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本篇文章給大家分享的是有關分頁查詢功能如何在JavaWeb項目中實現，小編覺得挺實用的，因此分享給大家學習，希望大家閱讀完這篇文章后可以有所收獲，話不多說，跟著小編一起來看看吧。
一、MySql實現分頁查詢的SQL語句
1、分頁需求：
客戶端通過傳遞pageNo(頁碼)，counter(每頁顯示的條數)兩個參數去分頁查詢數據庫表中的數據，那我們知道MySql數據庫提供了分頁的函數limit m,n，但是該函數的用法和我們的需求不一樣，所以就需要我們根據實際情況去改寫適合我們自己的分頁語句，具體的分析如下：
比如：
查詢第1條到第10條的數據的sql是：select * from table limit 0,10; ->對應我們的需求就是查詢第一頁的數據：select * from table limit (1-1)*10,10;
查詢第10條到第20條的數據的sql是：select * from table limit 10,20; ->對應我們的需求就是查詢第二頁的數據：select * from table limit (2-1)*10,10;
查詢第20條到第30條的數據的sql是：select * from table limit 20,30; ->對應我們的需求就是查詢第三頁的數據：select * from table limit (3-1)*10,10;
2、總結
通過上面的分析，可以得出符合我們自己需求的分頁sql格式是：select * from table limit (pageNo-1)*counter,counter; 其中pageNo是頁碼，counter是每頁顯示的條數。
二、JavaWeb程序
1、創建PageBeanUtils.java工具類
package com.ambow.utils;
import java.util.List;
public class PageBeanUtils<T> {
private int prePage;//上一頁
private int nextPage;//下一頁
private int firstPage=1;//首頁
private int lastPage;//尾頁
private int currentPage = 1;//當前
private int totalPage;//總頁數
private int pageSize;//每頁顯示條數，默認顯示10條
private int totalData;//數據總條數
private List<T> pageData;//數據
public PageBeanUtils(int currentPage,int pageSize, int totalData) {
this.currentPage = currentPage;
this.pageSize = pageSize;
this.totalData = totalData;
//計算獲得總頁數（尾頁）
// this.totalPage = this.lastPage = (totalData+pageSize-1)/pageSize;
this.totalPage = this.lastPage = (int)Math.ceil((double)totalData/pageSize);
//防止當前頁小于1
this.currentPage = Math.max(this.currentPage, 1);
//防止當前頁大于總的頁數
this.currentPage = Math.min(this.totalPage, this.currentPage);
//設置上一頁，上一頁不能小于1
this.prePage = Math.max(this.currentPage-1, 1);
//設置下一頁，下一頁不能大于總頁數
this.nextPage = Math.min(this.currentPage+1, this.totalPage);
/**
* ceil
public static double ceil(double a)
返回最小的（最接近負無窮大） double 值，該值大于等于參數，并等于某個整數。特殊情況如下：
如果參數值已經等于某個整數，那么結果與該參數相同。
如果參數為 NaN、無窮大、正 0 或負 0，那么結果與參數相同。
如果參數值小于 0，但是大于 -1.0，那么結果為負 0。
注意， Math.ceil(x) 的值與 -Math.floor(-x) 的值完全相同。
參數：
a - 一個值。
返回：
最小（最接近負無窮大）浮點值，該值大于等于該參數，并等于某個整數。
*/
}
public PageBeanUtils(int prePage, int nextPage, int firstPage, int lastPage, int currentPage, int totalPage,
int pageSize, int totalData, List<T> pageData) {
super();
this.prePage = prePage;
this.nextPage = nextPage;
this.firstPage = firstPage;
this.lastPage = lastPage;
this.currentPage = currentPage;
this.totalPage = totalPage;
this.pageSize = pageSize;
this.totalData = totalData;
this.pageData = pageData;
}
public int getPrePage() {
return prePage;
}
public void setPrePage(int prePage) {
this.prePage = prePage;
}
public int getNextPage() {
return nextPage;
}
public void setNextPage(int nextPage) {
this.nextPage = nextPage;
}
public int getFirstPage() {
return firstPage;
}
public void setFirstPage(int firstPage) {
this.firstPage = firstPage;
}
public int getLastPage() {
return lastPage;
}
public void setLastPage(int lastPage) {
this.lastPage = lastPage;
}
public int getCurrentPage() {
return currentPage;
}
public void setCurrentPage(int currentPage) {
this.currentPage = currentPage;
}
public int getTotalPage() {
return totalPage;
}
public void setTotalPage(int totalPage) {
this.totalPage = totalPage;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public int getTotalData() {
return totalData;
}
public void setTotalData(int totalData) {
this.totalData = totalData;
}
public List<T> getPageData() {
return pageData;
}
public void setPageData(List<T> pageData) {
this.pageData = pageData;
}
/*
*
*
* totalPage = (totalData+pageSize-1)/pageSize;
*
*
* */
}2、在接口里面定義分頁查詢的方法
package com.ambow.dao;
import java.util.List;
import com.ambow.pojo.Good;
public interface IGoodDao {
//增刪改查
public void add(Good good);
public void delete(Good good);
public void update(Good good);
public void query(Good good);
public Good queryOne(Good good);
public List<Good> queryMore(Good good);
public List<Good> queryByName(String name);//根據商家名稱進行模糊查詢
//條件分頁查詢
public List<Good> queryByName(String name,int currentPage,int pageSize);
//獲取滿足某個條件的總記錄數
public int getTotalNum(String name);
}3、在接口的實現類里面實現方法
package com.ambow.dao.impl;
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.ambow.dao.IGoodDao;
import com.ambow.pojo.Good;
import com.ambow.utils.DBUtils;
public class GoodDaoImpl implements IGoodDao {
DBUtils db = new DBUtils();
@Override
public void add(Good good) {
Connection conn = null;
PreparedStatement pstmt = null;
String sql = "insert into good (name,address,tel,dishes) values (?,?,?,?)";
try {
conn = DBUtils.getConnection();
pstmt = conn.prepareStatement(sql);
pstmt.setString(1, good.getName());
pstmt.setString(2, good.getAddress());
pstmt.setString(3, good.getTel());
pstmt.setString(4, good.getDishes());
int isOk = pstmt.executeUpdate();
//System.out.println("add-----"+isOk);
} catch (SQLException e) {
e.printStackTrace();
}
}
@Override
public void delete(Good good) {
Connection conn = null;
PreparedStatement pstmt = null;
String sql = "delete from good where id = ?";
try {
conn = DBUtils.getConnection();
pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, good.getId());
int isOk = pstmt.executeUpdate();
System.out.println("delete-----"+isOk);
} catch (SQLException e) {
e.printStackTrace();
}
}
@Override
public void update(Good good) {
Connection conn = null;
PreparedStatement pstmt = null;
String sql = "update good set name=?,address=?,tel=?,dishes=? where id=?";
try {
conn = DBUtils.getConnection();
pstmt = conn.prepareStatement(sql);
pstmt.setString(1, good.getName());
pstmt.setString(2, good.getAddress());
pstmt.setString(3, good.getTel());
pstmt.setString(4, good.getDishes());
pstmt.setInt(5,good.getId());
int isOk = pstmt.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
}
@Override
public void query(Good good) {
// TODO Auto-generated method stub
}
@Override
public Good queryOne(Good good) {
Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
String sql = "select * from good where id = ?";
Good gd = null;
try {
conn = DBUtils.getConnection();
pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, good.getId());
rs = pstmt.executeQuery();
while(rs.next()){
gd = new Good(rs.getInt(1),rs.getString(2),rs.getString(3),
rs.getString(4),rs.getString(5));
}
} catch (SQLException e) {
e.printStackTrace();
}
return gd;
}
@Override
public List<Good> queryMore(Good good) {
// TODO Auto-generated method stub
return null;
}
@Override
public List<Good> queryByName(String name) {
Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
String sql = "select * from good where name like ?";
List<Good> goodList = new ArrayList<Good>();
try {
conn = DBUtils.getConnection();
pstmt = conn.prepareStatement(sql);
pstmt.setString(1, "%"+name+"%");
rs = pstmt.executeQuery();
while(rs.next()){
goodList.add(new Good(rs.getInt(1),rs.getString(2),rs.getString(3),
rs.getString(4),rs.getString(5)));
}
} catch (SQLException e) {
e.printStackTrace();
}
return goodList;
}
@Override
public List<Good> queryByName(String name, int currentPage, int pageSize) {
Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
String sql = "select * from good where name like ? limit ?,?";
List<Good> goodList = new ArrayList<Good>();
try {
conn = DBUtils.getConnection();
pstmt = conn.prepareStatement(sql);
pstmt.setString(1, "%"+name+"%");
pstmt.setInt(2,(currentPage-1)*pageSize);
pstmt.setInt(3,pageSize);
rs = pstmt.executeQuery();
while(rs.next()){
goodList.add(new Good(rs.getInt(1),rs.getString(2),rs.getString(3),
rs.getString(4),rs.getString(5)));
}
} catch (SQLException e) {
e.printStackTrace();
}
return goodList;
}
@Override
public int getTotalNum(String name) {
Connection conn = null;
PreparedStatement pstmt = null;
ResultSet rs = null;
String sql = "select count(id) from good where name like ?";
int total = 0;
try {
conn = DBUtils.getConnection();
pstmt = conn.prepareStatement(sql);
pstmt.setString(1, "%"+name+"%");
rs = pstmt.executeQuery();
while(rs.next()){
total = rs.getInt(1);
}
} catch (SQLException e) {
e.printStackTrace();
}
return total;
}
}4.在Servlet里面調用實現類里面的分頁查詢方法
package com.ambow.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.ambow.dao.IGoodDao;
import com.ambow.dao.impl.GoodDaoImpl;
import com.ambow.pojo.Good;
import com.ambow.utils.PageBeanUtils;
@WebServlet("/QueryServlet")
public class QueryServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private IGoodDao goodDao = new GoodDaoImpl();
public QueryServlet() {
super();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request,response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
String keywords = request.getParameter("kw");
String method = request.getParameter("method");
if("add".equals(method)){
String name = request.getParameter("name");
String address = request.getParameter("address");
String tel = request.getParameter("tel");
String dishes = request.getParameter("dishes");
Good good = new Good(0,name,address,tel,dishes);
goodDao.add(good);
//調用dao的查詢方法，返回一個List
List<Good> goods = goodDao.queryByName(keywords);
request.setAttribute("list", goods);
request.getRequestDispatcher("goods.jsp").forward(request, response);
}else if("search".equals(method)){
if(null==keywords) {
keywords="";
}
int currentPage = 1;
try {
currentPage=Integer.parseInt(request.getParameter("curPage"));
if(currentPage<=0) {
currentPage = 1;
}
}catch(Exception e) {
currentPage = 1;
}
int pageSize=10;
int totalData = goodDao.getTotalNum(keywords);
int totalPage = (int)Math.ceil((double)totalData/pageSize);
if(currentPage>totalPage){
currentPage = totalPage;
}
List<Good> goods = goodDao.queryByName(keywords,currentPage,pageSize);
PageBeanUtils pg = new PageBeanUtils(currentPage,pageSize,totalData);
pg.setPageData(goods);
request.setAttribute("pg", pg);
request.getRequestDispatcher("good2.jsp").forward(request, response);
}else if("delete".equals(method)){
System.out.println(keywords);
//實現刪除
String id = request.getParameter("id");
Good good = new Good();
good.setId(Integer.valueOf(id));
goodDao.delete(good);
//調用dao的查詢方法，返回一個List
List<Good> goods = goodDao.queryByName(keywords);
request.setAttribute("list", goods);
request.getRequestDispatcher("goods.jsp").forward(request, response);
}else if("queryById".equals(method)){
//查詢一個
String id = request.getParameter("id");
Good good = new Good();
good.setId(Integer.valueOf(id));
good = goodDao.queryOne(good);
//調用dao的查詢方法，返回一個good
request.setAttribute("good", good);
request.getRequestDispatcher("update.jsp").forward(request, response);
}else if("update".equals(method)){
String id = request.getParameter("id");
String name = request.getParameter("name");
String address = request.getParameter("address");
String tel = request.getParameter("tel");
String dishes = request.getParameter("dishes");
Good good = new Good(Integer.valueOf(id),name,address,tel,dishes);
goodDao.update(good);
//調用dao的查詢方法，返回一個List
List<Good> goods = goodDao.queryByName(keywords);
request.setAttribute("list", goods);
request.getRequestDispatcher("goods.jsp").forward(request, response);
}else{
//調用dao的查詢方法，返回一個List
List<Good> goods = goodDao.queryByName(keywords);
request.setAttribute("list", goods);
request.getRequestDispatcher("goods.jsp").forward(request, response);
}
}
}5.在JSP頁面獲取Servlet里面傳過來的數據
<%@ page language="java" contentType="text/html; charset=utf-8"
pageEncoding="utf-8" import="java.util.ArrayList,com.ambow.pojo.Good,
com.ambow.pojo.User,com.ambow.utils.PageBeanUtils"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>外賣系統的搜索功能</title>
</head>
<body>
<form action="QueryServlet?method=search" method="POST">
<input type="text" name="kw"/><input type="submit" value="搜索"/><a href=" ">添加商家</a >
<table border="1">
<tr><th>商家店名</th><th>商家地址</th><th>商家電話</th><th>經營菜品</th><th colspan="2">編輯</th></tr>
<c:forEach items="${pg.pageData}" var="g">
<tr><td>${g.name}</td><td>${g.address}</td><td>${g.tel}</td><td>${g.dishes}</td>
<td><a href="QueryServlet?method=queryById&id=${g.id}">修改</a ></td>
<td><a href="QueryServlet?method=delete&id=${g.id}" onClick="return confirm('確認刪除本條數據嗎？');">刪除</a ></td></tr>
</c:forEach>
</table>
<a href="QueryServlet?method=search&curPage=${pg.firstPage}">首頁</a >
<a href="QueryServlet?method=search&curPage=${pg.currentPage - 1}">上一頁</a >
<a href="QueryServlet?method=search&curPage=${pg.currentPage + 1}">下一頁</a >
<a href="QueryServlet?method=search&curPage=${pg.lastPage}">尾頁</a >
當前第${pg.currentPage}頁/共${pg.totalPage}頁
每頁顯示${pg.pageSize}條
</form>
</body>
</html>以上就是分頁查詢功能如何在JavaWeb項目中實現，小編相信有部分知識點可能是我們日常工作會見到或用到的。希望你能通過這篇文章學到更多知識。更多詳情敬請關注億速云行業資訊頻道。
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