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From David Smith <>
Subject Re: Session IDs & XMLHttpRequests
Date Mon, 21 May 2007 18:49:09 GMT
I'd say if there are differences, it's in the javascript of the client.  
Have you used any sort of monitoring tool to find out if XMLHttpRequest 
is sending the session cookie?  Have you tried encoding the JSESSIONID 
in the XMLHttpRequest via javascript?


Williams, Allen wrote:

>I had posted this question to four different Java fora over four days
>and gotten zero replies, when it occurred to me how stupid not to ask
>the community that wrote Tomcat.  I was just going to post this, which
>is a summary that describes what I've found so far:
>-- QUOTE --
>In the interest of informing the community, I'm publishing the results
>of four days of testing and debugging of XMLHttpRequests and attributes.
>This has led me to the conclusion that servlets invoked with an
>XMLHttpRequest do not have the same access to server-side objects
>(actually, attributes) as those invoked via the normal URL mechanism. I
>don't know why, because if I insert a filter, the filter gets executed,
>albeit the first time with the wrong session ID.
>I began this odyssey when a filter in place to check if a user's session
>had timed out would fail the first time when invoked with an
>XMLHttpRequest, but would work each time thereafter. What I discovered
>there was that there were two JSESSIONID cookies stored and being sent
>in the browser and the jsp and other servlets were requesting the
>correct one. The xml request was not, it was requesting the (old? I
>don't know) invalid JSESSIONID. One would think, "OK, I'll just read the
>cookies in my servlet, check each ID with
>request.isRequestedSessionIdValid(), and force the right one". Wrong.
>All of the http session APIs that allow one to manipulate the session ID
>and force a good one are deprecated, according to Sun's web site, so the
>programmer isn't allowed to find & use a good session ID.
>In order to progress while I waited vainly for a reply, I just removed
>the filter from the servlet's path so it didn't invoke it. I want the
>filter to check, but decided to move on in the meantime. That's when I
>discovered that, evidently, the servlet does not get a valid session ID
>I had the following line in my XMLHttpRequest servlet:
>HttpSession sess= req.getSession();
>This seemed to execute and work fine, until I needed to access
>session-scoped attributes I had defined in other pages or servlets. The
>were repeatedly null. When I changed the above line to this:
>HttpSession sess= req.getSession(false);
>the reason was apparent: the servlet was generating a brand new session
>for me. So, for some reason, XMLHttpRequests don't get the same
>treatment that normal servlets get. I'm going to have to go and modify a
>lot of code to pass stuff around as query parameters in URLs, which I
>really don't want to do for both aesthetic & security reasons, but see
>no alternative. Hopefully, there really is someone out there that knows
>more about this than I do and can explain to the community & me what's
>going on.
>-- END QUOTE --
>1. So the last paragraph has my main question in it: why can't I access
>attributes in a servlet invoked via an XMLHttpRequest?  However, I have
>a another important question and a couple of ancillary ones as well:
>2. What is the difference in the servlet invocation between a regular
>URL invocation & an XMLHttpInvocation?
>3. How can I get my filter to work?  I. e., get it the correct session
>4.  WHY are all the session manipulation APIs deprecated, and, at least
>according to Sun's web site, not being replaced?  It seems unusual to be
>removing control from the programmer/software engineer instead of trying
>to give him more control over his environment.  With those APIs I could
>have fixed this (well, kludged it up, anyway).
>If you need me to post any code, I'll be glad to, but it's really pretty
>straightforward.  In fact, when I started this adventure, the servlet
>was empty except for print statements, and the filter has been in place
>& working for months.
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