Are you a experienced Spring Boot developer gearing up for your next big interview? We’ve listed of in-depth questions and answers covering core concepts, advanced features, best practices, and real-world scenarios. Whether you’re an experienced professional or a recent graduate, this article will help you solidify your understanding and ace your interview.
Spring boot interview questions for experienced with answers
1. What is Spring Boot, and how does it differ from the traditional Spring Framework?
2. Explain the significance of the @SpringBootApplication annotation.
3. How do Spring Boot’s @SpringBootApplication and @EnableAutoConfiguration annotations work?
4. Explain the concept of Auto-Configuration in Spring Boot.
5. How can you create a custom Auto-Configuration in Spring Boot?
6. What is the use of Spring Boot Starters?
7. What are the different ways to create a Spring Boot application?
8. Explain the Spring Boot Actuator and its purpose.
9. How do you enable and customize Spring Boot Actuator endpoints?
10. What are Spring Profiles, and how do you use them in Spring Boot?
11. How does Spring Boot handle application configuration files?
12. What is the role of application.properties and application.yml in Spring Boot?
13. How can you manage security in Spring Boot applications?
14. What are the ways to deploy a Spring Boot application?
15. How does Spring Boot handle error handling by default?
16. What is Spring Boot DevTools, and what advantages does it provide?
17. Explain Spring Boot’s @RestController and @RequestMapping annotations.
18. What is Spring Boot’s CommandLineRunner interface used for?
19. How can you handle exceptions in Spring Boot applications?
20. How do you use caching in Spring Boot applications?
21. What is a Spring Boot Starter Test?
22. How do you configure a DataSource in Spring Boot?
23. What is the purpose of Spring Boot’s @ConfigurationProperties annotation?
24. Explain the concept of Embedded Servers in Spring Boot.
25. How can you use Spring Boot with Microservices architecture?
26. What is the difference between @RestController and @Controller in Spring Boot?
27. How do you integrate Spring Boot with a messaging service like Kafka?
28. How does Spring Boot handle dependency management?
29. How can you change the default server port in Spring Boot?
30. What is the purpose of the @RestController annotation in Spring Boot?
31. Describe the use of @PathVariable and @RequestParam in Spring Boot.
32. Explain the role of @RequestMapping and its variations (@GetMapping, @PostMapping, etc.).
33. How do you connect a Spring Boot application to a database?
34. What is Spring Data JPA, and how does it work with Spring Boot?
35. How do you create a custom starter in Spring Boot?
36. Explain the significance of the @SpringBootTest annotation.
37. How does Spring Boot handle externalized configuration?
38. Explain the importance of @Entity and @Repository in Spring Boot.
39. How does Spring Boot support logging?
1. What is Spring Boot, and how does it differ from the traditional Spring Framework?
Answer:
Spring Boot is a framework that simplifies the development of production-ready Spring applications by reducing the need for boilerplate configuration. Unlike the traditional Spring Framework, it uses conventions, embedded servers, and pre-configured setups to accelerate application development.
2. Explain the significance of the @SpringBootApplication annotation.
Answer:
@SpringBootApplication is a composite annotation combining three important annotations: @Configuration, @EnableAutoConfiguration, and @ComponentScan. It streamlines configuration by enabling automatic component scanning and configuring Spring Beans and other components without requiring XML configurations.
3. How do Spring Boot’s @SpringBootApplication and @EnableAutoConfiguration annotations work?
Answer:
@SpringBootApplication is a meta-annotation that combines @Configuration, @EnableAutoConfiguration, and @ComponentScan. @EnableAutoConfiguration automatically configures beans based on application dependencies, making development faster and easier.
4. Explain the concept of Auto-Configuration in Spring Boot.
Answer:
Auto-Configuration automatically configures application beans based on the presence of specific classes in the classpath. It uses @ConditionalOnClass and @ConditionalOnMissingBean to determine which beans to configure based on the environment.
5. How can you create a custom Auto-Configuration in Spring Boot?
Answer:
You can create a custom auto-configuration by defining configuration classes annotated with @Configuration, then using conditions (@Conditional annotations) to control bean creation. Place your custom configuration in a separate package and include it in spring.factories under META-INF.
6. What is the use of Spring Boot Starters?
Answer:
Starters are dependency descriptors with predefined dependencies for different use cases (like spring-boot-starter-web). They simplify the addition of specific functionalities to a Spring Boot project.
7. What are the different ways to create a Spring Boot application?
Answer:
You can create a Spring Boot application by using Spring Initializr, directly in your IDE, or by using Maven/Gradle commands to set up dependencies and structure.
8. Explain the Spring Boot Actuator and its purpose.
Answer:
Spring Boot Actuator provides production-ready features, such as health checks, metrics, and environment details, that help monitor and manage applications in production.
9. How do you enable and customize Spring Boot Actuator endpoints?
Answer:
Actuator endpoints can be enabled in application.properties or application.yml using management.endpoint.<endpoint>.enabled properties. Custom endpoints can be created using @Endpoint, @ReadOperation, and @WriteOperation.
10. What are Spring Profiles, and how do you use them in Spring Boot?
Answer:
Spring Profiles allow different configurations for different environments (e.g., dev, prod). They can be set using @Profile annotation or with the spring.profiles.active property in application.properties.
11. How does Spring Boot handle application configuration files?
Answer:
Spring Boot uses application.properties or application.yml files to handle configuration. Profiles can be configured through application-{profile}.properties for environment-specific settings.
12. What is the role of application.properties and application.yml in Spring Boot?
Answer:
These files are used to define configurations and properties for the Spring Boot application. application.yml provides a more hierarchical configuration style compared to the application.properties format.
13. How can you manage security in Spring Boot applications?
Answer:
Spring Boot Security starters provide default security settings that can be customized. Configurations are done in SecurityConfig classes using @EnableWebSecurity, @Configuration, and custom HttpSecurity rules.
14. What are the ways to deploy a Spring Boot application?
Answer:
Spring Boot applications can be deployed as standalone JARs using embedded servers (like Tomcat), or they can be packaged as WAR files and deployed to external servers.
15. How does Spring Boot handle error handling by default?
Answer:
Spring Boot provides a basic error-handling mechanism that returns a JSON response with error details. Custom error pages and handling can be configured using @ControllerAdvice and @ExceptionHandler.
16. What is Spring Boot DevTools, and what advantages does it provide?
Answer:
DevTools is a module that helps developers by providing automatic restart, live reload, and configurations for quicker development feedback.
17. Explain Spring Boot’s @RestController and @RequestMapping annotations.
Answer:
@RestController is a combination of @Controller and @ResponseBody, used to create RESTful web services. @RequestMapping maps HTTP requests to handler methods in controllers.
18. What is Spring Boot’s CommandLineRunner interface used for?
Answer:
CommandLineRunner is used to execute code after the application context is loaded. Implementations of this interface can run scripts or initialize components when the application starts.
19. How can you handle exceptions in Spring Boot applications?
Answer:
Exceptions are handled using @ControllerAdvice for global handling, @ExceptionHandler for specific exceptions, and ResponseStatusException to set HTTP response status codes.
20. How do you use caching in Spring Boot applications?
Answer:
Caching in Spring Boot is enabled by adding @EnableCaching and using cache annotations like @Cacheable, @CachePut, and @CacheEvict to control cache behavior.
21. What is a Spring Boot Starter Test?
Answer:
spring-boot-starter-test is a testing module that provides testing libraries and configurations for JUnit, Mockito, Spring Boot Test, and other test dependencies.
22. How do you configure a DataSource in Spring Boot?
Answer:
DataSource is configured automatically if a database driver is present in the classpath. Custom configurations can be specified in application.properties or application.yml.
23. What is the purpose of Spring Boot’s @ConfigurationProperties annotation?
Answer:
@ConfigurationProperties binds external configuration properties to JavaBeans, simplifying the management of complex configurations by grouping related properties.
24. Explain the concept of Embedded Servers in Spring Boot.
Answer:
Spring Boot supports embedded servers (like Tomcat, Jetty, Undertow) that allow applications to run as standalone JARs without external servers. This simplifies deployment.
25. How can you use Spring Boot with Microservices architecture?
Answer:
Spring Boot facilitates microservices with features like embedded servers, REST endpoints, and easy integration with Spring Cloud for service discovery, load balancing, and configuration management.
26. What is the difference between @RestController and @Controller in Spring Boot?
Answer:
@Controller is used for MVC-based web applications, while @RestController is a specialization for RESTful web services, returning data directly as JSON/XML.
27. How do you integrate Spring Boot with a messaging service like Kafka?
Answer:
Use the spring-kafka dependency and configure producers and consumers with Kafka properties in application.properties. The @KafkaListener annotation listens to topics for message processing.
28. How does Spring Boot handle dependency management?
Answer:
Spring Boot uses the spring-boot-starter dependencies, which bundle commonly used dependencies for various Spring modules, like web (spring-boot-starter-web), JPA (spring-boot-starter-data-jpa), and security (spring-boot-starter-security). This reduces the need to manage individual versions, as Spring Boot ensures compatibility among included dependencies.
29. How can you change the default server port in Spring Boot?
Answer:
The default server port can be changed by setting the server.port property in the application.properties file, for example, server.port=8081.
30. Describe the use of @PathVariable and @RequestParam in Spring Boot.
Answer:
@PathVariable is used to extract values from the URI path, while @RequestParam extracts query parameters. Both are often used in REST controllers to handle HTTP request data.
31. How do you connect a Spring Boot application to a database?
Answer:
You configure a Spring Boot application to connect to a database by specifying the data source properties in application.properties or application.yml, such as spring.datasource.url, spring.datasource.username, and spring.datasource.password.
32. What is Spring Data JPA, and how does it work with Spring Boot?
Answer:
Spring Data JPA is a Spring module that provides JPA-based repositories with standard methods for CRUD operations, leveraging ORM capabilities. Spring Boot simplifies its configuration, providing easy integration with databases through repositories.
33. How do you create a custom starter in Spring Boot?
Answer:
Custom starters in Spring Boot involve creating a library with the required dependencies and configurations and registering it under META-INF/spring.factories. They are used to encapsulate custom functionality for easy reuse.
34. Explain the significance of the @SpringBootTest annotation.
Answer:
@SpringBootTest is used for integration testing in Spring Boot, which loads the complete application context and allows for testing the application in a simulated environment similar to production.
35. How does Spring Boot handle externalized configuration?
Answer:
Spring Boot allows externalized configuration using properties files, YAML files, environment variables, and command-line arguments. It follows a predefined order of precedence, enabling flexible and dynamic configurations.
36. Explain the importance of @Entity and @Repository in Spring Boot.
Answer:
@Entity marks a class as a JPA entity, allowing it to be mapped to a database table. @Repository is used to define a repository interface, which is a data access layer for CRUD operations on entities.
37. How does Spring Boot support logging?
Answer:
Spring Boot uses SLF4J and Logback as the default logging framework. Logging can be configured using application.properties or logback-spring.xml, providing different log levels for packages or classes.
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