/**
* Extracts the {@link RoutingType} annotation to derive the stable
* routing type.
*/
private int getRoutingId(Class<?> i) {
RoutingType routingTypeAnnotation = i.getAnnotation(RoutingType.class);
Preconditions.checkNotNull(routingTypeAnnotation,
"RoutingType annotation must be specified for all subclasses of RoutableDto. " +
i.getName());
return routingTypeAnnotation.type();
}