send SAP data as attachment in REST call

Hi All

Attaching file from application directory in REST call using CL_HTTP_CLIENT class.

I am able to send XML data in XString format from SAP ECC to CPI using CL_HTTP_CLIENT class POST method. It is being sent in body even if I use 'Header tag "Content-Disposition: 'Attachement' filename='sample.xml'". Please suggest any process to attach the XML file from application directory so that I will keep my internal table data in application directory and attach in REST call.

Regards

Anil