Hi Ravi,
please incase if you have some small client and most importantly the "web service" which would accept the attachments
"Soap with Attachments"(SwA) is one of the niche subjects within Web Services and I understand your problem that you couldn't find useful examples in your case. This is because not many people use this API. You must note that depending on the type of attachment (for mime type extensions refer
here), the code changes considerably if not completely. I don't know what file extension types you are interested in. But, whatever it is SwA is normally used along with JAX-RPC or JAX-WS in the latest web services where service provider WSDL should describe attachment mime parts in the soap binding element and correspondingly service provider code should handle attachments differently based on their mime types.
For example if an attachment of pdf (I picked pdf as you mentioned "docs") is expected, then
Partial WSDL:
Web Service end point interface
Sample client (partial code)
Web Service end point implementation (partial code)
There is a topic on this at the end of
RMH book. Though, it has not provided any complete example, understanding the theory would be sufficient for anyone to write their own code.