Prepare for Your Spring Boot Interview with These Essential Questions
Whether you’re a fresher, have 1-3 years of experience, or are a seasoned developer with 3-6 years in the field, mastering Spring Boot is key for modern Java development. This guide features 30 carefully curated Spring Boot interview questions arranged from basic to advanced, covering conceptual, practical, and scenario-based topics. Each answer is explained simply with code examples where relevant.
Basic Spring Boot Interview Questions (1-10)
1. What is Spring Boot?
Spring Boot is a framework that simplifies the development of Spring-based applications by providing auto-configuration, embedded servers, and starter dependencies to reduce boilerplate code.[1][2][3]
2. How does Spring Boot differ from the Spring Framework?
Spring Boot offers auto-configuration, starter POMs, embedded servers, and actuators, while Spring requires manual configuration for these features.[1][2][5]
3. What are the key advantages of using Spring Boot?
Spring Boot provides easier configuration, standalone applications, production-ready features like actuators, and simplified dependency management.[1][2][3][5]
4. What are the key components of Spring Boot?
The main components include Spring Boot auto-configuration, Spring Boot CLI, starter POMs, and actuators.[2][3]
5. What is a Spring Boot Starter?
Spring Boot Starters are pre-configured dependency sets for specific functionalities like web, data JPA, or security, simplifying project setup.[1][2]
6. What is auto-configuration in Spring Boot?
Auto-configuration automatically configures beans based on classpath dependencies, using conditional annotations like @EnableAutoConfiguration.[1][2][3][4]
7. What is the purpose of the @SpringBootApplication annotation?
This annotation combines @EnableAutoConfiguration, @ComponentScan, and @Configuration to bootstrap a Spring Boot application.[1][3]
8. What is an embedded server in Spring Boot?
Spring Boot includes embedded servers like Tomcat or Jetty, allowing applications to run standalone without external server deployment.[2][3][5]
9. How do you run a Spring Boot application?
Run it using java -jar app.jar or from your IDE after adding the Spring Boot Maven/Gradle plugin.[3][5]
10. What is Spring Boot CLI?
Spring Boot CLI is a command-line tool for quickly prototyping and developing Spring applications using Groovy scripts.[2][3]
Intermediate Spring Boot Interview Questions (11-20)
11. What is the difference between @Controller and @RestController?
@Controller maps to views for rendering, while @RestController returns data directly as JSON/XML (combines @Controller and @ResponseBody).[2][6]
12. How do you create a basic REST API in Spring Boot?
Use @RestController and @GetMapping/@PostMapping on methods in a controller class. Example:
@RestController
public class UserController {
@GetMapping("/users")
public String getUsers() {
return "Users list";
}
}[1][6]
13. What is the role of @Autowired annotation?
@Autowired enables dependency injection by automatically wiring beans into fields, constructors, or setters.[5][6]
14. Explain Spring Boot profiles.
Profiles allow environment-specific configurations like dev, test, prod using application-{profile}.properties and @Profile annotation.[1]
15. What is Spring Boot Actuator?
Actuator provides production-ready features like health checks, metrics, and endpoints (/actuator/health, /actuator/metrics).[1][2]
16. How do you handle exceptions in Spring Boot?
Use @ControllerAdvice and @ExceptionHandler for global exception handling. Example:
@ControllerAdvice
public class GlobalExceptionHandler {
@ExceptionHandler(Exception.class)
public ResponseEntity handle(Exception e) {
return ResponseEntity.status(500).body("Error occurred");
}
} [1][6]
17. What is the difference between @Component, @Service, @Repository, and @Controller?
All are stereotypes for component scanning: @Component (general), @Service (business logic), @Repository (data access), @Controller (web layer).[6]
18. How does Spring Boot handle dependency management?
It uses starter POMs with curated versions to avoid conflicts and simplify additions like spring-boot-starter-web.[5][6]
19. What is externalized configuration in Spring Boot?
Configurations from application.properties, YAML, environment variables, or command-line arguments override defaults.[1][6]
20. How do you change the embedded Tomcat port in Spring Boot? (Scenario: At Paytm, you need to deploy multiple services)
Set server.port=8081 in application.properties.[5]
Advanced Spring Boot Interview Questions (21-30)
21. What is the purpose of @Configuration annotation?
@Configuration marks a class as a source of bean definitions, often used with @Bean methods.[6]
22. Explain the flow of an HTTP request in a Spring Boot application.
Request hits DispatcherServlet → Controller handles → Service for business logic → Repository for data → Response back.[3]
23. How do you implement data validation in Spring Boot?
Use Bean Validation annotations like @NotNull, @Size on DTO fields; Spring auto-validates and populates errors.[4]
24. What are Spring Boot properties and how to use @Value?
Properties in application.properties; @Value(“${property.name}”) injects them into fields.[5][6]
25. How do you package a Spring Boot application? (Scenario: For deployment at Zoho)
Use Maven/Gradle plugin to build executable JAR: mvn spring-boot:repackage.[6]
26. What is CORS in Spring Boot and how to enable it?
CORS handles cross-origin requests; enable globally with @CrossOrigin or WebMvcConfigurer.[5]
27. Explain @EnableAutoConfiguration.
It enables auto-configuration based on classpath; part of @SpringBootApplication.[3][4]
28. How does Spring Boot support microservices? (Scenario: Building services for Swiggy)
Via lightweight JARs, embedded servers, actuators for monitoring, and starters for common patterns.[3][5]
29. What is the IoC container in Spring Boot?
The IoC (Inversion of Control) container manages bean lifecycle and dependency injection.[2]
30. How do you secure a Spring Boot application? (Scenario: At Salesforce, protecting APIs)
Add spring-boot-starter-security; configure with @EnableWebSecurity and SecurityFilterChain bean for authentication/authorization.[6]
Master these Spring Boot interview questions to confidently tackle interviews across experience levels. Practice implementing the code snippets for hands-on preparation.
