Hexagonal Architecture

A way to isolate business logic in code

Kong To

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Table of contents

  • History
  • Purpose
  • Principles
  • The separation of concerns
  • Three Layers
  • Inner layer isolation — dealing with dependencies
  • Ports and Adapters
  • Domain in isolation
  • Direction of flow
  • Ease of testing
  • Sample with Spring and Kotlin
  • Hexagonal vs Onion vs Clean
  • Conclusion
  • Reference

A bit of history

Published in a blog by Alistair Cockburn in 2005

The hexagonal architecture is synonym to “ports and adapters pattern”, but nowadays “hexagonal architecture” is better known. Moreover, it is a step further than the four (4) layered architecture that allows to separate the layers per responsibility. The hexagonal architecture on the other hand clearly suggests a focus on the domain isolation.

The term “hexagonal” comes from the graphical conventions that shows the application component like a hexagonal cell. The six borders represents the multiple interfaces that the component may expose to the external world.

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Kong To

Architect, code crafter. Code quality matters. Technical writer @TheFork, a Tripadvisor company