parametrize CallbackLogic in CallbackController

[unkarjedy]

For some reason org.pac4j.play.CallbackController has a hardcoded CallbackLogic:

private CallbackLogic<Result, PlayWebContext> callbackLogic = new DefaultCallbackLogic<>();

Callback logic can be set in org.pac4j.core.config.Config:

public void setCallbackLogic(final CallbackLogic callbackLogic)

but it is not used.

It would be great to be able to parametrize the callbackLogic, parhaps to read it from config after it is injected.

[unkarjedy]

probably related to #242 because config is injected

[leleuj]

Generally, you only have one CallbackController and thus one CallbackLogic. This is a bit strange to be able to set the CallbackLogic at the Config logic, I honestly don't remember the reason behind this design.
Do you really have a use case for that?

[unkarjedy]

@leleuj The only reason we have only one CallbackController is just that it delegates the real work to CallbackLogic. There is no need for extra abstraction interface CallbackLogic while we do not allow user to change it. The main purpose of Strategy Pattern is to be able to change the logic at a runtime.

In my current prod project, I've created a custom MyCallbackLogic extends DefaultCallbackLogic[Result, PlayWebContext] that a bit modifies redirectToOriginallyRequestedUrl (to support redirection to SinglePageApplications that are deployed on a separate domain). And just because CallbackController has a hardcoded logic I had to create my custom MyCallbackController. So I create 2 classes instead of 1. More of that I have to extend Java-based play.mvc.Controller in my Scala code just because PlayWebContext requires Java-based play.mvc.Context

Actually the same logic for LogoutController and DefaultLogoutLogic

If you agree that we should be able to change the default logic I could prepare a pull-request.

[leleuj]

Yes, sure, we should be able to plug in a new CallbackLogic without creating a new CallbackController class.
Please submit a PR, this must be backward compatible as it will target the version 6.1.0.