Configuration & Profiles

SpringApplication.run() creates the ApplicationContext, auto-configures beans from the classpath, starts the embedded Tomcat server, and runs startup tasks, while graceful shutdown drains in-flight requests before stopping.

Spring Boot resolves properties in a strict priority order where command-line arguments win over environment variables, which win over profile-specific files, which win over the base application.yml, and @ConfigurationProperties binds these into type-safe validated objects.