Top 50 Spring Boot Interview Questions and Answers

Spring Boot is a popular framework for building Java applications quickly and efficiently. Whether you’re just starting or have been working with it for a while, you might have some questions. This blog post covers the top 50 Spring Boot Interview questions and answers to help you understand Spring Boot better.

Spring Boot Interview Questions and Answers

1. What is Spring Boot, and why should I use it?

Spring Boot is a framework built on top of the Spring Framework. It simplifies the setup and development of new Spring applications by providing default configurations and embedded servers, reducing the need for boilerplate code.

2. How do I create a Spring Boot application?

You can create a Spring Boot application using Spring Initializr (start.spring.io), an IDE like IntelliJ IDEA, or by using Spring Boot CLI:

1. Go to Spring Initializr.
2. Select your project settings (e.g., Maven, Java, Spring Boot version).
3. Add necessary dependencies.
4. Generate the project and unzip it.
5. Open the project in your IDE and start coding.

3. What is the main class in a Spring Boot application?

The main class in a Spring Boot application is the entry point and is annotated with @SpringBootApplication. It includes the main method which launches the application using SpringApplication.run().

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

4. What does the @SpringBootApplication annotation do?

@SpringBootApplication is a convenience annotation that combines three annotations: @Configuration (marks the class as a source of bean definitions), @EnableAutoConfiguration (enables Spring Boot’s auto-configuration mechanism), and @ComponentScan (scans the package of the annotated class for Spring components).

5. How can you configure properties in a Spring Boot application?

You can configure properties in a Spring Boot application using application.properties or application.yml files located in the src/main/resources directory.

# application.properties
server.port=8081
spring.datasource.url=jdbc:mysql://localhost:3306/mydb

6. How do you handle exceptions in Spring Boot?

You can handle exceptions in Spring Boot using @ControllerAdvice and @ExceptionHandler annotations to create a global exception handler.

@ControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(ResourceNotFoundException.class)
    public ResponseEntity<ErrorResponse> handleResourceNotFoundException(ResourceNotFoundException ex) {
        ErrorResponse errorResponse = new ErrorResponse("NOT_FOUND", ex.getMessage());
        return new ResponseEntity<>(errorResponse, HttpStatus.NOT_FOUND);
    }
}

7. What is Spring Boot Actuator and what are its benefits?

Spring Boot Actuator provides production-ready features such as health checks, metrics, and monitoring for your Spring Boot application. It includes various endpoints that give insights into the application’s health and environment.

8. How can you enable and use Actuator endpoints in a Spring Boot application?

Add the Actuator dependency in your pom.xml or build.gradle file:

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

Configure the endpoints in application.properties:

management.endpoints.web.exposure.include=health,info

9. What are Spring Profiles and how do you use them?

Spring Profiles allow you to segregate parts of your application configuration and make it only available in certain environments. You can activate profiles using the spring.profiles.active property.

# application-dev.properties

spring.datasource.url=jdbc:mysql://localhost:3306/devdb

# application-prod.properties

spring.datasource.url=jdbc:mysql://localhost:3306/proddb

10. How do you test a Spring Boot application?

Spring Boot supports testing with various tools and annotations like @SpringBootTest, @WebMvcTest, and @DataJpaTest. Use MockMvc to test MVC controllers without starting a full HTTP server.

@SpringBootTest
public class MyApplicationTests {
    @Test
    void contextLoads() {
    }
}

11. How can you secure a Spring Boot application?

You can secure a Spring Boot application using Spring Security. Add the dependency and configure security settings:

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

12. What is a Spring Boot Starter and why is it useful?

Spring Boot Starters are a set of convenient dependency descriptors you can include in your application. They provide a one-stop-shop for all the dependencies you need for a particular feature.

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

13. How can you configure a DataSource in Spring Boot?

You can configure a DataSource by adding properties in the application.properties file:

spring.datasource.url=jdbc:mysql://localhost:3306/mydb
spring.datasource.username=root
spring.datasource.password=secret
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

14. What is Spring Boot DevTools and how does it enhance development?

Spring Boot DevTools provides features to enhance the development experience, such as automatic restarts, live reload, and configurations for faster feedback loops. Add the dependency to your project:

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

15. How can you handle different environments in a Spring Boot application?

You can handle different environments using Spring Profiles. Define environment-specific properties files like application-dev.properties, application-prod.properties, and activate a profile using spring.profiles.active.

16. What are the differences between @Component, @Service, @Repository, and @Controller annotations?

These annotations are specializations of @Component:

• @Component: Generic stereotype for any Spring-managed component.
• @Service: Specialization for service layer classes.
• @Repository: Specialization for persistence layer classes.
• @Controller: Specialization for presentation layer (MVC controllers).

17. How can you create a RESTful web service using Spring Boot?

Use @RestController and @RequestMapping annotations to create REST endpoints.

@RestController
@RequestMapping("/api")
public class MyController {
 
    @GetMapping("/greeting")
    public String greeting() {
        return "Hello, World!";
    }
}

18. What is Spring Boot CLI and how is it used?

Spring Boot CLI is a command-line tool that allows you to quickly prototype with Spring. It supports Groovy scripts to write Spring applications.

$ spring init --dependencies=web my-app
$ cd my-app
$ spring run MyApp.groovy

19. How can you connect to a database using Spring Data JPA?

Add the necessary dependencies and create a repository interface extending JpaRepository.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

public interface UserRepository extends JpaRepository<User, Long> {
}

20. How can you use the H2 Database for development and testing in Spring Boot?

Add the H2 dependency and configure the database settings in application.properties:

<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <scope>runtime</scope>
</dependency>

spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=password
spring.h2.console.enabled=true

21. What is the purpose of @Autowired?

@Autowired is used to inject beans (dependencies) automatically by Spring’s dependency injection mechanism. It can be used on constructors, fields, or setter methods.

For Remaining Please Visit: https://javadzone.com/top-50-spring-boot-interview-questions-and-answers/

DO YOU LIKE THIS POST? SUBSCRIBE TO OUR BLOG AND BE THE FIRST TO KNOW ABOUT NEW CONTENT. https://javadzone.com/