本文通过两个方法：（1）计算总的页数。 （2）查询指定页数据，实现简单的分页效果。
思路：首先得在 DAO 对象中提供分页查询的方法，在控制层调用该方法查到指定页的数据，在表示层通过 EL 表达式和 JSTL 将该页数据显示出来。
先给大家展示下效果图：
题外话：该分页显示是用 “表示层-控制层-DAO层-数据库”的设计思想实现的，有什么需要改进的地方大家提出来，共同学习进步。废话不多说了，开始进入主题，详细步骤如下所示：
1.DAO层-数据库
JDBCUtils 类用于打开和关闭数据库，核心代码如下：
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import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;public class JDBCUtils {private Connection conn=null;private PreparedStatement pstmt=null; /*** connect 连接数据库* @return*/public Connection connect(){String user="root";String password="1234";String driverClass = "com.mysql.jdbc.Driver";String jdbcUrl = "jdbc:mysql://localhost:3306/book";try {Class.forName(driverClass);conn = DriverManager.getConnection(jdbcUrl, user, password);} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}return conn;}/*** close 关闭数据库* @param conn* @param pstmt* @param resu*/public void close(Connection conn,PreparedStatement pstmt,ResultSet result){if(conn != null){try {conn.close();} catch (SQLException e) {// TODO Auto-generated catch block}}if(pstmt != null){try {pstmt.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}if(result != null){try {result.close();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}} |
UserDao 类中的方法 getPage() 和方法 listUser() 分别用来计算总页数和查询指定页的数据，核心代码如下：
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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.db.JDBCUtils;public class UserDao {/*** 计算总的页数* @return*/public int getPage(){int recordCount=0,t1=0,t2=0;PreparedStatement pstmt=null;ResultSet result=null;JDBCUtils jdbc=new JDBCUtils();Connection conn=jdbc.connect();String sql="select count(*) from books";try {pstmt=conn.prepareStatement(sql);result=pstmt.executeQuery();result.next();recordCount=result.getInt(1);t1=recordCount%5;t2=recordCount/5;} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}finally{jdbc.close(conn, pstmt, result);}if(t1 != 0){t2=t2+1;}return t2;}/*** 查询指定页的数据* @param pageNo* @return*/public List<User> listUser(int pageNo){PreparedStatement pstmt=null;ResultSet result=null;List<User> list=new ArrayList<User>();int pageSize=5;int page=(pageNo-1)*5;JDBCUtils jdbc=new JDBCUtils();Connection conn=jdbc.connect();String sql="select * from books order by id limit ?,?";try {pstmt=conn.prepareStatement(sql);pstmt.setInt(1, page);pstmt.setInt(2, pageSize);result=pstmt.executeQuery();while(result.next()){User user=new User();user.setId(result.getInt(1));user.setName(result.getString(2));user.setNumber(result.getString(3));list.add(user);}} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}finally{jdbc.close(conn, pstmt, result);}return list;}} |
User 类用于存储查询到的数据，核心代码如下：
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public class User {private int id;private String name;private String number;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getNumber() {return number;}public void setNumber(String number) {this.number = number;}} |
2.控制层
ListUser 类内部调用 UserDao 对象查询数据并指派页面显示数据，核心代码如下：
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import java.io.IOException;import java.io.PrintWriter;import java.util.ArrayList;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.User;import com.dao.UserDao;public class ListUser extends HttpServlet {public ListUser() {super();}public void destroy() {super.destroy(); // Just puts "destroy" string in log// Put your code here}public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doPost(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setCharacterEncoding("utf-8");int pageNo = 1;UserDao userdao=new UserDao();List<User> lists=new ArrayList<User>();String pageno=request.getParameter("pageNos");if(pageno != null){pageNo=Integer.parseInt(pageno);}lists=userdao.listUser(pageNo);int recordCount=userdao.getPage();request.setAttribute("recordCount", userdao.getPage());request.setAttribute("listss", lists);request.setAttribute("pageNos", pageNo);request.getRequestDispatcher("userlist.jsp").forward(request, response);}public void init() throws ServletException {// Put your code here}} |
3.表示层
输出页面 userlist.jsp ,使用 EL 和 JSTL 输出查询结果，核心代码如下：
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<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %><%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt"%> <%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><base href="<%=basePath%>"><title>My JSP 'userlist.jsp' starting page</title><meta http-equiv="pragma" content="no-cache"><meta http-equiv="cache-control" content="no-cache"><meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"><meta http-equiv="description" content="This is my page"><!--<link rel="stylesheet" type="text/css" href="styles.css">--><style type="text/css">th,td{width: 150px;border: 2px solid gray;text-align: center;}body{text-align: center;}a{text-decoration: none;}table {border-collapse: collapse;}</style></head><body><h2 align="center">图书信息</h2><table align="center"><tr><td>书号</td><td>书名</td><td>库存量</td></tr></table><table align="center"><c:forEach items="${listss}" var="person"><tr><td class="hidden-480">${person.id}</td><td class="hidden-480">${person.name }</td><td class="hidden-480">${person.number }</td></tr></c:forEach></table><br><c:if test="${pageNos>1 }"><a href="ListUser?pageNos=1" >首页</a><a href="ListUser?pageNos=${pageNos-1 }">上一页</a></c:if><c:if test="${pageNos <recordCount }"><a href="ListUser?pageNos=${pageNos+1 }">下一页</a><a href="ListUser?pageNos=${recordCount }">末页</a></c:if><form action="ListUser"><h4 align="center">共${recordCount}页 <input type="text" value="${pageNos}" name="pageNos" size="1">页<input type="submit" value="到达"></h4></form></body></html> |
以上所述是小编给大家介绍的Java Web 简单的分页显示实例代码，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对服务器之家网站的支持！
