RE: Barracuda: Multiple listeners

Hi Ron,

Consider the following event hierarchy snippet...

<build-events pkg="com.atmr.nxgenw.events">
    <req-events>
        <event name="LocalReqEvent">
            <event name="PublicEvent">
            <event name="LoginEvent">
                <event name="GetLogin"/>
                <event name="DoLogin"/>
                <event name="GetEmailPassword"/>
                <event name="DoEmailPassword"/>
            </event>
            <event name="BackupDatabase"/>
            <event name="GetTableOfContents"/>
        </event>
        <event name="AuthEvent">
            <event name="HomeReq">
                <event name="GetHome"/>
            </event>

If the client browse fires GetHome.event, the Barracuda event model will
first dispatch to listeners (assuming they exist) interested in AuthEvent,
HomeReq, and finally GetHome. So if I have a listener on AuthEvent, it will
get the chance to handle the request _before_ the listener for GetHome does.
If AuthEvent actually sends back a response (isHandled = true), GetHome will
never get notified, since the request has been handled and a response has
been sent back to the client. The only exception to this would be if the
listener interface implements notifyAlways = true (ie. I am logging, so
always notify me of this event, even if its already been handled by someone
else).

The point of this example is that the event model is hierarchical based on
how your events extend from DefaultBaseEvent. ControlEvents are always
dispatched DOWN the event hierarchy (Polymorphic interface), ViewEvents are
always dispatched UP the event hierarchy (Exceptional interface).

If you have multiple listeners listening for the exact same event, then they
will get notified based on who registered first (I think).

If you have questions, maybe give us a little more information regarding
your app domain/event hierarchy so we can understand what you are trying to
accomplish and then better recommend how to go about achieving it...

Christian
----------------------------------------------
Christian Cryder [[email protected]]
Internet Architect, ATMReports.com
Barracuda - http://barracuda.enhydra.org
----------------------------------------------
"Coffee? I could quit anytime, just not today"


> -----Original Message-----
> From: [email protected] [mailto:[email protected]]On
> Behalf Of Ron Alsobrook
> Sent: Wednesday, December 11, 2002 3:28 PM
> To: [email protected]
> Subject: Re: Barracuda: Multiple listeners
>
>
> That helps tremendously and everything's working now.  One quick
> question:
> What do you mean by "higher up the event chain"?  Does that just mean the
> order in which interests were specified or does it mean something
> else?  I'm
> pretty much in the dark when it comes to the internals of the
> event model.
>
> Ron
>
>
> -----Original Message-----
> From: Christian Cryder
> Sent: Wednesday 11 December 2002 10:52 am
> Subject: RE: Barracuda:  Multiple listeners
>
> > Hi Ron,
> >
> > Whichever one is higher up the event chain will get called first. By
> > default, DefaultBaseEventListener returns true from the
> isHandled() method,
> > meaning subsequent listeners won't get notified. If all you are doing is
> > logging in the parent listener, then override this method to
> return false
> > (thereby telling teh event handler to keepo dispatching)
> >
> > That help?
> >
> > Christian
> > ----------------------------------------------
> > Christian Cryder [[email protected]]
> > Internet Architect, ATMReports.com
> > Barracuda - http://barracuda.enhydra.org
> > ----------------------------------------------
> > "Coffee? I could quit anytime, just not today"
> >
> > > -----Original Message-----
> > > From: [email protected]
[mailto:[email protected]]On
> > Behalf Of Ron Alsobrook
> > Sent: Wednesday, December 11, 2002 1:15 PM
> > To: [email protected]
> > Subject: Barracuda: Multiple listeners
> >
> >
> > I'm not clear on some of the details when using multiple
> > listeners on a single
> > event.  I have two control event handlers in two different
> > gateways listening
> > to a single event.  That event is actually a parent event that never
gets
> > explicitly generated by the client, but all of the child events
> > are specified
> > as interests in various gateways.  It seems I can't get both handlers to
> > execute, only one at a time.  Do I need to do something special
> > to make this
> > work?  Also, in what order are events queued in such a case?
> > Thanks again.
> >
> > Ron
> >
> > _______________________________________________
> > Barracuda mailing list
> > [email protected]
> > http://www.enhydra.org/mailman/listinfo.cgi/barracuda
> > FAQ - http://www.jguru.com/faq/Barracuda
>
> _______________________________________________
> Barracuda mailing list
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