分页,是一种将所有数据分段展示给用户的技术.用户每次看到的不 是全部数据,而是其中的一部分,如果在其中没有找到自己想要的内容,用户可以通过指定页码或是点上/下一页的方式进行翻页。
本例演示静态分页，也就是先设置好每页显示10行，再根据总行数，来算出总页数，并且只显示10个页码。增加查询功能，并且查询后的页面也进行分页。页码也进行分页 ！
查询功能的实现，需要我们在servlet向后台传输一个person,封装我们的查询条件
相关算法(技术):
总行数(num): select count(1) from stud;
每页显示的行数(n): 固定值---已知的一个常量
页数: pageSize= num/n +( (num%n==0)?0:1 )
当前页号: currentPage
当前要显示的页面数据的起始行号和终止行号
startN: (currentPage-1)*pageSize
如何显示从startN开始的pageSize条记录
select * from stud limit startN, pageSize;
增加了：
开始的页码：
showStart
结束的页码：
showEnd像这样：
数据库数据：
创建的数据库表，还有需要准备的jar包，请看本篇博客：
http://blog.csdn.net/qq_26525215/article/details/52222472
源码：
PageJdbc.java
package cn.hncu.dao;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.MapListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import cn.hncu.domain.Person;
import cn.hncu.pubs.C3p0Pool;
public class PageJdbc implements IPageDAO {
private final int pageSize = 10;// 每页显示的行数
@Override
public Map<String, Object> query(Integer pageNo, Person person)
throws NumberFormatException, SQLException {
Map<String, Object> result = new HashMap<String, Object>();
// 获取总页数 pageCount = rows/pageSize + ( (rows%pageSize==0)?0:1 )
// 总行数rows
String sql = "select count(1) from person where 1=1 ";// 用来查总行数
String sql2 = "select * from person where 1=1 ";// 用来查表内容
if (person.getId() != null && person.getId().trim().length() != 0) {
sql = sql + "and id like '%" + person.getId() + "%'";
sql2 = sql2 + "and id like '%" + person.getId() + "%'";
}
if (person.getName() != null && person.getName().trim().length() != 0) {
sql = sql + "and name like '%" + person.getName() + "%'";
sql2 = sql2 + "and name like '%" + person.getName() + "%'";
}
//System.out.println(sql2);
QueryRunner run = new QueryRunner(C3p0Pool.getDataSource());
int rows = Integer.parseInt("" + run.query(sql, new ScalarHandler()));
// 总页数
int pageCount = rows / pageSize + ((rows % pageSize == 0) ? 0 : 1);
result.put("pageCount", pageCount);// 封装到result
// 分页页面内容datas
// 起始行号
int startN = (pageNo - 1) * pageSize;
sql2 = sql2+ " limit "+startN+", "+pageSize;
List<Map<String, Object>> datas = run.query(sql2, new MapListHandler());
result.put("datas", datas);//封装到result
return result;
}
}
PageServlet.java
package cn.hncu.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.SQLException;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import cn.hncu.domain.Person;
import cn.hncu.service.IPageService;
import cn.hncu.service.PageServiceImpl;
public class PageServlet extends HttpServlet {
//注入servlet
IPageService service = new PageServiceImpl();
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
String pageNo = request.getParameter("page");
if(pageNo==null || pageNo.trim().length()==0){
pageNo = "1";
}
Integer iPageNo =1;
try {
iPageNo = Integer.parseInt(pageNo);
} catch (NumberFormatException e) {
request.getRequestDispatcher(request.getContextPath()+"/index.jsp").forward(request, response);
}
Person person =null;
//区分是Post还是GET方式请求，前者是新的查询，后者是原查询结果中进行翻页
if(request.getMethod().equalsIgnoreCase("get")){//翻页
//从session中把旧的查询条件值对象取出来
person = (Person) request.getSession().getAttribute("person");
if(person==null){//没有进行第一次查询之前，person就是需要我们new出来一个空的
person = new Person();
}
}else{//POST方式---新的查询
//收集模糊查询的输入参数
String id = request.getParameter("id");
String name = request.getParameter("name");
person = new Person();
person.setId(id);
person.setName(name);
//放入session,这样下一次翻页才能读取出来
request.getSession().setAttribute("person", person);
}
try {
Map<String, Object> result = service.query(iPageNo, person);
//给结果集补一个数据:currentPage --当前页号
result.put("currentPage", iPageNo);
//把结果集放入容器中
request.setAttribute("result", result);
//分页后的分页--向前端多传送两个数据(起始和末尾页号)：showStart和showEnd
int showSize=10;//每页显示几行
int showStart=0;//从第几个页号开始显示
int showEnd=0;//显示到第几个页号
//pageCount---总页数
//如果所有页码不足showSize: showStart=1,showEnd=pageCount
int pageCount = Integer.parseInt(""+result.get("pageCount"));
if(pageCount<=showSize){//不需要二次分页
showStart=1;
showEnd=pageCount;
}else{//需要二次分页
//如果当前页号iPageNo<=showSize/2时，showStart=1
if(iPageNo<=showSize/2){
showStart=1;
showEnd=showSize;
}else{
showStart = iPageNo - showSize/2;
showEnd = showStart + showSize-1;
}
if(showEnd>pageCount){
showEnd=pageCount;
showStart = showEnd-showSize-1;
}
}
//存储showStart和showEnd
request.setAttribute("showStart", showStart);
request.setAttribute("showEnd", showEnd);
//转到结果页面
request.getRequestDispatcher("/jsps/show.jsp").forward(request, response);
} catch (NumberFormatException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
show.jsp
<%@ 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>
<title>演示数据分页</title>
<link rel="stylesheet" href="<c:url value='/css/table.css' />" />
<script type="text/javascript">
function sub(obj){
window.location.href="<c:url value='/PageServlet?page=' />"+obj.value;
}
</script>
</head>
<body>
<h3>数据查询</h3>
<form action="<c:url value='/PageServlet'/>" method="post">
ID:<input type="text" name="id" value="${person.id }">
姓名:<input type="text" name="name" value="${person.name }" >
<input type="submit" value="模糊查询">
</form>
<h3>当前页的内容:</h3>
<table>
<tr><th>学号</th><th>姓名</th><th>地址</th><th>年龄</th></tr>
<c:forEach items="${result.datas}" var="map">
<tr>
<td>${map.id}</td>
<td>${map.name}</td>
<td>${map.address}</td>
<td>${map.age}</td>
</tr>
</c:forEach>
</table>
<c:if test="${result.currentPage!=1}">
<span class="pc">
<a href='<c:url value="/PageServlet?page=${result.currentPage-1}"></c:url>'>上一页</a>
</span>
</c:if>
<c:forEach begin="${showStart}" end="${showEnd}" var="idx">
<c:if test="${idx==result.currentPage}" var="isNow">
<span class=now>${idx}</span>
</c:if>
<c:if test="${!isNow }">
<span class="pc">
<a href='<c:url value="/PageServlet?page=${idx}"></c:url>'>${idx}</a>
</span>
</c:if>
</c:forEach>
<c:if test="${result.currentPage!=result.pageCount}">
<span class="pc">
<a href="<c:url value='/PageServlet?page=${result.currentPage+1}'></c:url>">下一页</a>
</span>
</c:if>
<br/><br/>
<!-- 复选框 -->
<select onchange="sub(this)">
<c:forEach begin="1" end="${result.pageCount}" var="idx">
<option <c:if test="${idx==result.currentPage}">selected="selected"</c:if> value="${idx}" >
第${idx}页
</option>
</c:forEach>
</select>
</body>
</html>
演示结果：
整个项目源码链接：
https://github.com/chenhaoxiang/Java/tree/master/myPagesDividedWeb2
myPagesDividedWeb2.zip文件
转载请附上原文博客链接：
http://blog.csdn.net/qq_26525215
