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Screaming Architecture translated to practice

I like Uncle Bob’s post on Screaming Architecture.

On a small scale, I can visualize how code should look like what it does: meaningful identifiers, functions that do one thing, etc. On a larger scale, the challenge is getting the right balance between embracing frameworks and keeping them at arms’ length. Tight coupling to frameworks can add friction by obscuring your domain with generic framework-management code. But adding too many extra layers to hide the frameworks can add even more friction, especially if the extra layers prevent you from using the frameworks idiomatically.

If you use the right frameworks the right way, your project may scream “Spring!” or “Entity Framework!” but, in return, the frameworks eliminate the clutter of tedious boilerplate code, which makes it possible for your project to scream “Accounting system!” at the same time. The key is to choose and leverage frameworks that make your domain logic stand out, rather than obscure it, and to accept that trying to hide the frameworks might be counterproductive.

How does that translate in practice? If I’m writing an ASP.NET application with Entity Framework and Angular, my application is going to look like I’m using all those frameworks, but I’m going to use them in a way that my domain logic is still clear and at least somewhat framework-agnostic. The sweet spot I’ve found with both Spring and ASP.NET is something like:

  • Keep controllers thin, with business logic handled elsewhere. That way you can invoke business logic directly for test purposes.
  • Don’t be afraid to put domain logic directly in domain objects, when the logic is local to a single entity. The whole point of ORM is to map real domain objects – if the domain object only represents a row in a table, we could just use hashes.
  • Likewise, there is no need to copy attributes from persistent entities to separate “real” domain objects. The additional boilerplate of copying data around clutters the true domain.
  • ORM is already an abstraction layer around the database so it’s often not necessary to put another layer around the ORM.
  • On the client side, presentation code is likely coupled to a framework, but there may be some logic that can be extracted and invoked independently. That can be isolated the same way as you would separate a service from a controller on the server.
Written on October 25, 2015