How to implement Domain-driven Design and Hexagonal Architecture in your own Joomla custom components

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About 8mn to read

HOW IT WORKS:

There are mainly 3 layers :

3 - Infrastructure : Code specific to your favorite CMS (Drupal,Joomla,TYPO3,WordPress,etc...)
2 - Application : Code where you put Interfaces of Repository pattern, Clock Service to alter time
1 - Domain : Code of your Value Objects, your Entities and your Business Rules specific to your Domain

I would like to add 2 more layers which are "horizontal layers" that can be used cross layers on all other layers

B - Libraries : PHP Libraries for example from packagist.org
A - Internal : PHP Core (or any language used by your component. It's the foundation on everything else depends)

SUMMARY:

Basically a layer MAY depend on itself and/or lower layers

EXAMPLE USE CASE: You own a Digital Marketing Agency

You want to be able to publish your content simultanuously on Drupal, Joomla, TYPO3 and WordPress because
that's what your VIP clients use. So you hire a team of 6 developers aware of DDD best practices. One of them used Joomla and stumbled on this article. How would these principles apply in real life for your agency?

3: Infrastructure
- Drupal
  - Drupal specific code implementing Application layer code and/or using Domain layer code
- Joomla
  - Joomla specific code implementing Application layer code and/or using Domain layer code
- TYPO3
  - TYPO3 specific code implementing Application layer code and/or using Domain layer code
- WordPress
  - WordPress specific code implementing Application layer code and/or using Domain layer code
  - Your favorite CMS and/or Framework here
  - CMS and/or Framework specific code implementing Application layer code and/or using Domain layer code
2: Application:
- VIPClient
  - VIPClientRepositoryInterface
  - VIPClientRepositoryServiceInterface
  - ...
- ClockInterface (Could use PSR-20 from Libraries "horizontal" layer)
1: Domain
- BusinessRules
  - DeployArticlesToVIPClientsOnly
    - ...
- Common
  - AbstractValueObject
    - Name
    - Company
    - Role
    - ...
- VIPClient
  - Reward
    - LifetimeCustomerValue
    - ...
- ...
B : Libraries layer
- composer packages, npm packages, ...
A : Internal layer
- PHP Core (the language), Javascript (the language), etc...

Created: 26 June 2024

Last Updated: 23 March 2025

About the author:

Hi! Alex here,

Joomla Developer since 2009, focused on Web Services since 2017,

first in Joomla! 3 with jBackend and com_api

More recently leveraging Web Services built-in Joomla! core.

I like paperback format books, challenging projects and defensive cybersecurity "Blue Team".

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