Thanks Craig for sharing ur experiances. I'll put more questions if I have
some doubt.
-mukul
>> The lines below which Craig has written seem to be quite important to
>> understand. But here I have a confusion. Say in doGet() method I write a
>> statement creating a session object [ HttpSession session =
>> request.getSession(true) ]. Lets assume sessions are managed using
>> persistent cookies..
>>
>
>In other words, the servlet engine will set a particular cookie name to a
value
>equalling the session identifier of this user's session, and send it back
with
>the response..
>
>>
>> Now lets say a particular user has invoked a servlet from a particular
>> client PC. Now that user's session is maintained by a cookie set by the
>> servlet on his PC. Lets now say the same user on the same PC invokes the
>> servlet again(either simultaneously or after some time lag). This another
>> request by the same user would overwrite the cookie on his PC. Or does here
>> the cookie is created new for another request by the same client ?
>>
>
>You can read the Cookie specs (RFC 2109 I think) for more details, but
what will
>happen is that your browser will send the session ID cookie along with any
>request to the same host (and, with most 2.1-based apps, to the same
>application). It does not matter which window sends it (although the
browsers
>vary somewhat in their behavior here), and it does not matter whether you are
>going back to the same servlet or a different servlet..
>
>The servlet engine will see that the session ID was already included in the
>request. When the user calls:
>
> HttpSession session = request.getSession(true);
>
>this time, the old session object will be returned (insetead of creating a
new
>one). This is how information can be maintained across multiple requests
-- the
>same session object will always be returned, until that session is
invalidated..
>
>
>>
>> I think it could be a different cookie. If its a different cookie then the
>> same person is operating two sessions, otherwise there is only one session
>> for that user..
>> If there are seperate cookies for two invocations by the same client PC,
>> then by identifying that cookie in servlet we could run different code for
>> the same client. Otherwise, if cookie is same(i.e overwritten) for two
>> different invocations from the same PC, everytime a new session is supposed
>> to be created..
>> Can somebody please clarify these concepts ? Specially synchronisation
>> issue involved here(in relation to cookies & also using url rewriting
>> mechanism)..
>>
>
>>From the servlet author's point of view, there isn't much difference between
>cookie-maintained and URL-rewrite-maintained session identitiy, except for
the
>case where a user might have more than one window open to the same
application
>at the same time. In that case, some browsers send the same session ID
for both
>windows (and the server thus thinks they are part of the same session),
but they
>will be considered distinct sessions if URL rewriting is used..
>
>Reminder -- even if there is only one window, or you are using URL
rewritijng to
>have distinct sessions no matter what, you *still* need to be aware that
>simultaneous requests are possible. Consider the following scenario:
>* User submits a form to do a database search
> that will take a while..
>* That request starts running..
>* User presses STOP because they do not want
> to wait, and then issues a different request
> to the application (say, they go back to the
> main menu)
>* This second request starts running, at the same
> time that the database search is still running --
> the servlet engine has no idea that the user
> pressed STOP..
>
>It may or may not make any difference, depending on your application
design, but
>you need to be aware that it's possible..
>
>>
>> -mukul
>>
>
>Craig
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