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Java Interview Questions

Spring Boot Interview Questions

Spring Boot fundamentals — auto-configuration on top of Spring, and building REST controllers quickly.

Question 1: What is Spring Boot?

Ans

Spring Boot is a Spring-based framework that simplifies application development through auto-configuration, starter dependencies, embedded servers, externalized configuration, and production-oriented features.

It lets developers create deployable Spring applications with much less configuration.

Example

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

Important Point

Spring Boot does not replace Spring; it provides conventions and tooling around the Spring ecosystem.

Question 2: What is @RestController?

Ans

@RestController is a Spring annotation used for classes whose methods handle web requests and return response data directly, commonly serialized as JSON.

It combines controller semantics with response-body behavior.

Example

java
@RestController
class HelloController {
    @GetMapping("/hello")
    String hello() { return "Hello"; }
}

Important Point

For complex APIs, also consider explicit status codes, validation, exception handling, and consistent response contracts.

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