Introduce IComponentOnInitializeListener for cross-cutting concerns
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                 Key: WICKET-3082
                 URL: https://issues.apache.org/jira/browse/WICKET-3082
             Project: Wicket
          Issue Type: New Feature
          Components: wicket
    Affects Versions: 1.4.12
            Reporter: Sven Ludwig


I suggest the introduction of 
org.apache.wicket.application.IComponentOnInitializeListener for 
onInitialize-cross-cutting-concerns on Components. Such a listener should be 
called for a Component right after the onInitialize Method of the Component has 
been executed. I hope this has not been discussed already. I have not found any 
such issues.

A use case: For implementing cross-cutting concerns in Wicket, there are 
several Listeners that are called at various points during the life-cycle of a 
Component. Such listeners as in Wicket 1.4.12 are 
IComponentInstantiationListener, IComponentOnBeforeRenderListener, 
IComponentOnAfterRenderListener. However, for adding a Validator to all 
IValidateable Components of a certain type, non of the existing Listeners is 
really a good option. IComponentInstantiationListener cannot successfully add a 
Validator in general, because such a listener is executed before the member 
variable validators in the FormComponent class is actually set to null during 
instantiation. IComponentOnAfterRenderListener will obviously be to late. And 
with IComponentOnBeforeRenderListener, the validator itself would (without 
extra coding) be instantiated and added in each request, which would be an 
unnecessary overhead.


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