I'm more thinking of something like Vaadin/GWT where you compose the GUI in Java code, in a similar style as e.g. JavaFX, and the framework takes care of displa

I'm more thinking of something like Vaadin/GWT where you compose the GUI in Java code, in a similar style as e.g. JavaFX, and the framework takes care of displaying it in a web front end. Or, if the application is not strongly coupled to other server-side systems, make it standalone with a Swing, JavaFX or whatever front end.