I am planning to build an adapter between a PC and devices which have the same function but which have different interfaces. The adapter will probably be based on a Raspberry Pi and will have a touch display. The PC app will know nothing about which device is actually connected and the device will be selected via the touch screen on the adapter.
I would like the adapter to provide a REST API which will allow the PC to communicate in a standardised way with the attached device. The adapter will indicate on the display which type of device is attached, display the current status and perhaps logging information.
My first idea was to create a Java app on the RPi which has a GUI and is also a REST server. After doing some research I haven't found any examples of this kind of app.
Am I missing something? Is there reason not to mix a REST server and a GUI?