What processes are launched at the start of a Spring Boot application?

When starting a Spring Boot application, several key stages occur:

1. Main method execution — SpringApplication.run() is called, which initializes the application context.
2. Creating ApplicationContext — Spring Boot creates and configures the ApplicationContext (usually AnnotationConfigApplicationContext or SpringApplicationContext).
3. Auto-configuration — classes annotated with @EnableAutoConfiguration are triggered, configuring beans and components based on dependencies and properties.
4. Component scanning — Spring scans packages for components with annotations like @Component, @Service, @Repository, @Controller and registers them.
5. Dependency injection — dependencies are injected into beans.
6. Execution of CommandLineRunner and ApplicationRunner — if beans implementing these interfaces exist, their run() methods are called after the context is initialized.
7. Starting the embedded server (if a web application) — for example, Tomcat or Jetty starts and begins listening for HTTP requests.

Thus, Spring Boot simplifies application configuration and startup, automatically selecting the necessary components and creating a ready-to-run application.