it doesn’t feel right when domain model leaves business layer (service layer) Makes you feel like you are pulling the guts out right? According to Martin Fowler: the Service Layer defines the application’s boundery, it encapsulates the domain. In other words it protects the domain. Sometimes service needs to return data object that wasn’t defined … Read more
Firstly, if you don’t know that you need it then it’s possible that you don’t need it. If you don’t recognize the problems that DDD solves then maybe you don’t have those problems. Even DDD advocates will frequently point out that DDD is only intended for large (>6 month) projects. Assuming that you’re still reading … Read more
Services come in 3 flavours: Domain Services, Application Services, and Infrastructure Services. Domain Services : Encapsulates business logic that doesn’t naturally fit within a domain object, and are NOT typical CRUD operations – those would belong to a Repository. Application Services : Used by external consumers to talk to your system (think Web Services). If … Read more
The difficulty with DDD samples is that they’re often very domain specific and the technical implementation of the resulting system doesn’t always show the design decisions and transitions that were made in modelling the domain, which is really at the core of DDD. DDD is much more about the process than it is the code. … Read more
DAO is an abstraction of data persistence. Repository is an abstraction of a collection of objects. DAO would be considered closer to the database, often table-centric. Repository would be considered closer to the Domain, dealing only in Aggregate Roots. Repository could be implemented using DAO‘s, but you wouldn’t do the opposite. Also, a Repository is … Read more