Mysql学习总结（32）——MySQL分页技术详解

1.什么是数据分页：数据分页就是将很多条记录像书本一样分页，每页显示多少行记录；

2.为什么要数据分页：当我们进行sql语句查询时，假如数据有成千上万行记录，如果在同一个页面去显示，那这个页面得有多大，数据就要很多，而我们所需的记录又很少，不使用分页，查看起来那么繁琐，而且一不小心容易看着眼花。使用数据分页，就行书本一样，有页数，一目了然。相当简洁。

3.核心sql语句：SELECT * FROM stud LIMIT m,n ————m表示要显示的页数，n表示显示的记录行数

4.核心思想：

总行数(rows): select count(1) from stud;
每页显示的行数(PAGE_SIZE): 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 :startRow: (currentPage-1)*pageSize
如何显示从startN开始的pageSize条记录 select * from stud limit startN, pageSize;
当前显示的开始页号：showStart=currentPage-showSize/2;
当前显示的结束页号：showEnd=showStart+showSize-1;
模糊查询：select count(*) from stud where 1=1 and........

5.成果图：

Mysql学习总结（32）——MySQL分页技术详解

6.代码实现

需要的包和配置文件：

[html] view
plain copy

Mysql学习总结（32）——MySQL分页技术详解

myConUtil.jar----自己写的c3p0pool工具类
commons-dbutils-1.4.jar
mysql-connector-java-5.1.34-bin.jar
c3p0-0.9.1.2.jar
c3p0-config.xml

index.jsp

[html] view
plain copy

Mysql学习总结（32）——MySQL分页技术详解

<%@ 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>
</head>
<body>
<a href='<c:url value="/PageServlet"></c:url>'>查看分页技术</a>
</body>
</html>

show,jsp

[html] view
plain copy

Mysql学习总结（32）——MySQL分页技术详解

<span style="font-size:12px;"><%@ 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>演示数据分页</title>
<link rel="stylesheet" href='<c:url value="/css/table.css"></c:url>'
media="screen">
<script type="text/javascript">
function onsub(obj){
window.location.href="<c:url value='/PageServlet?page='></c:url>"+obj.value;
}
</script>
</head>
<body>
<h3>以下是当前页的内容</h3>
<form action="<c:url value='/PageServlet'/>" method="post" >
请输入要查询的关键字：<br/>
学号:<input type="text" name="serachId" value="${stud.id }"><br/>
姓名:<input type="text" name="serachName" value="${stud.name }"><br/>
<input type="submit" value="搜索">
</form>
<table>
<c:if test="${!empty map.datas}">
<tr>
<th>学号</th>
<th>姓名</th>
</tr>
</c:if>
<c:forEach items="${map.datas}" var="stud">
<tr>
<td>${stud.id }</td>
<td>${stud.name }</td>
</tr>
</c:forEach>
</table>
<c:if test="${map.currentPage!=1}" var="boo">
<a href="<c:url value='/PageServlet?page=${map.currentPage-1}'></c:url>" >上一页</a>
</c:if>
<c:forEach var="idx" begin="${map.showStart }" end="${map.showEnd }">
<c:if test="${map.currentPage==idx}" var="boo">
<font face="STCAIYUN"><a
href="<c:url value='/PageServlet?page=${idx}'></c:url>">${idx}</a>
</font>
</c:if>
<c:if test="${!boo}">
<a href="<c:url value='/PageServlet?page=${idx}'></c:url>">${idx}</a>
</c:if>
</c:forEach>
<c:if test="${map.currentPage!=map.pageCount}" var="boo">
<a href="<c:url value='/PageServlet?page=${map.currentPage+1}'></c:url>">下一页</a>
</c:if>
<br/>
<br/>
<br/>
<select onchange="onsub(this)">
<c:forEach var="i" begin="1" end="${map.pageCount }">
<option <c:if test="${i==map.currentPage }" >selected="selected" </c:if> value="${i}" >
<a href="<c:url value='/PageServlet?page=${i}'></c:url>">第 ${i } 页</a>
</option>
</c:forEach>
</select>
</body>
</html></span>

table.css

[html] view
plain copy

Mysql学习总结（32）——MySQL分页技术详解

<span style="font-size:12px;">table{
color: green;
border: 1px solid blue;
border-collapse: collapse;
width:500px;
margin: auto;
}
td{
border: 1px solid blue;
}
th{
border: 1px solid blue;
}
body{
text-align: center;
}</span>

PageServlet.Java

[html] view
plain copy

Mysql学习总结（32）——MySQL分页技术详解

<span style="font-size:12px;">package cn.hncu.page1.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.page1.domain.Stud;
import cn.hncu.page1.service.IPageService;
import cn.hncu.page1.service.PageService;
public class PageServlet extends HttpServlet {
private IPageService service=new PageService();
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
//这里是搜索区域的操作
Stud stud=null;
if(request.getMethod().equals("POST")){
if (stud==null) {
stud = new Stud();
}
String serachId = request.getParameter("serachId");
String serachName = request.getParameter("serachName");
stud.setId(serachId);
stud.setName(serachName);
request.getSession().setAttribute("stud", stud);
}else{
stud=(Stud) request.getSession().getAttribute("stud");
if (stud==null) {
stud = new Stud();
}
}
//封装studs对象
int currentPage=1;
try {
currentPage = Integer.parseInt(request.getParameter("page"));
} catch (NumberFormatException e) {
currentPage=1;
}
Map<String, Object> map=null;
try {
map=service.query(currentPage,stud);
} catch (SQLException e) {
e.printStackTrace();
}
map.put("currentPage", currentPage);
//显示滚动页号
int showStart=0;//从第几个页号开始显示
int showEnd=0;//从第几个页号结束显示
int showSize=10;//显示多少页数
int pageCount=Integer.parseInt(""+map.get("pageCount"));
if(showSize>pageCount){//显示页数大于于总页数
showStart=1;
showEnd=pageCount;
}else{
if(currentPage<=showSize/2){
showStart=1;
showEnd=showSize;
}else{
showStart=currentPage-showSize/2;
showEnd=showStart+showSize-1;
}
}
if(showEnd>pageCount){
showEnd=pageCount;
showStart=showEnd-showSize;
}
map.put("showStart", showStart);
map.put("showEnd", showEnd);
request.setAttribute("map", map);
request.getRequestDispatcher("/jsps/show.jsp").forward(request, response);
}
}</span>

IPageService.java

[html] view
plain copy

Mysql学习总结（32）——MySQL分页技术详解

<span style="font-size:12px;">package cn.hncu.page1.service;
import java.sql.SQLException;
import java.util.Map;
import cn.hncu.page1.domain.Stud;
public interface IPageService {
public Map<String, Object> query(int currentPage, Stud stud) throws SQLException;
}</span>

PageService.java

[html] view
plain copy

Mysql学习总结（32）——MySQL分页技术详解

<span style="font-size:12px;"> package cn.hncu.page1.service;
import java.sql.SQLException;
import java.util.Map;
import cn.hncu.page1.dao.PageDao;
import cn.hncu.page1.dao.PageDaoJdbc;
import cn.hncu.page1.domain.Stud;
public class PageService implements IPageService{
private PageDao dao=new PageDaoJdbc();
@Override
public Map<String, Object> query(int currentPage, Stud stud)
throws SQLException {
return dao.query(currentPage,stud);
}
}</span>

PageDao.java

[html] view
plain copy

Mysql学习总结（32）——MySQL分页技术详解

<span style="font-size:12px;">package cn.hncu.page1.dao;
import java.sql.SQLException;
import java.util.Map;
import cn.hncu.page1.domain.Stud;
public interface PageDao {
public Map<String, Object> query(int currentPage, Stud stud) throws SQLException;
}</span>

PageDaoJdbc.java

[html] view
plain copy

Mysql学习总结（32）——MySQL分页技术详解

<span style="font-size:12px;">package cn.hncu.page1.dao;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.sql.DataSource;
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.page1.domain.Stud;
import cn.hncu.page1.service.IPageService;
import cn.hncu.pool.C3p0Pool;
public class PageDaoJdbc implements PageDao{
private static final int PAGE_SIZE=10;
@Override
public Map<String, Object> query(int currentPage, Stud stud) throws SQLException {
Map<String, Object> map=new HashMap<String, Object>();
DataSource pool=C3p0Pool.getPool();
QueryRunner qr=new QueryRunner(pool);
String sql="select count(*) from stud where 1=1 ";
if(stud.getId()!=null&&stud.getId().trim().length()>0){
sql+="and id like '%"+stud.getId()+"%'";
}
if(stud.getName()!=null&&stud.getName().trim().length()>0){
sql+="and name like '%"+stud.getName()+"%'";
}
int rows=Integer.parseInt(""+ qr.query(sql, new ScalarHandler()));
int pageCount=rows/PAGE_SIZE+((rows%PAGE_SIZE==0)?0:1);
map.put("pageCount", pageCount);
int startRow=(currentPage-1)*PAGE_SIZE;
map.put("startRow", startRow);
String sql2="select * from stud where 1=1 ";//这种判断方法，很不错
if(stud.getId()!=null&&stud.getId().trim().length()>0){
sql2+="and id like '%"+stud.getId()+"%'";
}
if(stud.getName()!=null&&stud.getName().trim().length()>0){
sql2+="and name like '%"+stud.getName()+"%' ";
}
sql2+="limit "+startRow+" , "+PAGE_SIZE;
List<Map<String, Object>> datas=qr.query(sql2, new MapListHandler());
map.put("datas", datas);
return map;
}
}</span>

Stud.java

[html] view
plain copy

Mysql学习总结（32）——MySQL分页技术详解

<span style="font-size:12px;">package cn.hncu.page1.domain;
public class Stud {
private String id;
private String name;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Stud [id=" + id + ", name=" + name + "]";
}
}

秒客网

Mysql学习总结（32）——MySQL分页技术详解

相关文章