equals("")){
					curpage="1";
				}
				pb.setCurpage(Integer.parseInt(curpage));
		
		
		
		
		//计算每页显示的数据
		pb.setDatas(dao.queryfindAll(pb.getCurpage(), pb.getCursize()));
		
		request.setAttribute("pb", pb);
		request.getRequestDispatcher("/index.jsp").forward(request,response);
	}

	
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		doGet(request, response);
	}

}


在页面上进行数据和分页的显示 
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<%
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="styles.css">
	-->
	
	
  </head>
  
  <body>
    <c:forEach items="${pb.datas }" var="pb">
    	<table border="1px">
    		<tr>
    			<th>编号</th>
    			<th>姓名</th>
    			<th>性别</th>
    			<th>部门</th>
    			<th>薪水</th>
    		</tr>
    		<tr>
    			<td>${pb.id }</td>
    			<td>${pb.name }</td>
    			<td>${pb.gender }</td>
    			<td>${pb.dept }</td>
    			<td>${pb.salary }</td>
    		</tr>
    	</table>
    </c:forEach>
    <a href="<c:url value='/QueryServlet?curpage=${pb.firstpage }' />" >首页</a>
    <a  href="<c:url value='/QueryServlet?curpage=${pb.prepage }' />" >上一页</a>
    <a  href="<c:url value='/QueryServlet?curpage=${pb.nextpage }' />" >下一页</a>
    <a href="<c:url value='/QueryServlet?curpage=${pb.lastpage }' />" >尾页</a>
 	<form action="<c:url value='/QueryServlet' />">
 	  跳转到 <input type="text" name="curpage" size="2" />页 <input value="跳转" type="submit" />
 	  </form>
 	   跳转到 <input type="text" name="pageno" id="pagenoId" size="2" />页 <input value="跳转" type="button" onclick="tiaozhuan()" />
 	当前为${pb.curpage }页 /共有${pb.lastpage }页 每页有${pb.cursize }数据 总记录数${pb.totalsize } 
  </body>
  
  <script type="text/javascript">
   function tiaozhuan(){
   	var pageid = document.getElementById("pagenoId");
   	var url = "<c:url value='/QueryServlet?curpage="+pageid+"' />";
   	window.location.href = url;
   }
  </script>
</html>

这样的简单小示例能够跟大家分享一下分页的效果，希望能够帮助到大家的理解。实现分页的最主要的就是要定义一个分页类，和实现上一页，下一页，总记录数和每页显示数的实现。
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