🌱 Spring Boot Learning Series — Episode 2 | Spring Core

Episode 2 | Spring Core | Understanding IoC, Dependency Injection & Beans In Episode 1, I covered the WHY behind Spring — tight coupling, and how Spring takes over creating and providing objects (IoC + DI) instead of classes creating their own dependencies. This episode picks up from there with the parts I hadn't covered yet: how Spring actually does that under the hood — Beans, the Spring Container, and Component Scanning. 🔑 Keywords → 🧠 Understand → 💡 Why? → 💻 Practice → 🎯 Interview Questions → 🛠️ Project 🔑 Keywords for This Episode IoC & Dependency Injection (quick recap) Spring Bean Spring Container / ApplicationContext Component Scanning 1️⃣ Quick Recap: IoC & Dependency Injection From Episode 1: instead of a class creating its own dependency — public class TicketService { private TicketRepository repository ; public TicketService () { repository = new TicketRepository (); } } — Spring creates the dependency and hands it to the class. That's Inversion of Control (IoC) . In code, this usually looks like a constructor parameter: public class TicketService { private final TicketRepository repository ; public TicketService ( TicketRepository repository ) { this . repository = repository ; } } TicketService no longer says "let me create a TicketRepository." It says "I need a TicketRepository" — and Spring supplies one. That act of supplying it is Dependency Injection (DI) . IoC = who's in control of creating/managing objects → Spring. DI = how a class actually receives what it needs → passed in, not self-created. That's the recap. Now — where do these objects Spring creates actually come from, and where do they live? 2️⃣ Spring Bean — what Spring actually manages When Spring creates and manages an object for you, that object is called a Bean . This is the vocabulary you'll see everywhere in Spring code and docs, so it's worth being precise about it. @Service public class TicketService { } The @Service annotation is a signal to Spring: "this class should be managed b