Hi.
Thanks all for your replies.
I am not providing the same user name and password in all the browser
windows. They are different.
Also, I checked the session id in the login servlet, it is different for
each request made by the browsers on the same m/c. Still I am getting all
responses in a single browser!
As sought, here is the code for you to take a look ---
regards,
bhaskar.
CODE :
public class loginServlet extends HttpServlet
{
private String user_name = null;
private String email = null;
private int user_type = 0;
private PrintWriter out = null;
private Connection myConnection = null;
private ResultSet rs = null;
Connector dbConnector;
// Connector class initialises a pool of 3 connections and allots connection
upon request from // any other servlet, and also revokes the connection
when passed to it by other classes.
public void init(ServletConfig sc) throws ServletException
{
super.init(sc);
System.out.println("Before instantiation of Connector class in init");
try
{
dbConnector = new Connector("jdbc:odbc:loginDB");
// Connector class constructor takes the db URL to connect
}
catch (IllegalArgumentException iae)
{
System.out.println("---------------------");
System.out.println(iae.getMessage());
System.out.println("Returned instance of Connector is :"+dbConnector);
}
} // end of init method
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException
{
System.out.println("Entered do post");
String str_login_name = req.getParameter("login_name");
String str_password = req.getParameter("password");
out = res.getWriter();
res.setContentType("text/html");
out.println("<html> <head> <title> Intranet - Library
</title> </head> <body>");
out.println("<P><FONT COLOR = \"green\">Hi
<B>"+str_login_name+"</B>");
out.println(" </FONT> </P>");
out.flush();
int validType =
validatePassword(str_login_name,str_password);
if(validType != -1)
{
HttpSession session = req.getSession(true);
system.out.println("The session id is : "+session.getId());
// only Objects are stored in the session. Primitive types are not stored.
// Hence, java.lang.Integer.toString(user_type).
session.putValue("user_name",user_name);
String str_user_type =
java.lang.Integer.toString(user_type);
session.putValue("user_type",str_user_type);
session.putValue("email",email);
out.println("You are successfully logged into the
site !");
} // end of if block
if(validType == 4) // to indicate guest status
{
HttpSession session = req.getSession(true);
// only Objects are stored in the session. Primitive types are not stored.
// Hence, java.lang.Integer.toString(user_type).
session.putValue("user_name",user_name);
String str_user_type =
java.lang.Integer.toString(user_type);
session.putValue("user_type",str_user_type);
session.putValue("email",email);
out.println("You are logged into the site as a GUEST
as your password is not correct !");
}
// else do nothing
// out.println("Pl. try again!.");
} // end of doPost method
private synchronized int validatePassword(String login, String
password)
{
String login_name = login;
String pwd = password;
Connection allotedConnection = null;
try
{
while(allotedConnection == null)
{
System.out.println("Inside validatePassword.. just before calling
allotConnection ");
allotedConnection =
dbConnector.allotConnection();
System.out.println("back in validatePassword and Alloted Connection
is: "+allotedConnection);
Statement st =
allotedConnection.createStatement();
String sqlQuery = "select
emp_email,emp_type,emp_password from empInfo where emp_login_name =
'"+login_name+"'";
System.out.println("SQL Query is : "+sqlQuery);
rs = st.executeQuery(sqlQuery);
if(rs.next())
// if at least a row is returned in the result set i.e. resultset is not
empty, there is a record which matches given login_name
{
email = rs.getString(1);
user_type = rs.getInt(2);
String emp_password =
rs.getString(3);
System.out.println("email = "+email+" user type = "+user_type+" password =
"+emp_password);
// job of the connection is over. So, it can be returned to the pool !
if (pwd.equals(emp_password))
{
System.out.println("password validated");
user_name = login_name;
}
else
user_type = 4; //
indicating guest status !
} // end of if block where result set is
checked
// if result set does not have any rows : just revoke connection.
Thereafter, sequence is followed.
else
{
dbConnector.revokeConnection(allotedConnection);
out.println("<B> Login name does not
exist! </B><BR>");
user_type = -1; // to indicate to
the caller that something is wrong
}
System.out.println("Just about to call revoke connection....");
try
{
dbConnector.revokeConnection(allotedConnection);
}
catch (IllegalArgumentException iae)
{
System.out.println("---------------------");
System.out.println(iae.getMessage());
}
} // end of while block where allotedConnection is
tested for null value
if(user_name == null && user_type != -1)
{
out.println("<B> Password is invalid !
</B><BR>");
user_type = -1; // to indicate to the
caller that something is wrong
}
} // end of try block
catch(SQLException sqle)
{
System.out.println("SQL Exception occured in
validatePassword()"+ sqle.getMessage());
sqle.printStackTrace();
}
return user_type;
} // end of validatePassword method.
} // end of loginServlet class
-----Original Message-----
From: A mailing list for discussion about Sun Microsystem's Java Servlet
API Technology. [mailto:[EMAIL PROTECTED]]On Behalf Of Kevin
Mukhar
Sent: Thursday, October 12, 2000 7:32 PM
To: [EMAIL PROTECTED]
Subject: Re: A question about the fundamentals!
Vijaya Bhaskar Varanasi wrote:
>
> I have a simple html form submitting login name and password to a simple
> servlet. The servlet validates the password and tells the user whether he
is
> logged in or not.
>
> When I open 4 browser windows (all of IE 5.0 on same m/c) and submit the
> parameters at the SAME time, three browser windows are blank (no response
> info is displayed in them) and one browser window displays four messages
> corresponding to all four attempts to login.
>
> Can we related this behaviour related to what has been discussed here ?
But,
> we do not have any 'dynamically' changing variable defined out side the
> doPost method!. All the servlet does is to respond to the client with
> relevant info whether the user is logged-in or not !
Yes, this behavior is the same problem. You probably have two problems
here.
If you are running four instances of IE on the same machine, these four
browsers are probably identified by the server as being part of the same
session. You can verify this by examining the session id in the servlet.
Make a request from a browser, check the session id. Make a request from
a different browser window from the same machine, check the session id.
Are they the same? (I think they will be.) If they are the same, then
you need to change your testing strategy to use different machines to
test concurrent requests.
The behavior of three browsers being blank and one browser showing four
messages sounds very strongly like a problem with concurrent requests
messing with the same variable. You claim that "we do not have any
'dynamically' changing variable defined out side the doPost method."
Yet, all four responses are going to the same output stream. Usually
this indicates that you are using some servlet instance variable for the
output stream rather than a method local variable. The other possibility
in your case is that you are correctly using a method local variable to
reference the output stream, but that because you are running four
browsers from the same machine that this is causing the problem.
K Mukhar
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