Hi,
I think that this is definitelly thread issue because data is shared between
multiple threads. Even when every page instance would have it's own *copy*
of the data, it is still shared between multiple instances at the end.
Of cource yes - every page will run in it's own thread but this does not
erase thread problems.
Regards,
Kristjan Kelt
nille hammer wrote:
>
> Hi,
>
> This is NOT a thread issue, but behavoiour that one would expect with
> values persisted in the session. The requests coming all from within the
> same session store and fetch the (same) value in the sesion.
>
> Add this to the java file
> @PageAttached
> private void showPageInstance() {
> System.out.println(this);
> }
> You'll see that each request is handled by a different instance of the
> page therefore handled in a thread safe manner.
>
> The only problem observed here is the double submit problem. That is not a
> bug of Tapestry but must be handled by every webapp no matter what
> framework. Ways to do this are unique ids for forms or a state field.
>
> Regards, nillehammer
> ==
> http://www.winfonet.eu
>
> ----- original Nachricht --------
>
> Betreff: Re: T5 Page field persistance and multithread problems
> Gesendet: Di, 14. Jul 2009
> Von: Robert Zeigler<[email protected]>
>
>> Well, it /is/ the case that page fields and pages are thread-safe.
>> But persistent fields are accessing their data from the session, and
>> session-bound data is only thread-safe if you explicitly make it so.
>> You're right, though: the documentation should probably be more clear
>> in that regard, as you pointed out.
>>
>> Robert
>>
>> On Jul 13, 2009, at 7/133:21 PM , kristjankelt wrote:
>>
>> >
>> > Hi,
>> >
>> > After a little thinking about Tapestry persistence, I constructed a
>> > sample
>> > that shows how Tapestry page field persistence handling is not
>> > thread safe.
>> >
>> > This is a page class and it's template:
>> >
>> > http://www.nabble.com/file/p24468298/NotSafe.java NotSafe.java
>> > http://www.nabble.com/file/p24468298/NotSafe.tml NotSafe.tml
>> >
>> > Now when you hit the "update" button more than once in IE (Firefox
>> > prevents
>> > multiple requests, but remember that this is only client side
>> > security) you
>> > will still see value incremented only by one. You will see also in the
>> > console multiple outputs with the same value.
>> >
>> > This is so because each request will get it's copy of the counter at
>> > the
>> > beginning of the request and will write it back after it finishes
>> > processing.
>> >
>> > Alternative would be moving this code into "Setup Render" method and
>> > hitting
>> > the refresh button many times - this will work also with Firefox.
>> >
>> > I'm writing about this because Tapestry documentation creates sense
>> > of false
>> > security because it states that Page classes could be written in not
>> > thread
>> > safe manner (what is true when you do not have persistent fields)
>> > but this
>> > statement does not hold in all the cases.
>> >
>> > I played with the locks in the session and it kind of worked (you
>> > can make
>> > another request to wait or raise a exception to indicate duplicate
>> > request).
>> >
>> > When anyone has more ideas about this problem then I'm more than
>> > thankful to
>> > hear about them.
>> >
>> > Regards,
>> > Kristjan Kelt
>> > --
>> > View this message in context:
>> http://www.nabble.com/T5-Page-field-persistance-and-multithread-problems-tp2
>> 4468298p24468298.html
>> > Sent from the Tapestry - User mailing list archive at Nabble.com.
>> >
>> >
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>
> --- original Nachricht Ende ----
>
>
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