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 &nbsp
<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