为什么要对数据进行分页？当数据较多时，页面就会变的很庞大，不仅会影响到用户的使用，而且还有加重服务器的负担。下面简单的实现了数据的分页。
第一步：导入相应的jar包
需要导入c3p0，dbutils,mysql驱动等jar包。
第二步：创建数据库和表, 配置c3p0， 创建工具类，User类
创建数据库，并准备测试数据（可以自行生成）
create database contacts;use contacts;create table users(id varchar(32),username varchar(36),password varchar(36),constraint user_pk primary key(id));
c3p0-config.xml
<?xml version="1.0" encoding="UTF-8"?><c3p0-config><!– 默认配置，只可以出现一次 –><default-config><!– 连接超时设置30秒 –><property name="checkoutTimeout">30000</property><!– 30秒检查一次connection的空闲 –><property name="idleConnectionTestPeriod">30</property><!–初始化的池大小 –><property name="initialPoolSize">2</property><!– 最多的一个connection空闲时间 –><property name="maxIdleTime">30</property><!– 最多可以有多少个连接connection –><property name="maxPoolSize">10</property><!– 最少的池中有几个连接 –><property name="minPoolSize">2</property><!– 批处理的语句 –><property name="maxStatements">50</property><!– 每次增长几个连接 –><property name="acquireIncrement">3</property><property name="driverClass">com.mysql.jdbc.Driver</property><property name="jdbcUrl"><![CDATA[jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=UTF-8]]></property><property name="user">root</property><property name="password">123456</property></default-config><named-config name="contacts"><property name="checkoutTimeout">1000</property><property name="idleConnectionTestPeriod">30</property><property name="initialPoolSize">2</property><property name="maxIdleTime">30</property><property name="maxPoolSize">5</property><property name="minPoolSize">2</property><property name="maxStatements">50</property><property name="acquireIncrement">3</property><property name="driverClass">com.mysql.jdbc.Driver</property><property name="jdbcUrl"><![CDATA[jdbc:mysql://127.0.0.1:3306/contacts?useUnicode=true&characterEncoding=UTF-8]]></property><property name="user">root</property><property name="password">123456</property></named-config> </c3p0-config>
DataSourceUtil.java
package cn.zq.util;import java.sql.Connection;import java.sql.SQLException;import javax.sql.DataSource;import com.mchange.v2.c3p0.ComboPooledDataSource;public class DataSourceUtil {private static DataSource ds;static{ds = new ComboPooledDataSource("contacts"); }public static DataSource getDataSource(){return ds;}public static Connection getConnection() throws SQLException{return ds.getConnection();}}User.javapackage cn.zq.domain;public class User {private String id;private String username;private String password;public User() {}public User(String id, String username, String password) {this.id = id;this.username = username;this.password = password;}public void setId(String id) {this.id = id;}public void setUsername(String username) {this.username = username;}public void setPassword(String password) {this.password = password;}public String toString() {return "User [id=" + id + ", username=" + username + ", password="+ password + "]";}public String getId() {return id;}public String getUsername() {return username;}public String getPassword() {return password;}}第三步：创建并配置servlet，创建显示页面
UserServlet.java
package cn.zq.servlet;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 org.apache.commons.dbutils.QueryRunner;import org.apache.commons.dbutils.handlers.BeanListHandler;import org.apache.commons.dbutils.handlers.ScalarHandler;import cn.zq.domain.User;import cn.zq.util.DataSourceUtil;public class UserServlet extends HttpServlet {public void init() throws ServletException {try {Class.forName("cn.zq.util.DataSourceUtil");} catch (ClassNotFoundException e) {e.printStackTrace();}}public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doPost(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//which page to show.String pn = request.getParameter("pn");int pageNum = 1;try{pageNum = Integer.parseInt(pn);}catch(Throwable t){//ignore}int pageSize = 10;QueryRunner run = new QueryRunner(DataSourceUtil.getDataSource());try {String sql = "SELECT COUNT(1) from users";int totalRecord = run.query( sql, new ScalarHandler<Long>() ).intValue();System.err.println("totalRecord = " + totalRecord);//(11 + ( 10 -1))/10int pageCount = (totalRecord + (pageSize – 1)) / pageSize;if(pageNum < 0){pageNum = 1;}if(pageNum > pageCount){pageNum = pageCount;}//0, 10 10, 20int m = (pageNum – 1)*pageSize;int n = pageSize;sql = "SELECT * FROM users LIMIT ?, ?";List<User> userList = run.query(sql, new BeanListHandler<User>(User.class), m, n);//分页显示多少个页号int no = 10;int beginPageIndex = 0;int endPageIndex = 0;if(pageCount <= no){beginPageIndex = 1;endPageIndex = pageNum;}else{beginPageIndex = pageNum – no/2;endPageIndex = beginPageIndex + (no -1);if(beginPageIndex < 1){beginPageIndex = 1;endPageIndex = no;}if(endPageIndex > pageCount){endPageIndex = pageCount;beginPageIndex = endPageIndex – (no – 1);}}request.setAttribute("pageCount", pageCount);request.setAttribute("totalRecord", totalRecord);request.setAttribute("pageNum", pageNum);request.setAttribute("beginPageIndex", beginPageIndex);request.setAttribute("endPageIndex", endPageIndex);request.setAttribute("userList", userList);request.getRequestDispatcher("/page/user.jsp").forward(request, response);;} catch (Exception e) {e.printStackTrace();}}}勇敢的冷静的理智的去接受失败，有时不但是必要的，而且是很有必要的。
