Workflow Call HTTP Web Service returns xml instead of Json

Question

I developed a Workflow that uses http call webservice in our devlopment site on O365. When I rebuilt the identical workflow in production, it fails with the error:

System.IO.InvalidDataException: Unable to deserialize HTTP response content. Expected ContentType : 'application/json', 'text/plain' or 'text/html', Received ContentType : 'application/atom+xml'

This indicates to me that the headers that specify Json response are not getting to SharePoint.

I am setting the request headers in both calls the same - and the log shows the values are the same in both: {"Accept":"application\/json;odata=verbose","Content-Type":"application\/json;odata=verbose"}

What could be different in the two environments - and what would I have to change to make it work in production?

Answer 1

A co-worker ran across this issue, and I found the resolution to it on another site. It boils down to this:

"To resolve this issue we need to pass Accept and Content-Type as application/json;odata=verbose to both the response headers and request headers. This way we will get JSON response."

For a full explanation and walk-through, please see Prasad Pathak's Technology Blog post on this from Feb 2015. SharePoint 2013: Desinger workflow error with 'Call HTTP web service' action.

Answer 2

Just in case the accepted answer fix does not work -

I too had ran into this issue. In my code, I verified the point mentioned in the accepted answer but that was not the mistake which I had made.

So on further investigation, I realized that there were some look-up columns used in the list which was being queried using REST api. The correction required for was that a select condition was needed to be added in the REST url for making the fix.