How do I open a generated html file in Vaadin OSGi, deployed on Felix

I have a Vaadin OSGi demo coming up and cannot find how to use a dynamically created html file.
I’m using Felix as the OSGi framework.
The UI consists of a tabsheet with for each installed bundle a tab.
The code in one of the tabs generates an html file, that need to be opened in a separate pop-up window.

When I run that bundle as a non-OSGi Vaadin app this works fine. I’m using
to get the physical path and file
is then written into the resource subfolder. The html file can then be opened with this url:

How can I do this similar in OSGi? I cannot find a physical directory where the html file can be written into.
The main app is opened with

I like to be able to open my html file using e.g

Any help would greatly be appreciated!