RE: Event Flow?

Might you be able use a servlet filter to intercept requests before they 
even get processed by the Barracuda event model?  I wonder if the event 
model could benefit from servlet filters to solve problems like this?  Just 
one more reason to adopt servlet 2.3.

Jake

At 02:13 PM 4/15/2003 +0200, you wrote:
>Hi Diez,
>
>I tried point 1.
>
>I changed it to the following code.
>Actually snippet here...
>
>if ((moduleId == null) && (browseId == null)) {
>   ValidateApplication_Listener validateApplication_Listener = new
>ValidateApplication_Listener();
>   listener = validateApplication_Listener.getInstance();
>   listener.handleEvent(context);
>
>} else if ((moduleId != null) && (browseId == null)) {
>   ValidateModule_Listener validateModule_Listener = new
>ValidateModule_Listener();
>   listener = validateModule_Listener.getInstance();
>   listener.handleEvent(context);
>
>} else if ((moduleId != null) && (browseId != null)) {
>   ValidateBrowseListing_Listener validateBrowseListing_Listener = new
>ValidateBrowseListing_Listener();
>   listener = validateBrowseListing_Listener.getInstance();
>   listener.handleEvent(context);
>}
>
>Unfortunately... this won't work...
>E.g.
>Calling ValidateBrowseListing_Listener() won't work.. because it relies on
>the fact that
>the parent listener..ValidateModule_Listener is already called.
>
>Here's my actual event hierachy...
>->privateEvent
>-->ValidateApplication
>---->ValidateUser
>------>ValidateModule
>--------> ValidateBrowseListing.
>
>Here's the crux of the matter.
>I can dynamically... add Template Models to a page based on some config
>information.
>So eg. MyPageHTML.class can be associated with MyCarModel or MyHouseModel.
>
>My models use the information populated in the event validators.
>Which application to get information from, etc, etc.
>
>However... since I can reuse a page with a different model...
>I sometimes pass more params to MyPageHTML under certain conditions.
>
>The idea was to automatically validate and populate the structure if the
>param exists in
>the url.
>
>I suppose I could manually call each eventListener in the correct sequence.
>E.g.
>
>ValidateApplication_Listener validateApplication_Listener = new
>ValidateApplication_Listener();
>ValidateModule_Listener validateModule_Listener = new
>ValidateModule_Listener();
>ValidateBrowseListing_Listener validateBrowseListing_Listener = new
>ValidateBrowseListing_Listener();
>ValidateUser_Listener validateUser_Listener = new ValidateUser_Listener();
>
>if ((moduleId == null) && (browseId == null)) {
>   listener = validateApplication_Listener.getInstance();
>   listener.handleEvent(context);
>
>} else if ((moduleId != null) && (browseId == null)) {
>   listener = validateApplication_Listener.getInstance();
>   listener.handleEvent(context);
>
>   listener = validateUser_Listener.getInstance();
>   listener.handleEvent(context);
>
>   listener = validateModule_Listener.getInstance();
>   listener.handleEvent(context);
>
>} else if ((moduleId != null) && (browseId != null)) {
>
>   listener = validateApplication_Listener.getInstance();
>   listener.handleEvent(context);
>
>   listener = validateUser_Listener.getInstance();
>   listener.handleEvent(context);
>
>   listener = validateModule_Listener.getInstance();
>   listener.handleEvent(context);
>
>   listener = validateBrowseListing_Listener.getInstance();
>   listener.handleEvent(context);
>}
>
>But if the hierarchy ever changed.. I'd need to change the validateParams
>listener.. :(
>
>Ideally.. I'd like to see a 'addEventForImmediateExecution' method added to
>the dispatch queue.
>Ok... it's a terrible name.... but you get the gist.
>
>This would solve the above problem. ;)
>
>Regards
>KD
>
>
>-----Original Message-----
>From: Diez B. Roggisch [mailto:[email protected]]
>Sent: 15 April 2003 01:28
>To: [email protected]
>Subject: Re: [Barracuda] Event Flow?
>
>
>Hi Kirk,
>
> >       //Read parms fromt request..
> >       ....bla code here
> >
> >       if ((param1 == null) && (param2 == null)) {
> >         newEvent = new DefaultValidationEvent();
> >
> >       } else if ((param1 != null) && (param2 == null)) {
> >         newEvent = new ValidateAndPopulateXYZ();
> >
> >       } else if ((param1 != null) && (param2 != null)) {
> >         newEvent = new ValidateAndPopulateBlaBla();
> >       }
> >
> >       if (newEvent != null) {
> >         newEvent.setSource(event);
> >         DispatchQueue queue = context.getQueue();
> >         queue.addEvent(newEvent);
> >       }
>
>Hmm. two thoughts:
>
>1) Why don't you just call the code instead of loose-coupling it? It
>might be less beautiful. But "perverting" the event system isn't
>beautiful either. The ideas you had would complicate things a great
>deal, I believe.
>
>2) What about splitting your functionality - SomeEvent, and
>SomeEventWorker. So SomeEvent-handler simply adds SomeEventWorker to the
>queue. By the time that has been done, the ValidationAndPopulateEvent is
>already in the queue and will be processed first.
>
>Diez
>
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