Top 15 Spring Boot Annotations You Must Know for Interviews

Top 15 Spring Boot Annotations You Must Know for Interviews – Explained with Examples

Spring Boot heavily relies on annotations to reduce configuration and boilerplate code. Whether you are appearing for a Java backend interview or want to strengthen your Spring Boot knowledge, knowing these annotations is a must.

Here are the top 15 Spring Boot annotations that are frequently asked in interviews – along with explanations and real-world use cases.

1. @SpringBootApplication

Use: Entry point of every Spring Boot app.
Why: Combines @Configuration, @ComponentScan, and @EnableAutoConfiguration.
Example:

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

2. @RestController

Use: Simplifies the creation of REST APIs.
Why: Combines @Controller and @ResponseBody – automatically converts return data to JSON.
Use case: RESTful endpoints for frontend apps.

3. @RequestMapping

Use: Maps HTTP requests to handler methods.
Why: Can be used at class or method level with GET, POST, etc.
Example: @RequestMapping("/api/users")

4. @GetMapping / @PostMapping / @PutMapping / @DeleteMapping

Use: Shorthand for @RequestMapping(method = ...).
Example: @GetMapping("/user")

5. @Autowired

Use: Injects Spring-managed beans automatically.
Why: Helps in Dependency Injection without manual wiring.
Example:

@Autowired
private UserService userService;

6. @Component

Use: Declares a class as a Spring Bean.
Why: Generic stereotype for any Spring-managed component.

7. @Service

Use: Marks a class as a service layer component.
Why: Specialization of @Component used for business logic.

8. @Repository

Use: Indicates DAO (data access) layer.
Why: Adds automatic exception translation for DB exceptions.

9. @PathVariable

Use: Binds URI template variables to method arguments.
Example: @GetMapping("/user/{id}") → public String getUser(@PathVariable int id)

10. @RequestParam

Use: Binds query parameters from URL.
Example: @RequestParam("page") int pageNo

11. @RequestBody

Use: Converts JSON request body into Java object.
Used in: POST and PUT methods with DTOs.

12. @ResponseBody

Use: Tells Spring to serialize return value to JSON.
Already included in: @RestController

13. @Value

Use: Injects values from properties/yml file.
Example: @Value("${server.port}")

14. @EnableAutoConfiguration

Use: Enables auto-configuration for Spring Boot app.
Why: Automatically sets up beans based on classpath.

15. @Configuration

Use: Defines a class as source of Spring bean definitions.
Why: Used in Java-based configuration instead of XML.

✅ Final Tips:

Don't just memorize – practice these annotations in projects
Use @RestController, @Autowired, and @RequestMapping in a CRUD demo
Understand which annotation applies to which layer: Controller, Service, Repository

📅 Last Updated: 15 May 2025
📎 #SpringBootAnnotations #JavaInterview2025 #SpringBootQnA #BackendPrep

Top 15 Spring Boot Annotations You Must Know for Interviews – Explained with Examples