Hi Eric, I certainly like the idea of using a proxy in the lower domain layer, as the domain objects are completely agnostic to the fact a DB is being used or ...
Good question, Nick. Transactionality is an interesting aspect of domain-driven design. I use TOPLink, which has both proxies and UnitOfWork, and which uses...
Hi Randy. I have to admit in the past I have given in to the ease of informing the UOW from within the domain layer, though it always troubled me. Thinking...
... I like the application layer to control the transaction, the entities and value objects to be ignorant of it (except that dependency info and aggregate...
... Good question. I have seen three basic approaches to aggregates. 1. Noone thinks about aggregates, but to make the system work, they implicitely and...
... to ... knowledge of ... A proxy definitely does have knowledge of a query, and possibly a repository. The point was that it encapsulates this knowledge so ...
... You're lucky if you have the framework to work with. I am finding this more interesting looking at it from a poor mans project - we dont have any tools or...
This question was included in the original "Lazy Loading" post, but ... I agree with you that domain-driven design is not the best approach to everything. The...
Eric Evans wrote (some snipping done to remove non-relevant text): How should one implement lazy load for domain objects in DDD? For example, if we have a...
... Thanks for the insight, Eric. Since I have sent the email, I have begun my own little experiment in the actual implementation of an aggregate root. I...
Oops! What I meant to say was that the *Customer* has no knowledge of repositories or queries. The proxy does have that knowledge, which is its whole reason...
... Griffin, one thing to consider is creating Value Objects rather than value structs. I know you are only "exploring", but be aware of boxing issues which...
... Could you quantify what you mean by "boxing issues"? I am always interested in hearing about possible performance hits. ... That was my original...
... When you pass structs around, they are passed by value. To improve performance you will need to "box/unbox", but this involves copying data around too....
... Good point. But, I think one of the reasons I implemented them as structs was because they are passed by value. I was looking for a way to enforce the...
... When an object is passed out of the aggregate, no reference to it can be held. It isn't really a value object, though (unless it already was, inside the...
... Right. That's what I trying to accomplish. I was trying to create the objects inside the aggregate as value objects, so I wouldn't have to go through a ...
... Eric, in the above do I take it you mean, "During the lifetime of an aggregate part, it may transiently be referenced by collaborators, but only for the...
Hello all, I'm new to this group, but a long-time advocate of domain modeling. I'm now waiting for my "Domain-Driven Design" book to arrive in the mail. In the...
I have! Hello Matthew, and hello everyone else on the list. Welcome...I've been monitoring this group for a couple of weeks now, but have not yet participated...
Hi Matthew, I haven't read this or known of its existence, but I'll give it a shot - thanks for the pointer. Jill Nicola is a longtime associate of Peter...
Hah hah! I'm not too surprised to find you here, Robin! To the group, I also am a member of the JDO expert group, so my take on persistence is understandably...
Hi Robin, Persistence has never been, and probably never will be, truly "transparent". You yourself said on page 53 of your JDO book that "it is necessary for...
I have to agree with you Randy on this topic. I dont think we could ever build software and be agnostic to persistence. I also feel Robins comments while...
Hi, I too have been monitoring this list for a little while, Robin/Matthew nice to see you have joined...I'm also a JDO-pro person on the JDO expert...
I have read SOM and am reading DDD. I look at the association patterns in SOM to be *one* mechanism to contemplate candidate classes (especially entities)...
Keiron, To help us non-Java people, could you explain how repositories, factories and lazy loading actually works in JDO? I havent got a clue and it would...
... look at the association ... I think that is a very good point. SOM brings value to the table along with the other tools you mention. For some reason, if...
I'll try to give it to you in a nutshell, highly glossed over: Using JDO, you author your java classes as you normally would. Then, you create a JDO metadata...
Matthew thats cool! So, am right in assuming the PersistenceManager, the Transaction etc are part of the JDO framework and you didnt have to write any of...
