Explaining how DI can help us build more modular and open for extension code.

1. DI AND HOW IT
SHAPES YOUR
APPLICATION

2. Marian Zlatev
Senior Software Engineer at
Paysafe
Java and Go
marian.zlatev@paysafe.com

6. Class A Class B
What is DI?

7. Constructor Injection

8. Setter Injection

9. Field Injection

10. • Writing modular code
• Keeping the code open for extension
• Design by interface and increase cohesion
• Easy to test
How to benefit from DI

11. • Spring
• Guice
• Dagger
• Other
DI Frameworks

13. Modularity

14. Constructing the application

15. Guice Modules

16. Class A
Class B Class C
Class D Class E Class F Class G
High level policy depending on Low level policy
Level 1
Level 2
Level 3

17. CoffeeMachine ElectricCoffeePumpCoffeeMachine ElectricCoffeePump
CoffeePum
p
ManualCoffeePump

18. Class A
Class B Impl Class C Impl
Class D Impl
Interface B Interface C
Interface D Interface E
Class E ImplLevel 3
Level 2
Level 1

19. Inversion of control

20. BUSINESS
LOGIC
WEB
PERSISTEN
CE
PAYMENT
GATEWAY
Hexagonal Architecture

21. CORE Details
Primary/Driving
Adapters
PRIMARY ADAPTER
Use Case
Secondary/Driven
Adapters
<I> <I>

22. BUSINESS
LOGIC

24. BUSINESS
LOGIC

25. DEMO

26. What to remember from this Talk
• Spend time to research
• Pick a DI framework
• Use constructor Injection (unless you have a good reason not to)
• Separate functionality into modules (packages)
• Depend on Interfaces when details are involved
• Interfaces should express intention

27. Q & A time?

28. Thank you
NewestUser/Hexagonal
marian.zlatev@paysafe.com