Re: How to support multiple AbstractTransformerBehavior per component, if at all?

[Martin Grigorov <mg...@apache.org>]

On Mon, Aug 31, 2020, 19:14 Sven Meier <sv...@meiers.net> wrote:

> Hi Thorsten,
>
> > changed implementation is simply reversing the order of how behaviours
> are called per component
>
> the solution I was able to came up with: reverse the order of
> #afterRender() only!
> This way callbacks to behaviors are 'nested', i.e. the first behavior has
> the first *and* last word on rendering -
> something you can see in other frameworks/architectures too where
> resources are managed:
>
>    behaviorA#beforeRender()
>      behaviorB#beforeRender()
>      behaviorB#afterRender()
>    behaviorA#afterRender()
>
> I agree with Martin that we shouldn't change this lightheartedly - it
> might break existing applications.
> AbstractTransformerBehaviour is special and I don't know of any other
> behavior that needs this if more than one instance is added to a component.
>
> You can just use a single behavior and let it manage a list of
> transformators.
>
> +1 for changing this in Wicket 10
> +0 for Wicket 9
>

Same votes from me too


> Best regards
> Sven
>
>
> On 31.08.20 12:48, Thorsten Schöning wrote:
> > Hi all,
> >
> > multiple instances of AbstractTransformerBehaviour on one component
> > don't work properly currently. Reason is that all of those change
> > response objects and are always executed in the order they were
> > registered, which doesn't properly take the replaced responses into
> > account. At some point, later registered and executed transformers
> > replace the response with what they think is the original one, while
> > it actually is a temporary one of former transformers as well.
> >
> > This behaviour can be tested with the attached quickstart by simply
> > changing the following two lines. Details are documented in the linked
> > JIRA-issue as well.
> >
> >> label.add(new FooTrans());
> >> //label.add(new BarTrans());
> > https://issues.apache.org/jira/browse/WICKET-6823
> >
> > This thread is about discussion whether or not to support multiple
> > transformers per component at all, if so how and in which release of
> > Wicket.
> >
> > One suggestion for a changed implementation is simply reversing the
> > order of how behaviours are called per component. Another one is to
> > change instead who manages the replaced responses how, e.g. by
> > introducing some container-concept wrapping multiple transformers.
> >
> > Mit freundlichen Grüßen,
> >
> > Thorsten Schöning
> >
>