Java Web 简单的分页显示实例代码

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：

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 block
e.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 block
e.printStackTrace();
}
}

if(result != null){

try {
result.close();

} catch (SQLException e) {
// TODO Auto-generated catch block
e.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：

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 block
e.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 block
e.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：

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：

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：

<%@ 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。