OSGi environment: MOXy as JSON provider gives MarshalException - json

Question

Environment: OSGi via Equinox with Jersey and MOXy
I have a simple class as ReST component:
package test.rest;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import test.domainobjects.TestDomainObject;
#Path( "/test" )
public class TestTheRest {
#GET
#Produces(MediaType.APPLICATION_JSON)
//#Produces(MediaType.APPLICATION_XML)
public Object getTestEntity() {
return new TestDomainObject();
}
}
and a simple entity
package test.domainobjects;
public class TestDomainObject {
public int fieldA = 1;
public String fieldB = "Some content";
}
When I start my launch configuration and run a GET on <server>:<port>/services/test, I get a 500 error and an exception which I can only see in the debugger:
javax.xml.bind.MarshalException
- with linked exception:
[Exception [EclipseLink-25003] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: An error occurred marshalling the object
Internal Exception: Exception [EclipseLink-25007] (Eclipse Persistence Services - 2.5.0.v20130507-3faac2b): org.eclipse.persistence.exceptions.XMLMarshalException
Exception Description: A descriptor for class test.domainobjects.TestDomainObject was not found in the project. For JAXB, if the JAXBContext was bootstrapped using TypeMappingInfo[] you must call a marshal method that accepts TypeMappingInfo as an input parameter.]
The thing is that I am using the OSGi - JAX-RS Connector (with MOXy provider), so all the wiring happens under the hood.
How am I supposed to supply a descriptor? And why? Shouldn't MOXy be able to convert a POJO to JSON without additional details?