Spring Boot Interview Guide 2024

Spring Boot has become the de-facto standard for building Java-backend applications. Whether you are a fresher or an experienced developer, these questions will help you solidify your understanding.

1. What is Spring Boot and how is it different from the Spring Framework?

**Spring Framework** provides a comprehensive programming and configuration model for modern Java-based enterprise applications. It focuses on *Dependency Injection (DI)* and *Aspect-Oriented Programming (AOP)*.

**Spring Boot**, on the other hand, is an extension of the Spring Framework that eliminates the boilerplate configuration required for setting up a Spring application.

**Key Differences:**

2. Explain the concept of "Auto-Configuration".

Auto-configuration attempts to automatically configure your Spring application based on the jar dependencies that you have added.

For example, if `HSQLDB` is on your classpath, and you have not manually configured any database connection beans, Spring Boot auto-configuration will automatically configure an in-memory database.

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

3. What is the @SpringBootApplication annotation?

It is strictly a convenience annotation that is equivalent to declaring:

1. `@Configuration`: Marks the class as a source of bean definitions.

2. `@EnableAutoConfiguration`: Tells Spring Boot to start adding beans based on classpath settings.

3. `@ComponentScan`: Tells Spring to look for other components, configurations, and services in the `com.example` package.

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

public class MyServiceApplication {

public static void main(String[] args) {

SpringApplication.run(MyServiceApplication.class, args);

}

}

4. How do you handle exceptions in Spring Boot?

The standard way to handle exceptions globally is using `@ControllerAdvice` (or `@RestControllerAdvice`) combined with `@ExceptionHandler`.

@RestControllerAdvice

public class GlobalExceptionHandler {

@ExceptionHandler(ResourceNotFoundException.class)

public ResponseEntity<String> handleResourceNotFound(ResourceNotFoundException ex) {

return new ResponseEntity<>(ex.getMessage(), HttpStatus.NOT_FOUND);

}

}

5. Microservices with Spring Boot

Spring Boot is widely used for microservices because:

Conclusion

Mastering these core concepts—Auto-configuration, Annotations, and Error Handling—is crucial 80% of the interview. The rest depends on your system design knowledge. Good luck!