144 Questions · Full Answers · Code Examples · Real-World Production Scenarios

🔷 Spring Core

🧠 Mental Model: Think of Spring IoC as a Restaurant Kitchen. You (the code) don’t fetch ingredients yourself. The Kitchen Manager (Spring Container) prepares beans and hands them to you when needed. You just declare what you need — Spring delivers it. “Don’t call us, we’ll call you.”

[ Your Code ]  declares → [ IoC Container ]  injects → [ Dependencies ]
   OrderService            ApplicationContext          PaymentService
                                                       InventoryService

• 1. What is Inversion of Control (IoC)?

• 2. What is Dependency Injection (DI)?

• 3. Difference between BeanFactory and ApplicationContext

• 4. What are Spring Bean Scopes?

• 5. What is the lifecycle of a Spring Bean?

• 6. What is Autowiring in Spring?

• 7. Difference between @Autowired and @Qualifier