RESTEasy should have some Provider to produce primitive types without @Produces annotation
In RESTEasy 2, DefaultTextPlain provider was used to process return value of end-points, that don't have @Produces annotation and return primitives:
In RESTEasy 3, DefaultTextPlain is not used (see comments of this jira). RESTEasy should contains provider for this purpose.
This jira solves partially RESTEASY-1403