On 9/29/06, Madhwaraj Rao <[EMAIL PROTECTED]> wrote:
Hi Rahul,
I found it difficult to implement your suggestion.
Events are asynchronous in my system, and having this
approach of first triggering an event, and verifying
that it resulted in a state transition (in an
EntryListener.onTransition()) is error prone. What if
an event didn't result in a state transition?
<snip/>
Then you know its "invalid" (I keep quoting it since there is no such
thing, I'm just using the term in the context of your application).
Can you please sned me a code snippet with your
approach so I can really verify that it could be
applicable for me?
<snap/>
Sure. Here are examples of the workarounds I was talking about:
<example-1>
Set before = executor.getCurrentStatus().getStates();
// fire the event(s) ... executor.triggerEvent(...) etc.
Set after = executor.getCurrentStatus().getStates();
// compare before and after (ofcourse, won't work if there are self transitions)
</example-1>
-- OR --
<example-2>
// say tracer tracks the count of the number of transitions followed
SCXMLListener tracer = new TransitionTracer();
executor.addListener(scxml, tracer); // scxml is the oacsm.SCXML instance
int before = tracer.count();
// fire the event(s) ... executor.triggerEvent(...) etc.
int after = tracer.count();
// if after == before, invalid
</example-2>
etc. ...
Ideally, I would have liked a onEvent() callback in
the EntryListener.
<snip/>
Not sure I understand.
My other requirement is to prevent some events to
effect a state transition if the user role doesn't
have the right privileges.
<snap/>
Yes, this is a common requirement. You can implement it:
* As a layer around Commons SCXML, using whatever means you choose to
verify the user access rights as a function of the current user and
current status of the state machine
* As conditionals inside the SCXML document itself, guarding
transitions and datamodel access appropriately (possibly using custom
functions within the expression language chosen)
-Rahul
Thanks
--
Raj
--- Rahul Akolkar <[EMAIL PROTECTED]> wrote:
> On 9/27/06, Madhwaraj Rao <[EMAIL PROTECTED]>
> wrote:
> > Hello,
> >
> > I tried sending an invalid event to the state
> machine
> > and didn't see any error being reported. By
> invalid I
> > mean this event was not expected in the current
> state.
> >
> > Does the SCXMLSemanticsImpl report an error (via
> the
> > the ErrorReporter) when such an event is silently
> > discarded?
> >
> <snip/>
>
> No, because the semantics treat it as simply an
> inconsequential
> trigger (causing no change to the state machine),
> rather than an
> error.
>
> One of the ways you could track this is to register
> a SCXMLListener on
> the executor and track onTransition() callbacks (if
> you get none, the
> trigger is "invalid" -- per your definition above).
>
> -Rahul
>
>
> > Thanks
> > --
> > Raj
> >
>
>
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