I've been using Postman to test some RESTful services and came across a strange error in the body of the response from a service - "Unexpected 'N'". I knew for a fact that the service was not returning this error so something else must have been going haywire.

This is what I was seeing in Postman...


However when I switched to raw output, I could see it was displaying 'Not Found'. That was an error string that the service could return. So what was going on here?


Well the service was annotated with this:


That meant that Postman was expecting a JSON object response and was getting a simple string instead!

So Postman was correctly saying that the service response was returning an unexpected value based on the application specification (via the @Produces annotation).



-i