[jwt-dev] Good dev practices : writing extension points

[Marc Dutoo <marc.dutoo@xxxxxxxxxxx>]

Hi all

On the more generic topic of extension point coding :

  * extension point code should be externalized in its own class(es). 
At least code that reads in the plugin registry should be externalized 
such. Thanks to this, there will be no more registry introspection code 
lost in UI classes !

  * for extensions that are made to configure a choice of 
implementation(s), there should be an Xxx interface that these 
implementations have to implement. Often there should also be a 
descriptor or factory interface (XxxDescriptor or XxxFactory) that is 
read and configured from the registry and know how to instanciate said 
implementations. Possibly there should be a 
dedicatedXxx(Descriptor/Factory)Registry interface that gives access to 
them.

  * there are already in JWT several patterns or code snippets that do 
this.
     * look at how Mickaël does in ex. PropertyDescriptor 
ExtensionPoint : a singleton class to hold the extension point code, and 
other interfaces from there
     * things more in line with what is done in EMF is good for 
low-level stuff, like is done in aspects / profile code 
(jwt-we-conf-model : look at AspectFactory interface and singleton impl)

Regards,
Marc