Clean Architecture Example: Code for an Onion Architecture

Details: 02 August 2013

A couple days ago I wrote about Clean Architecture. I was also excited, how it will look like within code. How does it feel? How can I progress.

Yesterday I started to hack for a while. I was very surprised since a long time ago. I started right off with the use cases. Just defined a bunch of them:

CreateOrUpdateItem
CreateOrUpdateUser
ListItems
ListOrders
PlaceOrder

I defined my application model, the boundaries. After that I lifted off by going Test-Driven. This was an amazing experience. My use cases were done in less than two hours. Everything. Done.

In the second step I integrated JPA, some In-Memory-Database and got stuck in relations mapping for some hours. The collections I mapped didn’t want do load. Persistence was fine, but loading did not work out. After some 2 hours I figured it out and everything went smooth then. This is an indicator, that external integrations are way more complex than internal use cases.

JSF and REST were as well easy-peasy. Some resources, models and controllers, now we can run.

Take a look on the code: https://github.com/mp911de/CleanArchitecture

There you’ll find a fully running example. All you need then is Maven and a JBoss 7.2 (JBoss EAP 6.1). This way of working is really amazing, it feels even faster than Rapid Application Development.