I would recommend finding an existing Java-based component and just
seeing if it will work in your environment. In general I'd like to
push back against the idea that we need "OSGi compliant" versions of
everything...
Unfortunately I don't actually know any existing Java-based Shoppings
Carts or payment processors. There is Apache OFBiz but I have no idea
if it will do what you want.
By the way, was there a particular reason for sending this to the
Vaadin-OSGi list? You might have better luck emailing a more generic
list.
Regards,
Neil