we have a requirement wherein we need to send a file attachment

we need to send Siebel file attachment  along with its metadata to external system using web service call.
file attachment should be with Content-Type: multipart/form and metadata should be sent in a json structure in a post call.
Can you please help how we can achieve this requirement from Siebel and if not , in built siebel than how we can achieve it using java business service. Can you help with java code as well for the smae requirement.