1. @bednarz_andrzej#DevoxxPL
Platinum Sponsors:
Clean architecture
Andrzej Bednarz

2. @bednarz_andrzej#DevoxxPL
About me
Img src: https://crisismapper.wordpress.com/2012/08/20/agile-development-manifesto-for-ict4d-projects/

3. @bednarz_andrzej#DevoxxPL
A new project
Image courtesy of adamr at FreeDigitalPhotos.net

4. @bednarz_andrzej#DevoxxPL
Main guidelines
Image src: http://www.dlr.de/en/desktopdefault.aspx/tabid-78/7420_read-14264/
Fast development No fear to change
Image courtesy of dan at FreeDigitalPhotos.net

6. @bednarz_andrzej#DevoxxPL
Clean architecture – principles by
UB
• The only way to go fast is
to go well 
• Architecture is not about
tools or frameworks
instead it screams
intended usage
• It allows to defer/change
decisions about UI, DB,
DI, frameworks
• It’s decoupled - aka
Hexagonal Architecture,
Plugin Architecture
• It’s testable (TDD)
• See Uncle Bob’s
presentation online

7. @bednarz_andrzej#DevoxxPL
Screaming architecture
Top level visibility:
modules & functionalities
frameworks and tools e.g. Spring MVC, Akka
Img src: https://www.flickr.com/photos/juhansonin/2147259806

8. @bednarz_andrzej#DevoxxPL
Demo

9. @bednarz_andrzej#DevoxxPL
Clean architecture – schema

10. @bednarz_andrzej#DevoxxPL
Application core
Source: Uncle Bob, http://blog.8thlight.com/uncle-bob/2011/11/22/Clean-Architecture.html

11. @bednarz_andrzej#DevoxxPL
Interactor = use case
Source: Uncle Bob, http://blog.8thlight.com/uncle-bob/2011/11/22/Clean-Architecture.html

12. @bednarz_andrzej#DevoxxPL
How do we call an interactor?
Source: Uncle Bob, http://blog.8thlight.com/uncle-bob/2011/11/22/Clean-Architecture.html

13. @bednarz_andrzej#DevoxxPL
How do we return results?
Source: Uncle Bob, http://blog.8thlight.com/uncle-bob/2011/11/22/Clean-Architecture.html

14. @bednarz_andrzej#DevoxxPL
How do we call infrastructure
services?
Source: Uncle Bob, http://blog.8thlight.com/uncle-bob/2011/11/22/Clean-Architecture.html

15. @bednarz_andrzej#DevoxxPL
All pieces together
Source: Uncle Bob, http://blog.8thlight.com/uncle-bob/2011/11/22/Clean-Architecture.html

16. @bednarz_andrzej#DevoxxPL
Demo

17. @bednarz_andrzej#DevoxxPL
Layers?

18. @bednarz_andrzej#DevoxxPL
Traditional layered architecture

19. @bednarz_andrzej#DevoxxPL
Layers in clean architecture

20. @bednarz_andrzej#DevoxxPL
Source: Uncle Bob, http://blog.8thlight.com/uncle-bob/2012/08/13/the-clean-architecture.html

21. @bednarz_andrzej#DevoxxPL
Summary & discussion

22. @bednarz_andrzej#DevoxxPL
• Lots of additional code:
classes and interfaces
• DTOs and conversions
• Cost ...
The Dark Side
Img src: Uncle Bob, http://blog.8thlight.com/uncle-bob/2011/11/22/Clean-Architecture.html

23. @bednarz_andrzej#DevoxxPL
Cost – example with Rails
controller
Source: David Heinemeier Hansson - DHH, https://gist.github.com/dhh/4849a20d2ba89b34b201
Based on: Jim Weirich's "Decoupling from Rails"

24. @bednarz_andrzej#DevoxxPL
Cost – example with Rails
controller
Source: David Heinemeier Hansson - DHH, https://gist.github.com/dhh/4849a20d2ba89b34b201
Based on: Jim Weirich's "Decoupling from Rails"

25. @bednarz_andrzej#DevoxxPL
• „Coding an app in Rails is
always fun...
for the first 3 months”
• „After some time, small, little
things show up. Thin
controllers are not really so
thin anymore. The tests are
no longer below 1 minute.”
Troubles with the Rails way
Source: Andrzej Krzywda, http://rails-refactoring.com/,
http://blog.jetbrains.com/ruby/2015/03/interview-with-andrzej-krzywda/

26. @bednarz_andrzej#DevoxxPL
Excellent testability
• Every component and
layer could be tested in
isolation.
• Tests are fast and
precise.
Clean arch – good sides

27. @bednarz_andrzej#DevoxxPL
Easy to understand
• Explicit by design
• Clearly defined
separation of concerns
• Full control of
frameworks and tools
Clean arch – good sides
FAST
development
High
Maintainability &
Flexibility
with tests

28. @bednarz_andrzej#DevoxxPL
• Our way
• model mapper, generic classes,
lombok
• Uncle Bob’s suggestion
• Another (isolated) boundary
for DTO
• Greg Young’s suggestion
• CQRS
But DTOs and conversions - still
pain
Img src: https://www.microsoftpressstore.com/articles/article.aspx?p=2248809

29. @bednarz_andrzej#DevoxxPL
Think, what is fast and clean for
you
Img src: https://thesunnyseason.files.wordpress.com/2015/01/closet-before-and-after-1024x781.jpg

30. @bednarz_andrzej#DevoxxPL
Not new
Not only Java related
Not rocket science
Not home-grown

31. @bednarz_andrzej#DevoxxPL
• http://blog.8thlight.com/uncle-
bob/2012/08/13/the-clean-architecture.html
• http://blog.8thlight.com/uncle-
bob/2011/11/22/Clean-Architecture.html
• http://blog.8thlight.com/uncle-
bob/2011/09/30/Screaming-Architecture.html
• http://alistair.cockburn.us/Hexagonal+archite
cture
• http://www.growing-object-oriented-
software.com/
• http://jeffreypalermo.com/blog/the-onion-
architecture-part-1/
• http://martinfowler.com/articles/is-tdd-dead/
• https://groups.google.com/forum/#!forum/cle
an-code-discussion
• http://en.wikipedia.org/wiki/Data,_context_an
d_interaction
• http://andrzejonsoftware.blogspot.com/2013/
12/the-four-architectures-that-will.html
• Object Oriented Software Engineering: A
Use Case Driven Approach, Ivar Jacobson,
1992
References

32. @bednarz_andrzej#DevoxxPL
• My project on GitHub:
https://github.com/andbed/clean-
architecture
• http://obvious.retromocha.com/
• https://github.com/michelchenrich/cru
drefactorkata.git
• https://github.com/lukasz-
duda/ArchitectureSample
• http://www.whitewashing.de/2012/08/
13/oop_business_applications_entity_
boundary_interactor.html
• Google 
Examples

33. @bednarz_andrzej#DevoxxPL
Thank you!
Questions?