Spring Boot Interview Questions and Answers for 10 years experience

1. What is Spring Boot and why is it used?

   • Answer: Spring Boot is a framework built on top of Spring Framework that simplifies the development of stand-alone, production-grade Spring-based applications. It eliminates boilerplate configurations and provides a fast and efficient way to create Spring applications. It's used because it drastically reduces development time, provides auto-configuration for common scenarios, simplifies deployment (often as a single JAR), and offers features for building microservices.

2. Explain Spring Boot's auto-configuration mechanism.

   • Answer: Spring Boot's auto-configuration automatically configures your application based on the JARs on the classpath. It uses conditional configurations (@Conditional) to activate or deactivate beans based on the presence or absence of other beans or classes. This drastically reduces the need for explicit configuration, making development faster and easier.

3. How does Spring Boot handle dependency injection?

   • Answer: Spring Boot uses Spring's dependency injection mechanism, leveraging annotations like `@Autowired`, `@Inject`, and `@Qualifier` to manage bean dependencies. It automatically detects and injects required dependencies into beans based on type or name.

4. Describe different ways to configure Spring Boot applications.

   • Answer: Spring Boot applications can be configured through several ways: `application.properties` or `application.yml` files for external configuration; using command-line arguments; environment variables; and programmatically within the application code using `@Configuration` classes and `@Bean` methods.

5. Explain the role of `@SpringBootApplication` annotation.

   • Answer: `@SpringBootApplication` is a convenience annotation that combines `@Configuration`, `@EnableAutoConfiguration`, and `@ComponentScan`. It marks a class as the main configuration class for a Spring Boot application, enabling auto-configuration and component scanning.

6. What are Spring profiles and how are they used?

   • Answer: Spring profiles allow you to activate different configurations for different environments (e.g., development, testing, production). You can define separate configurations for each profile and activate the desired profile using command-line arguments, environment variables, or programmatically.

7. How to handle exceptions in Spring Boot?

   • Answer: Spring Boot provides robust exception handling using `@ControllerAdvice` and `@ExceptionHandler` annotations. A `@ControllerAdvice` class can handle exceptions globally, while `@ExceptionHandler` methods handle specific exception types, allowing for custom error responses and logging.

8. Explain Spring Boot Actuator.

   • Answer: Spring Boot Actuator provides production-ready features to monitor and manage your application. It exposes endpoints for health checks, metrics, and other information, allowing you to monitor the application's performance and troubleshoot issues.

9. How to secure a Spring Boot application?

   • Answer: Spring Boot applications can be secured using Spring Security. It provides features for authentication (verifying user identity) and authorization (controlling access to resources). Common approaches include using in-memory authentication, database authentication, or integrating with external authentication providers like OAuth 2.0.

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