I don't argue that Jackson is a superior object mapper to the Grails 2.2.x internal one, but you're deviating from a fairly standard pattern (esp within the app) to make use of Jackson. I would prefer to see an [`ObjectMarshaller`](https://github.com/grails/grails-core/blob/master/grails-plugin-converters/src/main/groovy/org/codehaus/groovy/grails/web/converters/marshaller/ObjectMarshaller.java) implementation that made use of Jackson for the whole app. I'm sure somebody has already done this, and if not, it might be a worthwhile plugin.

If not, please at least set the response headers appropriately.