Java REST API Interview Questions and Answers for 2 years experience

1. What is a RESTful API?

   • Answer: A RESTful API (Representational State Transfer) is an architectural style for building web services. It uses HTTP methods (GET, POST, PUT, DELETE) to interact with resources, identified by URIs. Key constraints include statelessness, client-server architecture, cacheability, and a uniform interface.

2. Explain the difference between GET and POST requests.

   • Answer: GET requests retrieve data from a server; they are idempotent (multiple calls have the same effect as one) and should not have side effects. POST requests send data to the server to create or update a resource; they are not idempotent and can have side effects.

3. What are HTTP status codes and explain some common ones?

   • Answer: HTTP status codes indicate the outcome of a client request. 200 OK (successful), 400 Bad Request (client error), 404 Not Found (resource not found), 500 Internal Server Error (server error).

4. What is HATEOAS and why is it important in RESTful APIs?

   • Answer: HATEOAS (Hypermedia as the Engine of Application State) is a constraint of RESTful APIs. It means that the response from the server includes links to other resources, allowing the client to discover available actions without hardcoding URLs.

5. How do you handle exceptions in a REST API?

   • Answer: Use exception handling mechanisms (try-catch blocks) to gracefully handle errors. Return appropriate HTTP status codes (e.g., 400, 404, 500) and structured error messages in the response body (e.g., JSON).

6. What are different ways to serialize data in a REST API?

   • Answer: JSON (JavaScript Object Notation) and XML (Extensible Markup Language) are common formats. JSON is generally preferred for its simplicity and efficiency.

7. Explain the concept of REST API versioning.

   • Answer: Versioning allows for backward compatibility when API changes are made. Methods include URI versioning (e.g., /v1/users), header versioning (e.g., Accept header), and content negotiation.

8. What is Spring Boot? How does it simplify REST API development?

   • Answer: Spring Boot is a framework that simplifies Spring application development. For REST APIs, it provides auto-configuration, embedded servers (Tomcat, Jetty), and starter dependencies, reducing boilerplate code and setup time.

9. Explain the role of annotations like @RestController, @RequestMapping, @GetMapping, @PostMapping, etc., in Spring Boot.

   • Answer: These annotations define REST controllers and map HTTP requests to specific handler methods. `@RestController` combines `@Controller` and `@ResponseBody`. `@RequestMapping` maps requests to methods, while `@GetMapping` and `@PostMapping` are specialized for GET and POST requests, respectively.

10. How do you handle authentication and authorization in a REST API?

    • Answer: Common approaches include OAuth 2.0, JWT (JSON Web Tokens), and basic authentication. Authentication verifies the identity of the client, while authorization determines what actions the client is permitted to perform.

11. What are some common security best practices for REST APIs?

    • Answer: Input validation, output encoding, using HTTPS, protecting against common attacks like SQL injection and cross-site scripting (XSS), rate limiting, and proper authentication/authorization mechanisms.

12. What is dependency injection and how is it used in Spring?

    • Answer: Dependency Injection is a design pattern where dependencies are provided to a class rather than the class creating them. Spring uses annotations like `@Autowired` to manage dependencies.

13. Explain the difference between `@PathVariable`, `@RequestParam`, and `@RequestBody` in Spring.

    • Answer: `@PathVariable` extracts values from the URI path, `@RequestParam` extracts values from query parameters, and `@RequestBody` binds the request body to a Java object.

14. How do you test a REST API?

    • Answer: Use tools like Postman or curl to manually test endpoints. For automated testing, frameworks like JUnit and Mockito can be used along with testing libraries like Spring Test.

15. What is Swagger/OpenAPI? How is it used in API documentation?

    • Answer: Swagger/OpenAPI is a specification for describing REST APIs. It generates interactive API documentation from annotations or YAML/JSON files, making it easier for developers to understand and use the API.

16. Explain the concept of caching in REST APIs.

    • Answer: Caching improves performance by storing frequently accessed data. HTTP headers like `Cache-Control` and `ETag` are used to control caching behavior. CDNs (Content Delivery Networks) can also be used for caching.

17. What are some common design patterns used in REST API development?

    • Answer: Repository pattern, Factory pattern, Singleton pattern, Template method pattern are some commonly used design patterns.

18. How do you handle pagination in a REST API?

    • Answer: Implement pagination to return only a subset of results at a time. Use query parameters like `page` and `size` to specify the page number and number of results per page. Include links to previous and next pages in the response.

19. Explain how you would handle rate limiting in a REST API.

    • Answer: Implement rate limiting to prevent abuse and denial-of-service attacks. Techniques include using a sliding window, token bucket, or leaky bucket algorithms. Libraries or frameworks can assist in this implementation.

20. What is the difference between a microservice architecture and a monolithic architecture?

    • Answer: A monolithic architecture has all components in a single application, while a microservice architecture breaks down the application into smaller, independent services that communicate over a network. Microservices offer better scalability, maintainability, and fault isolation.

21. Describe your experience with database interactions in a REST API context. (e.g., using JPA/Hibernate)

    • Answer: [Describe specific experience with JPA, Hibernate, or other ORMs. Mention specific database technologies used and any challenges faced.]

22. How do you handle asynchronous operations in a REST API?

    • Answer: Use message queues (e.g., RabbitMQ, Kafka) or asynchronous programming techniques (e.g., using threads or CompletableFuture) to handle long-running operations without blocking the main thread. Return a unique ID to allow the client to check the status of the operation later.

23. What is your experience with API gateways?

    • Answer: [Describe experience with API gateways, such as Kong, Zuul, or Spring Cloud Gateway. Mention their role in routing, authentication, and security.]

24. How do you ensure the scalability and performance of your REST APIs?

    • Answer: Use appropriate caching strategies, database optimization, load balancing, efficient algorithms, asynchronous processing, and monitoring tools. Consider using a cloud-based infrastructure for scalability.

25. Describe a challenging problem you faced while developing a REST API and how you solved it.

    • Answer: [Describe a specific challenge, including the context, the problem, the steps taken to diagnose the issue, and the solution implemented.]

26. What are your preferred tools and technologies for developing and deploying REST APIs?

    • Answer: [List preferred IDEs, build tools (Maven, Gradle), testing frameworks, deployment tools (Docker, Kubernetes), and other relevant technologies.]

27. What is your understanding of REST API design principles?

    • Answer: Discuss the importance of resource-based URLs, proper use of HTTP methods, statelessness, and client-server architecture. Mention the benefits of HATEOAS (if applicable) and versioning.

28. How do you stay up-to-date with the latest trends and technologies in REST API development?

    • Answer: Mention following blogs, attending conferences, participating in online communities, reading relevant documentation, and experimenting with new tools and frameworks.

29. What are your strengths and weaknesses as a REST API developer?

    • Answer: [Provide honest and specific examples. Focus on strengths relevant to the role and weaknesses you are actively working to improve.]

30. Why are you interested in this position?

    • Answer: [Express genuine interest in the company, the team, and the specific projects. Highlight how your skills and experience align with the requirements.]

31. Where do you see yourself in 5 years?

    • Answer: [Show ambition and a desire for growth, but be realistic and grounded. Connect your goals to the company's potential for advancement.]

Thank you for reading our blog post on 'Java REST API Interview Questions and Answers for 2 years experience'.We hope you found it informative and useful.Stay tuned for more insightful content!