You know beautiful code when you see it. But what about lots and lots of beautiful code; is it still beautiful at a distance? “Structure” is how all the snippets of code are recursively organised into containers (methods, classes, packages, namespaces, folders, jars, projects, etc.) and how the resulting containers relate to each other due to the dependencies that emerge from the code. The same code can be organised one way into a hopelessly tangled mess, or another way … into a Beautiful Structure. This talk explores how “locality of relationship” affects coupling, cohesion, and the width of interfaces. It shows how some structural patterns dramatically increase complexity, and how alternative patterns can massively decouple and simplify. The structure of open-source Java projects (such as the beautifully-structured Spring framework) is used to illustrate the principles.

1. Beautiful Structure
Chris Chedgey
Structure101

9. • Map for developers
• Phased testing and
release
• Divide work across
organizations, teams,
individuals
• Modularity: interfaces
+ info hiding
• Reuse or replace
subsystems or layers
• Impact/regression
control
• Help new developers
• …

11. Aspects of Structure
• Containment

12. Aspects of Structure
• Containment

13. Aspects of Structure
• Containment

14. • Containment
Aspects of Structure

15. • Containment
– Cyclomatic Complexity
Aspects of Structure

16. Aspects of Structure
• Containment
• Dependence

17. Aspects of Structure
• Containment
• Dependence  Containment

18. Aspects of Structure
• Containment
• Dependence  Containment

19. Aspects of Structure
• Containment
• Dependence  Containment

20. Aspects of Structure
• Containment
• Dependence  Containment

21. Aspects of Structure
• Containment
• Dependence  Containment

22. Aspects of Structure
• Containment
• Dependence  Containment

23. Aspects of Structure
• Containment
• Dependence  Containment

24. Aspects of Structure
• Containment
• Dependence  Containment

25. Aspects of Structure
• Containment
• Dependence  Containment
• Levels

26. Aspects of Structure
• Containment
• Dependence  Containment
• Levels

27. Aspects of Structure
• Containment
• Dependence  Containment
• Levels

28. Aspects of Structure
• Containment
• Dependence  Containment
• Levels

29. Aspects of Structure
• Containment
• Dependence  Containment
• Levels

30. Aspects of Structure
• Containment
• Dependence  Containment
• Levels

31. Aspects of Structure
• Containment
• Dependence  Containment
• Levels
• Cumulative Dependency (CCD)

32. Aspects of Structure
• Containment
• Dependence  Containment
• Levels
• Cumulative Dependency (CCD)
• Locality of dependency

33. Aspects of Structure
• Containment
• Dependence  Containment
• Levels
• Cumulative Dependency (CCD)
• Locality of dependency

34. Aspects of Structure
• Containment
• Dependence  Containment
• Levels
• Cumulative Dependency (CCD)
• Locality of dependency

35. Aspects of Structure
• Containment
• Dependence  Containment
• Levels
• Cumulative Dependency (CCD)
• Locality of dependency

36. Aspects of Structure
• Containment
• Dependence  Containment
• Levels
• Cumulative Dependency (CCD)
• Locality of dependency

37. Structural Beauty
• Enough containment

38. Structural Beauty
• Enough containment
• Acyclic container dependencies

39. Structural Beauty
• Enough containment
• Acyclic container dependencies
CCD = (1*1) + (11*2) + (7*3) + …
~ 164
CCD = 362 = 1,296 !!!

40. Structural Beauty
• Enough containment
• Acyclic container dependencies
• Dependencies more local
– Higher cohesion
– Lower coupling

41. Structural Beauty
• Enough containment
• Acyclic container dependencies
• Dependencies more local
• Narrower interfaces
– Implementation hiding

42. Structural Beauty
• Enough containment
• Acyclic container dependencies
• Dependencies more local
• Narrower interfaces
• Lower level dependencies
– Co-location based on co-
dependence

43. Structural Beauty
• Enough containment
• Acyclic container dependencies
• More local dependencies
• Narrower interfaces
• Lower level dependencies
• Restructuring
– Recompose first
– Refactor second

44. Structural Beauty
• Enough containment
• Acyclic container dependencies
• More local dependencies
• Narrower interfaces
• Lower level dependencies
• Restructuring
– Restructure first
– Refactor second

45. DSM - Dependency Structure Matrix
LSM – Levelized Structure Map
You’re going to need a bigger tool!
• That parses code
• Hierarchical dependency model
• Malleable
• SonarGraph
• Lattix
• IntelliJ Idea Ultimate
• Structure101
Hierarchical
dependency graph

46. Interactive

47. Thank you!
@chedgey
chris@structure101.com
www.structure101.com