What is Spring? Why is it needed? What is DI and IoC?

Spring is a popular framework for developing applications in Java, which simplifies the creation of enterprise applications through dependency management, configuration, and integration with various technologies.

DI (Dependency Injection) is a pattern where objects receive their dependencies from outside rather than creating them themselves. This increases modularity and testability of the code.

IoC (Inversion of Control) is a principle where the creation and binding of objects are delegated to a container (such as Spring), rather than being implemented manually in the code. DI is one way to implement IoC.

Spring implements IoC through a container that creates and manages the lifecycle of objects, automatically injecting dependencies. This allows developers to focus on business logic rather than infrastructure.