Java 实现分页功能

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/test?allowMultiQueries=true&useUnicode=true&characterEncoding=utf8
user=LF
password=LF

package cn.zr.testpage.entity;

public class User {

    private String name;
    private int age;
    private String hobby;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getHobby() {
        return hobby;
    }
    public void setHobby(String hobby) {
        this.hobby = hobby;
    }
    public User() {
    }
    public User(String name, int age, String hobby) {
        this.name = name;
        this.age = age;
        this.hobby = hobby;
    }
    @Override
    public String toString() {
        return "User [name=" + name + ", age=" + age + ", hobby=" + hobby + "]";
    }

}

package cn.zr.testpage.service;

import java.util.List;

import cn.zr.testpage.entity.User;
import cn.zr.testpage.utils.Page;

public interface UserService {

    /**
     * 获取总数量
     * @return 返回总数
     */
    int getAmount();

    /**
     * 获取当前页的数据
     * @param page
     * @return 返回前页的数据
     */
    List<User> getUserInfo(Page page);

}

package cn.zr.testpage.service.impl;

import java.util.List;

import cn.zr.testpage.dao.UserDao;
import cn.zr.testpage.dao.impl.UserDaoImpl;
import cn.zr.testpage.entity.User;
import cn.zr.testpage.service.UserService;
import cn.zr.testpage.utils.Page;

public class UserServiceImpl implements UserService {
    private UserDao userDao;
    // 通过代码块加载实现类
    {
        userDao = new UserDaoImpl();
    }

    @Override
    public int getAmount() {
        return userDao.getAmount();
    }

    @Override
    public List<User> getUserInfo(Page page) {
        return userDao.getUserInfo(page);
    }

}

package cn.zr.testpage.dao;

import java.util.List;

import cn.zr.testpage.entity.User;
import cn.zr.testpage.utils.Page;

public interface UserDao {

    /**
     * 获取总数量
     * @return 返回总数
     */
    int getAmount();

    /**
     * 获取当前页的数据
     * @param page
     * @return 返回前页的数据
     */
    List<User> getUserInfo(Page page);

}

package cn.zr.testpage.dao.impl;

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import cn.zr.testpage.dao.UserDao;
import cn.zr.testpage.entity.User;
import cn.zr.testpage.utils.JdbcUtils;
import cn.zr.testpage.utils.Page;
import cn.zr.testpage.utils.UserBasicalImpl;

public class UserDaoImpl extends UserBasicalImpl implements UserDao{

    /**
     * 获取总数
     */
    @Override
    public int getAmount() {
        connection = JdbcUtils.getConnection();
        String sql = "SELECT COUNT(*) FROM USERINFO";
        int count = 0;
        try {
            pStatement = connection.prepareStatement(sql);
            rSet = pStatement.executeQuery();
            if(rSet.next()){
                count = rSet.getInt(1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            // 调用父类方法关闭资源
            super.close();
        }
        return count;
    }

    /**
     * 获取当前页的数据
     * @param page
     * @return 返回前页的数据
     */
    @Override
    public List<User> getUserInfo(Page page) {

        connection = JdbcUtils.getConnection();
        //基于MySQL的函数的分页
        String sql = "SELECT 姓名,年龄,爱好 FROM USERINFO LIMIT ?,?";
        // 创建集合
        List<User> list = new ArrayList<User>();
        try {
            pStatement = connection.prepareStatement(sql);
            //设置相关参数
            pStatement.setInt(1, page.getStart());
            pStatement.setInt(2, page.getSize());
            rSet = pStatement.executeQuery();
            while(rSet.next()){
                User user = new User();
                user.setName(rSet.getString("姓名"));
                user.setAge(rSet.getInt("年龄"));
                user.setHobby(rSet.getString("爱好"));
                list.add(user);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            // 调用父类方法关闭资源
            super.close();
        }
        return list;
    }

}

package cn.zr.testpage.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 cn.zr.testpage.entity.User;
import cn.zr.testpage.service.UserService;
import cn.zr.testpage.service.impl.UserServiceImpl;
import cn.zr.testpage.utils.BaseServlet;
import cn.zr.testpage.utils.Page;

public class ListServlet extends BaseServlet{

    private static final long serialVersionUID = 1L;

    @Override
    public void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {

        System.out.println("...doGet...");

        // 获取当前页
        String curpage = req.getParameter("curpage");
        UserService userService = new UserServiceImpl();
        // 获取总数量
        int count = userService.getAmount();
        //字符串转成整型
        int currentpage = super.currentPage(curpage);
        // 创建page对象
        Page page = new Page(count, currentpage, pagesize);
        // 获取当前页的数据
        List<User> users = userService.getUserInfo(page);
        //将相关数据存储起来
        req.setAttribute("page", page);
        req.setAttribute("users", users);

        System.out.println(count);
        System.out.println(users);
        //转发
        req.getRequestDispatcher("/WEB-INF/jsp/list.jsp").forward(req, resp);

    }

}

package cn.zr.testpage.utils;

import javax.servlet.http.HttpServlet;

public class BaseServlet extends HttpServlet {

    public int pagesize = 2;

    public int currentPage(String cpage){
        int currentpage = cpage!=null && !"".equals(cpage) && isint(cpage)? currentpage=Integer.parseInt(cpage):1;
        return currentpage;
    }

    public boolean isint(String str){
        boolean bo = true;
        try {
            Integer.parseInt(str);
        } catch (Exception e) {
            bo = false;
        }
        return bo;
    }

}

package cn.zr.testpage.utils;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
/**
 *
 * @author lf
 *
 */
public class JdbcUtils {

    // 获取数据库连接
    public static Connection getConnection() {
        String url="jdbc:mysql://localhost:3306/test?allowMultiQueries=true&useUnicode=true&characterEncoding=utf8";
        String user="LF";
        String password ="LF";
        Connection connection = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }

        try {
            connection =  DriverManager.getConnection(url, user, password);
        } catch (SQLException e) {
            e.printStackTrace();
        }

        return connection;
    }
}

package cn.zr.testpage.utils;

public class Page {

    // 页数（第几页）
    private int currentpage;

    // 查询数据库里面对应的数据有多少条
    private int total;// 从数据库查处的总记录数

    // 每页查询的数量条
    private int size;

    // 下页
    private int next;

    // 最后一页
    private int last;

    private int lpage;

    private int rpage;

    //从哪条开始查
    private int start;

    public Page() {
        super();
    }

    public int getCurrentpage() {
        return currentpage;
    }

    /****
     *
     * @param currentpage
     * @param total
     * @param pagesize
     */
    public void setCurrentpage(int currentpage,int total,int pagesize) {
        //如果整除表示正好分N页，如果不能整除在N页的基础上+1页
        int totalPages = total%pagesize==0? total/pagesize : (total/pagesize)+1;

        //总页数
        this.last = totalPages;

        //判断当前页是否越界,如果越界，我们就查最后一页
        if(currentpage>totalPages){
            this.currentpage = totalPages;
        }else{
            this.currentpage=currentpage;
        }
        if(currentpage<=0){
            this.currentpage=1;
        }

        //计算start   1----0    2  ------ 5
        this.start = (this.currentpage-1)*pagesize;

    }

    public int getTotal() {
        return total;
    }

    public void setTotal(int total) {
        this.total = total;
    }

    public int getSize() {
        return size;
    }

    public void setSize(int size) {
        this.size = size;
    }

    public int getNext() {
        return  currentpage<last? currentpage+1: last;
    }

    //上一页
    public int getUpper() {
        return currentpage>1? currentpage-1: currentpage;
    }

    public int getLast() {
        return last;
    }

    //总共有多少页，即末页
    public void setLast(int last) {
        this.last = total%size==0? total/size : (total/size)+1;
    }

    public int getLpage() {
        return lpage;
    }

    public void setLpage(int lpage) {
        this.lpage = lpage;
    }

    public int getRpage() {
        return rpage;
    }

    public void setRpage(int rpage) {
        this.rpage = rpage;
    }

    /****
     *
     * @param total   总记录数
     * @param currentpage    当前页
     * @param pagesize    每页显示多少条
     */
    public Page(int total,int currentpage,int pagesize) {
        //总记录数
        this.total = total;
        //每页显示多少条
        this.size=pagesize;

        //计算当前页和数据库查询起始值以及总页数
        setCurrentpage(currentpage, total, pagesize);

        //分页计算
        int leftcount =5,    //需要向上一页执行多少次
            rightcount =4;
        //起点页
        this.lpage =currentpage;
        //结束页
        this.rpage =currentpage;

        //2点判断
        this.lpage = currentpage-leftcount;            //正常情况下的起点
        this.rpage = currentpage+rightcount;        //正常情况下的终点

        //页差=总页数和结束页的差
        int topdiv = this.last-rpage;                //判断是否大于最大页数

        /***
         * 起点页
         * 1、页差<0  起点页=起点页+页差值
         * 2、页差>=0 起点和终点判断
         */
        this.lpage=topdiv<0? this.lpage+topdiv:this.lpage;

        /***
         * 结束页
         * 1、起点页<=0   结束页=|起点页|+1
         * 2、起点页>0    结束页
         */
        this.rpage=this.lpage<=0? this.rpage+(this.lpage*-1)+1: this.rpage;

        /***
         * 当起点页<=0  让起点页为第一页
         * 否则不管
         */
        this.lpage=this.lpage<=0? 1:this.lpage;

        /***
         * 如果结束页>总页数   结束页=总页数
         * 否则不管
         */
        this.rpage=this.rpage>last? this.last:this.rpage;
    }

    public int getStart() {
        return start;
    }

}

package cn.zr.testpage.utils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class UserBasicalImpl {

    protected Connection connection;
    protected PreparedStatement pStatement;
    protected ResultSet rSet;

    public void close(){
        // 关闭资源
        try {
            if (rSet!=null) {
                rSet.close();
            }
            if (pStatement!=null) {
                pStatement.close();
            }
            if (connection!=null) {
                connection.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>

    <title>用户信息</title>

  </head>

  <body>

    <table>
        <tr>
            <th>姓名</th>
            <th>年龄</th>
            <th>爱好</th>
        </tr>
        <c:forEach items="${users }" var="user" varStatus="userindex">
            <tr>
                <td>${user.name }</td>
                <td>${user.age }</td>
                <td>${user.hobby }</td>
            </tr>
        </c:forEach>
    </table>    

    <div>
        <a href="?curpage=1">首页</a>
        <c:forEach begin="${page.lpage}" end="${page.rpage}" var="pageNum">
            <a href="?curpage=${pageNum }">${pageNum }</a>
        </c:forEach>
        <a href="?curpage=${page.last }">尾页</a>
    </div>

  </body>
</html>