I'm a little late to this conversation but here are my thoughts. But before that, it would be useful if you specify your PI version and whether it is on single stack or dual in your queries - it affects the solution that others offer.
Note that you will need ESR objects for this, so here it goes (take particular note those items highlighted in red):-
i) Define source data type (for sender file) with single dummy field occurrence 0-1
ii) Define target data type (for receiver proxy) with single dummy field occurrence 1-1
iii) Create all the necessary Message Type, Service interface for sender and receiver
iv) Create message mapping - Map a constant of any value to the target dummy field
v) Create operation mapping
vi) Configure all the necessary objects in Integration Directory (either classical scenario or ICO/iFlow)
- Make sure for your sender agreement, receiver determination that you do not specify the SWCV for the sender interface (this is to prevent it from performing XML parsing on the empty file)
viii) For your sender File comm channel, make sure Empty File Handling = Process Empty File
That is it. The source system can give you an empty file and you don't need a UDF to write the filename.
I have something like this that works, but on a slightly different scenario - on the response portion of an outbound sync interface, the response payload is empty but I have to return a status field to the calling proxy. So I just created a mapping with a constant mapped to the status field.
Rgds
Eng Swee