Hexagonal Architecture, or how to completely overengineer your application

HEXAGONAL ARCHITECTURE
OR HOW TO COMPLETELY OVER-ENGINEER YOUR APPLICATION

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OR HOW TO DECOUPLE FROM YOUR FRAMEWORK

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ON THE MENU TODAY
An Introduction
Small Amount of Interaction
Mainly Me, Explaining Things
Illustrated By Some Code
An O er of Links and Tools
Small Amount of Interaction

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© Carlos Buenosvinos
DDD ARCHITECTURAL STYLES TRIP

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Who considers themselves still at the spaguetti level?
Who considers themselves at the framework level?
Who considers themselves at a further level?
SMALL AMOUNT OF INTERACTION

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Who remembers their reaction when rst being introduced to a
framework?
SMALL AMOUNT OF INTERACTION

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Boils down to
I Not Understands :'(

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Boils down to
OVER-ENGINEERING!!
(or any other generalization)

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TO AVOID GENERALIZATIONS, LET ME TRY TO EXPLAIN

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Ports & Adapters
Message Oriented Architecture
2005, Alistair Cockburn

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The Hexagonal Architecture allows an application to be equally
driven by users, programs, automated tests or batch scripts, and
to be developed and tested in isolation from its eventual run-time
devices and databases

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RESULT
Infrastructure Agnostic
Easy To Test
Easy To Maintain

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KEYWORDS
Message
Port
Adapter

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MESSAGE
Carries the data of a communication
Cross boundaries
Examples: telephone message, fax, letter

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PORT
Enables an incoming message to enter a system
Examples: telephone horn, letterbox, ears

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ADAPTER
Translate the message to something useful for the system
Examples: modem, hairs in your ears

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HTTP Message ➞ Web Server ➞ PHP-FPM
CLI Command ➞ PHP Binary ➞ PHP Script
ALREADY PART OF YOUR APPLICATION

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THAT'S IT! DONE!

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YOUR APPLICATION
Uses framework
Uses libraries (composer anyone?)

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YOUR APPLICATION
Creates dependencies between components

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YOUR APPLICATION
Stu that makes you money
The rest

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YOUR APPLICATION
Essential part
Non-essential part
↳ Framework, libraries, DB, Message Queue, ...

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THE ESSENTIAL PART
DOES NOT CARE ABOUT
THE NON-ESSENTIAL
DETAILS

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Framework & Libraries abstract infrastructure details away

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YOUR APPLICATION
Domain
Infrastructure

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Is about separating your domain from your infrastructure

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TWO DISTINCT LAYERS
Boundaries between Domain & Infrastructure

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Cross boundaries with
MESSAGE

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CROSSING BOUNDARIES COMES WITH RULES

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Dependencies only point inward
THE DEPENDENCY RULE

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(or how to not leak infrastructure details)
Depend on I
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Inject concrete implementation
THE DEPENDENCY INVERSION PRINCIPLE

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Create a Message in the Infrastructure layer
Use a Port to get it to the Domain layer
An Adapter creates something useful
↳ Your Domain code
CROSSING BOUNDARIES IN YOUR APPLICATION

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HOW?

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MESSAGE
⇨ COMMAND
Contains only data
Name expresses intent
Suggests a change
Repeatable

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PORT & ADAPTER
⇨ HANDLER
Receives a Message/Command
Knows what to do with it

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Receive Command
Match Handler
Centralized con guration
Middlewares
COMMAND BUS

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Slim controllers
Infrastructure independent / Reusable
Easily testable
Easy to maintain
OVERENGINEERD?

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TIPS / CONSIDERATIONS

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They don't return things
COMMANDS CHANGE THINGS

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But how can you get the thing you just created?

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GENERATE NECESSARY STUFF OUTSIDE HANDLER

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C
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r & E
d
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s
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r
⇨ S
a
v
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U
s
e
r
Reusable
Easier to maintain
SMART NAMING

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No immediate result
May require changes to your code
ASSUME COMMAND'S ARE PUT ON A QUEUE

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! THE DEPENDENCY RULE !

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Allistair Cockburn - Hexagonal Architecture -
http://alistair.cockburn.us/Hexagonal+architecture
Tactician - Command Bus -
https://tactician.thephpleague.com/
SimpleBus - Command Bus & more -
http://simplebus.github.io/MessageBus/
Matthias Noback - Slides PHPBenelux 2016
DDD in PHP - https://leanpub.com/ddd-in-php
TOOLS / LIBRARIES

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THANK YOU!

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QUESTIONS?

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HTTPS://LEGACY.JOIND.IN/19077

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Hexagonal Architecture, or how to completely overengineer your application

Hexagonal Architecture, or how to completely overengineer your application

Tom Van Herreweghe

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