The @SpringBootApplication Main Class — Spring Technical Interview Questions & Answers

Combines @Configuration, @EnableAutoConfiguration and @ComponentScan.

The @SpringBootApplication Main Class

  • The main class starts the whole Spring Boot application.
  • @SpringBootApplication combines @Configuration, @EnableAutoConfiguration, and @ComponentScan.
  • main method calls SpringApplication.run(MyApp.class, args).
  • That call starts the container, creates beans, and (for web apps) starts the server.
  • Putting main class too deep so component scan misses controllers.
  • Break @SpringBootApplication into its three parts.

Technical Interview Tip: @SpringBootApplication = configuration + auto-config + component scan.

Code Examples for The @SpringBootApplication Main Class

The @SpringBootApplication Main Class — working example

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication // @Configuration + @EnableAutoConfiguration + @ComponentScan
public class DemoApplication {
  public static void main(String[] args) {
    SpringApplication.run(DemoApplication.class, args);
  }
}

// pom.xml / build idea:
// spring-boot-starter-web pulls Tomcat + Spring MVC

The @SpringBootApplication Main Class — @SpringBootApplication boots auto-config, component scan, and the app context; starters are curated dependency bundles.

How to Explain The @SpringBootApplication Main Class to an Interviewer

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