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如何用jsp+mysql实现网页的分页查询

WBOY
WBOY转载
2023-05-30 15:58:251730浏览

一、实现分页查询的核心sql语句

（1）查询数据库的记录总数的sql语句：

select count(*) from +（表名）;

（2）每次查询的记录数的sql语句：

其中：0是搜索的索引，2是每次查找的条数。

select * from 表名 limit 0,2;

二、代码实现

在上一篇中，我已经介绍了DBconnection类和Author对象类，前者用于获取数据库连接，后者用于表示作者对象。这两个类的代码点击连接查看。点击链接以查看 DBconnection 类和 Author 对象类

（1）登录页面：index.jsp。

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Insert title here</title>
</head>
<body>
    <a href="AuthorListPageServlet">用户列表分页查询</a>
</body>
</html>

（2）显示页面：userlistpage.jsp。

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>查询页面</title>
</head>
<body>
<table border="1">
  <tr>
    <td>编号</td>
    <td>名称</td>
    <td>价格</td>
    <td>数量</td>
    <td>日期</td>
    <td>风格</td>
  </tr>
  <c:forEach items="${pageBean.list}" var="author">
  <tr>
    <td>${author.id}</td>
    <td>${author.name }</td>
    <td>${author.price }</td>
    <td>${author.num }</td>
    <td>${author.dates}</td>
    <td>${author.style}</td>
  </tr>
  </c:forEach>
</table>
<c:if test="${ pageBean.record>0}">
<div>
      
      <c:if test="${pageBean.currentPage <= 1}">
      <span>首页</span>
      <span>上一页</span>
      <a href ="AuthorListPageServlet?currPage=${pageBean.currentPage + 1 }">下一页</a>
      <a href ="AuthorListPageServlet?currPage=${pageBean.totalPage }">尾页</a>
      </c:if>
      
      <c:if test="${pageBean.currentPage > 1 && pageBean.currentPage < pageBean.totalPage  }">
       <a href ="AuthorListPageServlet?currPage=1">首页</a>
      <a href ="AuthorListPageServlet?currPage=${pageBean.currentPage - 1 }">上一页</a>
      <a href ="AuthorListPageServlet?currPage=${pageBean.currentPage + 1 }">下一页</a>
      <a href ="AuthorListPageServlet?currPage=${pageBean.totalPage }">尾页</a>
      </c:if>
     
     <c:if test="${ pageBean.currentPage >= pageBean.totalPage}">
      <a href ="AuthorListPageServlet?currPage=1">首页</a>
      <a href ="AuthorListPageServlet?currPage=${pageBean.currentPage - 1 }">上一页</a>
     <span>下一页</span>
     <span>尾页</span>
     </c:if>
</div>
</c:if>
</body>
</html>

（3）功能实现：AuthorDao.java。

package com.dao;

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

import com.entity.Author;

public class AuthorDao {
    
     public  Author check(String username ,int  password ) {
         
         Author obj = null ;
         try {
            DBConnection db = new DBConnection();
            //获取数据库连接
            Connection conn = db.getConn();
            
            String sql="select *from furnitures where name = ? and id = ?";
            
            PreparedStatement ps=conn.prepareStatement(sql);
            //设置用户名和密码作为参数放入sql语句
            ps.setString(1,username);
            ps.setInt(2,password);
            //执行查询语句
            ResultSet rs = ps.executeQuery();
            //用户名和密码正确，查到数据  欧式风格  茶几
            if(rs.next()) {
                obj = new Author();
                obj.setId(rs.getInt(1));
                obj.setName(rs.getString(2));
                obj.setPrice(rs.getInt(3));
                obj.setNum(rs.getInt(4));
                obj.setDates(rs.getString(5));
                obj.setStyle(rs.getString(6));
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
         return obj;
     }
     /**
      * 用户列表信息查询
      * @return
      */
     public List<Author> queryAuthorList(){
         Author obj = null ;
         List<Author> list = new ArrayList<Author>();
         try {
            DBConnection db = new DBConnection();
            //获取数据库连接
            Connection conn = db.getConn();
            
            String sql="select *from furnitures";
            
            PreparedStatement ps=conn.prepareStatement(sql);
    
            //执行查询语句
            ResultSet rs = ps.executeQuery();
            //用户名和密码正确，查到数据  欧式风格  茶几
            //循环遍历获取用户信息
            while(rs.next()) {
                
                obj = new Author();
                obj.setId(rs.getInt(1));
                obj.setName(rs.getString(2));
                obj.setPrice(rs.getInt(3));
                obj.setNum(rs.getInt(4));
                obj.setDates(rs.getString(5));
                obj.setStyle(rs.getString(6));
                //将对象加入list里边
                list.add(obj);
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
         return list;
     }
     
     
     /**
      * 查询用户表总记录数
      * @return
      */
     public int queryUserListCount() {
         DBConnection db;
        try {
             db = new DBConnection();
             Connection conn = db.getConn();
             String sql = "select count(*) from furnitures";
             
             PreparedStatement ps = conn.prepareStatement(sql);
             ResultSet rs = ps.executeQuery();
             
             
             if(rs.next()) {
                 return rs.getInt(1);
             }
             
             
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        
         return 0;
     }
     /**
      * 查询用户分页数据
      * @param pageIndex数据起始索引
      * @param pageSize每页显示条数
      * @return
      */
     public List<Author>queryUserListPage(int pageIndex,int pageSize){
         
         Author obj = null;
         List<Author> list = new ArrayList<Author>();
         
         try {
            Connection conn = new DBConnection().getConn();
            String sql = "select * from furnitures limit ?,?;";
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setObject(1, pageIndex);
            ps.setObject(2,pageSize);
            
            ResultSet rs = ps.executeQuery();
            //遍历结果集获取用户列表数据
            
            while(rs.next()) {
                obj = new Author();
                
                obj.setId(rs.getInt(1));
                obj.setName(rs.getString(2));
                obj.setPrice(rs.getInt(3));
                obj.setNum(rs.getInt(4));
                obj.setDates(rs.getString(5));
                obj.setStyle(rs.getString(6));
                
                list.add(obj);
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
         return list;
     }
     /**
      * 用户新增
      * @param obj
      */
     public void add(Author obj) {
        
        try {
            
            DBConnection db = new DBConnection();
            //获取数据库连接
            Connection conn = db.getConn();
            
            String sql="insert into furnitures values(id,?,?,?,?,?)";
            
            PreparedStatement ps=conn.prepareStatement(sql);
            ps.setObject(1, obj.getName());
            ps.setObject(2, obj.getPrice());
            ps.setObject(3, obj.getNum());
            ps.setObject(4,obj.getDates());
            ps.setObject(5, obj.getStyle());
            
            //执行sql语句
           ps.execute();
           
            
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
            
     }
     //删除用户
     public void del(int id) {
         try {
                
                DBConnection db = new DBConnection();
                //获取数据库连接
                Connection conn = db.getConn();
                
                String sql="delete from furnitures where id = ?";
                
                PreparedStatement ps=conn.prepareStatement(sql);
                
                ps.setObject(1, id);
                
                //执行sql语句
               ps.execute();
               
                
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
                
     }
    
}

（4）交互层：AuthorListPageServlet.java。

package com.servlet;

import java.io.IOException;
import java.util.List;

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.dao.AuthorDao;
import com.entity.Author;
import com.util.PageBean;

/**
 * Servlet implementation class AuthorListPageServlet
 */
@WebServlet("/AuthorListPageServlet")
public class AuthorListPageServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public AuthorListPageServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        int pageSize = 2;
        AuthorDao ad = new AuthorDao();
        //总记录数
        int record = ad.queryUserListCount();
        //接收页面传入的页码
        String strPage = request.getParameter("currPage");
        int currPage = 1;//默认第一页
        if(strPage != null) {
            currPage = Integer.parseInt(strPage);
    
        }
        
        PageBean<Author> pb = new PageBean<Author>(currPage,pageSize,record);
        //查询某一页的结果集
        List<Author> list = ad.queryUserListPage(pb.getPageIndex(), pageSize);
        pb.setList(list);
        request.setAttribute("pageBean", pb);
        request.getRequestDispatcher("userlistpage.jsp").forward(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

（5）工具类：PageBean.java。作用是：获取结果集。

package com.util;

import java.util.List;

public class PageBean<T>{
    private int currentPage;//当前页码
    private int pageIndex;//数据起始索引
    private int pageSize;//每页条数
    
    
    private int record;//总记录数
    private int totalPage;//总页数
    
    private List<T>list;//每页显示的结果集
    /**
     * 构造方法初始化pageIndex和totalPage
     * @param currentPage
     * @param pageIndex
     * @param pageSize
     */
    public PageBean(int currentPage,int pageSize,int record) {
        
        this.currentPage = currentPage;
        this.pageSize = pageSize;
        this.record = record;
        
        //总页数
        if(record % pageSize == 0) {
            //整除，没有多余的页
            this.totalPage = record / pageSize;
            
        }
        else {
            //有多余的数据，在增加一页
            this.totalPage = record / pageSize + 1;
        }
        
        //计算数据起始索引pageIndex
        if(currentPage < 1) {
            this.currentPage = 1;
        }
        else if(currentPage > this.totalPage) {
            this.currentPage = this.totalPage;
        }
        this.pageIndex = (this.currentPage -1)*this.pageSize;
    }
    
    public int getCurrentPage() {
        return currentPage;
    }

    public void setCurrentPage(int currentPage) {
        this.currentPage = currentPage;
    }

    public int getPageIndex() {
        return pageIndex;
    }

    public void setPageIndex(int pageIndex) {
        this.pageIndex = pageIndex;
    }

    public int getPageSize() {
        return pageSize;
    }

    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }

    public int getRecord() {
        return record;
    }

    public void setRecord(int record) {
        this.record = record;
    }

    public int getTotalPage() {
        return totalPage;
    }

    public void setTotalPage(int totalPage) {
        this.totalPage = totalPage;
    }

    public List<T> getList() {
        return list;
    }

    public void setList(List<T> list) {
        this.list = list;
    }
    
}

三、运行结果

（1）首页：

如何用jsp+mysql实现网页的分页查询

（2）中间页：

如何用jsp+mysql实现网页的分页查询

（3）尾页：

如何用jsp+mysql实现网页的分页查询

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