Isn't it a problem that you add entities to an aggregate from a different aggregate?

https://github.com/citerus/dddsample-core/blob/master/src/main/java/se/citerus/dddsample/application/impl/BookingServiceImpl.java#L38

    final TrackingId trackingId = cargoRepository.nextTrackingId();
    final Location origin = locationRepository.find(originUnLocode);
    final Location destination = locationRepository.find(destinationUnLocode);
    final RouteSpecification routeSpecification = new RouteSpecification(origin, destination, arrivalDeadline);

    final Cargo cargo = new Cargo(trackingId, routeSpecification);

    cargoRepository.store(cargo);

Here the Location is an entity, actually it looks like an aggregate root. Still you pass it as a parameter to the RouteSpecification. Afaik. aggregates cannot access each other directly. You should have added only a verified LocationId to the RouteSpecification, which is not necessarily the UnLocode you use for finding it. But correct me if I am wrong.

[chrisselwyn]

I too have recently started on the path of learning about DDD. I am finding that this example is very confusing because it appears to break the rules that I have been reading about in Eric Evans’s book and Vaughn Vernon’s book.

For example, just looking at the cargo root aggregate, I see that it imports several entities from other root aggregates. Some of these are not even roots of their respective aggregates.

Here is a list of such cases that I have found :-

• handling.HandlingHistory used in Cargo.java Delivery.java

• handling.HandlingEvent used in Delivery.java Itinerary.java HandlingActivity.java

• voyage.Voyage used in HandlingActivity.java Delivery.java Leg.java

• location.Location used in Cargo.java Delivery.java HandlingActivity.java Itinerary.java Leg.java RouteSpecification.java

Is there something that I am missing that makes it OK for these classes to import classes (including non-root aggregate classes) from other aggregates? It maybe that my understanding is wrong. In which case I would love to know how!

[npathai]

@inf3rno My apologies, I didn’t go through the whole comment, but there is one thing I read recently. It’s that DDD is only good if the domain logic has complexity and not a good fit if the technology is complicated. It only works in case of domain complexity. Maybe that’s something you can review, make sure you are not using incorrect approach.

Otherwise to get help on DDD, you can try reaching out at: DDD-CQRS-ES Slack. At the very least you can ask there for better community where you can ask this question. And anyways it’s a good community to be a part of if you are interested in DDD.