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>

    &nbsp;&nbsp;
    <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>
        &nbsp;&nbsp;
    </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