This document discusses the principles of clean architecture. It begins by introducing clean architecture and its main guidelines, including that architecture focuses on intended usage rather than tools/frameworks. This allows deferring decisions and changes. Clean architecture is decoupled and testable. The document then covers clean architecture schemas, with application core and layers separated from frameworks. It discusses using use cases/interactors to define interactions. While clean architecture enables flexibility and testability, it can increase code complexity through additional classes and conversions. The document debates these tradeoffs and references sources for further information.

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Platinum Sponsors:
Clean architecture
Andrzej Bednarz

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About me
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A new project
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Main guidelines
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Fast development No fear to change
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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

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

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Demo

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Clean architecture – schema

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

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

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

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

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

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

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Demo

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Layers?

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Traditional layered architecture

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Layers in clean architecture

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

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Summary & discussion

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• 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

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

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

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• „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/

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

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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

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• 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
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Think, what is fast and clean for
you
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Not new
Not only Java related
Not rocket science
Not home-grown

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• 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

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• 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

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Thank you!
Questions?