The strange thing about the error is that the programmer isn't using
any frame, or reloading before the previous request ended (it's a local
connection, it's pretty fast..) Anyway, at least we found a bug
I did this approach of store the desired key names... in an Vectory,
it looks ugly, but it seems it works :-)
Thank you all!
On Wed, 2002-12-18 at 15:49, Craig R. McClanahan wrote:
>
>
> On 18 Dec 2002, Felipe Schnack wrote:
>
> > Date: 18 Dec 2002 09:12:20 -0200
> > From: Felipe Schnack <[EMAIL PROTECTED]>
> > Reply-To: Tomcat Users List <[EMAIL PROTECTED]>
> > To: Tomcat Users List <[EMAIL PROTECTED]>
> > Subject: Re: HttpSession issues
> >
> > Yes, but this is related to an user session. How is possible to have
> > concurrent updates on an user session when an user have only one browser
> > window open and does a refresh?
>
> Here's at least two very simple ways:
>
> * Use frames (the requests for each frame will happen
> simultaneously yet belong to the same session)
>
> * User presses REFRESH before the previous request
> has completed. (Same thing could happen if you're
> using a meta refresh tag to automatically refresh).
>
> In either case, your session will be processed by more than one request at
> the same time (on different request processing threads), so anything you
> store in the session needs to be thread safe.
>
> > This iteration is done in a taglib. And
> > why this only happens when he refreshes the pages, but not when he hits
> > enter in the url bar?
> > BTW, inside this loop in some circumstances I change the session
> > attributes. In other words, the code look like this:
> >
> > Enumeration attrs = session.getAttributeNames();
> > while(attrs.hasMoreElements())
> > {
> > String name = (String)attrs.nextElement();
> > Object value = session.getAttribute(name);
> > if (<some weird conditions>)
> > {
> > session.removeAttribute(name);
> > }
> > }
> >
> > This removeAttribute() is the problem?
> >
>
> Yes. And it's not a thread safety issue.
>
> You are modifying the collection (i.e. the internal HashMap of session
> attributes) that you are enumerating over. Such behavior does not need to
> be supported by a java collections class.
>
> The safe way to do this is accumulate a separate list of just the session
> keys you want to remove, then run a separate iteration over those keys and
> call session.removeAttribute().
>
> Craig
>
>
> --
> To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]>
> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
>
--
Felipe Schnack
Analista de Sistemas
[EMAIL PROTECTED]
Cel.: (51)91287530
Linux Counter #281893
Faculdade Ritter dos Reis
www.ritterdosreis.br
[EMAIL PROTECTED]
Fone/Fax.: (51)32303328
--
To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]>
For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
