Organizing source code as layers

There are two popular choices for organizing source code as layers. In Kotlin, the first approach is to put files into their belonging packages as layers.

In the real-life example we used, we could have the following packages in each architectural style:

• Clean Architecture:

  org.example.service.negotiation.entity
  org.example.service.negotiation.usecase
  org.example.service.negotiation.interface
  org.example.service.negotiation.framework
  org.example.service.negotiation.framework.rest

• Hexagonal architecture:

  org.example.service.negotiation.core
  org.example.service.negotiation.core.port
  org.example.service.negotiation.adapter
  org.example.service.negotiation.adapter.rest

• FCIS:

  org.example.service.negotiation.core
  org.example.service.negotiation.shell
  org.example.service.negotiation.shell.rest

Enforcing the layered architecture, where only the outer layer can use the inner layer and not the other way round, can easily be done using test...