The service I am trying to connect accepts selective content type. It requires file in multipart form-data, while the filename, extension, folderid in text. Referring to the post 

https://collaborate.pega.com/question/how-pass-file-form-data-connect-rest-post-method-body

I have set the 4 required properties for file on page pyRequestAttachmentPage on index 1, for the remaining additional data I have added subsequent values in the value list properties as:

pyAttachNames(2): "extension" pyAttachValues(2):@Base64Encode("txt") pyAttachTypes(2):"application/text"

and so on for others.

In Pega with the above configuration, I am facing 500 error code Failed to convert value of type 'org.springframework.web.multipart.support.StandardMultipartHttpServletRequest$StandardMultipartFile' to required type  'java.lang.String'; nested exception is java.lang.IllegalStateException