Hexagonal Architecture

The goal of the Hexagonal architecture, also known as Port & Adapter is to isolate the core of the application from the other systems.

Inside vs Outside

Once identified, the outside systems are divided in two categories:

• Driver: that needs our application to work
• Driven: that we need for our application to work

The rest of the code is the application itself, the inside part of the hexagon

Ports & Adapter

Ports

The application contains the description of the needed services. Those descriptions are the ports

Adapters

For the Driver, it will be the use of the ports that we can call. For the Driven, it will be the implementation of the needed service

Source: Hexagonal me

Implementation

Package organization

A package organization of this architecture can be

<src>
  | <module name>
     | domain classes (organized as you want) 
     | adapter
        | in
        | out
     | ports
        | in
        | out
     

Dependencies

As a recap of the whole dependencies:

• The Driver side uses the application logic
• The application implements the provided use cases
• The Driven side implements the services needed by the application

Source: Hexagonal me

Kata

Goal

Implement the port & adapter aka hexagonal architecture for a simple use case.

This is a quite guided tour on how to setup it.

Steps

• Step 1 - Implement the hexagon
• Step 2 - Add a creation use case
• Step 3 - Inter module communication