Example: Interfaces and abstract classes
For example: public interface IFoo {} @XmlRootElement public class RealFoo implements IFoo {} @Path("/jaxb") public class MyResource { @PUT @Consumes("application/xml") public void put(IFoo foo) {...} } In this example, you would get an error from RESTEasy of something like "Cannot find a MessageBodyReader for...". This is because RESTEasy does not know that implementations of IFoo are JAXB classes and doesn't know how to create a JAXBContext for it.