输入框实现新闻列表分页显示（一）

今天学了新闻发布系统中的使用分页技术实现页面的分页显示，感觉开始很难做，渐渐的需要动手，慢慢透析。

分页显示的步骤

1、确定每页显示的数据数量

2、计算显示的页数

3、编写SQL语句

 

第一步：连接数据库

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.util.ArrayList;

import java.util.List;







/**

 * 数据库连接帮助类

 * @author zql_pc

 * 单例设计模式

 */

public class DbHelp {



    

    //数据库连接对象

    private Connection conn = null;





    //数据库连接帮助

    public Connection lianjie() {

        

        if(conn==null){

        

            //数据库配置

            String driver = "oracle.jdbc.driver.OracleDriver";//驱动

            String url = "jdbc:oracle:thin:@localhost:1521:NEWS";//url

            String username = "epet";//用户名

            String password = "123456";//密码

            

            //1.加载驱动类

            try {

                Class.forName(driver);

                //2.建立连接

                conn = DriverManager.getConnection(url,username,password);

            } catch (ClassNotFoundException e) {

                e.printStackTrace();

            } catch (SQLException e) {

                e.printStackTrace();

            }

            

        }

        

        return conn;

        

    }

    

    

}

第二步：编写新闻实体类，进行封装

/**

 * 新闻实体类

 * @author zql_pc

 *

 */

public class news {



    private int id;

    private int t_id;

    private String title;

    private String author;

    private String createdate;

    private String picpath;

    private String content;

    private String modifydate;

    private String summay;

    

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public int getT_id() {

        return t_id;

    }

    public void setT_id(int tId) {

        t_id = tId;

    }

    public String getTitle() {

        return title;

    }

    public void setTitle(String title) {

        this.title = title;

    }

    public String getAuthor() {

        return author;

    }

    public void setAuthor(String author) {

        this.author = author;

    }

    public String getCreatedate() {

        return createdate;

    }

    public void setCreatedate(String createdate) {

        this.createdate = createdate;

    }

    public String getPicpath() {

        return picpath;

    }

    public void setPicpath(String picpath) {

        this.picpath = picpath;

    }

    public String getContent() {

        return content;

    }

    public void setContent(String content) {

        this.content = content;

    }

    public String getModifydate() {

        return modifydate;

    }

    public void setModifydate(String modifydate) {

        this.modifydate = modifydate;

    }

    public String getSummay() {

        return summay;

    }

    public void setSummay(String summay) {

        this.summay = summay;

    }

}

第三步：查询新闻

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.ArrayList;

import java.util.List;



/**

 * 查询新闻

 * @author zql_pc

 *

 */

public class SelectNews {

    

    DbHelp help = new DbHelp();

    

    //查询新闻数目

    public int newsCount() throws SQLException{

        //查询新闻条目

        Connection con = help.lianjie();

        

        //创建数据库操作对象

        Statement st = con.createStatement();

        

        String sql = "select count(*) from news";

        

        //获得结果集

        ResultSet rs = st.executeQuery(sql);

        

        //新闻数目

        int newsCount = 0;

        

        while(rs.next()){

            

            newsCount = rs.getInt(1);

            

        }

        

        return newsCount;

    }

    

    //计算分页

    public int getPages(int newsSize) throws SQLException{

        

        

        int newsCount = newsCount();

        

        int num = (newsCount%newsSize==0)?newsCount/newsSize:newsCount/newsSize+1;

        

        return num;

    }

    

    //根据要求查询新闻

    public List<news> getList(int pageIndex,int newsSize) throws SQLException{

        

        //计算上限和下限 

        //第1页  1 - 5

        //  2   6 - 10

        int up = newsSize * pageIndex;

        

        int down = newsSize * (pageIndex-1)+1;

        

        //获取数据库连接对象

        Connection con = help.lianjie();

        

        String sql = "select * from " +

                "(select n.*,rownum r from " +

                "(select * from news order by ncreatedate desc) n " +

                "where rownum<=?) where r>=?";

        

        PreparedStatement pst = con.prepareStatement(sql);

        

        pst.setInt(1, up);

        pst.setInt(2, down);

        

        //获取结果集

        ResultSet rs =  pst.executeQuery();

        

        //创建集合装新闻对象

        List<news> list = new ArrayList<news>(); 

        

        while(rs.next()){

            

            //创建新闻对象

            news news = new news();

            

            news.setTitle(rs.getString("ntitle"));

            news.setCreatedate(rs.getString("ncreatedate"));

            

            list.add(news);

        }

        

        return list;

    }

}

第四步：在页面分页显示

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<%@page import="tools.SelectNews"%>

<%@page import="tools.news"%>





<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

  <head>

  </head>

  <body>

    <table align="center" border="0">

        

        

        

        <%

            //展示新闻条数

            int newsSize = 5;

        

            //实例化新闻帮助对象

            SelectNews sn = new SelectNews();

            

            //获取页面数量

            int pages = sn.getPages(newsSize);

            

            //当前页码

            int pageIndex = 1;

            

            //获取提交页码

            String Pagetemp = request.getParameter("pageIndex");

            

            //判断页面是否是当前页提交

            if(Pagetemp!=null){

                

                pageIndex = Integer.parseInt(Pagetemp);

                

            }

            

            //=============查询新闻

            //获取装有新闻的集合

            List<news> NewsList = sn.getList(pageIndex,newsSize);

            

            //遍历打印

            for(news temp : NewsList){

                

                

            

        %>

            <tr>

                <td><%=temp.getTitle() %></td>

                <td><%=temp.getCreatedate() %></td>

            </tr>

        

        <%    } %>

        

        <tr>

            <td colspan="2">

                <%if(!(pageIndex<=1)){ %>

                    <a href="index.jsp?pageIndex=<%=1 %>">首页</a>

                    <a href="index.jsp?pageIndex=<%=pageIndex-1 %>">上一页</a>

                <%}

                if(!(pageIndex>=pages)){

                %>

                    <a href="index.jsp?pageIndex=<%=pageIndex+1 %>">下一页</a>

                    <a href="index.jsp?pageIndex=<%=pages %>">尾页</a>

                <%} %>

                

                <form action="index.jsp" method="post">

                    <input type="text" name="pageIndex" value="<%=pageIndex %>"/>

                    <input type="submit" />

                </form>

                 

            </td>

        </tr>

    </table>

    

    

    

  </body>

</html>