Java web訪問MySql資料庫分頁查詢
阿新 • • 發佈：2019-01-07
有時候我們查詢資料庫表時，但是很多時候表中的記錄很多，需要顯示出來的話怎麼辦？這時可以使用分頁的方法，就是指定從資料庫表的什麼位置開始查詢顯示，以及指定顯示的記錄數目。
Mysql資料庫提供了limit a,b的關鍵字，a是資料庫表的查詢起始位置，是個偏移量，b是指定本次查詢的記錄數目
下面是我的資料表：
資料庫的連結類：
package com.tools; import java.sql.*; public class DBConnection { private Connection con; //定義資料庫連線類物件 private PreparedStatement pstm; private String user="root"; //連線資料庫使用者名稱 private String password="123456"; //連線資料庫密碼 private String driverName="com.mysql.jdbc.Driver"; //資料庫驅動 private String url="jdbc:mysql://localhost:3306/shoppingcart"; //連線資料庫的URL,後面的是為了防止插入資料 庫出現亂碼，?useUnicode=true&characterEncoding=UTF-8 //建構函式 public DBConnection(){ } /**建立資料庫連線*/ public Connection getCon(){ try{ Class.forName("com.mysql.jdbc.Driver"); }catch(ClassNotFoundException e){ System.out.println("載入資料庫驅動失敗！"); e.printStackTrace(); } try { con=DriverManager.getConnection(url,user,password); //獲取資料庫連線 } catch (SQLException e) { System.out.println("建立資料庫連線失敗！"); con=null; e.printStackTrace(); } return con; //返回資料庫連線物件 } /** *@功能：對資料庫進行增、刪、改、查操作 *@引數：sql為SQL語句；params為Object陣列，裡面儲存的是為sql表示的SQL語句中"?"佔位符賦值的資料 */ public void doPstm(String sql,Object[] params){ if(sql!=null&&!sql.equals("")){ if(params==null) params=new Object[0]; getCon(); if(con!=null){ try{ System.out.println(sql); pstm=con.prepareStatement(sql,ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY); for(int i=0;i<params.length;i++){ pstm.setObject(i+1,params[i]); } pstm.execute(); }catch(SQLException e){ System.out.println("doPstm()方法出錯！"); e.printStackTrace(); } } } } public ResultSet getRs() throws SQLException{ return pstm.getResultSet(); } public int getCount() throws SQLException{ return pstm.getUpdateCount(); } public void closed(){ try{ if(pstm!=null) pstm.close(); }catch(SQLException e){ System.out.println("關閉pstm物件失敗！"); e.printStackTrace(); } try{ if(con!=null){ con.close(); } }catch(SQLException e){ System.out.println("關閉con物件失敗！"); e.printStackTrace(); } } }
javabean的程式碼：
DAO的程式碼：package com.beans; public class Book { public static final int PAGE_SIZE=6;//每一頁中顯示的數目 private int bookId; private String name; private String author; private String publisher; private String price; public Book(){ } public Book(int bookId, String name,String author,String publisher,String price){ this.bookId=bookId; this.name=name; this.author=author; this.publisher=publisher; this.price=price; } public int getBookId() { return bookId; } public void setBookId(int bookId) { this.bookId = bookId; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getAuthor() { return author; } public void setAuthor(String author) { this.author = author; } public String getPublisher() { return publisher; } public void setPublisher(String publisher) { this.publisher = publisher; } public String getPrice() { return price; } public void setPrice(String price) { this.price = price; } }
負責分頁查詢的Servlet程式碼：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.beans.Book; import com.tools.DBConnection; public class BookDao { DBConnection DB=new DBConnection();//資料庫的連結類 Connection conn=null; //返回所有圖書列表 public List<Book> getBookList(){ List<Book> list=new ArrayList<Book>(); try { conn=DB.getCon(); String sql="select * from books"; PreparedStatement pstm=conn.prepareStatement(sql); ResultSet rs=pstm.executeQuery(); while(rs.next()){ Book book=new Book(); book.setBookId(rs.getInt(1)); book.setName(rs.getString(2)); book.setAuthor(rs.getString(3)); book.setPublisher(rs.getString(4)); book.setPrice(rs.getString(5)); list.add(book); } return list; } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return null; } //根據圖書ID返回這本書的資訊 public Book getBookById(int bookid){ Book book=new Book(); try { conn=DB.getCon(); String sql="select * from books where BookID=?"; PreparedStatement pstm=conn.prepareStatement(sql); pstm.setInt(1, bookid); ResultSet rs=pstm.executeQuery(); while(rs.next()) { book.setBookId(rs.getInt(1)); book.setName(rs.getString(2)); book.setAuthor(rs.getString(3)); book.setPublisher(rs.getString(4)); book.setPrice(rs.getString(5)); } return book; } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } return null; } }
package com.servlets;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.Dao.PageQueryDao;
import com.beans.Book;
public class PageQueryServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
int currpage=1;//開始時是第一頁
if(request.getParameter("page")!=null){
currpage=Integer.parseInt(request.getParameter("page"));
}
PageQueryDao pagedao=new PageQueryDao();//查詢資料庫的dao
List<Book> list=pagedao.getPageList(currpage);//查詢當前頁記錄
request.setAttribute("list", list); //把記錄放在request裡邊
int pages; //計算查詢總頁數
int count=pagedao.FindCounts();
if(count%Book.PAGE_SIZE==0){
pages=count/Book.PAGE_SIZE;
}
else{
pages=count/Book.PAGE_SIZE+1;
}
StringBuffer sb=new StringBuffer();
//構建分頁條
for(int i=1;i<=pages;i++){
if(i==currpage){
sb.append("『" + i + "』");
}
else{ sb.append("<a href='PageQueryServlet?page="+i+"'>"+i+"</a>");//連結到本servlet
}
sb.append(" ");
}
request.setAttribute("bar", sb.toString());
request.getRequestDispatcher("books.jsp").forward(request, response); //請求轉發
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@page import="java.util.List"%>
<%@page import="com.beans.Book"%><html>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>圖書資訊列表</title>
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
<style type="text/css">
a:link{color:red;text-decoration:none}/*未訪問，紅色，無下劃線*/
a:active{color:blue;}/*啟用，紅色*/
a:visited{color:purple;text-decoration:none}/*已訪問，紫色，無下劃線*/
a:hover{color:blue;text-decoration:underline}/*滑鼠移動上面，藍色，下劃線*/
</style>
</head>
<body bgcolor="#98FB98">
<table align="center" >
<tr>
<td align="center" colspan="8" >
<h2 style=" font-family:隸書;color:#9A32CD">喵喵網上書店</h2>
</td>
</tr>
<%! int i=1,j=1; %>
<% List<Book> list=(List<Book>)request.getAttribute("list");%>
<% for(j=1;j<=2;j++){ %><!--這裡的我的工作專案是這樣的，也可以迴圈顯示成列表形式，只需要修改下表的迴圈程式碼即可-->
<tr>
<%
for(Book b:list){
if(j==2){
if(b.getBookId()<=3||(b.getBookId()>=7&&b.getBookId()<=9)) continue;
}
%>
<td width="100" height="140"><img src="images/<%=String.valueOf(b.getBookId()-1) %>.jpg"/></td>
<td width="160">
<font color="#0000FF">ISDN :<%=b.getBookId() %></font><br>
<font color="#0000FF"> 書 名:<%=b.getName() %></font><br>
<font color="#0000FF"> 作 者:<%=b.getAuthor() %></font><br>
<font color="#0000FF">出 版:<%=b.getPublisher() %></font><br>
<font color="#0000FF">價 格:<%=b.getPrice() %> </font><br>
<a href="">檢視詳細資訊</a>
</td>
<% if(b.getBookId()%3==0) break; %>
<%} %>
</tr>
<%} %>
<tr>
<td align="right" colspan="8"><%= request.getAttribute("bar") %></td>
</tr>
</table>
</body>
</html>
