Advanced Application Architecture Symfony Live Berlin 2018

1. ADVANCED
APPLICATION
ARCHITECTURE
I - Layers
Matthias Noback
@matthiasnoback

2. MATERIALS
ARE ON
TWITTER
https://twitter.com/
matthiasnoback

3. matthiasnoback/
layers-ports-and-adapters-
workshop
Clone from GitHub
docker-compose pull
bin/composer.sh install
docker-compose up -d

4. DEMO TIME
Navigate to localhost (or localhost:8080)

5. ARCHITECTURE
Decisions about coupling and cohesion

6. COUPLING
How are things linked to each other?

7. COHESION
Which things belong together?

8. LAYERED ARCHITECTURE
An answer to both questions

9. LAYERS
Help you protect what's in a deeper layer

10. LAYERS
Allow you to define dependency rules

11. LAYERS
Define the right place to put things

12. TRADITIONAL LAYERING
MVC
view
controller
model

13. TRADITIONAL LAYERING
Works well with JS
view
model
data

14. LAYERS
Horizontal division (as opposed to...)

15. USE CASES
Vertical division

16. COHESION
A basic set of layers
infrastructure
application
domain

17. COUPLING
The dependency rule
Layers should only depend on deeper layers

18. COUPLING
The dependency rule
infrastructure
application
domain

19. COUPLING
Dependency inversion principle
Classes should always depend on things that are more abstract

20. COUPLING
Dependency inversion principle
low-levelconcrete class specific
abstract interface generic high-level

21. COUPLING
Dependency inversion principle
use

22. COUPLING
Dependency inversion principle
use implement

23. COUPLING
Is about dependencies in code
Use Dependency Injection

24. LAYER CONVENTIONS
Domain layer
Domain model:
➤ Entities
➤ Value objects
➤ Domain services
➤ Factories
Business logic
Decisions
Data
State
Behavior

25. LAYER CONVENTIONS
Application layer
➤ Find an object
➤ Change something
➤ Notify something
➤ Get some information
Use cases
Orchestration

26. LAYER CONVENTIONS
Infrastructure layer
Communication with:
➤ HTTP client
➤ Database
➤ Filesystem
➤ Email server
➤ Message broker
Connecting the
application to
the world
outside

27. MATTHIASNOBACK/LAYERS-
PORTS-AND-ADAPTERS-
WORKSHOP
Assignments are on GitHub in assignments/
php -S 0.0.0.0:8080 -t public/

28. assignment/01.md
Layers

29. ADVANCED
APPLICATION
ARCHITECTURE
II - Ports & adapters

30. MESSAGING
... is the big idea

31. PORTS (COHESION)
Web, CLI, test client, messages, database queries
User interface
Persistence

32. PORTS... AND ADAPTERS
Translation
HTTP
SQL

33. HEXAGONAL ARCHITECTURE
Same thing!
User interface
Persistence

34. PORTS... AND ADAPTERS
(De)serialization, translation, structural validation
HTTP
SQL

35. assignment/02.md
Ports

36. PORT ADAPTERS
...in the Infrastructure layer

37. APPLICATION SERVICES
... in the Application layer

38. DOMAIN MODEL
in the Domain layer

39. APPLICATION SERVICES
Delivery-mechanism agnostic

40. assignment/03.md
Input adapters

41. APPLICATION SERVICES
Most often they are "command handlers"
Command object is a DTO
Represents a user's intention
Contains primitive-type values

42. APPLICATION SERVICES
Translate, and orchestrate
From primitive-type values to rich domain objects
Manipulates an entity
Persists it
May dispatch events

43. VALIDATION
At different levels
Structural validation of messages
User-friendly input validation
Domain invariant protection

44. STRUCTURAL VALIDATION
Infrastructure layer
Form keys
JSON schema

45. USER-FRIENDLY INPUT
VALIDATION
Infrastructure layer
Usability concern
Prevent problems later on
Localized, translated
Friendly

46. DOMAIN INVARIANT PROTECTION
Application & Domain layer
Domain objects: always valid
Valid state
Valid state transitions

47. assignment/04.md
Input validation

48. APPLICATION SERVICES
Transactional consistency

49. assignment/05.md
Output adapter

50. INCOMPLETE ENTITY
A Meetup without an ID...

51. DATABASE-GENERATED ID
Faux-auto increment (check out the code)

52. ALTERNATIVE: UUID
Universally Unique Identifier
7d7fd0b2-0cb5-42ac-b697-3f7bfce24df9

53. assignment/06.md
A hidden dependency on the persistence mechanism

54. ALTERNATIVE: SEQUENCE
MeetupId encapsulates the type of ID used

55. ADVANTAGES OF USING LAYERS,
PORTS & ADAPTERS
Offers insight into the application
Provides a useful convention for the team
Isolates the low-level details
Allows for alternative implementations
Helps with testing

56. ADVANCED
APPLICATION
ARCHITECTURE
III - Testing

57. UNIT TESTS
Testing your units of code
One class at a time
No IO
No setup required
Mocking only dependencies "you own"

58. INTEGRATION TESTS
Testing your adapters
Maybe multiple classes
Including IO
Some setup required
Mocking no dependencies

59. ACCEPTANCE TESTS
Testing your application services
Multiple classes
Use cases
Infrastructure stand-ins

60. SYSTEM TESTS
Testing your application end-to-end
The real deal

61. TESTING PYRAMID
Make it well-balanced
Unit
Integration
System
Acceptance
Development
Regression

62. TESTING PYRAMID
Make it well-balanced
Supports development
Prevents regressionSlow, brittle
Fast, stable
Proof of effectiveness
Proof of Correctness

63. assignment/07.md
Different types of tests

64. ACCEPTANCE TESTS
Use infrastructure stand-ins
Acceptance test
test the
application
layer

65. Persistence
FileBased InMemory
Port
Adapters

66. MeetupRepository
FileBasedMeetupRepository InMemoryMeetupRepository
Domain
Infrastructure
implements implements

67. assignment/08.md
A test double for the Persistence port

68. assignment/09.md
An acceptance test for the application layer

69. A WELL-BALANCED TEST SUITE
Adapters can be easily replaced
Test suite is fast
Feedback is quick
Small amount of fragile tests
Enables continuous delivery

70. https://training.matthiasnoback.nl/

71. Feedback?
@matthiasnoback
training.matthiasnoback.nl

72. assignment/10.md
Notifications