What is @SpringBootApplication and what does it combine?

// @SpringBootApplication = @SpringBootConfiguration
//                          + @EnableAutoConfiguration
//                          + @ComponentScan

@SpringBootApplication  // the one annotation to rule them all
public class OrderServiceApplication {

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

// What each constituent annotation does:

// @SpringBootConfiguration: marks this as a Spring configuration class
// (specialisation of @Configuration)

// @EnableAutoConfiguration: tells Spring Boot to scan the classpath
// and auto-configure beans based on what is found
// e.g., finds spring-boot-starter-data-jpa -> auto-configures DataSource

// @ComponentScan: scans the current package and sub-packages
// for @Component, @Service, @Repository, @Controller, etc.
// Default: scans the package of the annotated class

// Customisations:
@SpringBootApplication(
    // exclude specific auto-configurations:
    exclude = {DataSourceAutoConfiguration.class},
    // scan additional packages:
    scanBasePackages = {"com.example.orders", "com.example.shared"}
)
public class App { ... }

// SpringApplication customisation in Boot 4:
@SpringBootApplication
public class App {
    public static void main(String[] args) {
        var app = new SpringApplication(App.class);
        app.setBannerMode(Banner.Mode.OFF);  // disable ASCII art banner
        app.setLazyInitialization(true);     // lazy init for faster startup
        app.run(args);
    }
}