02_分页_01_简单设计

【分页流程图】



【数据库设计】

设计字段



传入一些数据



【工程截图】



一. domain层

【User.java】

public class User {
private int id;
private String name;
private String sex;
private String phone;
private String email;
　　.......忽略get和set方法
}

【QueryInfo.java】前端发送给Servlet的请求数据

package com.Higgin.page.domain;

/**
* 分页界面传递过来的数据
* @author YH
*
*/
public class QueryInfo {
private int currentpage=1; //用户当前看的页 ，默认为1
private int pagesize=5;   //记住用户想看的页面大小，默认为5（1页5行）
private int startindex;   //记住用户看的页的数据在数据库的起始位置

......//忽略currentpage和pagesize的get和set方法。

　　public int getStartindex() {
this.startindex=(this.currentpage-1)*this.pagesize;
return startindex;
}

}

【QueryResult.java】从数据库查询返回的结果，在UserDao体现！

package com.Higgin.page.domain;

import java.util.List;

/**
* 从数据库中查询的数据
* @author YH
*
*/
public class QueryResult {
private List list;        //记住用户看的页的数据
private int totalrecord;//记住总记录数
........忽略两者的get和set方法
}

【PageBean.java】在UserService层体现！

package com.Higgin.page.domain;

import java.util.Arrays;
import java.util.List;

/**
* 返回给分页前端界面的对象
* @author YH
*
*/
public class PageBean {
private List list;
private int totalrecord;  //总记录数
private int pagesize;      //每页显示的记录数
private int totalpage;    //总页数，可根据总记录数和每页记录数算出，无需set方法
private int currentpage;  //当前页
private int previouspage; //上一页  无需set方法
private int nextpage;      //下一页 无需set方法
private int[] pagebar;    //页码条

　　public List getList() {
return list;
}
public void setList(List list) {
this.list = list;
}

public int getTotalrecord() {
return totalrecord;
}
public void setTotalrecord(int totalrecord) {
this.totalrecord = totalrecord;
}

public int getPagesize() {
return pagesize;
}
public void setPagesize(int pagesize) {
this.pagesize = pagesize;
}
//总页数
public int getTotalpage() {
//假如100条数据 每页显示5条  共显示20页
//   101           5       21
//      99           5       20
if(this.totalrecord%this.pagesize==0){
this.totalpage=this.totalrecord/this.pagesize;
}else{
this.totalpage=this.totalrecord/this.pagesize+1;
}
return totalpage;
}

public int getCurrentpage() {
return currentpage;
}
public void setCurrentpage(int currentpage) {
this.currentpage = currentpage;
}

//上一页
public int getPreviouspage() {
if(this.currentpage-1<1){
this.previouspage=1;
}else{
this.previouspage=this.currentpage-1;
}
return previouspage;
}
//下一页
public int getNextpage() {
if(this.currentpage+1>=this.totalpage){
this.nextpage=this.currentpage;
}else{
this.nextpage=this.currentpage+1;
}
return nextpage;
}

//页码条
public int[] getPagebar() {
int pagebar[] = new int[this.totalpage]; //数组的长度即为 总页数this.totalpage
for(int i=1;i<=this.totalpage;i++){
pagebar[i-1] = i;
}
this.pagebar = pagebar;
return pagebar;
}
}

前端页面需要的数据如下图所示（对应PageBean）：



二.数据库连接相关

【db.properties】

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/paging
username=root
password=

【JdbcUtils.java】

package com.Higgin.page.utils;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class JdbcUtils {

private static Properties config = new Properties();
static{
try {
config.load(JdbcUtils.class.getClassLoader().getResourceAsStream("db.properties"));
Class.forName(config.getProperty("driver"));
} catch (Exception e) {
throw new ExceptionInInitializerError(e);
}
}

public static Connection getConnection() throws SQLException{
return DriverManager.getConnection(config.getProperty("url"), config.getProperty("username"), config.getProperty("password"));
}

public static void release(Connection conn,Statement st,ResultSet rs){
if(rs!=null){
try{
rs.close();   //throw new
}catch (Exception e) {
e.printStackTrace();
}
rs = null;
}
if(st!=null){
try{
st.close();
}catch (Exception e) {
e.printStackTrace();
}
st = null;
}
if(conn!=null){
try{
conn.close();
}catch (Exception e) {
e.printStackTrace();
}
}
}
}

三.Dao层

【UserDao.java】

package com.Higgin.page.dao;

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

import org.junit.Test;

import com.Higgin.page.domain.QueryResult;
import com.Higgin.page.domain.User;
import com.Higgin.page.utils.JdbcUtils;

public class UserDao {

//获取当前页数据和页面大小
public QueryResult pageQuery(int startindex,int pagesize){
Connection conn=null;
PreparedStatement st=null;
ResultSet rs=null;

QueryResult qr=new QueryResult();
try{
conn=JdbcUtils.getConnection();
String sql="select * from user limit ?,?";
st=conn.prepareStatement(sql);
st.setInt(1, startindex);  //从数据库user表的第startindex条数据开始查询
st.setInt(2, pagesize);    //根据页面的展示条数pagesize来获取对应的user数据记录数量
rs=st.executeQuery();
List list=new ArrayList();
while(rs.next()){
User u =new User();
u.setId(rs.getInt("id"));
u.setName(rs.getString("name"));
u.setSex(rs.getString("sex"));
u.setPhone(rs.getString("phone"));
u.setEmail(rs.getString("email"));  //一步步封装好User
list.add(u);  //每次封装出一条User数据，存放在list中
}
qr.setList(list);  //然后将list数据传递到QueryResult中

sql="select count(*) from user";
rs=conn.prepareStatement(sql).executeQuery();
if(rs.next()){
qr.setTotalrecord(rs.getInt(1));  //将获取的user表的总记录数rs.getInt(1)传递到QueryResult中
}
return qr;    //执行成功，就返回一个QueryResult对象数据
}catch(Exception e){
throw new RuntimeException(e);
}finally{
JdbcUtils.release(conn, st, rs);
}
}

}

四.Service层

【UserService.java】

package com.Higgin.page.service;

import com.Higgin.page.dao.UserDao;
import com.Higgin.page.domain.PageBean;
import com.Higgin.page.domain.QueryInfo;
import com.Higgin.page.domain.QueryResult;

//得到页面的查询条件，查询数据库，返回页面所需的数据
public class UserService {
private UserDao userDao =new UserDao();
//传入参数为QueryInfo
public PageBean pageQuery(QueryInfo queryInfo){
//调用dao获取到返回页面的数据
QueryResult qr=userDao.pageQuery(queryInfo.getStartindex(), queryInfo.getPagesize());

//根据dao的查询的QueryResult结果和传入参数的QueryInfo,封装成页面显示所需的PageBean！！！！！！！！！！！！！！！！！！！
PageBean bean=new PageBean();
bean.setCurrentpage(queryInfo.getCurrentpage());
bean.setList(qr.getList());
bean.setPagesize(queryInfo.getPagesize());
bean.setTotalrecord(qr.getTotalrecord());

return bean;
}
}

五.controller层

【ListUserServlet.java】(注解方式的Servlet)

package com.Higgin.page.controller;

import java.io.IOException;

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.Higgin.page.domain.PageBean;
import com.Higgin.page.domain.QueryInfo;
import com.Higgin.page.service.UserService;

//处理用户分页请求
@WebServlet("/ListUserServlet") //请求的路径为 http://localhost:8080/PagingTest00/ListUserServlet public class ListUserServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private UserService userService=new UserService();
public ListUserServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

　　　 　 QueryInfo queryInfo=new QueryInfo();

//获取前端发送过来的currentpage和pagesize请求数据，封装在queryInfo中
String curentpage=request.getParameter("currentpage");
if(curentpage!=null){
queryInfo.setCurrentpage(Integer.parseInt(curentpage));
}
String pagesize=request.getParameter("pagesize");
if(pagesize!=null){
queryInfo.setPagesize(Integer.parseInt(pagesize));
}

　　　　　//调用userService的pageQuery方法，参数为封装好的前端请求的queryInfo，返回值是封装好返回给前端页面的pageBean
PageBean pageBean=userService.pageQuery(queryInfo);

request.setAttribute("pageBean", pageBean);
request.getRequestDispatcher("/WEB-INF/listUser.jsp").forward(request, response);
}

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request,response);
}

}

六.前端页面展示

【index.jsp】关键代码

<body>
This is my JSP page. <br>
<a href="${pageContext.request.contextPath }/ListUserServlet" target="main">查看客户</a>

</body>

【listUser.jsp】

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

<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

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

</head>

<body>
<table frame="border" width="85%">
<tr>

<td>客户姓名</td>
<td>性别</td>
<td>手机</td>
<td>邮箱</td>
<tr>

<c:forEach var="c" items="${requestScope.pageBean.list}" varStatus="status">
<tr>
<td>${c.name }</td>
<td>${c.sex }</td>
<td>${c.phone }</td>
<td>${c.email }</td>
</tr>
</c:forEach>

</table>
<br>

<script type="text/javascript">
function gotopage(currentpage){
window.location.href='${pageContext.request.contextPath}/ListUserServlet?currentpage='+currentpage;
}
</script>
共[${pageBean.totalrecord }]条记录,
每页<input type="text" id="pagesize" value="${pageBean.pagesize }" style="width: 30px" maxlength="2">条,
共[${pageBean.totalpage }]页,
当前[${pageBean.currentpage }]页
   
<a href="javascript:void(0)" onclick="gotopage(${pageBean.previouspage})">上一页</a>
<c:forEach var="pagenum" items="${pageBean.pagebar}">
<a href="javascript:void(0)" onclick="gotopage(${pagenum})">${pagenum} </a>
</c:forEach>
 
<a href="javascript:void(0)" onclick="gotopage(${pageBean.nextpage})">下一页</a>
</body>
</html>

【运行结果】

首先输入http://localhost:8080/PagingTest00，进入了index.jsp





点击“查看客户”，访问路径为http://localhost:8080/PagingTest00/ListUserServlet，访问ListUserServlet.java，然后跳转至listUser.jsp，如下



点击“上一页”、“下一页”、“1 2 3 4 5 6 7”等等都会有不同的变化，并且“当前[X]页”也会相应变化。