I am looking for an alternative to swt for building the interface of an Eclipse plugin I want to develop. Is it possible to build the interface of the plugin with JavaFX or HTML5 instead of swt ?.
I am targeting Eclipse Juno 4.2 or later.
Eclipse 4 defines an application model, i.e. a model of all the parts forming the application UI. The application model is decoupled from its presentation.
This means that different UI toolkits (SWT,XWT,JavaFX,etc.), can be used to implement the model. Theoretically you can build a UI using any presentation technology you want.
That said, Eclipse 4.2 (the IDE) still relies on good ol' SWT for it's UI. Which means, your plug-in will require some additional dependencies to be able to use a different toolkit.
e(fx)clipse (already mentioned by jewelsea), provides the necessary Eclipse tooling to build your plug-in. Among other things it plugs a JavaFX ViewPart plug-in template, which creates an example plug-in and adds the necessary bundle dependencies for you.
Imho, this would be your best bet.