Spring Boot is one of the most widely used frameworks for building Java-based web applications and microservices. If you're a fresher starting out in Java development or preparing for your first interview, having a good understanding of Spring Boot is essential.
In this article, we’ve curated a list of commonly asked Spring Boot interview questions and answers specifically tailored for freshers. Each question is answered clearly, with examples and real-world context to help you stand out in interviews.
1. What is Spring Boot?
Spring Boot is a framework built on top of the Spring Framework that simplifies application development. It provides defaults and auto-configuration to help developers create stand-alone, production-ready Spring applications with minimal setup.
It eliminates boilerplate configuration by using embedded servers, starters, and sensible defaults. Developers can get started quickly without needing complex XML configuration.
This is a beginner's to expert Spring Boot tutorial. All the Spring Boot Tutorials are upgraded to Spring Boot 3 and Java…www.javaguides.net
2. How is Spring Boot different from the Spring Framework?
Spring Framework requires a lot of boilerplate and XML-based configuration, whereas Spring Boot auto-configures most components using sensible defaults.
Spring Boot is opinionated and aims to reduce the need for manual setup. It comes with embedded servers (like Tomcat), built-in starters, and production-ready features.
The complete compassion table:
In this article, we will learn the differences between Spring Framework and Spring Boot in Java.This is one of the…www.javaguides.net
3. What are Spring Boot starters?
Starters are a set of convenient dependency descriptors that you can include in your application. You get a one-stop shop for all the Spring and related technologies that you need without having to hunt through sample code and copy-paste loads of dependency descriptors.
For example:
spring-boot-starter-web Starter
While developing the REST service; we can use libraries like Spring MVC, Tomcat and Jackson — a lot of dependencies for a single application.
Spring Boot starters can help to reduce the number of manually added dependencies just by adding one dependency. So instead of manually specifying the dependencies just add one starter as in the following example:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>spring-boot-starter-data-jpa Starter
If you want to get started using Spring and JPA for database access, include the spring-boot-starter-data-jpa dependency in your project.
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>spring-boot-starter-test Starter
For testing, we usually use the following set of libraries: Spring Test, JUnit, Hamcrest, and Mockito. We can include all of these libraries manually, but Spring Boot starter can be used to automatically include these libraries in the following way:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>Starters are a set of convenient dependency descriptors that you can include in your application. You get a one-stop…www.javaguides.net
4. What is auto-configuration in Spring Boot?
AutoConfiguration in Spring Boot automatically configures beans and settings based on the dependencies on your classpath and application properties — so you don’t have to write manual configuration.
This is enabled by default when you use:
@SpringBootApplicationWhich is a shortcut for:
@Configuration
@EnableAutoConfiguration
@ComponentScan✅ So yes, @EnableAutoConfiguration is the key to Spring Boot’s “zero configuration” magic.
✅ Why Use Auto Configuration?
✔ Reduces Boilerplate Code — No need for explicit configurations.
✔ Simplifies Dependency Management — Automatically configures beans based on dependencies.
✔ Faster Development — Eliminates the need for repetitive configurations.
✔ Customizable — Can be enabled, disabled, or overridden.
Learn how Spring Boot Auto Configuration works, its benefits, and how to customize it using @Conditional…rameshfadatare.medium.com
5. What is Spring Boot CLI?
Spring Boot CLI (Command Line Interface) is a tool that allows you to quickly prototype Spring Boot applications using Groovy scripts.
It is useful for quick demos and testing ideas without writing full Java classes or configuration files.
6. How do you create a Spring Boot application?
You can create a Spring Boot application using Spring Initializr (https://start.spring.io/), Spring CLI, or manually by adding dependencies to a Maven/Gradle project.
Spring Boot applications must include a class with the @SpringBootApplication annotation and a main() method.
7. What is the purpose of the @SpringBootApplication annotation?
@SpringBootApplication is a convenience annotation that combines:
@Configuration@EnableAutoConfiguration@ComponentScan
This annotation marks the main class of a Spring Boot application and triggers auto-configuration and component scanning.
8. How is the embedded server used in Spring Boot?
Spring Boot includes embedded servers such as Tomcat, Jetty, or Undertow. You don’t need to deploy WAR files to external servers.
When you run the application, the embedded server starts automatically and hosts your web application.
9. How do you define application properties in Spring Boot?
Spring Boot uses application.properties or application.yml files to configure various application settings like port, database URL, logging level, etc.
You can also define environment-specific files like application-dev.properties and activate them using profiles.
10. What is Spring Boot DevTools?
Spring Boot DevTools is a set of tools that improves the development experience. It supports features like automatic restarts, live reload, and configurations to make development faster.
It is meant only for development purposes and should not be used in production.
11. What is actuator in Spring Boot?
Spring Boot Actuator provides ready-to-use endpoints to monitor and manage the application in production.
Common endpoints include /health, /metrics, /info, and /env. It helps in application health monitoring and diagnostics.
12. How do you expose REST APIs using Spring Boot?
You can use @RestController along with mapping annotations like @GetMapping, @PostMapping, etc. to expose REST endpoints.
Spring Boot automatically sets up Jackson for JSON serialization and provides easy integration with web frameworks.
13. How do you handle exceptions in Spring Boot REST APIs?
Use @ControllerAdvice and @ExceptionHandler annotations to handle exceptions globally or locally within a controller.
You can return meaningful error messages and HTTP status codes to the client using ResponseEntity.
14. What is the difference between @Component, @Service, and @Repository?
All three annotations mark a class as a Spring bean. However, they serve different semantic purposes:
@Component: Generic stereotype for any Spring-managed component.@Service: Indicates a service layer class.@Repository: Indicates a data access object (DAO) and enables exception translation.
15. How do you connect a Spring Boot application to a database?
Add a database driver dependency and configure properties in application.properties (e.g., spring.datasource.url, username, password).
Use Spring Data JPA repositories or define your own JdbcTemplate or EntityManager beans.
16. What is Spring Data JPA?
Spring Data JPA is a part of the Spring Data project that simplifies data access using JPA.
Spring Data JPA provides an out-of-the-box implementation for all the required CRUD operations for the JPA entity, so we don’t have to write the same boilerplate code again and again.
Spring Data JPA is not a JPA provider. It is a library/framework that adds an extra layer of abstraction on top of our JPA provider (like Hibernate).
Spring Data JPA uses Hibernate as a default JPA provider.
17. How do you implement pagination and sorting in Spring Boot?
Spring Data JPA supports pagination and sorting using the Pageable and Sort interfaces.
You can pass them as parameters in repository methods and get paginated responses easily.
Example for pagination and sorting — use the following code snippet to get the first page from the database, with 10 items per page and sort by title in ASC order:
long pageNo = 1;
pageSize = 10;
String sortBy = "title";
String sortDir = "ASC";
Sort sort = sortDir.equalsIgnoreCase(Sort.Direction.ASC.name()) ? Sort.by(sortBy).ascending()
: Sort.by(sortBy).descending();
// create Pageable instance
Pageable pageable = PageRequest.of(pageNo, pageSize, sort);
Page<Post> posts = postRepository.findAll(pageable);
// get content for page object
List<Post> listOfPosts = posts.getContent();18. What is the role of @EnableAutoConfiguration?
@EnableAutoConfiguration tells Spring Boot to automatically configure the application based on dependencies in the classpath.
It’s usually included as part of the @SpringBootApplication annotation.
19. What are custom starters in Spring Boot?
Custom starters are user-defined libraries that bundle dependencies and auto-configuration logic.
They work similarly to built-in starters and are useful when you want to share a set of configurations across multiple projects.
20. How do you profile Spring Boot applications?
You can define multiple profiles using application-{profile}.properties and activate them with the spring.profiles.active property.
Profiles allow different configurations for development, testing, and production environments.
21. How do you secure a Spring Boot application?
Use Spring Security to secure endpoints. You can configure HTTP security using WebSecurityConfigurerAdapter or the newer SecurityFilterChain (from Spring Security 5.7+).
Security features include authentication, authorization, CSRF protection, and role-based access control.
22. How do you test Spring Boot applications?
Use @SpringBootTest for integration tests and @WebMvcTest for controller layer tests.
Spring Boot also supports Mockito for unit testing and TestRestTemplate for testing REST endpoints.
23. What is the role of CommandLineRunner and ApplicationRunner?
These interfaces are used to execute code after the Spring Boot application starts. They are typically used for startup logic or initializing data.
ApplicationRunner provides access to application arguments, while CommandLineRunner gives the raw command-line arguments.
24. How do you deploy a Spring Boot application?
Spring Boot apps can be packaged as executable JARs and run with java -jar. You can also build Docker images and deploy to cloud platforms like AWS, GCP, or Azure.
Spring Boot supports WAR packaging if needed, but JAR is preferred for its simplicity.
25. What best practices can we follow while developing a Spring Boot application?
Complete guide: Top 20 Spring Boot Best Practices for Java Developers.
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