We also use an event/listener pattern with Wicket, but we use it in the other direction: rather than sending events to its children, the button bubbles an event up to a parent, usually the page, which handles it. Our events are verbs like SaveEvent, DeleteEvent, EditEvent, AddEvent, etc. and are generic so they can be used with different payloads (e.g., save person, save order, save company, etc.). We also use the WicketStuff annotation event dispatcher library to defined the handler methods with a simple annotation [1].
To implement this, we simply extend the AjaxButton class where the onSubmit method sends an event of a given type, using the model object of the associated form as the payload. This can be expressed very concisely in Java 8 where the event generator can be defined as a java.util.function.Function or BiFunction (e.g., (form, target) -> new SaveEvent<>(target, form.getModelObject())). While I like the idea of buttons and links sending events, I don't really see why this functionality should be in the core since it can be accomplished by sub-classing existing components and I don't think every component needs the functionality. Andrew [1] https://github.com/wicketstuff/core/tree/master/jdk-1.7-parent/annotationeventdispatcher-parent On Tue, Apr 28, 2015 at 7:56 AM, Martin Grigorov <[email protected]> wrote: > Hi Sven, > > The only problem I see with the interfaces approach is that it won't be > easy to extend them with extra functionality in a minor release if this is > ever needed. > > Martin Grigorov > Wicket Training and Consulting > https://twitter.com/mtgrigorov > > On Tue, Apr 28, 2015 at 12:47 PM, Sven Meier <[email protected]> wrote: > > > Hi Martin, > > > > why not just define interfaces in Components, and allow behaviors to > > implement these? > > Not that I'm convinced of the usefulness of this feature :P. > > > > Regards > > Sven > > > > > > > > On 28.04.2015 11:23, Martin Grigorov wrote: > > > >> Hi Sven, > >> > >> I imagine them as inner static classes in AbstractLink, Button and Form > >> classes. > >> AjaxRequestTarget will be an optional property for the event payload. > I.e. > >> AjaxButton will set it, Button will leave it null. > >> > >> Martin Grigorov > >> Wicket Training and Consulting > >> https://twitter.com/mtgrigorov > >> > >> On Tue, Apr 28, 2015 at 12:11 PM, Sven Meier <[email protected]> wrote: > >> > >> Hi, > >>> > >>> how (where) will these events (=payloads?) be defined? > >>> > >>> Sven > >>> > >>> > >>> On 28.04.2015 08:29, Martin Grigorov wrote: > >>> > >>> Hi Dan, > >>>> > >>>> On Mon, Apr 27, 2015 at 4:21 PM, Dan Haywood < > >>>> [email protected]> > >>>> wrote: > >>>> > >>>> Sounds a bit similar to Apache Isis' support for domain events > (albeit > >>>> > >>>>> at a > >>>>> higher level of abstraction). > >>>>> > >>>>> we've found that feature very useful, so I would imagine there would > be > >>>>> benefits from implementing this lower more general support in Wicket. > >>>>> > >>>>> Thanks for sharing your experience! > >>>>> > >>>> > >>>> You could also perhaps submit events for the validation (allowing > >>>> > >>>>> subscribers to veto changes). > >>>>> > >>>>> IMO there is no need to do this for validation. > >>>>> > >>>> Currently when an IValidator is added to a FormComponent it is > >>>> automatically wrapped in a Behavior [1]. > >>>> So Wicket will use the typesafer IValidator#validate(IValidatable) > >>>> instead > >>>> of Behavior#onEvent(IEvent) > >>>> > >>>> > >>>> 1. > >>>> > >>>> > >>>> > https://github.com/apache/wicket/blob/master/wicket-core/src/main/java/org/apache/wicket/markup/html/form/FormComponent.java#L515 > >>>> > >>>> > >>>> Cheers > >>>> > >>>>> Dan > >>>>> > >>>>> > >>>>> > >>>>> On 27 April 2015 at 13:13, Martin Grigorov <[email protected]> > >>>>> wrote: > >>>>> > >>>>> Hi, > >>>>> > >>>>>> https://issues.apache.org/jira/browse/WICKET-5884 suggest an > >>>>>> interesting > >>>>>> feature: > >>>>>> > >>>>>> All links/buttons/forms to broadcast Wicket events to their > Behaviors > >>>>>> > >>>>>> about > >>>>> > >>>>> the event. > >>>>>> I.e. a Link/Button will tell all its Behaviors that it has been > >>>>>> clicked, > >>>>>> > >>>>>> a > >>>>> > >>>>> Form will tell that it has been submitted. > >>>>>> The broadcast would be with type EXACT so only the current component > >>>>>> and > >>>>>> its behaviors will be notified via #onEvent(). > >>>>>> This way the application developer can reuse functionality that > should > >>>>>> be > >>>>>> executed for several links/submitters. > >>>>>> > >>>>>> While I see how this could be useful for some applications I also > see > >>>>>> > >>>>>> that > >>>>> > >>>>> it will add to the processing time for all applications no matter > >>>>>> whether > >>>>>> they use the feature or not. > >>>>>> > >>>>>> Also I guess some user will ask for OnBeforeButtonSubmitEvent + > >>>>>> OnAfterButtonSubmitEvent (same for Link and Form) so the extra > >>>>>> processing > >>>>>> time be doubled. > >>>>>> > >>>>>> What do you think about the feature? > >>>>>> > >>>>>> Martin Grigorov > >>>>>> Wicket Training and Consulting > >>>>>> https://twitter.com/mtgrigorov > >>>>>> > >>>>>> > >>>>>> > > >
