# Spring Core - IoC & DI (Spring Boot)

> Inversion of Control, Dependency Injection, annotations (@Component, @Autowired, @Bean), scopes, bean lifecycle

- 22 interview questions
- Junior
- [Interview Questions: Spring Boot](https://sharpskill.dev/en/technologies/spring-boot/interview-questions.md)

## 1. What is Inversion of Control (IoC) in Spring?

**Answer**

IoC is a principle where the Spring framework manages object creation and lifecycle, rather than the developer. This reverses the traditional control flow where application code directly instantiates its dependencies. Spring uses an IoC container to manage beans and their dependencies declaratively.

## 2. What is a bean in Spring?

**Answer**

A bean is an object managed by the Spring IoC container. It is instantiated, configured and assembled by Spring according to configuration metadata (annotations, XML or Java config). Beans are the core of a Spring application and benefit from dependency injection.

## 3. What is the purpose of the @Component annotation?

**Answer**

The @Component annotation marks a class as a Spring bean to be automatically detected during component scanning enabled by @ComponentScan. Spring creates an instance of this class and places it in the IoC container with a default name (class in camelCase). It's the generic stereotype annotation from which @Service, @Repository and @Controller derive to bring specific business semantics.

## 19 more questions available

- What are the three types of dependency injection in Spring?
- How does the @Autowired annotation work?

Sign up for free: https://sharpskill.dev/en/login

## Other Spring Boot interview topics

- [Spring Boot Auto-Configuration](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-boot-auto-configuration.md): 20 questions, Junior
- [Spring Boot Starters](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-boot-starters.md): 18 questions, Junior
- [Application Properties & YAML](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/application-properties-yml.md): 16 questions, Junior
- [Logging with SLF4J & Logback](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/logging.md): 20 questions, Junior
- [Spring Boot DevTools](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-boot-devtools.md): 15 questions, Junior
- [Spring MVC Basics](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-mvc-basics.md): 20 questions, Mid-Level
- [Spring REST Controllers](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-rest-controllers.md): 20 questions, Mid-Level
- [Request & Response Handling](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/request-response-handling.md): 20 questions, Mid-Level
- [Exception Handling](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/exception-handling.md): 25 questions, Mid-Level
- [Bean Validation](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/bean-validation.md): 25 questions, Mid-Level
- [Spring Data JPA Basics](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-data-jpa-basics.md): 25 questions, Mid-Level
- [JPA Entities & Relationships](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/jpa-entities-relationships.md): 30 questions, Mid-Level
- [JPA Queries](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/jpa-queries.md): 30 questions, Mid-Level
- [Spring Data Repositories](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-data-repositories.md): 25 questions, Mid-Level
- [Spring Security Basics](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-security-basics.md): 25 questions, Mid-Level
- [Spring Boot Actuator](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-boot-actuator.md): 20 questions, Mid-Level
- [Unit Testing with JUnit & Mockito](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/testing-junit-mockito.md): 30 questions, Mid-Level
- [Spring Boot Testing](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-boot-testing.md): 30 questions, Mid-Level
- [Profiles & Environment](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/profiles-environment.md): 20 questions, Mid-Level
- [RestTemplate & WebClient](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/resttemplate-webclient.md): 24 questions, Mid-Level
- [Async & Scheduling](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/async-scheduling.md): 25 questions, Mid-Level
- [Caching with Spring](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/caching.md): 25 questions, Mid-Level
- [Spring WebFlux (Reactive)](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-webflux.md): 25 questions, Mid-Level
- [Spring Transactions](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/transactions.md): 30 questions, Senior
- [Advanced Authentication & Authorization](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/authentication-authorization.md): 30 questions, Senior
- [JWT & Stateless Security](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/jwt-stateless-security.md): 20 questions, Senior
- [OAuth2 & Authorization Server](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/oauth2-authorization-server.md): 20 questions, Senior
- [Spring Boot & Docker](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-boot-docker.md): 19 questions, Senior
- [Microservices with Spring](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/microservices-basics.md): 25 questions, Senior
- [Spring Cloud Config](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-cloud-config.md): 19 questions, Senior
- [Performance Optimization](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/performance-optimization.md): 30 questions, Senior
- [GraalVM Native Images](https://sharpskill.dev/en/technologies/spring-boot/interview-questions/graalvm-native-images.md): 20 questions, Senior

---

Source: SharpSkill (https://sharpskill.dev), tech interview preparation for your real stack.
HTML version of this page: https://sharpskill.dev/en/technologies/spring-boot/interview-questions/spring-core-ioc-di