Slides from my presentation at Dp Tech Talk Bcn #5 (https://www.meetup.com/DocPlanner-Tech-Barcelona/events/265687281/)

2. Hexagonal
architecture: how,
why and when

3. Hexagonal Architecture: how, why and when - 11/2019 3
About meAbout me
Carlos Gándara
software developer at
@xoubaman

4. Hexagonal Architecture: how, why and when - 11/2019 4
Why?

5. Hexagonal Architecture: how, why and when - 11/2019 5
A journey through
architectural patterns

6. Hexagonal Architecture: how, why and when - 11/2019 6

7. Hexagonal Architecture: how, why and when - 11/2019 7
Spaghetti

8. Hexagonal Architecture: how, why and when - 11/2019 8
Spaghetti architecture
✅ Fun to revisit after some years...
✅ Valid for small proof of concept scripts
with a 10 minutes life expectancy
...although that means you have it on production

9. Hexagonal Architecture: how, why and when - 11/2019 9

10. Hexagonal Architecture: how, why and when - 11/2019 10
MVC

11. Hexagonal Architecture: how, why and when - 11/2019 11
HTTP
language
Database
language
Business
rules
Data
centric
MVC architecture

12. Hexagonal Architecture: how, why and when - 11/2019 12
Ctrl+C
Ctrl+V
We want to add
products from the
console
MVC architecture

13. Hexagonal Architecture: how, why and when - 11/2019 13
I just realized
products have also
a max price
WET code
(makes you sweat)
MVC architecture

14. Hexagonal Architecture: how, why and when - 11/2019 14
Controllers go fat
MVC architecture

15. Hexagonal Architecture: how, why and when - 11/2019 15
MVC architecture
❌ No isolation of business logic
✅ Valid for prototyping and purely CRUD applications
❌ Data centric
❌ Hard to test, infrastructure everywhere

16. Hexagonal Architecture: how, why and when - 11/2019 16

17. Hexagonal Architecture: how, why and when - 11/2019 17
Layered architecture

18. Hexagonal Architecture: how, why and when - 11/2019 18
Layered architecture
HTTP & CLI
Same application
service
Diagram from book DDD in PHP

19. Hexagonal Architecture: how, why and when - 11/2019 19
Layered architecture (the wrong way)
Now need to read
products from this
random API
And we should
notify warehouse
guys
Database
language
Outside
world
Outside
world
Our thing

20. Hexagonal Architecture: how, why and when - 11/2019 20
Layered architecture (the wrong way)
Hey, plz generate a
RSS feed with
products we read
from this weird
machine
And did I
mentioned we
are migrating to
Mongo?
Combinatorial explosion
Infrastructure coupling

21. Hexagonal Architecture: how, why and when - 11/2019 21
Layered architecture (the wrong way)
Hey, plz generate a
RSS feed with
products we read
from this weird
machine
And did I
mentioned we
are migrating to
Mongo?
Combinatorial explosion
Infrastructure coupling
Aren’t tests
taking too much
time?
Testability

22. Hexagonal Architecture: how, why and when - 11/2019 22
Layered architecture
❌ Data persistence is in the core*
✅ Separation of concerns
✅ Application layer encapsulating use cases
❌ Potential infrastructure leaks in other layers*
✅ You can build good stuff
❌ Lasagna antipattern
* if you do it wrong

23. Hexagonal Architecture: how, why and when - 11/2019 23

24. Hexagonal Architecture: how, why and when - 11/2019 24
Hexagonal architecture

25. Hexagonal Architecture: how, why and when - 11/2019 25
Aka Ports and Adapters
Coined by Alistair Cockburn in 2005
Hexagonal architecture
Check out Alistair in the "Hexagone" in Youtube

26. Hexagonal Architecture: how, why and when - 11/2019 26
Allow an application to equally be driven by users,
programs, automated test or batch scripts, and to be
developed and tested in isolation from its eventual run-time
devices and databases.
Hexagonal architecture

27. Hexagonal Architecture: how, why and when - 11/2019 27
Outside the application
A boundary
Application
Hexagonal architecture

28. Hexagonal Architecture: how, why and when - 11/2019 28
Port:
● Outside element
communicating with the
application
● Defined by an interface*
Application
Adapter:
● Implementation of a port
interface into what
application understands
*Not a code interface, although
sometimes represented by one
Ports and adapters

29. Hexagonal Architecture: how, why and when - 11/2019 29
Primary ports
Drivers
Secondary ports
Repositories and
recipients
Ports and adapters

30. Hexagonal Architecture: how, why and when - 11/2019 30
Test driver
User interface
Router + HTTP Controller
Ports and adapters
CLI
Console component
REST API
External application
Other adapter
Other adapter

31. Hexagonal Architecture: how, why and when - 11/2019 31
Ports and adapters
REST API adapter with Symfony:
● Routing component
● HTTP Kernel and Controller
● HTTP component Request

32. Hexagonal Architecture: how, why and when - 11/2019 32
Ports and adapters
Persistence
Queue
Feed
Interface implementation
Interface implementation
Interfaces
defined by the
application

33. Hexagonal Architecture: how, why and when - 11/2019 33
Ports and adapters
Persistence adapter with Doctrine ORM
Application defines the contract in its
own language
We don’t care about using database
or library language in the adapter

34. Hexagonal Architecture: how, why and when - 11/2019 34
Ports and adapters
Persistence adapter with Doctrine ORM
No infrastructure leaks
Testability improved!

35. Hexagonal Architecture: how, why and when - 11/2019 35
How?

36. Hexagonal Architecture: how, why and when - 11/2019 36
Allow an application to equally be driven by users,
programs, automated test or batch scripts, and to be
developed and tested in isolation from its eventual run-time
devices and databases.
Hexagonal architecture
No mention to
layers...

37. Hexagonal Architecture: how, why and when - 11/2019 37
Hexagonal architecture
You can put whatever you want inside the hexagon

38. Hexagonal Architecture: how, why and when - 11/2019 38
Hexagonal + Layered

39. Hexagonal Architecture: how, why and when - 11/2019 39
Hexagonal + Layered

40. Hexagonal Architecture: how, why and when - 11/2019 40
User Interface and Infrastructure layer:
● UI for primary ports adapters
● Infrastructure for secondary ports implementations
Application layer:
● Defines the system use cases
● Orchestrates the domain logic
● Command + Command Handler pattern
Domain layer:
● Holds all the business logic and invariants
● Defines the contracts implemented in infrastructure
Hexagonal + Layered: a proposal

41. Hexagonal Architecture: how, why and when - 11/2019 41
Hexagonal + Layered
Domain
Application
UI
Infrastructure

42. Hexagonal Architecture: how, why and when - 11/2019 42
Hexagonal + Layered: Domain layer
Domain
Application
UI
Infrastructure
Don’t leak
infrastructure in
your domain

43. Hexagonal Architecture: how, why and when - 11/2019 43
Hexagonal + Layered: Application layer
Domain
Application
UI
Infrastructure
More logic
than this is
suspicious

44. Hexagonal Architecture: how, why and when - 11/2019 44
Hexagonal + Layered: Driver port
Domain
Application
UI
Infrastructure

45. Hexagonal Architecture: how, why and when - 11/2019 45
Hexagonal + Layered: Repository port
Domain
Application
UI
Infrastructure
Dependency inversion

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When?

47. Hexagonal Architecture: how, why and when - 11/2019 47
When to apply hexagonal architecture?
ALWAYS*

48. Hexagonal Architecture: how, why and when - 11/2019 48
When to apply hexagonal architecture?
Pros
● Testability
● Promotes separation of
concerns
● Pushes accidental complexity
out of the domain
● Open/Closed
● Handy base for DDD
● Handy base for CQRS and ES
Cons
● Indirection
● Amount of boilerplate code

49. Hexagonal Architecture: how, why and when - 11/2019 49
When to apply hexagonal architecture?
Makes no sense for
● Scripting
● Prototyping
● Tooling
● Frameworks
Makes sense for
● Applications relying on external technologies
● CRUD applications
● Anything more complex than that

50. Hexagonal Architecture: how, why and when - 11/2019 50
When to apply hexagonal architecture?
Take decisions based on the context and needs
Keep in mind the reasons and the consequences
ALWAYS

51. Hexagonal Architecture: how, why and when - 11/2019 51
Questions?

52. Hexagonal Architecture: how, why and when - 11/2019
● Slides of this presentation anytime soon in @xoubaman
● Article: Hexagonal Architecture by Alistair Cockburn
● Article: Hexagonal Architecture by Fideloper
● Article: DDD, Hexagonal, Onion, Clean, CQRS, … How I put it all together by Hebert Graca
● Video: Introducción Arquitectura Hexagonal (Spanish) by CodelyTV
● Video: Hexagonal Architecture - Message-Oriented Software Design by Matthias Noback
● Video: Alistair in the “Hexagone” by DDD FR
● Book: DDD in PHP by Carlos Buenosvinos, Christian Soronellas, and Keyvan Akbary
● Book: Implementing Domain Driven Design by Vaughn Vernon
● Code samples glittered with Carbon
52
Some resources to follow up

53. Thank you!