IOC: Inversion on control container

AOP:Aspect Oriented Programming

MVC

DAF

Spring Bean

@Configuration declares class as ‘full’ configuration class

Class must be public and non-final

Step-by-step explanation 🧠

1️⃣ @Configuration

@Configuration
public class AppConfig {

This tells Spring:

“This class defines beans. I will manage them.”

Important:

Bean declares bean configuration inside configuration class

@Bean method must be non-final and non-private

What does proxy mean (in Spring)?

A proxy is a wrapper object that sits between your code and the real object.

👉 Your code thinks it’s calling the real class,
👉 but it’s actually calling a Spring-generated class that controls what happens.

Singleton behavior means:

Spring creates only one instance of a bean and always returns the same instance.

The most important concept 🔑

Even though you see:

new PaymentServiceImpl(...)
new JdbcAccountRepository(...)

Spring guarantees:

This works because:

Spring Component sample