Incorrect / valid JAXB instance using JAX-RS

Question

Incorrect / valid JAXB instance using JAX-RS

With JAX-RS, do I need to test a JAXB element?

Can (should) the container verify the validity of the contents?

Can (should) the container automatically respond to BAD_REQUEST when disconnected Itembefore calling the REST method?

Can (May) respond to container requests INTERNAL_SERVER_ERROR when a client sends unmarshallable (or empty) content?

@XmlRootElement
class Item {
}

@PUT
@Path("/items/{item_id: \\d+}")
@Consumes({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
public Response updateItem(@PathParam("item_id") final Long itemId,
                       final Item item) {

    assert itemId != null; // '\\d+'


    assert item != null; // is this make any sense?

    // is it ok to assert item is never null?
}

One more question, what about byte[]?

@Consumes({MediaType.APPLICATION_OCTET_STREAM})
@PUT
@Path("/players/{player_id: \\d+}/picture");
public Response updatePicture(..., final byte[] bytes) {

    assert bytes != null;

   // is it ok to assert bytes won't be null even for an empty request body?

}