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From "Eddie O'Neil (JIRA)" <...@beehive.apache.org>
Subject [jira] Updated: (BEEHIVE-1100) page flow shared by two threads can be destroyed by one but isn't reinitialized by the other
Date Wed, 19 Apr 2006 00:23:19 GMT
     [ http://issues.apache.org/jira/browse/BEEHIVE-1100?page=all ]

Eddie O'Neil updated BEEHIVE-1100:
----------------------------------

    Fix Version:     (was: v.next)
      Assign To:     (was: Eddie O'Neil)

In looking at this a bit more, it doesn't seem like a common scenario (no one else has reported
it), and I can only make it happen in contrived situations with several threads pounding on
the same HttpSession.  

I'm going to defer this till a subsequent release, but if anyone else runs into this problem,
feel free to ask for a fix...

> page flow shared by two threads can be destroyed by one but isn't reinitialized by the
other
> --------------------------------------------------------------------------------------------
>
>          Key: BEEHIVE-1100
>          URL: http://issues.apache.org/jira/browse/BEEHIVE-1100
>      Project: Beehive
>         Type: Bug

>   Components: NetUI
>     Versions: V1, 1.0.1, v.next
>     Reporter: Eddie O'Neil

>
> This is a JPF threading issue where two threads can start off sharing the same Page Flow.
 When one thread destroys that JPF, the second thread continues to reuse the destroyed instance.
 This can cause problems when re-running the destroyed JPF because any Controls or other fields
cleared in the "onDestroy" lifecycle handler can cause unexpected exceptions / behavior. 
For example:
> Thread 1:  current page flow is /a/A.jpf
> 1: reference /a/A.jpf
> 2: execute action "step 2"
> 5: attempt to execute action "step 3" -- strange behavior because
> internal state has been whacked by "destroy".
> Thread 2: current page flow is /a/A.jpf
> 3: reference /a/A.jpf
> 4: forward to /b/B.jpf -- causes onDestroy to be called on A.jpf
> I believe that the fix is to have the Thread1 re-create the JPF mid-request.  This means
that Thread1 will lose the state /a/A.jpf, but in the current architecture, that makes sense
because the JPF was destroyed.  When the JPF is re-created, it will attempt to run action
"step2" which could work but might also fail with an error or redirect to the beginning of
a wizard (for example).  Fortunately, this scenario is the same as the case where the user
types this into their browser window:
>   http://localhost:8080/fooWeb/somewizard/step2.do
> and the action either works or fails.  It's just like starting a JPF over again in the
middle of the request.

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