Demo之JavaEE的Web中数据分页显示

JavaWeb分页技术

关于java web上实现分页技术，方式实际上有很多，也各有特点，此处我只写我的认识。Java web分页无外乎两种，一种直接取出来，放到一个集合了，通过传begin和end参数控制分页，还有一种就是把分页工作交给数据库，让数据库读取需要的begin和end直接的数据。

我使用的是后一种方式就是将分页的工作交给了数据库：我使用的是MySQL数据库

页面显示效果：

页面代码：

<form action="PageServlet" method="post" id="myform">
        <table border="1">
            <c:forEach items="${pageBean.arrayObjs }" var="obj">
                <tr>
                    <td>${obj }</td>
                </tr>
            </c:forEach>
            <tr>
                <td colspan="3">
                
                    跳转到：<input id="currentPageNum" type="text" name="currentPageNum" value="${pageBean.currentPageNum }" />
                    每页记录数：<input type="text" name="pageCount" value="${pageBean.pageCount }" />
                    <br />
                    <input type="submit" value="跳转" />
                    共有${pageBean.totalPage }
                    <c:if test="${pageBean.previous }">
                        <a onclick="page(${pageBean.currentPageNum}-1);">上一页</a>
                    </c:if>
                    <c:if test="${pageBean.next }">
                        <a onclick="page(${pageBean.currentPageNum}+1);">下一页</a>
                    </c:if>
                    <a onclick="page(${pageBean.totalPage});">最后一页</a>
                </td>
            </tr>
        </table>
    </form>

Servlet中的Post方法的代码：

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        
        EmpBiz biz=new EmpBiz();
        
        int currentPageNum=1;
        int pageCount=4;
        
        String currentPageNumStr=request.getParameter("currentPageNum");
        
        String pageCountStr=request.getParameter("pageCount");
        if(currentPageNumStr!=null){
            
            currentPageNum=Integer.parseInt(currentPageNumStr);
        }
        if(pageCountStr!=null){
            
            pageCount=Integer.parseInt(pageCountStr);
        }
        
        PageBean pageBean = biz.lisEmps(currentPageNum, pageCount);
        
        request.setAttribute("pageBean", pageBean);
        request.getRequestDispatcher("list.jsp").forward(request, response);
    }

 

在这里自己写了一个存储数据的类PageBean

package com.leejie.page.bean;

import java.util.List;

public class PageBean {

    private List arrayObjs;    //从数据库中读出的集合
    private int totalCount;            //总条数
    private int currentPageNum;            //页数
    private int pageCount;            //每页的条数
    
    public PageBean(List arrayObjs,int pageCount,int currentPageNum,int totalCount){
        
        this.arrayObjs=arrayObjs;
        this.pageCount=pageCount;
        this.currentPageNum=currentPageNum;
        this.totalCount=totalCount;
    }
    
    
    public List getArrayObjs() {
        return arrayObjs;
    }
    
    public void setArrayObjs(List arrayObjs) {
        this.arrayObjs = arrayObjs;
    }
    
    public int getTotalCount() {
        return totalCount;
    }
    
    public void setTotalCount(int totalCount) {
        this.totalCount = totalCount;
    }
    
    public int getPageCount() {
        return pageCount;
    }
    
    public void setPageCount(int pageCount) {
        this.pageCount = pageCount;
    }

    public int getCurrentPageNum() {
        return currentPageNum;
    }

    public void setCurrentPageNum(int currentPageNum) {
        this.currentPageNum = currentPageNum;
    }
    
    public int getTotalPage(){
        
        if(this.totalCount%this.pageCount==0){
            
            return this.totalCount/this.pageCount;
        }else{
            
            return this.totalCount/this.pageCount+1;
        }
    }
    
    public boolean isNext(){
        
        return this.currentPageNum<this.getTotalPage();
    }
    
    public boolean isPrevious(){
        
        return this.currentPageNum>1;
    }
}

写了一个数据访问层的类EmpBiz：

 

package com.leejie.page.biz;

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

import com.leejie.dbcon.util.DBCon;
import com.leejie.page.bean.PageBean;

public class EmpBiz {
    
    public EmpBiz(){
        
    }

    public PageBean lisEmps(int currentPageNum,int pageCount){
        
        List emps = new ArrayList();
        
        int a = currentPageNum;
        int b = pageCount;
        String sql="select * from scores limit ?,?";
        
        PreparedStatement ps=DBCon.getPreparedStatement(sql);
        try {
            
            ps.setInt(1, a);
            ps.setInt(2, b);
            ResultSet rs=ps.executeQuery();
            int i=10;
            while(rs.next()){
    
                emps.add(i);
                i+=5;
            }
            
        
        
        String sqlTotal="select count(*) from scores";
        PreparedStatement psTotal = DBCon.getPreparedStatement(sqlTotal);
        int totalCount=0;
        
            ResultSet rsTotal=psTotal.executeQuery();
            while(rsTotal.next()){
                totalCount=rsTotal.getInt(1);
            }
            
        PageBean pageBean=new PageBean(emps, pageCount, currentPageNum, totalCount);
        
        return pageBean;
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            DBCon.close();
        }
        return null;
    }
}

还需要用到一个访问数据库的工具类：DBCon，这里也贴出来了：

package com.leejie.dbcon.util;

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

public class DBCon {

    private static final String DRIVERNAME="com.mysql.jdbc.Driver";
    private static final String URL="jdbc:mysql://localhost:3306/school";
    private static final String USERNAME="root";
    private static final String PASSWORD="li257298";
    
    private static Connection conn;
    private static PreparedStatement ps;
    
    static{
        try {
            Class.forName(DRIVERNAME);
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    
    public static Connection getConnection() {
        
        try {
            conn=DriverManager.getConnection(URL,USERNAME,PASSWORD);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return conn;
    }
    
    public static PreparedStatement getPreparedStatement(String sql){
        
        try {
            ps=getConnection().prepareStatement(sql);
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return ps;
    }
    
    public static void close(){
        
        if(ps!=null){
            try {
                ps.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(conn!=null){
            try {
                conn.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }
}