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Date: Mon, 11 Jun 2007 20:50:07 +0100
From: "Niall Pemberton" <niall.pemberton@gmail.com>
To: "Struts Users Mailing List" <user@struts.apache.org>
Subject: Re: How can one servlet (ActionServlet) effect another servlet
 (AxisServlet)...?
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On 6/11/07, Jeff Amiel <jeff.amiel@gmail.com> wrote:
> On 6/7/07, Jeff Amiel <jeff.amiel@gmail.com> wrote:
>
> > Thanks much....will continue to investigate.
> > I really appreciate the information and will post back if I get any
> > concrete results....
> >
>
> Shortly thereafter, while pouring through the tomcat issues
> repository, I stumbled across this:
>
> http://issues.apache.org/bugzilla/show_bug.cgi?id=41772
>
> After reading,  I became more convinced that re-used response objects
> was at the heart of my issue.
> I searched high-and low through my user code looking for anything that
> might retain a handle to a response object....finding nothing obvious.
>  Of course, such a bug could exist in any number of libraries we were
> using....DWR, DisplayTag, etc.....
>
> So.....I simply changed by startup config to run tomcat with a
> -Djava.security.manager  option (my policy file allowing everything to
> everybody).
>
> And ...voila!  No more issue!!!.  (And yes...I m sure.  During a
> period of time where we would have had dozens of these events
> normally, we now have zero)
>
> I am torn as to where to vent my displeasure (or even if I should have
> any displeasure now that my production issue has 'gone away'. )
>
> I notice that in Tomcat 6.0  that there is now an option for how the
> Reponse and Request objects are recycled (not just when a Security
> Manager is used).
> http://mail-archives.apache.org/mod_mbox/tomcat-dev/200611.mbox/%3C20061103105626.622A11A9846@eris.apache.org%3E
>
> There must be a reason for this.  While I'm sure there is some aspect
> of my code (or the libraries that I am using) that is violating the
> servlet specs by 'holding onto' the response and accessing it later, I
> am distraught that Tomcat's default behavior is to permit this.  I'm
> sure very few web applications out there are simple or stand-alone
> enough to not use a plethora of third party libraries (like jasper
> reports, jfreechart, displaytag, dwr, etc)...all of which might
> represent an underlying 'threat' to that recycled response object.
>
> I am still a bit concerned that I could not track my specific cause down.....
> If it was something as innocuous as what was seen by the submitter of
> the issue above, I would not be worried (garbage collection calling
> flush on a un-closed stream)....but My issue could be
> worse.....sending data intended for one response (that is long gone)
> to a different one...
>
> Any advice or thoughts would be appreciated.

I guess the question is whether using the security manager is acutally
solving the problem or just masking it. If its the latter I would,
like you, want to know the cause. I would start by asking on the
Tomcat user list to try and understand why it shouldn't happen with
re-cycled objects - or what must the application be doing for it to
happen. Since it is happening when the Axis servlet is calling
setBufferSize() - perhaps also a question to the Axis user list - to
see if they can shed some light on it - or if anyone else has hit the
same issue.

Niall

> Jeff

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