分页的总体思想：
分页包含什么：
1.当前页,每页显示的记录数,总的记录数,总的页码,集合List存放的是JavaBean,首页, 尾页,上一页,下一页
传递的參数：当前页,每页显示的记录数.这两个本来就是有的。
数据库中查询的：总的记录数,集合List存放的是JavaBean。这两个是从数据库中查询的。
通过已知的属性计算：首页, 尾页,上一页,下一页,总的页码 这些是通过计算得到了。
因此javaBean Page能够写成：
package com.itheima.domain;
import java.util.List;
public class Page {
private int thispage;//当前页
private int rowperpage;//每页显示的记录数
private int countrow;//总的记录数
private int countpage;//总的页数
private int firstpage;//首页
private int lastpage;//尾页
private int prepage;//上一页
private int nextpage;//下一页
private List<Customer> list;
public int getThispage() {
return thispage;
}
public void setThispage(int thispage) {
this.thispage = thispage;
}
public int getRowperpage() {
return rowperpage;
}
public void setRowperpage(int rowperpage) {
this.rowperpage = rowperpage;
}
public int getCountrow() {
return countrow;
}
public void setCountrow(int countrow) {
this.countrow = countrow;
}
public int getCountpage() {
return countpage;
}
public void setCountpage(int countpage) {
this.countpage = countpage;
}
public int getFirstpage() {
return firstpage;
}
public void setFirstpage(int firstpage) {
this.firstpage = firstpage;
}
public int getLastpage() {
return lastpage;
}
public void setLastpage(int lastpage) {
this.lastpage = lastpage;
}
public int getPrepage() {
return prepage;
}
public void setPrepage(int prepage) {
this.prepage = prepage;
}
public int getNextpage() {
return nextpage;
}
public void setNextpage(int nextpage) {
this.nextpage = nextpage;
}
public List<Customer> getList() {
return list;
}
public void setList(List<Customer> list) {
this.list = list;
}
}
2.首先要进行分页须要在cn.itheima.web包中写一个分页的Servlet,PageCustomerServlet
这个类的主要步骤是：
(1).得到传递的參数默认是首页
(2).每页显示的记录数,这里默认的是5
(3).调用service中分页的函数返回Page
(4).将Page放到request域中
(5).重定向到要实现分页的jsp进行显示分页
package com.itheima.web;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.itheima.domain.Customer;
import com.itheima.domain.Page;
import com.itheima.factory.BasicFactory;
import com.itheima.service.CustomerService;
public class PageCustomerServlet extends HttpServlet {
CustomerService service =BasicFactory.getFactory().getInstance(CustomerService.class);
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//1.获取当前页每页显示的记录
int thispage=Integer.parseInt(request.getParameter("thispage"));
int rowperpage=5;
//2.调用service的方法
Page page=service.findCustomerByPage(thispage,rowperpage);
request.setAttribute("page", page);
//3.请求转发到pageList.jsp
request.getRequestDispatcher("/pageList.jsp").forward(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
3.service实现类代码主要完毕的功能：
计算Page中的属性,设置到Page中
public Page findCustomerByPage(int thispage, int rowperpage) {
Page page=new Page();
//设置当前页
page.setThispage(thispage);
//每页显示的记录数 默认是5条
page.setRowperpage(rowperpage);
//查询数据库一共同拥有多少行
int countrow=dao.getCount();
page.setCountrow(countrow);
//一共同拥有多少页
int countpage=(countrow-1)/rowperpage+1;
page.setCountpage(countpage);
//设置首页
page.setFirstpage(1);
//设置尾页
page.setLastpage(countpage);
//前一页
page.setPrepage(thispage==1?1:thispage-1);
//下一页
page.setNextpage(thispage==countpage?countpage:thispage+1);
//
List<Customer> list=dao.getCustomerByPage((thispage-1)*rowperpage,rowperpage);
page.setList(list);
return page;
}4.数据库中使用limitkeyword进行查询
public List<Customer> getCustomerByPage(int from, int count) {
String sql="select * from customer limit ?,?";
QueryRunner runner=new QueryRunner(DataSourceUtil.getSource());
try {
return runner.query(sql, new BeanListHandler<Customer>(Customer.class),from,count);
} catch (SQLException e) {
e.printStackTrace();
throw new RuntimeException();
}
}5.jsp页面中显示：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<script type="text/javascript">
function selectAll(all){
var del=document.getElementsByName("del");
for(var i=0;i<del.length;i++){
del[i].checked=all.checked;
}
}
</script>
<title></title>
<meta http-equiv=" pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
</head>
<body style="text-align: center">
<h1>客户管理系统_显示列表</h1><hr>
<div align="center">
<form action="${pageContext.request.contextPath }/servlet/FindCustomerByConditionServlet" method="post">
姓名：<input type="text" name="name" value="${param.name }"/>
性别：<input type="radio" name="gender" value="男"
<c:if test="${param.gender=='男'}">checked="checked"</c:if>
/>男
<input type="radio" name="gender" value="女"
<c:if test="${param.gender=='女'}">checked="checked"</c:if>
/>女
客户类型：
<select name="type">
<option value=""/>
<option value="钻石用户"
<c:if test="${param.type=='钻石用户'}">selected="selected"</c:if>
>钻石用户</option>
<option value="黄金用户"
<c:if test="${param.type=='黄金用户'}">selected="selected"</c:if>
>黄金用户</option>
<option value="普通用户"
<c:if test="${param.type=='普通用户'}">selected="selected"</c:if>
>普通用户</option>
</select>
<input type="submit" value="条件查询">
</form>
<form action="${pageContext.request.contextPath}/servlet/BatchDeleteCustomer" method="post">
<table border="1" width="100%" cellpadding="0" cellspacing="0" style="text-align: center">
<tr>
<th><input type="checkbox" onclick="selectAll(this)">全选</th>
<th>客户姓名</th>
<th>客户性别</th>
<th>客户生日</th>
<th>客户电话</th>
<th>电子邮箱</th>
<th>客户爱好</th>
<th>客户类型</th>
<th>具体描写叙述</th>
<th colspan="2">操作类型</th>
</tr>
<c:forEach items="${requestScope.page.list}" var="li">
<tr>
<td><input type="checkbox" name="del" value="${li.id}"/></td>
<td><c:out value="${li.name}"></c:out></td>
<td><c:out value="${li.gender}"></c:out></td>
<td><c:out value="${li.birthday }"></c:out></td>
<td><c:out value="${li.cellphone }"></c:out></td>
<td><c:out value="${li.email }"></c:out></td>
<td><c:out value="${li.preference }"></c:out></td>
<td><c:out value="${li.type }"></c:out></td>
<td><c:out value="${li.description }"></c:out></td>
<td><a href="${pageContext.request.contextPath }/servlet/CustomerInfoServlet?id=${li.id}">改动</a></td>
<td><a href="${pageContext.request.contextPath }/servlet/DeleteCustomerServlet?id=${li.id}">删除</a></td>
</tr>
</c:forEach>
</table>
<input type="submit" value="批量删除"/>
</form>
</div>
${requestScope.page.countrow }条数据
共${requestScope.page.countpage} 页
<a href="${pageContext.request.contextPath }/servlet/PageCustomerServlet?thispage=${page.firstpage}">首页</a>
<a href="${pageContext.request.contextPath }/servlet/PageCustomerServlet?thispage=${page.prepage}">上一页</a>
<!-- 分页逻辑 -->
<c:if test="${page.countpage<=5}">
<c:set var="begin" value="1" scope="page"></c:set>
<c:set var="end" value="${page.countpage}" scope="page"></c:set>
</c:if>
<c:if test="${page.countpage>5}">
<c:choose>
<c:when test="${page.thispage<=3}">
<c:set var="begin" value="1" scope="page"></c:set>
<c:set var="end" value="5" scope="page"></c:set>
</c:when>
<c:when test="${page.thispage>=page.countpage-2}">
<c:set var="begin" value="${page.countpage-4}" scope="page"></c:set>
<c:set var="end" value="${page.countpage}" scope="page"></c:set>
</c:when>
<c:otherwise>
<c:set var="begin" value="${page.thispage-2}" scope="page"></c:set>
<c:set var="end" value="${page.thispage+2}" scope="page"></c:set>
</c:otherwise>
</c:choose>
</c:if>
<c:forEach begin="${begin}" end="${end}" step="1" var="i">
<c:if test="${i==page.thispage}"><!-- 当前页就不是超链接 -->
<font color="black">${i}</font>
</c:if>
<c:if test="${i!=page.thispage}"><!-- 非当前页就是超链接 -->
<a href="${pageContext.request.contextPath }/servlet/PageCustomerServlet?thispage=${i}"><font color="red">${i}</font></a>
</c:if>
</c:forEach>
<!-- 分页逻辑结束 -->
<a href="${pageContext.request.contextPath }/servlet/PageCustomerServlet?thispage=${page.nextpage}">下一页</a>
<a href="${pageContext.request.contextPath }/servlet/PageCustomerServlet?thispage=${page.lastpage}">尾页</a>
</body><br>
<a href="${pageContext.request.contextPath }/">返回到主页</a>
</html>
分页伪代码：
6.分页展示：
