Currently the jSON content type is not used. Instead the palin/text content type is used. The reason for this as I understand is to enable viewing the json response as as text in the browser. While this is valid argument, I do believe that there should at least be an option to configure this writer to use the JSON content type. According to RFC4627 the json content type needs to be application/json (and not text/x-json). The reason this can be very helpful is that today you have plugins for browsers (e.g. JSONView) that can render any page with application/json content type in a user friendly manner (just like xml is supported).