throw new MappingException("Could not get id for " + unwrapped.getClass().getName());
}
//remove (immutable) _id field for update.
final Object idValue = dbObj.get(Mapper.ID_KEY);
dbObj.removeField(Mapper.ID_KEY);
WriteResult wr;
final MappedClass mc = mapper.getMappedClass(unwrapped);
final DBCollection dbColl = getCollection(unwrapped);