In the next paragraphs, I'll try to clarify as much as I can. You can also read the stories of how we rewrote the FundraisingFontend to use the Clean Architecture and how we refactored towards Bounded Contexts.If you've been anywhere around enterprise software architecture these years, chances are high that you've run into questions like "what is the right granularity of Microservices?" or "Are Microservices and Bounded Contexts the same thing?" Both these contexts are also used by another application the code of which sadly enough is not currently public. For an application following this architecture, see the FundraisingFrontend, which uses both the Donation Context and Membership Context. This code can make use of libraries and of course the runtime (ie PHP) itself.Īs examples of Bounded Contexts following this approach, see the Donation Context and Membership Context. The applications and Bounded Contexts contain all the domain specific code. It also means that the code responsible for the domain logic cannot be directly accessed elsewhere, such as in the presentation layer of an application. This means that there is 0 binding to the persistence mechanisms outside of the Bounded Context. The UseCases, including their Request Models and Response Models, form the public interface of the Bounded Context. The only things that can use these service implementations are other Domain Services and the UseCases. These implementations are the only thing that is allowed to talk to and know about the low-level aspects of the Persistence Layer. It has implementations of domain services such as Repositories which are used by the UseCases. The Persistence Layer can use a relational database, files on the file system, a remote web API, a combination of these, etc. The Bounded Contexts include their own Persistence Layer. They also form a boundary around the two, meaning that no code outside of the Bounded Context is allowed to talk to the Domain Model or Domain Services. They can use both the Domain Model and the Domain Services. These include interfaces for persistence services such as Repositories. Around the Domain Model are the Domain Services. ![]() Dependencies can only point inwards, so the Domain model which is at the center cannot depend on anything more to the outside. At the core of each BC we have the Domain Model and Domain Services, containing the business logic part of the subdomain. ![]() Ideally one Bounded Context per subdomain. In the second layer we have the Bounded Contexts. That means there is 0 binding to mechanisms such as frameworks and presentation code outside of the applications. Since the applications are in the top layer, and dependencies can only go down, no code outside of the applications is allowed to depend on code in the applications. ![]() The applications contain ALL framework binding, hence they are the place where you will find the Controllers if you are using a typical web framework. Often this involves reading configuration from somewhere. All applications also somehow construct the dependency graph they need, perhaps using a Dependency Injection Container or set of factories. Each application has presentation code which in bigger applications tends to reside in a decoupled presentation layer using patterns such as presenters. These can be web applications, they can be console applications, they can be monoliths, they can be microservices, etc. In the top layer of the diagram we have applications. Clean Architecture + Bounded Contextsĭiagram by Jeroen De Dauw, Charlie Kritschmar, Jan Dittrich and Hanna Petruschat. ![]() If you are not yet familiar with The Clean Architecture, please first read Implementing the Clean Architecture. In that post and at the end of this one I link you to a real-world codebase that follows the abstract rules described in this post. For the story on how we got to this point and a more concrete description, see my post Bounded Contexts in the Wikimedia Fundraising Software. In this post I describe the structure we have and the architectural rules we follow in the abstract. In this follow-up to Implementing the Clean Architecture I introduce you to a combination of The Clean Architecture and the strategic DDD pattern known as Bounded Contexts.Īt Wikimedia Deutschland we use this combination of The Clean Architecture and Bounded Contexts for our fundraising applications.
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