Hexagonal Architecture, or how to completely overengineer your application

With this slidedeck, I try to explain what Hexagonal Architecture is. The main goal is to increase you knowledge about the subject, so that unfounded generalisations based on ignorance are a thing from the past!

Transcript

1. HEXAGONAL ARCHITECTURE OR HOW TO COMPLETELY OVER-ENGINEER YOUR APPLICATION
2. OR HOW TO DECOUPLE FROM YOUR FRAMEWORK
3. 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
4. © Carlos Buenosvinos DDD ARCHITECTURAL STYLES TRIP
5. 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
6. Who remembers their reaction when rst being introduced to a framework? SMALL AMOUNT OF INTERACTION
8. Boils down to I Not Understands :'(
9. Boils down to OVER-ENGINEERING!! (or any other generalization)
10. TO AVOID GENERALIZATIONS, LET ME TRY TO EXPLAIN
11. Ports & Adapters Message Oriented Architecture 2005, Alistair Cockburn HEXAGONAL ARCHITECTURE
12. 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
13. RESULT Infrastructure Agnostic Easy To Test Easy To Maintain
15. KEYWORDS Message Port Adapter
16. MESSAGE Carries the data of a communication Cross boundaries Examples: telephone message, fax, letter
17. PORT Enables an incoming message to enter a system Examples: telephone horn, letterbox, ears
18. ADAPTER Translate the message to something useful for the system Examples: modem, hairs in your ears
19. HTTP Message ➞ Web Server ➞ PHP-FPM CLI Command ➞ PHP Binary ➞ PHP Script ALREADY PART OF YOUR APPLICATION
20. THAT'S IT! DONE!
21. YOUR APPLICATION Uses framework Uses libraries (composer anyone?)
22. YOUR APPLICATION Creates dependencies between components
23. YOUR APPLICATION Stu that makes you money The rest
24. YOUR APPLICATION Essential part Non-essential part ↳ Framework, libraries, DB, Message Queue, ...
25. THE ESSENTIAL PART DOES NOT CARE ABOUT THE NON-ESSENTIAL DETAILS
26. Framework & Libraries abstract infrastructure details away
27. YOUR APPLICATION Domain Infrastructure
29. Is about separating your domain from your infrastructure HEXAGONAL ARCHITECTURE
30. TWO DISTINCT LAYERS Boundaries between Domain & Infrastructure
31. Cross boundaries with MESSAGE
32. CROSSING BOUNDARIES COMES WITH RULES
33. Dependencies only point inward THE DEPENDENCY RULE
34. (or how to not leak infrastructure details) Depend on I n t e r f a c e Inject concrete implementation THE DEPENDENCY INVERSION PRINCIPLE
35. < ? p h p n a m e s p a c e F o o \ B a r \ D o m a i n \ S e r v i c e ; u s e F o o \ B a r \ I n f r a s t r u c t u r e \ R e p o s i t o r y \ U s e r M y S q l R e p o s i t o r y ; c l a s s U s e r S e r v i c e { p u b l i c f u n c t i o n _ _ c o n s t r u c t ( U s e r M y S q l R e p o s i t o r y $ r e p o ) { / / . . . } }
36. < ? p h p n a m e s p a c e F o o \ B a r \ D o m a i n \ S e r v i c e ; u s e F o o \ B a r \ D o m a i n \ R e p o s i t o r y \ U s e r R e p o s i t o r y ; c l a s s U s e r S e r v i c e { p u b l i c f u n c t i o n _ _ c o n s t r u c t ( U s e r R e p o s i t o r y $ r e p o ) { / / . . . } }
37. < ? p h p n a m e s p a c e F o o \ B a r \ I n f r a s t r u c t u r e \ R e p o s i t o r y \ U s e r M y S q l R e p o s i t o r y ; u s e F o o \ B a r \ D o m a i n \ R e p o s i t o r y \ U s e r R e p o s i t o r y ; c l a s s U s e r M y S q l R e p o s i t o r y i m p l e m e n t s U s e r R e p o s i t o r y { p u b l i c f u n c t i o n _ _ c o n s t r u c t ( U s e r R e p o s i t o r y $ r e p o ) { / / . . . } }
38. 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
39. HOW?
40. MESSAGE ⇨ COMMAND Contains only data Name expresses intent Suggests a change Repeatable
41. < ? p h p c l a s s S a v e B l o g P o s t { p r i v a t e $ t i t l e ; p r i v a t e $ c o n t e n t ; p r i v a t e $ t a g s = [ ] ; p u b l i c f u n c t i o n _ _ c o n s t r u c t ( $ t i t l e , $ c o n t e n t , $ t a g s ) { $ t h i s - > t i t l e = $ t i t l e ; $ t h i s - > c o n t e n t = $ c o n t e n t ; $ t h i s - > t a g s = $ t a g s ; } }
42. PORT & ADAPTER ⇨ HANDLER Receives a Message/Command Knows what to do with it
43. < ? p h p c l a s s S a v e B l o g P o s t H a n d l e r { p r i v a t e $ r e p o ; p u b l i c f u n c t i o n _ _ c o n s t r u c t ( B l o g P o s t R e p o s i t o r y $ r e p o ) { $ t h i s - > r e p o = $ r e p o ; } p u b l i c f u n c t i o n h a n d l e ( S a v e B l o g P o s t $ c o m m a n d ) { $ p o s t = B l o g P o s t : : c r e a t e N e w ( $ c o m m a n d - > g e t T i t l e ( ) , $ c o m m a n d - > g e t C o n t e n t ( ) ) ; $ p o s t - > a d d T a g s ( $ c o m m a n d - > g e t T a g s ( ) ) ; $ t h i s - > r e p o - > a d d ( $ p o s t ) ; } }
44. < ? p h p c l a s s B l o g A d m i n C o n t r o l l e r e x t e n d s B a s e C o n t r o l l e r { p u b l i c f u n c t i o n c r e a t e A c t i o n ( $ r e q u e s t ) { / / c r e a t e f o r m e t c . i f ( $ r e q u e s t - > i s P o s t ( ) ) { $ c o m m a n d = n e w S a v e B l o g P o s t ( $ r e q u e s t - > g e t ( ' t i t l e ' ) , $ r e q u e s t - > g e t ( ' c o n t e n t ' ) , $ r e q u e s t - > g e t ( ' t a g s ' , [ ] ) ) ; $ h a n d l e r = $ t h i s - > g e t ( ' s a v e _ b l o g p o s t _ h a n d l e r ' ) ; $ h a n d l e r - > h a n d l e ( $ c o m m a n d ) ; $ r e s p o n s e - > r e d i r e c t ( ' / f o o ' ) ; } / / d i s p l a y t e m p l a t e
45. Receive Command Match Handler Centralized con guration Middlewares COMMAND BUS
46. < ? p h p c l a s s B l o g A d m i n C o n t r o l l e r { p u b l i c f u n c t i o n c r e a t e A c t i o n ( $ r e q u e s t ) { / / c r e a t e f o r m e t c . i f ( $ r e q u e s t - > i s P o s t ( ) ) { $ c o m m a n d = n e w S a v e B l o g P o s t ( $ r e q u e s t - > g e t ( ' t i t l e ' ) , $ r e q u e s t - > g e t ( ' c o n t e n t ' ) , $ r e q u e s t - > g e t ( ' t a g s ' , [ ] ) ) ; $ t h i s - > c o m m a n d B u s - > h a n d l e ( $ c o m m a n d ) ; $ r e s p o n s e - > r e d i r e c t ( ' / f o o ' ) ; } / / d i s p l a y t e m p l a t e } }
47. Slim controllers Infrastructure independent / Reusable Easily testable Easy to maintain OVERENGINEERD?
48. TIPS / CONSIDERATIONS
49. They don't return things COMMANDS CHANGE THINGS
50. But how can you get the thing you just created?
51. GENERATE NECESSARY STUFF OUTSIDE HANDLER
52. < ? p h p c l a s s B l o g A d m i n C o n t r o l l e r { p u b l i c f u n c t i o n c r e a t e A c t i o n ( $ r e q u e s t ) { / / c r e a t e f o r m e t c . i f ( $ r e q u e s t - > i s P o s t ( ) ) { $ i d = $ t h i s - > g e n e r a t o r - > g e n e r a t e I d ( ) ; $ c o m m a n d = n e w S a v e B l o g P o s t ( $ i d , $ r e q u e s t - > g e t ( ' t i t l e ' ) , $ r e q u e s t - > g e t ( ' c o n t e n t ' ) , $ r e q u e s t - > g e t ( ' t a g s ' , [ ] ) ) ; $ t h i s - > c o m m a n d B u s - > h a n d l e ( $ c o m m a n d ) ; $ r e s p o n s e - > r e d i r e c t ( ' / d e t a i l s / ' . $ i d ) ; }
53. C r e a t e U s e r & E d i t U s e r ⇨ S a v e U s e r Reusable Easier to maintain SMART NAMING
54. No immediate result May require changes to your code ASSUME COMMAND'S ARE PUT ON A QUEUE
55. ! THE DEPENDENCY RULE !
56. 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
57. THANK YOU!
58. QUESTIONS?
59. HTTPS://LEGACY.JOIND.IN/19077