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https://issues.apache.org/jira/browse/SCXML-207?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ate Douma resolved SCXML-207.
-----------------------------
Resolution: Fixed
Fix Version/s: 2.0
Fixed through SCXML-206
> Race condition in transition notification for SCXMLListeners
> ------------------------------------------------------------
>
> Key: SCXML-207
> URL: https://issues.apache.org/jira/browse/SCXML-207
> Project: Commons SCXML
> Issue Type: Bug
> Affects Versions: 2.0
> Reporter: Johannes Wienke
> Assignee: Ate Douma
> Fix For: 2.0
>
>
> When using a SimpleSCXMLListener we have seen impossible transitions occur in
> the log output of that listener. After digging around the source code I can
> see the issue that results in theses outputs.
> In order to derive the event name passed as the last argument to
> SCXMLListener#onTransition, the following code inside SCXMLSemanticsImpl is
> used:
> {code:java}
> public void notifyOnTransition(final SCXMLExecutionContext exctx, final
> Transition t,
> final TransitionTarget target) {
> EventVariable event =
> (EventVariable)exctx.getScInstance().getSystemContext().getVars().get(SCXMLSystemContext.EVENT_KEY);
> String eventName = event != null ? event.getName() : null;
> exctx.getNotificationRegistry().fireOnTransition(t, t.getParent(),
> target, t, eventName);
> exctx.getNotificationRegistry().fireOnTransition(exctx.getStateMachine(),
> t.getParent(), target, t, eventName);
> }
> {code}
> When triggering events on the engine from multiple threads (which is ok
> according to the online documentation), a different thread might have already
> replaced the contents of the SCXMLSystemContext.EVENT_KEY context item and
> hence a wrong event name might be used from this point on.
> Actually, I don't even understand why the event name is looked up from the
> context here at all, since is already available inside the transition.
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