The goal of this example project is to show how I create most of my project.
What I wanted to show:
- How I apply the
clean architecture(Hexagonal / Onion / Ports and Adapters) - How I use
reactive programming - How I apply
domain driven design - My
testing strategy(Unit/Integration/E2E) - How I use the
CQRS pattern(for this example just at code level)
To demonstrate what I wanted to show I needed to invent some requirements, I decided to go for a Newsletter subscription service with simplified rules.
Here are the spec:
- User can
subscribe to newsletter - User can
unsubscribe from newsletter - User can
see all of his subscription - User with
free plancan subscribe to5 newsletter maximum - User with
premium plancan subscribe to30 newsletter maximum - When a user change plan and go
from premium to freeand has more than 5 subscriptions he loses all subscription above free plan threshold and sogoes back to the first 5 subscriptionhe made - When a
new newsletter is publishedevery subscriber of this newsletter isnotified by an email
This service is focusing only on user subscription so all other aspects are supposedly made by others services.
When a user registers the imaginary service handling this requirement is sending an event, and this project catch it to instantiate a Subscriber on our side. Same applies when a user is changing his plan, we only catch the event saying the user has changed his plan.
Same goes for authentication, when a user subscribes/unsubscribes or wants to see all of his subscription, there is no authentication on our side, it's made by an imaginary service forwarding the request to our service after the authentication of the user.
I did this project in approximately 8 hours, so everything is not perfect, but it was not the goal. The only goal was to show briefly how I apply architecture and coding principle on a simple project.
Java 16, Spring, Reactor, Reactive RabbitMQ, R2DBC PostgreSQL, TestContainers, SendGrid