have a Vaadin portlet add document form which includes a file upload (with browse) ; for a pdf

I want to name the pdf file server side using the same as db primary key (postgresql 8.4)

Doc doc = DocLocalServiceUtil.create(0)
doc = DocLocalServiceUtil.addDoc(doc)

String fileName = doc.getDocId()

..

but for rollback, what if user just navigates away from the form ?

no longer needed

a class that implements Receiver allows for the filesystem filename to be changed after upload

turned into more of a Vaadin question than a Liferay one ; tho while on that point there are transaction challenges across LR/Vaadin