@Anjni Gupta.
I believe the content/type of your client is currently text/xml.
They may change this to multipart/form-data and send any file as an attachment. However, you will not longer receive a node as input instead you will receive a contentStream as input which will contain both your XML as well as your attachment.
You will have to use a different Parser, like HTTPServletRequest parser or apache file upload API. Refer FileUpload – Home.
#Integration-Server-and-ESB#webMethods