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From "Eddie O'Neil (JIRA)" <>
Subject [jira] Created: (BEEHIVE-1100) page flow shared by two threads can be destroyed by one but isn't reinitialized by the other
Date Fri, 14 Apr 2006 15:08:00 GMT
page flow shared by two threads can be destroyed by one but isn't reinitialized by the other

         Key: BEEHIVE-1100
     Project: Beehive
        Type: Bug

  Components: NetUI  
    Versions: V1, 1.0.1,    
    Reporter: Eddie O'Neil
 Assigned to: Eddie O'Neil 
     Fix For:

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:


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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