1. @SpringBootApplication Annotation

The @SpringBootApplication annotation is added to the main class of a Spring Boot application to run it as a standalone JAR or WAR. It is a composite annotation that combines three key annotations:

1.1 @Configuration

• Purpose: Designates the main class as a configuration class for Java-based configuration.
• Functionality: Allows the definition of additional beans via the @Bean annotation.
  • Methods annotated with @Bean in this class return objects that are registered as Spring beans in the application context.

1.2 @EnableAutoConfiguration

• Purpose: Enables Spring Boot’s autoconfiguration mechanism.
• Functionality: Automatically creates beans by scanning the classpath for dependencies, reducing manual configuration.

1.3 @ComponentScan

• Purpose: Instructs Spring Boot to scan the current package and its sub-packages for classes annotated with @Component, @Configuration, @Service, @Repository, etc.
• Functionality: Identifies and configures annotated classes as Spring beans, treating the current package as the root package for component scanning.

Additional Annotation (Automatically Added)

• • @EnableWebMvc **:
    • Purpose: Marks the application as a web application and activates the setup of key components like DispatcherServlet, HandlerMapping, and ViewResolver.
    • When Added: Automatically included by Spring Boot when the spring-webmvc dependency is detected on the classpath.

2. Using the @SpringBootApplication Annotation

To run a Spring Boot application, a main class annotated with @SpringBootApplication is required. This class serves as the entry point for the application.

Example

package com.app;

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

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

Explanation