JavaWeb入门教程之分页查询功能的简单实现

一、mysql实现分页查询的sql语句

1、分页需求：

客户端通过传递pageno(页码)，counter(每页显示的条数)两个参数去分页查询数据库表中的数据，那我们知道mysql数据库提供了分页的函数limit m,n，但是该函数的用法和我们的需求不一样，所以就需要我们根据实际情况去改写适合我们自己的分页语句，具体的分析如下：

比如：

查询第1条到第10条的数据的sql是：select * from table limit 0,10;   ->对应我们的需求就是查询第一页的数据：select * from table limit (1-1)*10,10;

查询第10条到第20条的数据的sql是：select * from table limit 10,20;  ->对应我们的需求就是查询第二页的数据：select * from table limit (2-1)*10,10;

查询第20条到第30条的数据的sql是：select * from table limit 20,30;  ->对应我们的需求就是查询第三页的数据：select * from table limit (3-1)*10,10;

2、总结

通过上面的分析，可以得出符合我们自己需求的分页sql格式是：select * from table limit (pageno-1)*counter,counter; 其中pageno是页码，counter是每页显示的条数。

二、javaweb程序

1、创建pagebeanutils.java工具类

package com.ambow.utils;
import java.util.list;
public class pagebeanutils<t> {
 private int prepage;//上一页
 private int nextpage;//下一页
 private int firstpage=1;//首页
 private int lastpage;//尾页
 private int currentpage = 1;//当前
 private int totalpage;//总页数
 private int pagesize;//每页显示条数，默认显示10条
 private int totaldata;//数据总条数
 private list<t> pagedata;//数据
 public pagebeanutils(int currentpage,int pagesize, int totaldata) {
 this.currentpage = currentpage;
 this.pagesize = pagesize;
 this.totaldata = totaldata;
 
 //计算获得总页数（尾页）
// this.totalpage = this.lastpage = (totaldata+pagesize-1)/pagesize;
 this.totalpage = this.lastpage = (int)math.ceil((double)totaldata/pagesize);
 //防止当前页小于1
 this.currentpage = math.max(this.currentpage, 1);
 //防止当前页大于总的页数
 this.currentpage = math.min(this.totalpage, this.currentpage);
 //设置上一页，上一页不能小于1
 this.prepage = math.max(this.currentpage-1, 1);
 //设置下一页，下一页不能大于总页数
 this.nextpage = math.min(this.currentpage+1, this.totalpage);
 
 /**
 * ceil
public static double ceil(double a)
返回最小的（最接近负无穷大） double 值，该值大于等于参数，并等于某个整数。特殊情况如下：
如果参数值已经等于某个整数，那么结果与该参数相同。
如果参数为 nan、无穷大、正 0 或负 0，那么结果与参数相同。
如果参数值小于 0，但是大于 -1.0，那么结果为负 0。
注意， math.ceil(x) 的值与 -math.floor(-x) 的值完全相同。
参数：
a - 一个值。
返回：
最小（最接近负无穷大）浮点值，该值大于等于该参数，并等于某个整数。
 */
 
 }
 
 public pagebeanutils(int prepage, int nextpage, int firstpage, int lastpage, int currentpage, int totalpage,
 int pagesize, int totaldata, list<t> pagedata) {
 super();
 this.prepage = prepage;
 this.nextpage = nextpage;
 this.firstpage = firstpage;
 this.lastpage = lastpage;
 this.currentpage = currentpage;
 this.totalpage = totalpage;
 this.pagesize = pagesize;
 this.totaldata = totaldata;
 this.pagedata = pagedata;
 }
 public int getprepage() {
 return prepage;
 }
 public void setprepage(int prepage) {
 this.prepage = prepage;
 }
 public int getnextpage() {
 return nextpage;
 }
 public void setnextpage(int nextpage) {
 this.nextpage = nextpage;
 }
 public int getfirstpage() {
 return firstpage;
 }
 public void setfirstpage(int firstpage) {
 this.firstpage = firstpage;
 }
 public int getlastpage() {
 return lastpage;
 }
 public void setlastpage(int lastpage) {
 this.lastpage = lastpage;
 }
 public int getcurrentpage() {
 return currentpage;
 }
 public void setcurrentpage(int currentpage) {
 this.currentpage = currentpage;
 }
 public int gettotalpage() {
 return totalpage;
 }
 public void settotalpage(int totalpage) {
 this.totalpage = totalpage;
 }
 public int getpagesize() {
 return pagesize;
 }
 public void setpagesize(int pagesize) {
 this.pagesize = pagesize;
 }
 public int gettotaldata() {
 return totaldata;
 }
 public void settotaldata(int totaldata) {
 this.totaldata = totaldata;
 }
 public list<t> getpagedata() {
 return pagedata;
 }
 public void setpagedata(list<t> pagedata) {
 this.pagedata = pagedata;
 }
 
 
 /*
 * 
 * 
 * totalpage = (totaldata+pagesize-1)/pagesize;
 * 
 * 
 * */
}

2、在接口里面定义分页查询的方法

package com.ambow.dao;
 
import java.util.list;
 
import com.ambow.pojo.good;
 
public interface igooddao {
 //增删改查
 public void add(good good);
 public void delete(good good);
 public void update(good good);
 public void query(good good);
 public good queryone(good good);
 public list<good> querymore(good good);
 public list<good> querybyname(string name);//根据商家名称进行模糊查询
 //条件分页查询
 public list<good> querybyname(string name,int currentpage,int pagesize);
 //获取满足某个条件的总记录数
 public int gettotalnum(string name);
}

3、在接口的实现类里面实现方法

package com.ambow.dao.impl;
 
import java.sql.connection;
import java.sql.preparedstatement;
import java.sql.resultset;
import java.sql.sqlexception;
import java.util.arraylist;
import java.util.list;
 
import com.ambow.dao.igooddao;
import com.ambow.pojo.good;
import com.ambow.utils.dbutils;
 
public class gooddaoimpl implements igooddao {
 dbutils db = new dbutils();
 @override
 public void add(good good) {
 connection conn = null;
 preparedstatement pstmt = null;
 string sql = "insert into good (name,address,tel,dishes) values (?,?,?,?)";
 try {
 conn = dbutils.getconnection();
 pstmt = conn.preparestatement(sql);
 pstmt.setstring(1, good.getname());
 pstmt.setstring(2, good.getaddress());
 pstmt.setstring(3, good.gettel());
 pstmt.setstring(4, good.getdishes());
 int isok = pstmt.executeupdate();
 //system.out.println("add-----"+isok);
 } catch (sqlexception e) {
 e.printstacktrace();
 }
 }
 
 @override
 public void delete(good good) {
 connection conn = null;
 preparedstatement pstmt = null;
 string sql = "delete from good where id = ?";
 try {
 conn = dbutils.getconnection();
 pstmt = conn.preparestatement(sql);
 pstmt.setint(1, good.getid());
 int isok = pstmt.executeupdate();
 system.out.println("delete-----"+isok);
 } catch (sqlexception e) {
 e.printstacktrace();
 }
 
 }
 
 @override
 public void update(good good) {
 connection conn = null;
 preparedstatement pstmt = null;
 string sql = "update good set name=?,address=?,tel=?,dishes=? where id=?";
 try {
 conn = dbutils.getconnection();
 pstmt = conn.preparestatement(sql);
 pstmt.setstring(1, good.getname());
 pstmt.setstring(2, good.getaddress());
 pstmt.setstring(3, good.gettel());
 pstmt.setstring(4, good.getdishes());
 pstmt.setint(5,good.getid());
 int isok = pstmt.executeupdate();
 } catch (sqlexception e) {
 e.printstacktrace();
 }
 
 }
 
 @override
 public void query(good good) {
 // todo auto-generated method stub
 
 }
 
 @override
 public good queryone(good good) {
 connection conn = null;
 preparedstatement pstmt = null;
 resultset rs = null;
 string sql = "select * from good where id = ?";
 good gd = null;
 try {
 conn = dbutils.getconnection();
 pstmt = conn.preparestatement(sql);
 pstmt.setint(1, good.getid());
 rs = pstmt.executequery();
 while(rs.next()){
  gd = new good(rs.getint(1),rs.getstring(2),rs.getstring(3),
  rs.getstring(4),rs.getstring(5));
 }
 } catch (sqlexception e) {
 e.printstacktrace();
 }
 return gd;
 
 }
 
 @override
 public list<good> querymore(good good) {
 // todo auto-generated method stub
 return null;
 }
 
 @override
 public list<good> querybyname(string name) {
 connection conn = null;
 preparedstatement pstmt = null;
 resultset rs = null;
 string sql = "select * from good where name like ?";
 list<good> goodlist = new arraylist<good>();
 try {
 conn = dbutils.getconnection();
 pstmt = conn.preparestatement(sql);
 pstmt.setstring(1, "%"+name+"%");
 rs = pstmt.executequery();
 while(rs.next()){
  goodlist.add(new good(rs.getint(1),rs.getstring(2),rs.getstring(3),
  rs.getstring(4),rs.getstring(5)));
 }
 } catch (sqlexception e) {
 e.printstacktrace();
 }
 return goodlist;
 }
 
 @override
 public list<good> querybyname(string name, int currentpage, int pagesize) {
 connection conn = null;
 preparedstatement pstmt = null;
 resultset rs = null;
 string sql = "select * from good where name like ? limit ?,?";
 list<good> goodlist = new arraylist<good>();
 try {
 conn = dbutils.getconnection();
 pstmt = conn.preparestatement(sql);
 pstmt.setstring(1, "%"+name+"%");
 pstmt.setint(2,(currentpage-1)*pagesize);
 pstmt.setint(3,pagesize);
 rs = pstmt.executequery();
 while(rs.next()){
  goodlist.add(new good(rs.getint(1),rs.getstring(2),rs.getstring(3),
  rs.getstring(4),rs.getstring(5)));
 }
 } catch (sqlexception e) {
 e.printstacktrace();
 }
 return goodlist;
 
 }
 
 @override
 public int gettotalnum(string name) {
 connection conn = null;
 preparedstatement pstmt = null;
 resultset rs = null;
 string sql = "select count(id) from good where name like ?";
 int total = 0;
 try {
 conn = dbutils.getconnection();
 pstmt = conn.preparestatement(sql);
 pstmt.setstring(1, "%"+name+"%");
 rs = pstmt.executequery();
 while(rs.next()){
  total = rs.getint(1);
 }
 } catch (sqlexception e) {
 e.printstacktrace();
 }
 return total;
 
 }
 
}

4.在servlet里面调用实现类里面的分页查询方法

package com.ambow.servlet;
 
import java.io.ioexception;
import java.util.list;
 
import javax.servlet.servletexception;
import javax.servlet.annotation.webservlet;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
 
import com.ambow.dao.igooddao;
import com.ambow.dao.impl.gooddaoimpl;
import com.ambow.pojo.good;
import com.ambow.utils.pagebeanutils;
 
@webservlet("/queryservlet")
public class queryservlet extends httpservlet {
 private static final long serialversionuid = 1l;
 private igooddao gooddao = new gooddaoimpl();
 public queryservlet() {
  super();
 }
 
 protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
 dopost(request,response);
 }
 protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
 request.setcharacterencoding("utf-8");
 response.setcharacterencoding("utf-8");
 string keywords = request.getparameter("kw");
 string method = request.getparameter("method");
 if("add".equals(method)){
 string name = request.getparameter("name");
 string address = request.getparameter("address");
 string tel = request.getparameter("tel");
 string dishes = request.getparameter("dishes");
 good good = new good(0,name,address,tel,dishes);
 gooddao.add(good);
 //调用dao的查询方法，返回一个list
 list<good> goods = gooddao.querybyname(keywords);
 request.setattribute("list", goods);
 request.getrequestdispatcher("goods.jsp").forward(request, response);
 }else if("search".equals(method)){
 if(null==keywords) {
 keywords="";
 }
 int currentpage = 1;
 try {
 currentpage=integer.parseint(request.getparameter("curpage"));
 if(currentpage<=0) {
  currentpage = 1;
 }
 }catch(exception e) {
 currentpage = 1;
 }
 int pagesize=10;
 int totaldata = gooddao.gettotalnum(keywords);
 int totalpage = (int)math.ceil((double)totaldata/pagesize);
 if(currentpage>totalpage){
 currentpage = totalpage;
 }
 list<good> goods = gooddao.querybyname(keywords,currentpage,pagesize); 
 pagebeanutils pg = new pagebeanutils(currentpage,pagesize,totaldata);
 pg.setpagedata(goods);
 request.setattribute("pg", pg);
 request.getrequestdispatcher("good2.jsp").forward(request, response);
 }else if("delete".equals(method)){
 system.out.println(keywords);
 //实现删除
 string id = request.getparameter("id");
 good good = new good();
 good.setid(integer.valueof(id));
 gooddao.delete(good);
 //调用dao的查询方法，返回一个list
 list<good> goods = gooddao.querybyname(keywords);
 request.setattribute("list", goods);
 request.getrequestdispatcher("goods.jsp").forward(request, response);
 }else if("querybyid".equals(method)){
 //查询一个
 string id = request.getparameter("id");
 good good = new good();
 good.setid(integer.valueof(id));
 good = gooddao.queryone(good);
 //调用dao的查询方法，返回一个good
 request.setattribute("good", good);
 request.getrequestdispatcher("update.jsp").forward(request, response);
 }else if("update".equals(method)){
 string id = request.getparameter("id");
 string name = request.getparameter("name");
 string address = request.getparameter("address");
 string tel = request.getparameter("tel");
 string dishes = request.getparameter("dishes");
 good good = new good(integer.valueof(id),name,address,tel,dishes);
 gooddao.update(good);
 //调用dao的查询方法，返回一个list
 list<good> goods = gooddao.querybyname(keywords);
 request.setattribute("list", goods);
 request.getrequestdispatcher("goods.jsp").forward(request, response);
 }else{
 //调用dao的查询方法，返回一个list
 list<good> goods = gooddao.querybyname(keywords);
 request.setattribute("list", goods);
 request.getrequestdispatcher("goods.jsp").forward(request, response);
 }
 }
 
}

5.在jsp页面获取servlet里面传过来的数据

<%@ page language="java" contenttype="text/html; charset=utf-8"
 pageencoding="utf-8" import="java.util.arraylist,com.ambow.pojo.good,
 com.ambow.pojo.user,com.ambow.utils.pagebeanutils"%>
 <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!doctype html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8">
<title>外卖系统的搜索功能</title>
</head>
<body>
 <form action="queryservlet?method=search" method="post">
 <input type="text" name="kw"/><input type="submit" value="搜索"/><a href=" ">添加商家</a >
 <table border="1">
 <tr><th>商家店名</th><th>商家地址</th><th>商家电话</th><th>经营菜品</th><th colspan="2">编辑</th></tr>
 <c:foreach items="${pg.pagedata}" var="g">
  <tr><td>${g.name}</td><td>${g.address}</td><td>${g.tel}</td><td>${g.dishes}</td>
  <td><a href="queryservlet?method=querybyid&id=${g.id}">修改</a ></td>
  <td><a href="queryservlet?method=delete&id=${g.id}" onclick="return confirm('确认删除本条数据吗？');">删除</a ></td></tr>
 
 </c:foreach>
 </table>
 <a href="queryservlet?method=search&curpage=${pg.firstpage}">首页</a >
 <a href="queryservlet?method=search&curpage=${pg.currentpage - 1}">上一页</a >
 <a href="queryservlet?method=search&curpage=${pg.currentpage + 1}">下一页</a >
 <a href="queryservlet?method=search&curpage=${pg.lastpage}">尾页</a >
 当前第${pg.currentpage}页/共${pg.totalpage}页
 每页显示${pg.pagesize}条
 </form>
 
</body>
</html>

总结

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