'already taking a transition' exception from listener

[awelsh]

I'm trying to add some exception paths into workflows using executionListeners to check conditions during the end event of an activity.

I am passing the execution as a parameter to a bean method on the end event of a service task as follows…

checkForErrorCondition(ActivityExecution execution) {
   if(errorCondition()) {
      PvmTransition exceptionTransition = execution.getActivity().findOutgoingTransition("exception");
      execution.take(exceptionTransition);
   }
}

when errorCondition() evaluates to true, and it tries to take the "exception" flow, an exception with the message "already taking a transition" is thrown.
I get the same exception when doing the same on the start event.

I wanted to check if this is the expected behaviour (i.e. there is no way to influence the execution flow from a listener)

As well as the above, I noticed that when calling the checkForErrorCondition method from a serviceTask directly (rather than through a listener) it works fine, but if the service task is part of an embedded subprocess, when transitioning out of the subprocess the same exception ("already taking a transition") is thrown.

[ronald_van_kuij]

you should *not* influence the flow in listeners. It can lead to all kinds of unexpected behaviour. Look in other posts in the forum

[frederikherema1]

Better to use an error boundry-event for this kind of behaviour I would say: http://activiti.org/userguide/index.html#bpmnBoundaryErrorEvent

[awelsh]

Thanks for replies,

Is it possible to trigger an error boundary event any way other than following a pre-defined flow to an error end event?

I have a use case where a message can be received to trigger cancellation of an in-progress workflow.
This should also trigger the cancellation of any sub-processes, but need to do some cleanup in each of the subprocesses when this occurs so calling deleteProcessInstance isnt an option.

I'm looking for a way to "jump" out to an error end event without having to add an extra error path to every transition.
Also prefer not to use explicit receive task/signal() combination for this since I already have these as part of the business processes so wouldnt want to trigger a cancellation with a normal signal() call.

Any advice welcome.

[jbarrez]

No, currently that's the only way.

But readin your process, it seems that maybe by modeling your process differently you could do it out of the box?

[gwaptiva]

Not sure if this is still accurate or even of interest, but in order to save myself (and other flow authors of our embedded Activiti setup) a lot of boiler plate "if error a else b" gateway XML, I have extended the *ActivitiBehaviour classes to take an (optional) Expression that defines the error handling service task to jump to on a Java exception.

Now, if any Java exception happens within a ServiceTask (as an exmple), the subclass will change the outgoing transition to the Activity defined in the Expression, and flow out there. Note that there's only a single instance/object in the context for each service task, so upon entering you'll have to ensure the outgoing transitions are reset to their "normal" exits.

May not be totally "per-standard" but thus far running well in our setup