What are alternatives to Eureka, and why might you choose them?

Alternatives: Consul, Zookeeper, Kubernetes Service Discovery.

Choose based on requirements like scalability, ease of setup, and cloud-native compatibility.

Can Eureka work in a cloud-native microservices environment? How?

Yes, by leveraging its service registry features, Eureka can integrate seamlessly with container orchestration tools like Kubernetes.

What is the role of an API gateway in microservices?

API Gateway acts as a single entry point for all clients. It handles routing, authentication, load balancing, caching, and service discovery.

What is the difference between synchronous and asynchronous communication in microservices?

Synchronous: Services communicate in real-time using protocols like HTTP/REST or gRPC (e.g., immediate responses).

Asynchronous: Communication happens via message queues (e.g., RabbitMQ, Kafka), allowing services to process requests independently.

How do microservices communicate with each other?

Through lightweight communication protocols such as:

Synchronous: HTTP/REST, gRPC

Asynchronous: Message brokers like RabbitMQ, Apache Kafka, or AWS SQS

What is the difference between @Controller and @RestController?
• @Controller is used to define a Spring MVC controller that returns a view (e.g., JSP, Thymeleaf).
• @RestController is a convenience annotation that combines @Controller and @ResponseBody. It is used when the controller returns data directly (e.g., JSON, XML) instead of a view.

What are Spring Profiles? How are they useful?
• Spring Profiles allow you to define different configurations for different environments (e.g., dev, test, prod).
• They are activated using spring.profiles.active in application.properties or via environment variables.
• Example: @Profile("dev") ensures a bean is only loaded in the dev environment.

Explain the difference between @Component, @Repository, and @Service.
• @Component: Generic annotation for Spring-managed components.
• @Repository: Specialized for Data Access Objects (DAO). It provides exception translation.
• @Service: Specialized for the service layer. Indicates a service class for business logic.

What is the difference between @Component and @Configuration in Spring?
• @Component: Marks a class as a Spring-managed bean. It’s generally used for classes like services, repositories, or controllers.
• @Configuration: A specialized @Component used for defining bean creation methods explicitly using @Bean. It ensures singleton behavior for beans defined within the class.

What is the difference between @RestController and @Controller?

Answer:

@Controller: A specialization of @Component used for defining controllers in Spring MVC. Typically used in conjunction with @RequestMapping to define request-handling methods. It returns views (HTML pages) via ModelAndView.

@RestController: Combines @Controller and @ResponseBody. It is used to create RESTful web services and automatically serializes Java objects into JSON or XML.

How does Spring Boot auto-configuration work?

Answer:

Spring Boot uses the @EnableAutoConfiguration annotation (or indirectly via @SpringBootApplication) to configure beans based on the libraries on the classpath and properties defined in application.properties or application.yml.

The spring.factories file inside META-INF lists all the auto-configuration classes, which are conditionally applied using @ConditionalOnClass, @ConditionalOnProperty, etc.

What is the difference between @Component, @Repository, and @Service?

Answer:

@Component: A generic stereotype annotation for any Spring-managed component.

@Repository: A specialization of @Component used to indicate a Data Access Object (DAO). Automatically translates database exceptions into Spring exceptions.

@Service: A specialization of @Component used to indicate a service layer bean. It is used to encapsulate business logic.

How does Spring Boot handle exceptions in REST APIs?

Answer:

Use @ControllerAdvice to define a global exception handler.

Handle exceptions with @ExceptionHandler methods in the advice class.

Return meaningful HTTP status codes and error messages in the response body.

What is the purpose of the @SpringBootApplication annotation?

Answer:

It is a combination of three annotations:

1. @SpringBootConfiguration: Similar to @Configuration.


2. @EnableAutoConfiguration: Enables Spring Boot's auto-configuration.


3. @ComponentScan: Scans the package where the application class resides.

What is the use of @Conditional annotations in Spring Boot?

Answer:

Spring Boot uses @Conditional annotations to enable conditional bean creation.

Examples:

@ConditionalOnClass: Bean is created only if a specific class is on the classpath.

@ConditionalOnProperty: Bean is created only if a specific property is defined in the configuration.