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no error message display for invalid user and password authentication

keerthana kuruba
Greenhorn

Joined: May 12, 2011
Posts: 22

Hi,

i have created one servlet for user and password validation considering one servlet example.The thing is when ever i login with database username and password it will redirect to the next page.but when ever i login with invalid username and password it doesnt show the error message with in(like alert message) that login page...shows blank login page.If i set the ${error} in login.jsp after the submit button in form.with out entering any thing it displaying the ${error} message.If i set the response.sendRedirect ("error.html") file in else part instead of request dispatcher it not taking the if(condition) condition at all.As am a beginner in web technologies.So please suggest me a way to work the else part and its error message.

Here is my jsp,servlet,web.xml...
----------------------------------------------------------------------------------

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

import java.sql.*;

import java.util.*;



public class School extends HttpServlet{



public void service (HttpServletRequest request, HttpServletResponse response)

throws ServletException,IOException

{

response.setContentType("text/html");

PrintWriter out = response.getWriter();

Connection conn = null;

String url = "jdbc:mysql://localhost:3306/track?user=root&password=root" ;

String driver = "com.mysql.jdbc.Driver";

String username=new String("");

String password=new String(" ");

String strQuery= "";

Statement st=null;

ResultSet rs=null;

//HttpSession session = request.getSession(false);



try {

Class.forName(driver).newInstance();

conn=DriverManager.getConnection(url);

strQuery="select userID,password from user";

System.out.println(strQuery);



st = conn.createStatement();

//rs=st.executeQuery("select * from user where userID='"+user+"' and password='"+pass+"'");

rs = st.executeQuery(strQuery);



//int count=0;

while(rs.next())

{

//session.setAttribute("user",rs.getString(1));

//session.setAttribute("pass",rs.getString(2));

username=rs.getString("userID");

password=rs.getString("password");

}

rs.close();

st.close();

// count++;

}



catch(Exception e)

{

e.printStackTrace();

}



String user=request.getParameter("user");

String pass=request.getParameter("pass");

if(username.equals(user)&& password.equals(pass))

{

//response.sendRedirect("Map2.jsp");

RequestDispatcher dispatcher = request.getRequestDispatcher("Map2.jsp");

dispatcher.forward( request, response);

}

else if (!username.equals(user)&& !password.equals(pass))

{



request.setAttribute("errorMessage", "Invalid username or password");

RequestDispatcher dispatcher = request.getRequestDispatcher("Track.jsp");

dispatcher.forward( request, response);

}



}



}
---------------------------------------------------------------------------------------------------------
<?xml version="1.0" encoding="ISO-8859-1"?>



<web-app xmlns="http://java.sun.com/xml/ns/j2ee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"

version="2.4">

<display-name>schoolTrack</display-name>

<description>Vehicle tracking</description>

<welcome-file-list>

<welcome-file>Track.html</welcome-file>

<welcome-file>Track.jsp</welcome-file>

</welcome-file-list>

<servlet>

<servlet-name>Tracklogin</servlet-name>

<servlet-class>Track</servlet-class>

</servlet>



<servlet-mapping>

<servlet-name>Tracklogin</servlet-name>

<url-pattern>/Track</url-pattern>

</servlet-mapping>



<servlet>

<servlet-name>Schooltrack</servlet-name>

<servlet-class>School</servlet-class>

</servlet>



<servlet-mapping>

<servlet-name>Schooltrack</servlet-name>

<url-pattern>/School</url-pattern>

</servlet-mapping>



<error-page>

<error-code>404</error-code>

<location>/error.jsp</location>

</error-page>



<error-page>

<error-code>java.lang.NullPointerException</error-code>

<location>/error.jsp</location>

</error-page>

</web-app>
--------------------------------------------------------------------------------------------------------------

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">



<!-- <!DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> -->

<html xmlns='http://www.w3.org/1999/xhtml' xmlns:v='urn:schemas-microsoft-com:vml'>



<!-- Head -->

<head>



<!-- meta -->



<meta name="author" content="GeoTelematic Solutions, Inc."/>

<meta http-equiv="content-type" content='text/html; charset=UTF-8'/>

<meta http-equiv="cache-control" content='no-cache'/>

<meta http-equiv="pragma" content="no-cache"/>

<meta http-equiv="expires" content="0"/>

<meta name="robots" content="none"/>





<!-- page title -->



<title> System</title>



<link rel="stylesheet" type="text/css" href="./css/General.css"/>



<!-- javascript -->

<script src= "/js/utils.js" type="text/javascript"></script>

<!-- script the username and password validation -->

<script>



function Validate()

{ var user=document.Login.user.value;

var invalid=/\W/; //Alphanumeric characters and Underscore permitted

if(user=="")

{

alert("Enter your username!");

return false;

}

if(invalid.test(user))

{

alert("Username contain Invalid characters!");

return false;

}

if(user.length<3 || user.length>15)

{ //username must be 6 - 15 letters length

alert("Entered Invalid user!");

return false;

}

var pass=document.Login.pass.value;

invalid=/[\W_]/; //Alphabets and digits only allowed

if(pass=="")

{

alert("Enter your password!");

return false;

}

if(pass.length<3 ){

alert("Password must contain atleast 3 letters!");

return false;

}

if(invalid.test(pass))

{

alert("Password contain Invalid characters!");

return false;

}

return true;

if(user)

{

alert("Username is invalid !");

return false;

}

return true;

}



</script>



<!-- local style -->

<style type="text/css">

BODY {

background-color: #FFFFFF;

}

TD.titleText {

background: #FFFFFF url('./images/Banner_WhiteShadow.png') center no-repeat;

font-family: arial,verdana,sans-serif;

font-size: 28pt;

font-weight: bold;

text-align: center;

color: #000000;

}

</style>



<!-- page specific style -->

<link rel="stylesheet" type="text/css" href="./css/AccountLogin.css"/>





<!-- custom override style -->

<link rel='stylesheet' type='text/css' href='custom/Custom.css'/>



</head>



<!-- ======================================================================================= -->



<body >



<table width="100%" height="100%" align="center" border="0" cellspacing="0" cellpadding="0" style="padding-top: 5px;">

<tbody>



<!-- Begin Page header/navigation ======================================== -->

<tr>

<td width="100%">

<table class="bannerTable" width="860" border="0" cellpadding="0" cellspacing="0" align="center">

<tbody>

<tr>



<!-- -->

<td width="860" height="120" halign="center">

<div align="center"><img src="./images/logo.jpg" alt="logo" width="1000" height="200">

</div>

</td>

<!-- -->

</tr>

</tbody>

</table>

</td>

</tr>

<tr>

<td align="center">

<table width="100" border="0" cellpadding="0" cellspacing="0">

<tbody>

<tr>



</tr>

</tbody>

</table>

</td>

</tr>



<!-- Begin Page contents ======================================== -->

<tr height="100%">

<td>

<table width="100%" height="100%" border="0" cellpadding="0" cellspacing="0">

<tbody>

<tr>

<td valign='top' align='center' height='100%'>

<table class="accountLoginTable_nobord" cellspacing='0' cellpadding='0' border='0'>

<tbody>

<!-- The MenuBar is display iff 'content.class.table' is "contentTable"/"contentMapTable" -->

<tr><!-- no menubar ['accountLoginTable_nobord'] --></tr>

<tr height='100%'>

<td class="accountLoginCell_nobord">

<table class='accountLoginContentTable' width='100%' cellpadding='0' cellspacing='0' border='0'>

<tr>

<td class='accountLoginTextCell'>

<span style='font-size:11pt'>Enter your Login ID and Password</span>

<hr style='height: 5px;'/><!--<div>${message}</div> -->

<!-- <div style="color:red">${errorMessage}</div>-->



<form name="Login" method="post" action="/schoolTrack/School" onsubmit="javascript:return Validate();">

<table class='accountLoginFormTable' cellpadding='0' cellspacing='0' border='0'>

<tr><td class='accountLoginFieldLabel'>User:</td><td class='accountLoginFieldValue'><input id='userLoginField' class='textInput' type='text' name='user' value='' size='24' maxlength='32'></td></tr>

<tr><td class='accountLoginFieldLabel'>Password:</td><td class='accountLoginFieldValue'><input class='textInput' type='password' name='pass' value='' size='24' maxlength='32'> </td></tr>

</table>

<br><input type='submit' name='submit' value='Login' >



</form>

<br/>

<hr style='height: 5px;'/>

<span style='font-size:8pt'><i><a href='register.jsp'>Sign up new account </a></i></span>

</td>

</tr>

</table>

<script type="text/javascript">

var loginFocusField = document.getElementById('accountLoginField');

if (loginFocusField) {

loginFocusField.focus();

loginFocusField.select();

}

</script>



</td>

</tr>

<tr>

<td id="contentMessage" class="contentMessage">



</td>

</tr>

</tbody>

</table>

</td>

</tr>

</tbody>

</table>

</td>

</tr>

<tr>

<td style="font-size: 1pt; border-bottom: 1px solid #888888;"> </td>

</tr>

<tr>

<td>

<table class="copyrightFooterClear" width="100%" border="0" cellpadding="0" cellspacing="0">

<tbody>

<tr>

<td style="padding: 0px 0px 2px 5px;"> </td>

<td width="100%" align="center">

 



</td>

<td nowrap style="padding-bottom: 2px;">

<span style="font-size: 1pt; font-style: oblique; color: #888888;">

2.2.8

</span>  


</td>

</tr>

</tbody>

</table>

</td>

</tr>



</tbody>

</table>

</body>




</html>


James Sabre
Ranch Hand

Joined: Sep 07, 2004
Posts: 781

Think about this line of your code for a bit and then correct it -



Hint - De Morgan's Theorem


Retired horse trader.
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