Don't use custom Spring servlet, Spring service, Spring session

[denis-anisimov]

@denis-anisimov commented on Wed Oct 11 2017

At the moment there are a number of class that are implemented for Spring: service, servlet, session.

It should be possible for the developer to create it's own implementations so that he doesn't know anything about a custom Spring vaadin servlet.

There should be a SpringInstantiator which is registered via Java SPI. To be able to keep Instantiator concept extensible we should change the implementation of creating/searching available Instantiator classes. If there is a several eligible classes then we should check the hierarchy. If they are subclasses of each others then just select the subclass.