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，将所有页数的页号都显示出来。
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;像这样： 
点击哪一页就显示哪一页的内容。
数据库数据：
数据库的表和数据在这一篇博客中已经准备好了：
http://blog.csdn.net/qq_26525215/article/details/52212571
create table person(
id varchar(30) primary key,
name varchar(30),
address varchar(30),
age int
);
DAO层：
接口：
package cn.hncu.dao;
import java.sql.SQLException;
import java.util.Map;
public interface IPageDAO {
public Map<String, Object> query(Integer pageNo) throws NumberFormatException, SQLException;
}
实现类：
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 org.junit.Test;
import cn.hncu.pubs.C3p0Pool;
public class PageJdbc implements IPageDAO {
//每页显示的行数
private final int pageSize = 10;
@Override
public Map<String, Object> query(Integer pageNo) 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";
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);
//分页后的当前页面内容datas
//起始行号
int startN = (pageNo-1)*pageSize;
sql = "select * from person limit "+startN+" , "+pageSize;
List<Map<String, Object>> datas = run.query(sql, new MapListHandler());
result.put("datas", datas);//封装到result
return result;
}
@Test
public void test() {
try {
Map<String, Object> map = query(5);
System.out.println(map);
} catch (NumberFormatException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
C3p0配置文件c3p0-config.xml:
<c3p0-config>
<!-- 默认配置，如果没有指定则使用这个配置 -->
<default-config>
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl">
<![CDATA[jdbc:mysql://127.0.0.1:3306/hncu?useUnicode=true&characterEncoding=UTF-8]]>
</property>
<property name="user">root</property>
<property name="password">1234</property>
<!-- 初始化池大小 -->
<property name="initialPoolSize">2</property>
<!-- 最大空闲时间 -->
<property name="maxIdleTime">30</property>
<!-- 最多有多少个连接 -->
<property name="maxPoolSize">10</property>
<!-- 最少几个连接 -->
<property name="minPoolSize">2</property>
<!-- 每次最多可以执行多少个批处理语句 -->
<property name="maxStatements">50</property>
</default-config>
<!-- 命名的配置 -->
<named-config name="demo">
<property name="driverClass">com.mysql.jdbc.Driver</property>
<property name="jdbcUrl"><![CDATA[jdbc:mysql://127.0.0.1:3306/hncu?useUnicode=true&characterEncoding=UTF-8]]></property>
<property name="user">root</property>
<property name="password">1234</property>
<property name="acquireIncrement">5</property><!-- 如果池中数据连接不够时一次增长多少个 -->
<property name="initialPoolSize">100</property>
<property name="minPoolSize">50</property>
<property name="maxPoolSize">1000</property>
<property name="maxStatements">0</property>
<property name="maxStatementsPerConnection">5</property> <!-- he's important, but there's only one of him -->
</named-config>
</c3p0-config>
C3p0数据库连接池：
package cn.hncu.pubs;
import java.sql.Connection;
import java.sql.SQLException;
import javax.sql.DataSource;
import com.mchange.v2.c3p0.ComboPooledDataSource;
public class C3p0Pool {
private static DataSource pool;
private static ThreadLocal<Connection> t = new ThreadLocal<Connection>();
static{
pool = new ComboPooledDataSource();
}
public static DataSource getDataSource(){
return pool;
}
public static Connection getConnection() throws SQLException{
Connection con=t.get();
if(con==null){
con = pool.getConnection();
t.set(con);
}
return con;
}
}
service层：
接口：
package cn.hncu.service;
import java.sql.SQLException;
import java.util.Map;
public interface IPageService {
public Map<String, Object> query(Integer pageNo) throws NumberFormatException, SQLException;
}
实现类
package cn.hncu.service;
import java.sql.SQLException;
import java.util.Map;
import cn.hncu.dao.IPageDAO;
import cn.hncu.dao.PageJdbc;
public class PageServiceImpl implements IPageService{
//注入dao
IPageDAO dao = new PageJdbc();
@Override
public Map<String, Object> query(Integer pageNo) throws NumberFormatException, SQLException {
return dao.query(pageNo);
}
}
index.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>
</head>
<body>
<c:redirect url="/PageServlet"></c:redirect>
</body>
</html>
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>演示数据分页显示</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>当前页的内容:</h3>
<table>
<tr><th>学号</th><th>姓名</th></tr>
<c:forEach items="${result.datas}" var="map">
<tr>
<td>${map.id}</td>
<td>${map.name}</td>
</tr>
</c:forEach>
</table>
<c:if test="${result.currentPage!=1}">
<span class="pc">
<a href='<c:url value="/PageServlet?page=${result.currentPage-1}"></c:url>'>上一页</a>
</span>
</c:if>
<c:forEach begin="1" end="${result.pageCount}" 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>
table.css:
body{
text-align: center;
}
table{
border: 1px solid blue;
width: 500px;
border-collapse: collapse;/*为表格设置合并边框模型：*/
margin: auto;
}
td,th,tr{
border: 1px solid blue;
}
.pc{
width: 30px;
height: 30px;
border: 1px solid #e1e2e3;
border-top-color: rgb(225, 226, 227);
border-top-style: solid;
border-top-width: 1px;
border-right-color: rgb(225, 226, 227);
border-right-style: solid;
border-right-width: 1px;
border-bottom-color: rgb(225, 226, 227);
border-bottom-style: solid;
border-bottom-width: 1px;
border-left-color: rgb(225, 226, 227);
border-left-style: solid;
border-left-width: 1px;
}
.now {
display: block;
}web.xml:
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<display-name></display-name>
<servlet>
<servlet-name>PageServlet</servlet-name>
<servlet-class>cn.hncu.servlet.PageServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>PageServlet</servlet-name>
<url-pattern>/PageServlet</url-pattern>
<!-- 这里的/代表项目根目录下 -->
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
PageServlet.java:
package cn.hncu.servlet;
import java.io.IOException;
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.service.IPageService;
import cn.hncu.service.PageServiceImpl;
public class PageServlet extends HttpServlet {
//注入service
IPageService service = new PageServiceImpl();
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
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) {
iPageNo=1;
}
try {
Map<String, Object> result = service.query(iPageNo);
//给结果集补一个数据:currentPage
result.put("currentPage", iPageNo);
//###注意，一定要把结果集放入容器中
request.setAttribute("result", result);
//转到结果页面
request.getRequestDispatcher("/jsps/show.jsp").forward(request, response);
} catch (NumberFormatException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
演示结果：
需要的第三方扩展包：
链接：
https://github.com/chenhaoxiang/Java/tree/master/Database-support-package
完整项目代码链接：
https://github.com/chenhaoxiang/Java/tree/master/myPagesDividedWeb
转载请附上原文博客链接：
http://blog.csdn.net/qq_26525215
时间： 2024-10-14 20:57:09