JavaWeb -- 分頁顯示技術

一、分頁顯示含義

每次翻頁的時候只從數據庫裏檢索出本頁需要的數據。

二、分頁顯示優點

• 數據清晰直觀
• 不受數據量限制
• 頁面不再冗長

三、分頁顯示實現

3.1 分頁查詢

3.1.1 分頁查詢步驟

• 查詢總數據量
• 確定每頁顯示的數據量
• 計算顯示的頁數
  頁數 = （總數據量 + 每頁顯示的數據量 - 1）/ 每頁顯示的數據量
• 編寫分頁查詢 SQL 語句
• 實現分頁查詢

3.1.2 分頁查詢關鍵點

• 計算顯示數據的總數量需要藉助 JDBC 內容
• 計算頁數時，聲明一個工具類將功能獨立出來，便於複用
• 編寫分頁查詢SQL語句（limit）
  select * from tableName where 條件 limit (當前頁碼-1) * 頁面容量 , 頁面容量

3.2 分頁顯示

3.2.1 分頁顯示關鍵點

• 確定當前頁
• 設置首頁、上一頁、下一頁、末頁的頁碼
• 對可能出現的異常進行控制
• 首頁與末頁的控制
• 可添加“GO”按鈕，根據輸入的頁碼，跳轉到相應頁碼（需判斷用戶輸入頁碼的正確性後再使用表單隱藏域傳遞頁碼）

四、MVC分層開發簡單項目展示

這裏僅展示某個項目使用分頁顯示技術的相關類和JSP的代碼。


CommodityController.java

package com.ishopn.controller;

import java.util.List;

import com.ishopn.dao.CommodityDao;
import com.ishopn.dao.impl.CommodityDaoImpl;
import com.ishopn.model.Commodity;

public class CommodityController {
	private CommodityDao commodityDao = null;
	
	public CommodityController() {
		commodityDao = new CommodityDaoImpl();
	}
	
	public List<Commodity> getCommodityList(){
		return commodityDao.getCommodityList();
	}
	
	public int istCommodity(String c_name, String c_madein, String c_type, String c_inprice, String c_outprice, String c_num) {
		Commodity c = new Commodity(System.currentTimeMillis()+"", c_name, c_madein, new Integer(c_type), new Integer(c_inprice), new Integer(c_outprice), new Integer(c_num));
		return commodityDao.istCommodity(c);
	}
	
	public int delCommodityById(String c_id) {
		return commodityDao.delCommodityById(c_id);
	}
	
	public Commodity getCommodityById(String c_id) {
		return commodityDao.getCommodityById(c_id);
	}
	
	public int updCommodity(String c_id, String c_name, String c_madein, String c_type, String c_inprice, String c_outprice, String c_num) {
		Commodity c = new Commodity(c_id, c_name, c_madein, new Integer(c_type), new Integer(c_inprice), new Integer(c_outprice), new Integer(c_num));
		return commodityDao.updCommodity(c);
	}
}

CommodityDao.java

package com.ishopn.dao;

import java.util.List;

import com.ishopn.model.Commodity;

public interface CommodityDao {
	List<Commodity> getCommodityList();
	int istCommodity(Commodity c);
	int delCommodityById(String c_id);
	Commodity getCommodityById(String c_id);
	int updCommodity(Commodity c);
	
	public List<Commodity> getCommodityListWithPage(int pageNo, int pageSize);
	public int getCommodityCount();
}

CommodityDaoImpl.java

package com.ishopn.dao.impl;

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

import org.junit.Test;

import com.ishopn.dao.CommodityDao;
import com.ishopn.model.Commodity;
import com.ishopn.util.DBHelper;

public class CommodityDaoImpl implements CommodityDao{

	@Test 
	public List<Commodity> getCommodityList() {
		List<Commodity> commodities = new ArrayList<Commodity>();
		Connection conn;
		try {
			conn = DBHelper.getConnection();
			
			String sql = "select * from Commodity";
			ResultSet rs = DBHelper.executeQuery(conn, sql, null);
			while(rs.next()) {
				Commodity c = new Commodity();
				c.setC_id(rs.getString("c_id"));
				c.setC_name(rs.getString("c_name"));
				c.setC_madein(rs.getString("c_madein"));
				c.setC_type(rs.getInt("c_type"));
				c.setC_inprice(rs.getInt("c_inprice"));
				c.setC_outprice(rs.getInt("c_outprice"));
				c.setC_num(rs.getInt("c_num"));
				c.setCt(new CommoditytypeDaoImpl().getCommoditytypeById(rs.getInt("c_type")));
				
				commodities.add(c);
			}
			
			DBHelper.closeConnection(conn);
		}catch(Exception e) {
			e.printStackTrace();
		}
		
		return commodities;
	}

	@Override
	public int istCommodity(Commodity c) {
		int line = 0;
		Connection conn = DBHelper.getConnection();
		
		String sql = "insert into commodity (c_id,c_name,c_madein,c_type,c_inprice,c_outprice,c_num) values (?,?,?,?,?,?,?)";
		List param = new ArrayList();
		param.add(c.getC_id());
		param.add(c.getC_name());
		param.add(c.getC_madein());
		param.add(c.getC_type());
		param.add(c.getC_inprice());
		param.add(c.getC_outprice());
		param.add(c.getC_num());
		line = DBHelper.executeUpdate(conn, sql, param);
		
		DBHelper.closeConnection(conn);
		return line;
	}

	@Override
	public int delCommodityById(String c_id) {
		int line = 0;
		Connection conn = DBHelper.getConnection();
		
		String sql = "delete from commodity where c_id=?";
		List param = new ArrayList();
		param.add(c_id);
		line = DBHelper.executeUpdate(conn, sql, param);
		
		DBHelper.closeConnection(conn);
		return line;
	}

	@Override
	public Commodity getCommodityById(String c_id) {
		Commodity c = new Commodity();
		Connection conn;
		
		try {
			conn = DBHelper.getConnection();
			
			String sql = "select * from Commodity where c_id=?";
			List param = new ArrayList();
			param.add(c_id);
			ResultSet rs = DBHelper.executeQuery(conn, sql, param);
			rs.next();
			c.setC_id(rs.getString("c_id"));
			c.setC_name(rs.getString("c_name"));
			c.setC_madein(rs.getString("c_madein"));
			c.setC_type(rs.getInt("c_type"));
			c.setCt(new CommoditytypeDaoImpl().getCommoditytypeById(rs.getInt("c_type")));
			c.setC_inprice(rs.getInt("c_inprice"));
			c.setC_outprice(rs.getInt("c_outprice"));
			c.setC_num(rs.getInt("c_num"));
			
			DBHelper.closeConnection(conn);
		}catch(Exception e) {
			
		}
		
		return c;
	}

	@Override
	public int updCommodity(Commodity c) {
		int line = 0;
		Connection conn = DBHelper.getConnection();
		
		String sql = "update commodity set c_name=?,c_madein=?,c_type=?,c_inprice=?,c_outprice=?,c_num=? where c_id=?";
		List param = new ArrayList();
		param.add(c.getC_name());
		param.add(c.getC_madein());
		param.add(c.getC_type());
		param.add(c.getC_inprice());
		param.add(c.getC_outprice());
		param.add(c.getC_num());
		param.add(c.getC_id());
		line = DBHelper.executeUpdate(conn, sql, param);
		
		DBHelper.closeConnection(conn);
		return line;
	}

	@Override
	public List<Commodity> getCommodityListWithPage(int pageNo, int pageSize) {
		List<Commodity> list = new ArrayList<Commodity>();
		Connection conn;
		
		try {
			conn = DBHelper.getConnection();
			
			String sql = "select * from commodity limit ?,?";
			List param = new ArrayList();
			param.add((pageNo - 1) * pageSize);
			param.add(pageSize);
			ResultSet rs = DBHelper.executeQuery(conn, sql, param);
			while(rs.next()) {
				Commodity c = new Commodity();
				c.setC_id(rs.getString("c_id"));
				c.setC_name(rs.getString("c_name"));
				c.setC_madein(rs.getString("c_madein"));
				c.setC_type(rs.getInt("c_type"));
				c.setC_inprice(rs.getInt("c_inprice"));
				c.setC_outprice(rs.getInt("c_outprice"));
				c.setC_num(rs.getInt("c_num"));
				c.setCt(new CommoditytypeDaoImpl().getCommoditytypeById(rs.getInt("c_type")));
				
				list.add(c);
			}
			
			DBHelper.closeConnection(conn);
		}catch(Exception e) {
			e.printStackTrace();
		}
		
		return list;
	}

	@Override
	public int getCommodityCount() {
		int count = 0;
		Connection conn;
		
		try {
			conn = DBHelper.getConnection();
			
			String sql = "select count(*) from commodity";
			ResultSet rs = DBHelper.executeQuery(conn, sql, null);
			rs.next();
			count = rs.getInt(1);
			
			DBHelper.closeConnection(conn);
		}catch(Exception e) {
			e.printStackTrace();
		}
		
		return count;
	}
}

Commodity.java

package com.ishopn.model;

/**
 * 商品表
 * @author Sowhite
 *
 */
public class Commodity {
	private String c_id;
	private String c_name;
	private String c_madein;
	private Integer c_type;	// c_type能夠確定位移的ct 1
	private Commoditytype ct;	// ct(ct_id:1, ct_name:'玩具')
	private Integer c_inprice;
	private Integer c_outprice;
	private Integer c_num;
	public Commodity() {
		super();
	}
	public Commodity(String c_id, String c_name, String c_madein, Integer c_type, Commoditytype ct, Integer c_inprice,
			Integer c_outprice, Integer c_num) {
		super();
		this.c_id = c_id;
		this.c_name = c_name;
		this.c_madein = c_madein;
		this.c_type = c_type;
		this.ct = ct;
		this.c_inprice = c_inprice;
		this.c_outprice = c_outprice;
		this.c_num = c_num;
	}
	public Commodity(String c_id, String c_name, String c_madein, Integer c_type, Integer c_inprice,
			Integer c_outprice, Integer c_num) {
		super();
		this.c_id = c_id;
		this.c_name = c_name;
		this.c_madein = c_madein;
		this.c_type = c_type;
		this.c_inprice = c_inprice;
		this.c_outprice = c_outprice;
		this.c_num = c_num;
	}
	public String getC_id() {
		return c_id;
	}
	public void setC_id(String c_id) {
		this.c_id = c_id;
	}
	public String getC_name() {
		return c_name;
	}
	public void setC_name(String c_name) {
		this.c_name = c_name;
	}
	public String getC_madein() {
		return c_madein;
	}
	public void setC_madein(String c_madein) {
		this.c_madein = c_madein;
	}
	public Integer getC_type() {
		return c_type;
	}
	public void setC_type(Integer c_type) {
		this.c_type = c_type;
	}
	public Commoditytype getCt() {
		return ct;
	}
	public void setCt(Commoditytype ct) {
		this.ct = ct;
	}
	public Integer getC_inprice() {
		return c_inprice;
	}
	public void setC_inprice(Integer c_inprice) {
		this.c_inprice = c_inprice;
	}
	public Integer getC_outprice() {
		return c_outprice;
	}
	public void setC_outprice(Integer c_outprice) {
		this.c_outprice = c_outprice;
	}
	public Integer getC_num() {
		return c_num;
	}
	public void setC_num(Integer c_num) {
		this.c_num = c_num;
	}
	@Override
	public String toString() {
		return "Commodity [c_id=" + c_id + ", c_name=" + c_name + ", c_madein=" + c_madein + ", c_type=" + c_type
				+ ", ct=" + ct + ", c_inprice=" + c_inprice + ", c_outprice=" + c_outprice + ", c_num=" + c_num + "]";
	}
}

PageModel.java

package com.ishopn.model;

import java.util.List;

public class PageModel<E> {
	private List<E> list;	// 結果集，用於存儲查詢處理的集合
	private int totalRecords;	// 查詢記錄數
	private int pageSize;	// 每頁多少數據
	private int pageNo;	// 第幾頁
	
	/**
	 * 總頁數
	 * @return
	 */
	public int getTotalPages() {
		return (totalRecords + pageSize - 1) / pageSize;
	}
	
	/**
	 * 取得首頁
	 * @return
	 */
	public int getTopPageNo() {
		return 1;
	}
	
	/**
	 * 上一頁
	 * @return
	 */
	public int getPreviousPageNo() {
		if(pageNo <= 1) {
			return 1;
		}
		return pageNo - 1;
	}
	
	/**
	 * 下一頁
	 * @return
	 */
	public int getNextPageNo() {
		if(pageNo >= getBottomPageNo()) {
			return getBottomPageNo();
		}
		return pageNo + 1;
	}
	
	/**
	 * 取得尾頁
	 * @return
	 */
	public int getBottomPageNo() {
		return getTotalPages();
	}

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

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

	public int getTotalRecords() {
		return totalRecords;
	}

	public void setTotalRecords(int totalRecords) {
		this.totalRecords = totalRecords;
	}

	public int getPageSize() {
		return pageSize;
	}

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

	public int getPageNo() {
		return pageNo;
	}

	public void setPageNo(int pageNo) {
		this.pageNo = pageNo;
	}
}

PageServlet.java

package com.ishopn.servlet;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.ishopn.controller.CommoditytypeController;
import com.ishopn.model.Commodity;
import com.ishopn.model.Commoditytype;
import com.ishopn.model.PageModel;
import com.ishopn.util.PageHelper;

public class PageServlet extends HttpServlet {

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		req.setCharacterEncoding("utf-8");
		resp.setCharacterEncoding("utf-8");
		
		int pageNo = Integer.parseInt(req.getParameter("pageNo"));
		int pageSize = Integer.parseInt(req.getParameter("pageSize"));
		
		PageModel<Commodity> page = PageHelper.findCommodity(pageNo, pageSize);
		HttpSession session = req.getSession();
		session.setAttribute("pageView", page);
		List<Commoditytype> ctList = new CommoditytypeController().getCommoditytypeList();
		session.setAttribute("ctList", ctList);
		
		resp.sendRedirect("/day_0910_web7/welcome.jsp");
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doGet(req, resp);
	}
}

PageHelper.java

package com.ishopn.util;

import java.util.List;

import com.ishopn.dao.impl.CommodityDaoImpl;
import com.ishopn.model.Commodity;
import com.ishopn.model.PageModel;

/**
 * 這個類就是用來對PageModel類的填充，返回PageModel的實例對象
 * @author Sowhite
 *
 */
public class PageHelper {
	public static PageModel findCommodity(int pageNo, int pageSize) {
		PageModel<Commodity> pageModel = new PageModel<Commodity>();
		List<Commodity> list = new CommodityDaoImpl().getCommodityListWithPage(pageNo, pageSize);
		int total = new CommodityDaoImpl().getCommodityCount();
		pageModel.setPageNo(pageNo);
		pageModel.setPageSize(pageSize);
		pageModel.setTotalRecords(total);
		pageModel.setList(list);
		return pageModel;
	}
}

welcome.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <%@ page import="com.ishopn.model.*" %>
    <%@ page import="java.util.*" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>歡迎界面</title>
<%
List<Commoditytype> ctList = (ArrayList<Commoditytype>)session.getAttribute("ctList");
//List<Commodity> cList = (ArrayList<Commodity>)session.getAttribute("cList");
PageModel p = (PageModel)session.getAttribute("pageView");
// 記錄當前頁數和頁面大小
int pageNo = p.getPageNo();
int pageSize = p.getPageSize();
List<Commodity> cList = p.getList();
%>
</head>
<body>
	<h1>歡迎您！<%=session.getAttribute("cu_name") %></h1>
	<hr />
	<!-- 商品列表的展示 List<Commodity> -->
	<form method="post" action="/day_0910_web7/insertCommodityServlet">
	<table>
		<tr>	
			<td colspan="1"><input type="text" name="c_name" /></td>
			<td><input type="text" name="c_madein" /></td>
			<td>
			<select name="c_type">
				<%
				for(Commoditytype ct : ctList)
				{
				%>
				<option value="<%=ct.getCt_id() %>"><%=ct.getCt_name() %></option>
				<%
				}
				%>
			</select>
			</td>
			<td><input type="text" name="c_inprice" /></td>
			<td><input type="text" name="c_outprice" /></td>
			<td><input type="text" name="c_num" /></td>
			<td><input type="submit" name="新增" /></td>
		</tr>
		<tr>
			<td>商品編號</td>		
			<td>商品名稱</td>
			<td>商品產地</td>
			<td>商品類型</td>
			<td>商品進價</td>
			<td>商品售價</td>
			<td>商品庫存</td>
			<td>編輯|刪除</td>
		</tr>
		<%
		for(Commodity c : cList){
		%>
			<tr>
				<td><%=c.getC_id() %></td>		
				<td><%=c.getC_name() %></td>
				<td><%=c.getC_madein() %></td>
				<td><%=c.getCt().getCt_name() %></td>
				<td><%=c.getC_inprice() %></td>
				<td><%=c.getC_outprice() %></td>
				<td><%=c.getC_num() %></td>
				<td><a href="/day_0910_web7/toUpdateServlet?c_id=<%=c.getC_id() %>">編輯</a>|<a href="/day_0910_web7/deleteCommodityById?c_id=<%=c.getC_id() %>">刪除</a></td>
			</tr>
		<%
		}
		%>
		<tr>
			<td colspan="7">
			<%
			// 首頁的輸出
			if(p.getTopPageNo() == pageNo){
				out.print("首頁");
			}else{
				out.print("<a href='/day_0910_web7/pageServlet?pageNo="+p.getTopPageNo()+"&pageSize="+p.getPageSize()+"'>首頁</a>");
			}
			//上一頁的輸出
			if(p.getPreviousPageNo()==pageNo){
				out.print("上一頁 ");
			}else{
				out.print("<a href='/day_0910_web7/pageServlet?pageNo="+p.getPreviousPageNo()+"&pageSize="+p.getPageSize()+"'>上一頁</a>");
			}
			//頁數的輸出
			for(int i=1;i<=p.getTotalPages();i++){
				if(i == pageNo){
					out.print(i+" ");
					continue;
				}
				out.print("<a href='/day_0910_web7/pageServlet?pageNo="+i+"&pageSize="+p.getPageSize()+"'>"+i+"</a> ");
			}
			//下一頁的輸出
			if(p.getNextPageNo()==pageNo){
				out.print("下一頁 ");
			}else{
				out.print("<a href='/day_0910_web7/pageServlet?pageNo="+p.getNextPageNo()+"&pageSize="+p.getPageSize()+"'>下一頁</a>");
			}
			//尾頁的輸出
			if(p.getBottomPageNo()==pageNo){
				out.print("尾頁 ");
			}else{
				out.print("<a href='/day_0910_web7/pageServlet?pageNo="+p.getBottomPageNo()+"&pageSize="+p.getPageSize()+"'>尾頁</a>");
			}
			%>
			<select onchange="javascript:location.href='/day_0910_web7/pageServlet?pageNo=1&pageSize='+this.value">
				<option value="5" <%=5==pageSize?"selected":"" %>>每頁5條記錄</option>
				<option value="10" <%=10==pageSize?"selected":"" %>>每頁10條記錄</option>
				<option value="15" <%=15==pageSize?"selected":"" %>>每頁15條記錄</option>
			</select>
		</tr>
	</table>
	</form>
</body>
</html>

效果：