After the frame was displayed the first time, I’ve needed to refactor everything a little bit. First the application itself is managed by an OSGI service (ApplicationManager). Here I use the idiom of having a public interface. The interface is exportet and visible to other packages and an internal implementation which is hidden inside the bundle. Also the service registers itself as bundle listener to show the frame after the bundle is started and dispose the frame when the bundle is stopped.
Also I started creating the managing interface for the content of the application. In the application everything is displayed in the main frame. So one can think of having different pages which are shown in the main frame.
Beside this I added some more projects with which I can create bundles for 3rd party libraries like Apache Commons Lang, JPA, etc.