Spring Boot Interview Questions & Answers

Spring Boot is one of the most popular Java frameworks used to build scalable, production-ready applications and REST APIs. Because of its wide adoption in enterprise and microservices-based projects, Spring Boot interview questions are commonly asked in Java backend and full-stack developer interviews.

In this long and well-structured guide, you’ll find Spring Boot interview questions with clear explanations, covering beginner to advanced concepts to help you prepare confidently.

Table of Contents

What Is Spring Boot?

Spring Boot is a Java-based framework built on top of the Spring framework. It simplifies application development by providing auto-configuration, embedded servers, and production-ready features with minimal setup.

Basic Spring Boot Interview Questions

1. What is Spring Boot?

Spring Boot is a framework that simplifies the development of Spring applications by reducing configuration and enabling faster setup with embedded servers.

2. Why is Spring Boot used?

Spring Boot is used to:

Reduce boilerplate code
Simplify configuration
Build standalone applications
Speed up development

3. What are the advantages of Spring Boot?

Key advantages include:

Auto-configuration
Embedded servers (Tomcat, Jetty)
Faster development
Production-ready features

4. What is auto-configuration in Spring Boot?

Auto-configuration automatically configures beans based on the dependencies present in the project.

5. What is Spring Initializr?

Spring Initializr is a web-based tool used to generate Spring Boot projects quickly with predefined dependencies.

6. What embedded servers does Spring Boot support?

Spring Boot supports embedded servers such as Tomcat, Jetty, and Undertow.

7. What is `@SpringBootApplication`?

@SpringBootApplication is a combination of:

@Configuration
@EnableAutoConfiguration
@ComponentScan

8. What is `application.properties` or `application.yml`?

These files are used to configure application settings such as server port, database credentials, and logging levels.

Core Spring Boot Concepts

9. What is Dependency Injection?

Dependency Injection allows Spring to manage object creation and inject required dependencies automatically.

10. What is Inversion of Control (IoC)?

IoC means the framework controls the lifecycle and dependencies of objects instead of the programmer.

11. What is a Bean in Spring Boot?

A bean is an object managed by the Spring container.

12. What is `@Component` annotation?

It marks a class as a Spring-managed component.

13. Difference between `@Component`, `@Service`, and `@Repository`?

They serve the same purpose but are used in different layers:

@Component – generic
@Service – service layer
@Repository – data access layer

14. What is `@Autowired`?

@Autowired is used to automatically inject dependencies into a class.

15. What is a Spring Boot Starter?

Starters are predefined dependency bundles that simplify dependency management.

Spring Boot Web & REST Interview Questions

16. What is Spring MVC?

Spring MVC is a framework for building web applications and RESTful services.

17. What is `@RestController`?

@RestController combines @Controller and @ResponseBody to return data directly as a response.

18. Difference between `@Controller` and `@RestController`?

@Controller returns views
@RestController returns JSON or XML data

19. What is `@RequestMapping`?

It maps HTTP requests to handler methods.

20. What HTTP methods are supported in Spring Boot?

Common HTTP methods include:

GET
POST
PUT
DELETE
PATCH

21. What is `@RequestBody`?

It maps the HTTP request body to a Java object.

22. What is `@PathVariable`?

It extracts values from the URL path.

23. What is `@RequestParam`?

It extracts query parameters from the request.

Database & JPA Interview Questions

24. What is Spring Data JPA?

Spring Data JPA simplifies database operations using repository interfaces.

25. What is `JpaRepository`?

JpaRepository provides CRUD operations, pagination, and sorting.

26. What is an Entity?

An entity represents a database table in Java.

27. What is Hibernate?

Hibernate is an ORM framework used as a JPA implementation.

28. What is lazy loading?

Data is loaded only when required.

29. What is eager loading?

Data is loaded immediately when the entity is fetched.

Security, Testing & Advanced Questions

30. What is Spring Security?

Spring Security provides authentication and authorization features.

31. What is JWT in Spring Boot?

JWT is used for stateless authentication in REST APIs.

32. How is exception handling done in Spring Boot?

Using @ExceptionHandler and @ControllerAdvice.

33. What is Spring Boot Actuator?

Actuator provides monitoring, health checks, and metrics.

34. What is logging in Spring Boot?

Logging tracks application behavior and errors for debugging and monitoring.

35. What are profiles in Spring Boot?

Profiles allow environment-specific configurations such as dev, test, and production.

Frequently Asked Questions (FAQ)

FAQ 1: Is Spring Boot suitable for microservices?

Yes, Spring Boot is widely used for building microservices due to its lightweight and scalable nature.

FAQ 2: Is Spring Boot faster than Spring?

Spring Boot reduces setup time and configuration, making development faster than traditional Spring.

FAQ 3: Do I need to know Spring before learning Spring Boot?

Basic Spring knowledge is helpful but not mandatory.

FAQ 4: Is Spring Boot used in real-world projects?

Yes, Spring Boot is widely used in enterprise and production-level applications.

Final Thoughts

Preparing for Spring Boot interview questions is essential for Java backend and microservices roles. Understanding core concepts, REST APIs, database integration, and security will help you perform confidently in interviews.

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