Basics of hexagonal architecture + Project

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Getting started with hexagonal architecture with simple questions

  • What is hexagonal architecture?

    Documented in 2005 by Alistair Cockburn, hexagonal architecture is a software tool which has a lot advantages and got your interest renewed in 2015.

  • Why to use it?

    To allow a application be equally driven by users, programs, automated tests or batch scrips and develop or tested in a totally isolated form from your devices and databases

  • A picture from how that architecture achieves that

    PortsAndAdapters

    • Domain layer:
      • The mains reason of the software existence
      • Entity
      • Business logic
    • Application Layer:
      • Use cases
      • Application flow
    • Framework Layer (adapters):
      • Serialization
      • HTTP
      • Visualization process

  • The main reason to use it

    • To isolate the core (Domain and application) as much as possible from the the framework layer

  • How does the application communicate with the other parts?

    • Through ports (like Interfaces in Java) and adapters, which are implemented in these ports

    • Adapters stays outside of the core, which means that can be easily replaced at any time

    • Inbound communication

      • When an action is required from outside of the core. Example: Any requisition from a browser

    • Outbound communication

      • When an action comes from inside of the core. Example: Persisting any data on the Database

    • The difference between the traditional layers architecture and hexagonal architecture

      • In the hexagonal architecture, there is no coupling between the core and the infrastructure

  • Pros

    • It’s easy to code unit tests
    • Independent of frameworks or other tools
    • Low or no coupling in the application core
    • It’s easy to replace any part of the infrastructure, like a database

  • Cons

    • Additional complexity
    • There is no organization standards to work with that architecture

Personal project using hexagonal architecture

To deepen my knowledge, I coded an API in Java which is totally uncoupled from the frameworks, you can find it here: Breaking bad API

At the beginning, I was struggling with interfaces and the communication between the domain layer and the framework layer, but I had a help from Gabryell who I’m grateful

Source:

ARQUITETURA HEXAGONAL EM MICROSERVICES (Portuguese) - Michelli Brito