Most Frequently Asked Spring Boot Interview Questions for 2025

Spring Boot remains a cornerstone of modern Java development, empowering developers to build production-ready applications with minimal configuration. As demand for Spring Boot expertise grows, acing technical interviews requires a deep understanding of its core concepts, annotations, and best practices. This blog compiles the most frequently asked Spring Boot interview questions, curated from industry trends. Let’s dive in!

1. What is Spring Boot?

Spring Boot is a framework built on top of Spring that simplifies application development by providing auto-configuration, embedded servers (e.g., Tomcat), and starter dependencies. It reduces boilerplate code and accelerates deployment.

Key Features:

• Auto-configuration based on classpath dependencies.
• Embedded servers for standalone execution.
• Production-ready tools like Actuator for monitoring.

2. How does Spring Boot differ from Spring Framework?

3. Explain the @SpringBootApplication Annotation

This annotation combines three annotations:

1. @Configuration: Marks the class as a configuration source.
2. @EnableAutoConfiguration: Enables auto-configuration based on dependencies.
3. @ComponentScan: Scans for components in the package.

Example:

@SpringBootApplication  
public class MyApp {  
    public static void main(String[] args) {  
        SpringApplication.run(MyApp.class, args);  
    }  
}  

4. What are Spring Boot Starters?

Starters simplify dependency management by bundling common libraries. Examples include:

• spring-boot-starter-web: For web applications.
• spring-boot-starter-data-jpa: For database access.
• spring-boot-starter-security: For authentication

5. How to Change the Embedded Tomcat Port?

Add server.port in application.properties:

server.port=8081  

6. What is Spring Boot Actuator?

Actuator provides production-ready endpoints to monitor and manage applications, such as:

• /health: Application health status.
• /metrics: Performance metrics.
• /info**: Custom application details. Enable it by adding the spring-boot-starter-actuator` dependency

7. How to Handle Exceptions Globally in Spring Boot?

Use @ControllerAdvice and @ExceptionHandler:

@ControllerAdvice  
public class GlobalExceptionHandler {  
    @ExceptionHandler(UserNotFoundException.class)  
    public ResponseEntity<String> handleError(UserNotFoundException ex) {  
        return ResponseEntity.status(HttpStatus.NOT_FOUND).body(ex.getMessage());  
    }  
}  

8. How to Secure a Spring Boot REST API?

1. Add spring-boot-starter-security.
2. Extend WebSecurityConfigurerAdapter to configure HTTP security:

@Configuration  
public class SecurityConfig extends WebSecurityConfigurerAdapter {  
    @Override  
    protected void configure(HttpSecurity http) throws Exception {  
        http.authorizeRequests().anyRequest().authenticated().and().httpBasic();  
    }  
}  

9. Explain Spring Profiles

Profiles allow environment-specific configurations (e.g., dev, prod). Activate them via application-{profile}.properties or set spring.profiles.active=dev

10. How to Connect Spring Boot to a Database Using JPA?

1. Add spring-boot-starter-data-jpa and database driver (e.g., MySQL).
2. Configure application.properties:

spring.datasource.url=jdbc:mysql://localhost:3306/mydb  
spring.datasource.username=root  
spring.datasource.password=secret  

3. Create a repository interface extending JpaRepository

11. What is the Role of @RestController?

@RestController combines @Controller and @ResponseBody, enabling RESTful web services that return JSON/XML instead of views.

12. How to Implement Pagination in Spring Data JPA?

Use Pageable in repository methods:

@GetMapping("/users")  
public Page<User> getUsers(Pageable pageable) {  
    return userRepository.findAll(pageable);  
}  

We have a detail post on how to implement pagination and sorting in Spring Boot.

13. What is Dependency Injection in Spring Boot?

Dependency Injection (DI) allows Spring to inject dependencies (e.g., services, repositories) into classes via @Autowired, promoting loose coupling.

14. How to Test a Spring Boot Application?

• Use @SpringBootTest for integration tests.
• Mock dependencies with @MockBean and @WebMvcTest for controller testing.

15. What is Spring Boot DevTools?

DevTools enhances development with features like automatic restarts, live reload, and debug configurations. Add the dependency below in your pom.xml file:

<dependency>  
    <groupId>org.springframework.boot</groupId>  
    <artifactId>spring-boot-devtools</artifactId>  
</dependency>  

16. How to Deploy a Spring Boot Application to Docker?

1. Create a Dockerfile:

FROM openjdk:17  
COPY target/myapp.jar /app.jar  
ENTRYPOINT ["java", "-jar", "/app.jar"]  

2. Build and run the image.

17. What are the Advantages of YAML over Properties Files?

YAML supports hierarchical configurations, improving readability for complex setups:

server:  
  port: 8081  
spring:  
  datasource:  
    url: jdbc:mysql://localhost/mydb  

18. How to Schedule Tasks in Spring Boot?

Use @EnableScheduling and @Scheduled:

@Scheduled(fixedRate = 5000)  
public void runTask() {  
    System.out.println("Task executed every 5 seconds");  
}  

19. What is Spring Cloud?

Spring Cloud extends Spring Boot for building distributed systems (microservices), offering tools for service discovery, configuration management, and load balancing.

20. How to Enable CORS in Spring Boot?

Use @CrossOrigin on controllers or configure globally:

@Bean  
public WebMvcConfigurer corsConfigurer() {  
    return new WebMvcConfigurer() {  
        @Override  
        public void addCorsMappings(CorsRegistry registry) {  
            registry.addMapping("/**").allowedOrigins("http://example.com");  
        }  
    };  
}  

21. What is the difference between @Controller and @RestController?

@Controller is used in Spring MVC to handle HTTP requests and return views (HTML pages). @RestController combines @Controller and @ResponseBody, returning data directly in JSON/XML format for RESTful APIs

22. How to disable Actuator security in Spring Boot?

Set management.security.enabled=false in application.properties. However, this is not recommended for production and should only be used in secured environments.

23. What is an IoC Container in Spring Boot?

The Inversion of Control (IoC) container manages object creation, dependencies, and lifecycle. It injects dependencies using @Autowired, promoting loose coupling.

24. Explain the @Transactional annotation.

@Transactional annonation ensures database operations are atomic. If an exception occurs, it rolls back changes. Commonly used in service layers for database transactions.

25. How to enable HTTP/2 in Spring Boot?

Add server.http2.enabled=true in application.properties. Requires an embedded server like Tomcat 9+ or Jetty.

26. What is the ELK Stack, and how does it integrate with Spring Boot?

The ELK Stack (Elasticsearch, Logstash, Kibana) aggregates and visualizes logs. Integrate it by configuring Logstash to collect logs and Elasticsearch to store them, then use Kibana for analysis.

27. How to implement JWT authentication in Spring Boot?

1. Add spring-boot-starter-security.
2. Create a JWT filter to validate tokens.
3. Configure WebSecurityConfigurerAdapter to enable JWT-based security

28. How to test a Spring Boot service using Mockito?

Use @MockBean to mock dependencies and @SpringBootTest for integration testing:

@SpringBootTest  
public class UserServiceTest {  
    @MockBean  
    private UserRepository userRepository;  

    @Test  
    public void testFindUserById() {  
        when(userRepository.findById(1L)).thenReturn(Optional.of(new User("Radha")));  
        assertEquals("Radha", userService.findUserById(1L).getName());  
    }  
}  

29. What is Spring Data JPA?

Spring Data JPA simplifies database operations by providing repository interfaces (e.g., JpaRepository) and reducing boilerplate code for CRUD operations.

30. What is Swagger, and how to integrate it with Spring Boot?

Swagger is an API documentation tool. Integrate it using springfox-boot-starter and annotate controllers with @Api and @ApiOperation.

31. How to handle file uploads in Spring Boot?

Use MultipartFile in a controller method:

@PostMapping("/upload")  
public String uploadFile(@RequestParam("file") MultipartFile file) {  
    // Save file logic  
    return "File uploaded!";  
}  

You can read the detail example on File Upload Spring Boot.

Configure file size limits in application.properties. You can also read how to define file upload size limit in spring boot for more detail.

32. What is Spring Boot Admin?

A community tool for monitoring Spring Boot applications. It provides a dashboard to view health, logs, and metrics via Actuator endpoints.

33. How to implement caching in Spring Boot?

1. Add spring-boot-starter-cache.
2. Enable caching with @EnableCaching.
3. Annotate methods with @Cacheable or @CacheEvict 

34. What is the difference between JPA and Hibernate?

JPA is a specification, while Hibernate is an implementation of JPA. Spring Boot uses Hibernate by default for ORM.

35. How to use H2 Database in Spring Boot?

Add h2 dependency and configure application.properties:

spring.datasource.url=jdbc:h2:mem:testdb  
spring.h2.console.enabled=true  

Access the H2 console at /h2-console.

36. How to customize the Spring Boot banner?

Well, this question may not be asked in an interview, but it is good to know.

Add a banner.txt file in src/main/resources or disable it with spring.main.banner-mode=off.

37. What are the best practices for Spring Boot logging?

• Use SLF4J with Logback.
• Configure levels in application.properties:

logging.level.root=INFO  
logging.level.com.example=DEBUG  

Conclusion

Mastering these Spring Boot interview questions will give you a competitive edge in 2025’s job market. Focus on hands-on practice, explore advanced topics like microservices and reactive programming, and stay updated with Spring Boot’s evolving ecosystem.