Applying Domain Driven Design and Patterns

I read Applying Domain-Driven Design and Patterns over the last week.


Nilsson synthesized thoughts from pretty much every other book in the Fowler series and then gave his own spin on creating an enterprise-read application. The book is the first that I have seen for such an ambitious goal – actually applying DDD to a real-world example. I thought he did a good job in exploring the different possibilities when confronted with design decisions. In addition, he writing style was clear and on-point.

The only problem I have with his book is that some of the patterns he selected are out of date (not his fault at the time of his writing, his fault for not releasing a new edition). For example, he spends a whole lot of time with NHibernate (Chapter 8-9), which has been eclipsed by Entity Frameworks. Also, his implementation of a validation pattern is obsolete (chapter 7) with the new constructs in .NET 4.0. I would use the validation patterns found in the Scotts’ Nerd Dinner solution. In addition, he spends a lot of time with the implementation of the query object pattern – which is LINQ to you and me now.

Finally, the separation into a Factory and Builder pattern, although still accepted in some parts of the community, is too much SOC. I believe that a single factory that is responsible for the creation (rehydration or new) and updating of a class makes much more intuitive sense.

The two patterns that I am planning to implement in the my next POC application is the State pattern and the Specification Patten. His description and implementation was a guide for me to follow. I am leaning to re-writing the Hurricane solution using these patterns.


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