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JSP+Servlet+JavaBean實現登錄網頁實例詳解

編輯：關於JSP

本文實例講述了JSP+Servlet+JavaBean實現登錄網頁的方法。分享給大家供大家參考。具體如下：

這裡涉及到四個文件:

1. 登錄頁面:login.html
2. 登錄成功歡迎頁面:login_success.jsp
3. 登錄失敗頁面:login_failure.jsp
4. Servlet處理文件:LoginServlet.java

其實還涉及到一個文件:web.xml,這個後面再說:

下面分別介紹這幾個文件:

1. 登錄頁面:login.html

<!-- 該Login頁面是一個簡單的登錄界面 -->
<!--
 該JSP程序是用來測試與MySQL數據庫的連接，
 需要一個數據庫：LearnJSP，和其中一個表：userinfo
 表中有兩個字段分別為：UserName varchar (20) not null,UserPwd varchar (20) not null
-->
<html>
 <head>
  <title>登錄</title>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  <meta http-equiv="Content-Language" content="ch-cn">
 </head>
 <body>
 <!-- Form 用來提取用戶填入並提交的信息-->
 <form method="post" name="frmLogin" action="LoginServlet">
  <h1 align="center">用戶登錄</h1><br>
  <div align="center">用戶名：
   <input type="text" name="txtUserName" value="Your name"
    size="20" maxlength="20"
    onfocus="if(this.value=='Your name')this.value='';"><br>密碼：
   <input type="password" name="txtPassword" value="Your password"
    size="20" maxlength="20"
    onfocus="if(this.value=='Your password')this.value='';"><br>
   <input type="submit" name="Submit"　value="提交" onClick="validateLogin();" >
         
   <input type="reset" name="Reset" value="重置"><br>
  </div>
 </form>
 <!-- javaScript 函數 validateLogin(),用來驗證用戶名和密碼是否為空 -->
  <script language="javaScript">
   function validateLogin()
   {
   var sUserName = document.frmLogin.txtUserName.value;
   var sPassword = document.frmLogin.txtPassword.value;
   if( sUserName=="" )
   {
    alert("請輸入用戶名！");
    return false;
   }
   if( sPassword=="" )
   {
    alert("請輸入密碼！");
    return false;
   }
   }
  </script>
 </body>
</html>

2. 登錄成功歡迎頁面:login_success.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
 <title>My JSP 'login_failure.jsp' starting page</title>
 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
 <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">
 -->
 </head>
 <body>
 <%
  String userName = (String)session.getAttribute ( "UserName" );
 %>
 <div align=center>
  <%=userName%>
  歡迎您，登錄成功！
 </div>
 </body>
</html>

3. 登錄失敗頁面:login_failure.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
 pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
 <head>
 <title>My JSP 'login_failure.jsp' starting page</title>
 <meta http-equiv="content-type" content="text/html; charset=UTF-8">
 <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">
 -->
 </head>
 <body>
 <%
 String userName = (String)session.getAttribute ( "UserName" );
 %>
 <div align=center>
  <%=userName%>
  對不起，登錄失敗！
 </div>
 </body>
</html>

4. Servlet處理文件:LoginServlet.java

/**
 * 該JSP程序是用來測試與MySQL數據庫的連接，
 * 需要一個數據庫：LearnJSP，和其中一個表：userinfo
 * 表中有兩個字段分別為：UserName varchar (20) not null,UserPwd varchar (20) not null
 */
package zieckey.login.servlet;
import java.sql.Statement;
import java.io.IOException;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class LoginServlet extends HttpServlet implements Servlet
{
 public LoginServlet ()
 {
 // TODO Auto-generated constructor stub
 }
 /*
 * (non-Javadoc)
 *
 * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest,
 * javax.servlet.http.HttpServletResponse)
 */
 @Override
 protected void doGet ( HttpServletRequest arg0, HttpServletResponse arg1 )
  throws ServletException, IOException
 {
 }
 /*
 * (non-Javadoc)
 *
 * @see javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest,
 * javax.servlet.http.HttpServletResponse)
 */
 @Override
 protected void doPost ( HttpServletRequest request, HttpServletResponse response )
  throws ServletException, IOException
 {
 response.setContentType ( "text/html" );
 String result = "";
 // 獲取用戶名
 String sUserName = request.getParameter ( "txtUserName" );
 if ( sUserName == "" || sUserName == null || sUserName.length ( ) > 20 )
 {
  try
  {
  result = "請輸入用戶名（不超過20字符）！";
  request.setAttribute ( "ErrorUserName", result );
  response.sendRedirect ( "login.html" );
  } catch ( Exception e )
  {
  }
 }
 // 獲取密碼
 String sPasswd = request.getParameter ( "txtPassword" );
 if ( sPasswd == "" || sPasswd == null || sPasswd.length ( ) > 20 )
 {
  try
  {
  result = "請輸入密碼（不超過20字符）！";
  request.setAttribute ( "ErrorPassword", result );
  response.sendRedirect ( "login.html" );
  } catch ( Exception e )
  {
  }
 }
 // 登記JDBC驅動程序
 try
 {
  Class.forName ( "org.gjt.mm.mysql.Driver" ).newInstance ( );
 } catch ( InstantiationException e )
 {
  // TODO Auto-generated catch block
  e.printStackTrace ( );
  System.out.println ("InstantiationException");
 } catch ( IllegalAccessException e )
 {
  // TODO Auto-generated catch block
  e.printStackTrace ( );
  System.out.println ("IllegalAccessException");
 } catch ( ClassNotFoundException e )
 {
  // TODO Auto-generated catch block
  e.printStackTrace ( );
  System.out.println ("ClassNotFoundException");
 }
 // 連接參數與Access不同
 String url = "jdbc:mysql://localhost/LearnJSP";
 // 建立連接
 java.sql.Connection connection = null;
 Statement stmt = null;
 ResultSet rs = null;
 try
 {
  connection = DriverManager.getConnection ( url, "root", "011124" );
  stmt = connection.createStatement ( );
  // SQL語句
  String sql = "select * from userinfo where username='" + sUserName
   + "' and userpwd = '" + sPasswd + "'";
  rs = stmt.executeQuery ( sql );// 返回查詢結果
 } catch ( SQLException e )
 {
  // TODO Auto-generated catch block
  e.printStackTrace ( );
 }
 try
 {
  if ( rs.next ( ) )// 如果記錄集非空，表明有匹配的用戶名和密碼，登陸成功
  {
  // 登錄成功後將sUserName設置為session變量的UserName
  // 這樣在後面就可以通過 session.getAttribute("UserName") 來獲取用戶名，
  // 同時這樣還可以作為用戶登錄與否的判斷依據
  request.getSession ( ).setAttribute ( "UserName", sUserName );
  response.sendRedirect ( "login_success.jsp" );
  } else
  {
  // 否則登錄失敗
  //response.sendRedirect ( "MyJsp.jsp" );
  response.sendRedirect ( "login_failure.jsp" );
  }
 } catch ( SQLException e )
 {
  // TODO Auto-generated catch block
  e.printStackTrace ( );
 }
 try
 {
  if ( null!=rs )
  {
  rs.close ( );
  }
  if ( null!=stmt )
  {
  stmt.close ( );
  }
  if ( null!=connection )
  {
  connection.close ( );
  }
 } catch ( SQLException e )
 {
  // TODO Auto-generated catch block
  e.printStackTrace ( );
 }
 }
 /**
 *
 */
 private static final long serialVersionUID = 1L;
}

為了讓這個網站正常運行還要到web.xml中注冊一下,
現該文件內容修改如下:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.4" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
 <servlet>
  <display-name>LoginServlet</display-name>
  <servlet-name>LoginServlet</servlet-name>
  <servlet-class>zieckey.login.servlet.LoginServlet</servlet-class>
 </servlet>
 <servlet-mapping>
  <servlet-name>LoginServlet</servlet-name>
  <url-pattern>/LoginServlet</url-pattern>
 </servlet-mapping>
</web-app>

好了,這幾個文件就可以構成我們的這個登錄界面了.

注意事項:

1. 文件目錄形式

login.html,login_success.html,login_failure.html這三個文件放在同一目錄,
LoginServlet.java該文件的字節碼文件LoginServlet.class放在WEB-INF/classes目錄下(注意jar包順序)
現在整個工程的目錄形式是:
M:/Tomcat5.5/webapps/JSP_Servlet_JavaBean_Login 的目錄
007-01-18 15:16    <DIR>          META-INF
007-01-18 15:16    <DIR>          WEB-INF
007-01-18 16:17             1,801 login.html
007-01-18 15:48               858 login_failure.jsp
007-01-18 15:40               234 login_success.html
007-01-18 15:46               781 MyJsp.jsp
007-01-18 16:12               859 login_success.jsp
M:/Tomcat5.5/webapps/JSP_Servlet_JavaBean_Login/WEB-INF 的目錄
007-01-18 15:16    <DIR>          classes
007-01-18 15:16    <DIR>          lib
007-01-18 16:21               606 web.xml
M:/Tomcat5.5/webapps/JSP_Servlet_JavaBean_Login/WEB-INF/classes/zieckey/login/servlet 的目錄
2007-01-18 16:18             3,900 LoginServlet.class

2. 其他注意事項

數據庫MySQL服務器程序要先啟動起來.

希望本文所述對大家的JSP程序設計有所幫助。