You can take a look at the OSGi enRoute project's tutorial. This is still work in progress but in phase 10 it actually uses JPA, transactions, etc.
https://github.com/osgi/osgi.enroute.blog
In the master branch there is a PDF that describes the tutorial in detail, step by step. Each step is a branch so you can look at the 10-jpa branch. It uses bndtools.
This is work in progress but it should give you a good idea.