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：
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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";
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"%>
<%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。