Hi Oliver, there is another thing I don't understand: Why you do not run into the following "problem" I ran with your code:
https://github.com/osx2000/finmath-service/blob/master/bundles/service/src/main/java/de/osx2000/finmath/service/OpenApiResource.java#L125 If a "json" reply is generated you stringify the object already and place the JSON string representation of the object as entity in the response. As media type JSON is chosen... For me the message body writer for the media type JSON is picked up by JAX-RS to encode the response's entity. The entity object (a string that already is a valid JSON string) is then again stringified as JSON... Why is this not been the cause for your message body writer?