8 minutes / published
Spring's DI Container for People Who Have Used Dagger and Koin
A practical bridge from dependency graphs you know to the Spring container you have to debug.
The Container Is Runtime Architecture
Spring's container is not magic once you force yourself to name the graph. Beans have creation rules, scopes, dependencies, and lifecycle hooks.
Constructor injection keeps that graph visible enough to reason about before the debugger opens.
Autoconfiguration Is a Bet
Every starter says: this dependency set is common enough that Spring can wire defaults. That is useful, but it is still a bet.
World 1 keeps the starter list small so each new dependency later becomes a lesson, not background noise.
The First Test Is Boring on Purpose
A SpringBootTest that proves controller -> service -> repository wiring will not impress anyone by itself.
It matters because the course will later ask the learner to distinguish wiring failures, transaction failures, lazy-boundary failures, and security filter failures. The first proof point has to be simple.