【jsp 分页】mysql limit方式进行分页

package com.balfish.bean;

public class Goods {
    private int goodsId;
    private String goodsName;
    private float goodsPrice;
    public int getGoodsId() {
        return goodsId;
    }
    public void setGoodsId(int goodsId) {
        this.goodsId = goodsId;
    }
    public String getGoodsName() {
        return goodsName;
    }
    public void setGoodsName(String goodsName) {
        this.goodsName = goodsName;
    }
    public float getGoodsPrice() {
        return goodsPrice;
    }
    public void setGoodsPrice(float goodsPrice) {
        this.goodsPrice = goodsPrice;
    }
}

package com.balfish.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;

import com.balfish.bean.Goods;
import com.balfish.util.DbConnection;

public class GoodsDao {
    
    Connection conn;
    PreparedStatement psmt;
    ResultSet rs;
    
    int pageSize = 5; //每页显示5条数据
    
    public ResultSet executeQuery(String sql)throws Exception{
        
        conn =DbConnection.getConnection();
        psmt = conn.prepareStatement(sql);
        rs = psmt.executeQuery(sql);
        return rs;
    }
    
     //核心还是mysql的limit分页，然后暂存到内存中的ArrayList中
    public ArrayList<Goods> getGoodsList(int currentPage) throws Exception{
        ArrayList<Goods> GoodsList = new ArrayList<Goods>();
        int beginRecord = (currentPage -1) * pageSize;
        int endRecord = currentPage * pageSize;
        rs = executeQuery("select * from goods limit " + beginRecord + "," + endRecord);
    
        while(rs.next()){
            Goods goods = new Goods();
            goods.setGoodsId(rs.getInt(1));
            goods.setGoodsName(rs.getString(2));
            goods.setGoodsPrice(rs.getFloat(3));
            GoodsList.add(goods);
        }
        return GoodsList;
    } 
    
    public int getPageCount() throws Exception{
        int total = 0;
        int pageCount = 0;
        rs = executeQuery("select count(*) from goods");
    
        //得到分页的总页数，由于整数除法结果的取整形式，这里要用一点技巧进行处理
        if(rs.next()){
            total = rs.getInt(1);
            pageCount =(total -1) /pageSize +1;
        }
        return pageCount ;
    }     
}

package com.balfish.servlet;

import java.io.IOException;
import java.util.ArrayList;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.balfish.bean.Goods;
import com.balfish.dao.GoodsDao;

public class MyServlet extends HttpServlet{
    public void doGet(HttpServletRequest req , HttpServletResponse resp)
    throws ServletException,IOException{
        doPost(req, resp);
    }
    
    public void doPost(HttpServletRequest req , HttpServletResponse resp)
            throws ServletException,IOException{
        
        resp.setContentType("text/html");
        String tmpCurrentPage = req.getParameter("currentPage");
       
    //下面这几句挺无趣的，容易看的吃力，其实就是如果前面浏览过有页数标记则去读哪个页数，否则从第一页开始
        int currentPage = 1;
        if(tmpCurrentPage != null)
            currentPage = Integer.parseInt(tmpCurrentPage);
        
        GoodsDao goodsDao = new GoodsDao();
        try{
            ArrayList<Goods> GoodsList = goodsDao.getGoodsList(currentPage);
            //把数据信息放到req作用域中，
            req.setAttribute("GoodsList",GoodsList);
            req.setAttribute("currentPage",currentPage);
            req.setAttribute("pageCount",goodsDao.getPageCount());
            req.getRequestDispatcher("/WEB-INF/page/myPage.jsp").forward(req,resp);
            
        }catch(Exception e){
            e.printStackTrace();
        }
    }
    
    public void destroy(){
        super.destroy();
    }
    
    public void init(ServletConfig config) throws ServletException {
        super.init(config);
    }
}

package com.balfish.util;

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

public class DbConnection {
    
    //抽象出单例，可作为模板
    private static Connection conn = null;
    private static String url = "jdbc:mysql://localhost/goods_test";
    private static String username ="root";
    private static String password ="";
    
    private DbConnection(){
  
    }
    
    public static Connection getConnection() throws Exception{
        Class.forName("com.mysql.jdbc.Driver");
        if(conn == null)
            conn =  DriverManager.getConnection(url,username,password);
        return conn;
    }
}

create database goods_test;
use goods_test;
create table goods(
    goodsId int,
    goodsName varchar(20),
    goodsPrice float
);


insert into goods values(1,‘bag‘,68.8);
insert into goods values(2,‘pen‘,10.0);
insert into goods values(3,‘pencil‘,2.0);
insert into goods values(4,‘mobile‘,968.8);
insert into goods values(5,‘bag‘,68.8);
insert into goods values(6,‘water‘,1.2);

    
<%@ 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>
        <meta http-equiv ="content-type" content="text/html;charset=utf-8">
    </head>
    
    <body>
        <center>
            <c:if test = "${currentPage >= 1 }">
                <a href ="getPage?curentPage = 1">首页</a>
                <a href ="getPage?currentPage=${ currentPage-1}">上一页</a>
            </c:if>
            
            <c:if test="${currentPage == 1 }">
                  <a href="getPage?currentPage=${ currentPage+1}">下一页</a>
                  <a href="getPage?currentPage=${ pageCount}">尾页</a>
              </c:if>
              
              <table width="%80" border="1" height="56" >
                  <tr align ="center">
                      <td>商品编号</td>
                      <td>商品名称</td>
                      <td>商品价格</td>
                  </tr>
                  
                  <c:forEach var="goods" items="${GoodsList}">
<!--  上面的GoodsList后面多些了一个} 就报下面意想不到的错误,查了好久...所以下次jstl表达式使用时一定注意                   
javax.el.PropertyNotFoundException: Property ‘goodsId‘ not found on type java.lang.String -->
                      <tr align="center">
                     <td>${goods.goodsId }</td>
                     <td>${goods.goodsName }</td>
                     <td>${goods.goodsPrice }</td>
                 </tr>
                  </c:forEach>
              </table>
        </center>
    </body>
</html>

<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app 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"
  version="3.0"
  metadata-complete="true">


    <servlet>
        <servlet-name>test1</servlet-name>
        <servlet-class>com.balfish.servlet.MyServlet</servlet-class>
    </servlet>
    
    <servlet-mapping>
        <servlet-name>test1</servlet-name>
        <url-pattern>/getPage</url-pattern>
    </servlet-mapping>

</web-app>