Cookies or session id ebmedded in the URI.
If you have two distinct browsers (say two instances of Netscape, or
Netscape and IE on the same machine) than the cookie or session id in
the URI can identify you uniquely, as opposed to an IP (which also
breaks when using proxies, firewalls, etc).
If you are trying to deal with two separate windows to the same server,
then your problem is that of HTTP not of EJB and simple examples like
those found in books do not work well.
One approach we've been using is to have a session within a session. Say
the user starts at page A and follows two links to pages B and C in
three separate windows. Each link gets its own identifier passed through
the URI which is used to identify the process handled by that browser
thread (for lack of a better term).
arkin
James Cook wrote:
>
> I thought I would start a new thread, because I think Dan Benanev's original
> question has gotten buried.
>
> Description
> ============
> J2EE examples from SUN and Ed Roman's "Mastering Enterprise Javabeans"
> describe a technique whereby a servlet stores a handle to a stateful session
> bean in an HTTP session object. When an incoming request is received by the
> servlet, the handle to the bean is restored and communication with the
> stateful session bean recommences.
>
> Problem
> =======
> Servlet's are most often deployed in a manner that allows multiple web
> client requests to be handled by the same instance of a servlet. If the user
> has two browsers open and pointing to the same servlet, it is possible for
> two separate threads of execution in the servlet to attempt access to the
> same stateful session bean. This will generate an exception.
>
> Challenge
> =========
> Are the standard examples of accessing stateful session beans from servlets
> flawed? How does your product determine that a client request is actually
> coming from a distinct client? How would you recommend these situations be
> implemented?
>
> Discussion Point
> ================
> It seems to me that a servlet represents a web application and it is not
> *wrong* that the two browser windows (or two frames in a single window)
> share the same HTTP object, and thus, the same stateful session bean handle.
> I think what many examples fail to mention is that this EJB reference is a
> shared resource that must be synchronized. The "best practice" that I would
> choose to put forth would read:
>
> Access to a stateful session bean object from within any application that is
> multithreaded (i.e. servlets) must be synchronized to ensure only one thread
> is executing at a time.
>
> Dooohhh. Sounds a lot like the spec, no?
>
> thanks,
> jim
>
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--
----------------------------------------------------------------------
Assaf Arkin www.exoffice.com
CTO, Exoffice Technologies, Inc. www.exolab.org
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