The DDD book mentions that ideally service implementations should be stateful. This makes perfect sense in terms of scalability and falls nicely in line with...
I think Fowler's first rule of distributed objects: "Don't distribute objects!" is worth remembering. ;) Be sure that its really necessary to *physically*...
... There's a whole set of patterns for dealing with things like this that fall under the rubric "dependency injection". ...
John Brewer
jbrewer@...
Aug 2, 2004 9:32 pm
1295
I'm responding slowly to this, but better late than never. The example (Yahoo's directory) helps bring out a few points about what aggregates are and even what...
... I thought this bore repeating. It was a big aha! for me just now. -- John Brewer Extreme Programming FAQ: http://www.jera.com/techinfo/xpfaq.html...
John Brewer
jbrewer@...
Aug 3, 2004 12:38 am
1297
Yes, thanks Eric, that was very helpful. So I guess we could say that one problem with using a single large hierarchy to model a domain is that they don't have...
Now you are on the right track. Brainstorm and experiment with different models. It seems to me this fits my way of thinking about a web directory better --...
Kris, I didnt see a reply for this message so heres mine. I believe it is best to localise the technical/implementation logic of your persistence choice to ...
Hi Nick, thanks for the response. I think the choice made so far falls in line with your recommendation. The repository contains the knowledge of how to...
Hello, I frequently come across with requirements such as these: "Customers are grouped by Customer Segments. There are a number of pre-defined Customer...
On Mon, 09 Aug 2004 18:19:40 -0000, joao_g_fonseca ... It looks like a role or "has-a" relationship. A Customer is a member of one CustomerSegment, and can...
John Brewer
jbrewer@...
Aug 9, 2004 6:38 pm
1303
Enumerations of value objects are common, as you say. For example, Currency comes up in many apps (and is included in Java 1.5). There seem to be a few...
Hello, Thanks for taking the time to write such a detailed answer. ... Exactly! ... This is one of my biggest issues with the reference tables. They exist just...
... I would very likely wait on this concern. Do a couple of changes manually if and when the "someone" requests them. Learn what "someone" really does, not...
I recently posted some thoughts regarding Repositories and Factories on my blog. I received a couple questions in response that I wanted to get some feedback...
... It could be handled by a CustomerRepository.deepSave() operation, or better, handled by a UnitOfWork. The unit of work contains collections of all domain...
Would you have the Unit of Work hand off to repositories or have the Unit of work perform all the persistence? Let's pretend for a moment that we don't have...
I'd let the mediator between the domain objects and whatever is providing the data source perform the persistence, invoked from the unit of work. Steve Eichert...
My name is Eric Rudahl and I attend the University of Wisconsin Eau Claire. I am in my last year of a Software Engineering degree. This summer I am doing an...
I would be tempted to use type-safe constant pattern to model this, as the number of customer segments seems small and the change - infrequent. Let's say you...
I'm not sure that I see the value of maintaining the data in both the typed constant and in the database. Unless you had a tightly controlled process for...
Hi all, Would you consider it OK and clean from a DDD-perspective to have one "global" Unit of Work per user session, which *spans* several repositories? The...
Short answer: yes. A unit of work represents a 'business transaction'. In the same way that XA system transactions can span several databases, a unit of work...
I would think this would have to be the case if transactions in services on the domain model span repository boundaries. "jnsk_jimmy2" <jimmy.nilsson@...>...
Hi Stephen and hi Jim, I've come to the same conclusion, but I'm not 100% sure that it's a good thing yet. ... Is this consensus for the whole DDD-group? Best...
How would you all handle the classic 'account transfer' scenario? Let's say we have these use cases: USE CASE #1 - Create New Account The user creates a new...
Why not? It is often the case that domain model have to be mapped to existing data sources in order to mine existing data or legacy applications for new...
