How does Spring Boot find and connect the necessary modules and components when starting an application?

Spring Boot uses an auto-configuration mechanism based on annotations and conditional checks within configuration classes. When starting the Spring Boot application, it scans the classpath and finds all available components and dependencies.

Main steps:

1. Auto-configuration (@EnableAutoConfiguration) — Spring Boot automatically includes configurations that match the libraries and settings found in the classpath.
2. Component scanning (@ComponentScan) — the framework searches for classes annotated with @Component, @Service, @Repository, and registers them as beans.
3. Using the application.properties or application.yml file — settings from these files influence the behavior of auto-configuration.

Thus, Spring Boot simplifies the process of connecting necessary modules by automatically configuring them if they are present in the project, without the need for manual configuration.

Example:

@SpringBootApplication // includes @EnableAutoConfiguration and @ComponentScan
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

If, for example, Spring Data JPA is present in the classpath, Spring Boot will automatically configure the database connection and repositories.