Spring Boot Interview Essentials: Top Questions for Freshers and Experts Quiz

Test your knowledge of Spring Boot with these frequently asked interview questions and answers, covering key concepts like starters, auto-configuration, annotations, microservices, and production-ready features. This quiz helps freshers and experienced developers prepare for Spring Boot interviews by focusing on practical Java backend and microservices topics.

1. Spring Boot Basics

   What is the primary goal of Spring Boot in Java application development?

   1. To eliminate the need for manual configuration and speed up development
   2. To replace the Java programming language
   3. To add more boilerplate code for developers
   4. To increase application startup time

   Explanation: Spring Boot's main purpose is to reduce the complexity of configuration and allow rapid development by providing sensible defaults. Adding more boilerplate code is the opposite of its intent, and it does not aim to replace Java. Increasing application startup time is a drawback rather than a benefit, making it incorrect.

2. Starter Dependencies

   Which Spring Boot feature provides ready-to-use dependencies for specific functionalities such as web or data access?

   1. Starters
   2. Injectors
   3. Loaders
   4. Modules

   Explanation: In Spring Boot, 'starters' are pre-configured dependency descriptors to get started quickly with a particular feature. While 'modules' and 'loaders' may sound familiar, they are not correct in this context. 'Injectors' relate to dependency injection, not dependency management.

3. Embedded Servers

   Which advantage does Spring Boot offer by providing an embedded server like Tomcat or Jetty?

   1. It prevents use of web frameworks
   2. It allows applications to run independently without external application servers
   3. It disables automatic configuration
   4. It requires manual server installation every time

   Explanation: With an embedded server, Spring Boot applications can be run directly without needing an external server setup. Manual server installation is not needed, and it doesn't interfere with web frameworks or automatic configuration, so those options are incorrect.

4. Auto-Configuration

   How does Spring Boot's auto-configuration feature benefit developers?

   1. By restricting developers to only one type of database
   2. By automatically setting up beans and configurations based on dependencies present
   3. By entirely removing configuration files
   4. By requiring all configurations in XML

   Explanation: Auto-configuration inspects the classpath and configures components as needed. It does not remove the possibility of configuration files entirely, nor does it restrict database choices or mandate XML configurations.

5. Key Annotations

   What is the purpose of the @SpringBootApplication annotation in a Spring Boot application?

   1. It combines several essential annotations to simplify configuration
   2. It disables all default configurations
   3. It replaces the Java Virtual Machine
   4. It is only used for database connections

   Explanation: The @SpringBootApplication annotation is a convenience annotation that combines @Configuration, @EnableAutoConfiguration, and @ComponentScan. It is not related to replacing the JVM or database connections alone, nor does it disable configurations.

6. Dependency Injection

   In Spring Boot, what does the @Autowired annotation do?

   1. It manages application logs
   2. It starts the embedded server
   3. It executes SQL queries
   4. It injects required dependencies into components automatically

   Explanation: @Autowired directs Spring to resolve and inject collaborating beans into a component. It does not handle SQL execution, logging, or server startup directly; those tasks are managed by other features or annotations.

7. Configuration Files

   Which file is commonly used in Spring Boot to externalize application configuration settings?

   1. config.txt
   2. data.yaml
   3. serverconfig.ini
   4. application.properties

   Explanation: application.properties (or application.yml) is the standard file for externalized configuration in Spring Boot. The other file formats are not commonly used in Spring Boot, making them incorrect options.

8. Actuator Features

   What is the main function of Spring Boot Actuator?

   1. To provide monitoring and management endpoints for applications
   2. To implement database migrations
   3. To display user interface components
   4. To create web controllers only

   Explanation: Actuator adds endpoints that help monitor and manage applications. It does not directly create user interface elements, controllers, or handle database migrations; those are handled through other mechanisms.

9. Profiles

   How do Spring Boot profiles help in application development?

   1. They allow different environments to use specific configurations
   2. They limit database connections
   3. They disable the embedded server
   4. They restrict the use of annotations

   Explanation: Profiles enable environment-specific bean registration and configuration, making it easy to switch between development, testing, and production settings. Profiles do not affect annotations, embedded servers, or limit database access.

10. Spring Boot vs Spring

    Which key difference sets Spring Boot apart from the traditional Spring Framework?

    1. Spring Boot provides preconfigured defaults and embedded servers
    2. Spring Boot does not support dependency injection
    3. Spring Boot requires XML-based configuration for all beans
    4. Spring Boot cannot build REST APIs

    Explanation: Spring Boot simplifies setup using preconfigured settings and comes with embedded servers like Tomcat. It supports annotation-based configuration, REST APIs, and dependency injection, so the other options are incorrect.

11. Microservices Support

    How does Spring Boot support microservices architecture?

    1. By reducing modularity in applications
    2. By removing support for REST controllers
    3. By restricting applications to only monolithic designs
    4. By integrating with tools that provide service discovery and distributed configuration

    Explanation: Spring Boot, often with extensions, can be integrated with features like service discovery and distributed configuration to support microservices. It does not restrict applications to monolithic architectures or reduce modularity. It also retains REST controller support.

12. DevTools Usage

    What is the primary purpose of Spring Boot DevTools during development?

    1. To enable automatic restarts and live reloading for improved productivity
    2. To remove all configuration files on build
    3. To increase application response time deliberately
    4. To encrypt application source code

    Explanation: DevTools helps developers by providing quick restarts and live reloading of changes. Increasing response time, deleting configuration files, or encrypting source code are not its goals or functionalities.

13. REST Controller Annotation

    Which annotation in Spring Boot is typically used to mark a class as a REST controller?

    1. @RestController
    2. @Repository
    3. @Bean
    4. @Entity

    Explanation: @RestController is specifically used for creating RESTful web services in Spring Boot. @Repository is for data repositories, @Bean for bean definitions, and @Entity for JPA entities, so none of these are suitable for REST controllers.

14. Application Entry Point

    Which method acts as the entry point for a Spring Boot application?

    1. startService()
    2. public static void main(String[] args)
    3. init()
    4. runBootApp()

    Explanation: Like most Java applications, Spring Boot starts from the standard main method. Other listed method names resemble potential custom methods but are not the designated entry point.

15. Starter Example

    If you are building a web application with Spring Boot, which starter would you likely include?

    1. spring-boot-starter-mail
    2. spring-boot-starter-data
    3. spring-boot-starter-cache
    4. spring-boot-starter-web

    Explanation: For web applications, spring-boot-starter-web includes the necessary dependencies for building web services. The mail and cache starters are used for email and caching respectively, while spring-boot-starter-data is incomplete and not a standard starter.

16. Properties Example

    How would you typically set the server port to 9090 in a Spring Boot application?

    1. By declaring @Server(port=9090)
    2. By editing the server.ini file
    3. By adding 'server.port=9090' in application.properties file
    4. By calling setPort(9090) in main()

    Explanation: Configuration properties like server port are set in the application.properties file. Calling setPort or editing non-existent files like server.ini, or using an imaginary annotation, would not achieve this in Spring Boot.