Presentation on how here at Coolblue we refactored an existing application from a layered architecture to ports & adapters and the benefits we achived by doing so.

1. Ports & Adapters
Architecture
Inside & Outside Application Thinking
Nathan Johnstone - Technical Pathfinder @ Coolblue

2. Focus

5. A Bit About Me ...

6. A Bit About Me ...

8. Pigs != Pegs

9. The Starting Point

10. Joining a Team

11. Infrastructure Dependencies
Web API
Message
Service
Scheduler

12. Application Assemblies
Web API
Message
Service
Scheduler
Data
Access
Domain Common

13. Application Dependencies
Web API
Message
Service
Scheduler
Data
Access
Domain Common

14. Class Library Dependencies
Web API
Message
Service
Scheduler
Data
Access
Domain Common

15. N-Tier
Web API
Data
Access
Domain

16. Isn't Something Missing ?

17. Pain

18. Leakage

19. DRY - Reuse Reuse Reuse !

20. Test Coverage
Unit Tests
Component Tests
Acceptance
Tests
Integration Tests

21. Implementing Integration Tests

22. Interfaces Colocated With Implementations
Data Access Domain
PurchaseOrderSubmitServiceIPurchaseOrderRetriever
PurchaseOrderRetriever
?

23. Who Owns The Interface ?

24. Colocation Problems
Data Access Domain
PurchaseOrderSubmitServiceIPurchaseOrderRetriever
PurchaseOrderPurchaseOrderDocument

25. Isolation Violation
PurchaseOrderDocument
Domain

26. Reference Direction vs Control Direction
Presentation
Layer
Data Access
Layer
Business Logic
Layer
Reference DirectionControl Direction

27. Ports & Adapters Introduction
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.

28. Hexagonal Architecture

29. Inside Outside Architecture

30. First Port - Persistence
Web API
Message
Service
Scheduler
Data
Access
Domain Common
Persistence
Adapter

31. Mikado Method

32. Second Port - Commands
Web API
Message
Service
Scheduler
Data
Access
Domain
Persistence
Adapter
Command
Adapter

33. Upstream & Downstream Ports

34. Third Port - Notification
Web API
Message
Service
Scheduler
Data
Access
Domain
Persistence
Adapter
Command
Adapter
Notification
Adapter

35. Clean Up
Web API
Message
Service
Scheduler
Data
Access
Domain
Persistence
Adapter
Command
Adapter
Notification
Adapter

36. Hexagonal - Domain
Domain
Web API
Message
Service
Scheduler
Persistence
Adapter
Command
Adapter
Notification
Adapter

37. Hexagonal - Persistence Port
Domain
Web API
Message
Service
Scheduler
Persistence
Adapter
Command
Adapter
Notification
Adapter
Persistence
Port

38. Hexagonal - Command Port
Domain
Web API
Message
Service
Scheduler
Persistence
Adapter
Command
Adapter
Notification
Adapter
Persistence
Port
CommandPort

39. Hexagonal - Notification Port
Domain
Web API
Message
Service
Scheduler
Persistence
Adapter
Command
Adapter
Notification
Adapter
Persistence
Port
CommandPort
Notification
Port

40. Hosts Are Types of Adapters
Web Service
Test Harness
Command
Line
Daemon
Windows
Service
Graphical UI

41. Hexagonal - Host Port
Domain
Web API
Message
Service
Scheduler
Persistence
Adapter
Command
Adapter
Notification
Adapter
Persistence
Port
CommandPort
Notification
Port
Host Port

42. Advantages - Domain Testability
Domain
Web API
Message
Service
Scheduler
Persistence
Adapter
Command
Adapter
Notification
Adapter
Persistence
Port
CommandPort
Notification
Port
Host Port

43. Advantages - Boundaries
Web API
Message
Service
Scheduler
Domain
Persistence
Adapter
Command
Adapter
Notification
Adapter

44. Advantages - Alternative Adapters
Domain
Web API
Message
Service
Scheduler
Persistence.Adapter Command.Adapter
Notification
Adapter
Persistence
Port
CommandPort
Notification
Port
Host Port
Persistence.Adapter
Csv
Command.Adapter
File

45. Notification via SMTP
Domain
Web API
Message
Service
Scheduler
Persistence
Adapter
Command
Adapter
Notification
Adapter
Persistence
Port
CommandPort
Notification
Port
Host Port

46. Code Examples - Book Ordering Service

47. Book Ordering Service - Client 1
● REST endpoints for adding books,
approving and submitting
● Notification to supplier to be via SMTP
● Persistence to MySQL

48. Book Ordering Service - Client 2
● RabbitMq message for adding books
● REST endpoints for adding approving and
submitting
● Notification to supplier to be via
RabbitMq message
● Persistence to MySQL

49. Book Ordering Service - Architecture
Domain
Host
Web API
Client 1
Web API
Client 2
Persistence
MySQL
Notification
SMTPRabbitMq
CommandRabbitMq

50. Warning Live Code Demo Ahead !

51. Takeaways
● Ports are just a name given to a common group of abstractions in your
domain
● Adapters are a group of specific implementations of a given port
● Onion Architecture, Clean Architecture and Ports & Adapters are
essentially the same thing
● Example repository on github for .NET
● Ports & Adapters is an architectural style that will produce applications
that are independent of infrastructure details

52. Links
● http://alistair.cockburn.us/Hexagonal+architecture
● http://blog.ploeh.dk/2013/12/03/layers-onions-ports-adapters-its-all-the-same/
● https://github.com/nrjohnstone/ports-adapters-examples
● https://www.linkedin.com/in/nrjohnstone
● https://nathanjohnstone.wordpress.com/
● n.johnstone@coolblue.nl
● locotewz@gmail.com