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页面分页实现详解编程语言

• 编程笔记

分页：
页面上需要显示的查询结果太多了，应该分为多页显示

数据库分页:
根据用户想查看的页码去数据库中查询对应的数据
用户访问第一页时，查询0~9条记录
用户访问第二页时，查询10~19条记录
数据库分页语句 select * from tableName limit 0,9;

数据库分页的实现步骤:
1. 进行需求分析
2. 根据需求建立模型 设计javabean
class Page {
private List pageData; // 页面显示的用户(10个)
private int pageNum; // 当前页码
private int totalRecord; // 总记录数
private int totalPageNum; // 总页数
}
3. 实现dao
getPageData()
getTotalRecords()
4. 实现service
查询分页数据
Page getPage(int pageNum);
pageData 查询数据库 调用dao
pageNum 参数
totalRecord 查询数据库 调用dao
totalPageNum 计算
5. servlet+jsp
获得用户指定的页码
调用service查询分页数据
将分页数据转发给jsp显示

准备jar包：
c3p0-0.9.2-pre5.jar：
commons-dbutils-1.4.jar
commons-logging-1.1.1.jar
mchange-commons-java-0.2.3.jar
mysql-connector-java-5.1.22-bin.jar
jstl.jar standard.jar（引入jstl）

准备数据库：

create database pagedb; 
 
use pagedb; 
 
create table users( 
    id int primary key auto_increment, 
    username varchar(50), 
    password varchar(32), 
    gender varchar(1),   
    age int  
); 
 
insert into users(username, password,gender, age) 
values('Tim1','1234','男',10); 
insert into users(username, password,gender, age) 
values('Tim2','1234','女',11); 
insert into users(username, password,gender, age) 
values('Tim3','1234','男',12); 
insert into users(username, password,gender, age) 
values('Tim4','1234','女',13); 
insert into users(username, password,gender, age) 
values('Tim5','1234','男',14); 
insert into users(username, password,gender, age) 
values('Tim6','1234','女',15); 
insert into users(username, password,gender, age) 
values('Tim7','1234','男',16); 
insert into users(username, password,gender, age) 
values('Tim8','1234','女',17); 
insert into users(username, password,gender, age) 
values('Tim9','1234','男',18); 
insert into users(username, password,gender, age) 
values('Tim19','1234','男',19); 
insert into users(username, password,gender, age) 
values('Tim11','1234','男',20); 
insert into users(username, password,gender, age) 
values('Tim12','1234','女',21); 
insert into users(username, password,gender, age) 
values('Tim13','1234','男',22); 
insert into users(username, password,gender, age) 
values('Tim14','1234','女',23); 
insert into users(username, password,gender, age) 
values('Tim15','1234','男',24); 
insert into users(username, password,gender, age) 
values('Tim16','1234','女',25); 
insert into users(username, password,gender, age) 
values('Tim17','1234','男',26); 
insert into users(username, password,gender, age) 
values('Tim18','1234','女',27); 
insert into users(username, password,gender, age) 
values('Tim19','1234','男'28);

项目结构：
这里写图片描述

实现代码：
User bean:

package com.page.bean; 
 
public class User { 
    private int id; 
    private String username; 
    private String password; 
    private String gender; 
    private int  age; 
 
    public int getId() { 
        return id; 
    } 
    public void setId(int id) { 
        this.id = id; 
    } 
    public String getUsername() { 
        return username; 
    } 
    public void setUsername(String username) { 
        this.username = username; 
    } 
    public String getPassword() { 
        return password; 
    } 
    public void setPassword(String password) { 
        this.password = password; 
    } 
    public String getGender() { 
        return gender; 
    } 
    public void setGender(String gender) { 
        this.gender = gender; 
    } 
    public int getAge() { 
        return age; 
    } 
    public void setAge(int age) { 
        this.age = age; 
    } 
 
}

Page Bean:

package com.page.bean; 
 
import java.util.List; 
 
public class Page { 
 
    private List<?> pageData;   // 页面实现的用户 
    private int pageNum;    // 当前页码 
    private int totalRecord;    // 总记录数 
    private int totalPageNum;   // 总页数 
    private int firstPageNum;   // 起始页码 
    private int lastPageNum;    // 结束页码 
    public List<?> getPageData() { 
        return pageData; 
    } 
    public void setPageData(List<?> pageData) { 
        this.pageData = pageData; 
    } 
    public int getPageNum() { 
        return pageNum; 
    } 
    public void setPageNum(int pageNum) { 
        this.pageNum = pageNum; 
    } 
    public int getTotalRecord() { 
        return totalRecord; 
    } 
    public void setTotalRecord(int totalRecord) { 
        this.totalRecord = totalRecord; 
    } 
    public int getTotalPageNum() { 
        return totalPageNum; 
    } 
    public void setTotalPageNum(int totalPageNum) { 
        this.totalPageNum = totalPageNum; 
    } 
    public int getFirstPageNum() { 
        return firstPageNum; 
    } 
    public void setFirstPageNum(int firstPageNum) { 
        this.firstPageNum = firstPageNum; 
    } 
    public int getLastPageNum() { 
        return lastPageNum; 
    } 
    public void setLastPageNum(int lastPageNum) { 
        this.lastPageNum = lastPageNum; 
    } 
 
}

c3p0-config.xml:

<c3p0-config> 
    <!-- 默认配置，如果没有指定则使用这个配置 --> 
    <default-config> 
        <property name="driverClass">com.mysql.jdbc.Driver</property> 
        <property name="jdbcUrl">jdbc:mysql://localhost:3306/pagedb</property> 
        <property name="user">root</property> 
        <property name="password">1234</property> 
    <!-- 如果池中数据连接不够时一次增长多少个 --> 
        <property name="acquireIncrement">5</property> 
        <property name="initialPoolSize">20</property> 
        <property name="minPoolSize">10</property> 
        <property name="maxPoolSize">40</property> 
        <property name="maxStatements">0</property> 
        <property name="maxStatementsPerConnection">5</property> 
    </default-config>  
</c3p0-config>

JdbcUtils:

package com.page.utils; 
 
import javax.sql.DataSource; 
 
import com.mchange.v2.c3p0.ComboPooledDataSource; 
 
public class JdbcUtils { 
 
    private static ComboPooledDataSource dataSource; 
 
    static { 
            dataSource = new ComboPooledDataSource(); 
    } 
 
    public static DataSource getDataSource(){ 
            return dataSource; 
    } 
 
}

PageDao:

package com.page.dao; 
 
import java.sql.SQLException; 
import java.util.List; 
 
import org.apache.commons.dbutils.QueryRunner; 
import org.apache.commons.dbutils.handlers.BeanListHandler; 
import org.apache.commons.dbutils.handlers.ScalarHandler; 
 
import com.page.bean.User; 
import com.page.utils.JdbcUtils; 
 
public class PageDao { 
 
    //查询总记录数 
    public int getTotalRecords() throws SQLException{ 
        String sql =  "select count(1) from users"; 
        QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());     
        long totalRecords =  (long) runner.query(sql, new ScalarHandler("count(1)")); 
        return (int) totalRecords; 
    } 
 
    //查询分页数据 
    public List<User> getPageData(int start, int length) throws SQLException{ 
        String sql = "select id,username,gender, age from users limit ?,?"; 
        Object[] params = new Object[]{start, length}; 
        QueryRunner runner = new QueryRunner(JdbcUtils.getDataSource());     
        List<User> dataList = runner.query(sql, new BeanListHandler(User.class),params); 
        return dataList; 
    } 
 
}

PageService:

package com.page.service; 
 
import java.sql.SQLException; 
import java.util.List; 
 
import com.page.bean.Page; 
import com.page.bean.User; 
import com.page.dao.PageDao; 
 
public class PageService { 
 
    private PageDao pageDao = new PageDao(); 
 
    public Page getPage(int pageNum, int count) throws SQLException { 
        // 查询总记录数 
        int totalRecord = pageDao.getTotalRecords(); 
        // 计算总页数 11/10 =1 11+9/10=2 19+9/10=2 20+9/10=2 
        int totalPageNum = (totalRecord + count - 1) / count; 
        // 查询分页显示的用户 
        // 1 0 2 10 3 20 
        int start = (pageNum - 1) * count; 
 
        List<User> pageData = pageDao.getPageData(start, count); 
 
        //页数很多的时候的，只显示前5页和最后5页的处理 
        // 计算 起始页码和结束页码 
        int firstPageNum = pageNum - 4; 
        int lastPageNum = pageNum + 5; 
        // 特殊情况判断 
        if (firstPageNum < 1) { 
            firstPageNum = 1; 
            lastPageNum = 10; 
        } 
        if (lastPageNum > totalPageNum) { 
            lastPageNum = totalPageNum; 
            firstPageNum = lastPageNum - 9; 
        } 
        if (totalPageNum < 10) { 
            firstPageNum = 1; 
            lastPageNum = totalPageNum; 
        } 
        Page page = new Page(); 
        page.setPageData(pageData); 
        page.setPageNum(pageNum); 
        page.setTotalPageNum(totalPageNum); 
        page.setTotalRecord(totalRecord); 
        page.setFirstPageNum(firstPageNum); 
        page.setLastPageNum(lastPageNum); 
 
        return page; 
    } 
 
}

UserListServlet:

package com.page.servlet; 
 
import java.io.IOException; 
import java.sql.SQLException; 
 
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.page.bean.Page; 
import com.page.service.PageService; 
 
@WebServlet("/userListServlet") 
public class UserListServlet extends HttpServlet { 
    private static final long serialVersionUID = 1L; 
 
    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.setContentType("text/html;charset=UTF-8"); 
        // 1 获得请求参数 
        int pageNum = 1; 
        String pageNumValue = request.getParameter("pageNum"); 
        if (pageNumValue != null) { 
            pageNum = Integer.parseInt(pageNumValue); 
        } 
        // 2 调用service 
        PageService pageService = new PageService(); 
 
        try { 
            Page page = pageService.getPage(pageNum, 5);//5  每页显示的记录数 
            // 3 请求转发 
            request.setAttribute("page", page); 
            request.getRequestDispatcher("/WEB-INF/pages/listuser.jsp").forward(request, response); 
        } catch (SQLException e) { 
            throw new RuntimeException(e); 
        } 
 
    } 
 
}

listUser jsp:

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> 
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 
<html> 
<head> 
<title>显示所有的用户</title> 
<script type="text/javascript"> 
function jump(pageNum){ 
window.location = "${pageContext.request.contextPath}/userListServlet?pageNum=" + pageNum; 
} 
function go() { 
var num = document.getElementById("num").value; 
var totalPageNum = ${page.totalPageNum}; 
if(num==null || num.match(/^[1-9][0-9]*$/)==null || num>totalPageNum) { 
num = 1; 
} 
jump(num); 
} 
</script> 
</head> 
<br><b>分页显示用户</b><hr> 
<body style="padding-left: 20%;padding-right: 20%"> 
<table border="1" width="600px" > 
<tr> 
<td>编号</td> 
<td>用户名</td> 
<td>性别</td> 
<td>年龄</td> 
</tr> 
<c:forEach items="${page.pageData}" var="user" varStatus="vs"> 
<tr> 
<td>${user.id}</td> 
<td><c:out value="${user.username}" ></c:out> </td> 
<td><c:out value="${user.gender}"></c:out> </td> 
<td><c:out value="${user.age}"></c:out> </td> 
</tr> 
</c:forEach> 
</table> 
<br><br> 
<a href="javascript:jump(1)">首页</a> 
<c:if test="${page.pageNum>1 }"> 
<a href="javascript:jump(${page.pageNum-1 })">上一页</a> 
</c:if> 
<c:forEach var="num" begin="${page.firstPageNum }" end="${page.lastPageNum }"> 
<c:choose> 
<c:when test="${num==page.pageNum }"> 
[ ${num } ] 
</c:when> 
<c:otherwise> 
[ <a href="javascript:jump(${num })">${num }</a> ] 
</c:otherwise> 
</c:choose> 
</c:forEach> 
<c:if test="${page.pageNum<page.totalPageNum }"> 
<a href="javascript:jump(${page.pageNum+1 })">下一页</a> 
</c:if> 
<a href="javascript:jump(${page.totalPageNum })">尾页</a> 
<br> 
当前第  ${requestScope.page.pageNum }  页 
总共 ${page.totalPageNum }   页 
总共 ${page.totalRecord }   条记录 
跳转至    
<input id="num" type="text" value="${page.pageNum }" style="width:50px;" /> 
<input type="button" value="GO" onclick="go()" /> 
</body> 
<br><hr> 
</html>

页面效果：
这里写图片描述

原创文章，作者：ItWorker，如若转载，请注明出处：https://blog.ytso.com/12065.html

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