@GET
@Produces({MediaType.APPLICATION_XML, MediaType.WILDCARD})
@ElementClass(response = MyList.class)
public Response listXML(){
    MyList list = getList();
    return Response.status(
    Response.Status.FOUND).
    entity(list).type(MediaType.APPLICATION_XML).build();
}



@GET
@Produces({MediaType.APPLICATION_JSON})
@ElementClass(response = MyList.class)
public Response listJson(){
    MyList list = getList();
    return Response.status(
    Response.Status.FOUND).
    entity(list).type(MediaType.APPLICATION_JSON).build();
}

No message body writer has been found for response class MyList.