VFSDeployment is an interface. You can implement it how you like.
The default is predertermined attachments stored in a HashMap.
There's nothing to stop you using something else, e.g. deserializing them
from the file system (which is what I think you are trying to do)?
Perhaps it would be easier if the parent Deployment interface had a
setAttachments() instead of implementing Attachments?
That way you use the same implementation and choose how you want
to pass your attachments.
The default should still be a HashMap.