IoC · Inversion of Control

Understand the idea

Without a container, a Servlet might construct its service and the service might construct a DAO. With Spring, classes declare their collaborators and the container supplies them. Dependency injection is the mechanism used to wire those collaborators.

A concrete example

Container creates repository
→ supplies repository to TodoService
→ supplies service to TodoController

In the application

Spring builds the controller → service → repository object graph when the application starts.

IoC does not mean Spring owns your business logic; it manages the object assembly and lifecycle.

See it in a working stage

• Stage 8: Let Spring supply a product-file reader

Related concepts

• Dependency injection
• Spring bean
• ApplicationContext