Spring Boot Fundamentals

Spring Boot is an opinionated layer on top of the Spring Framework that auto-configures the application based on the classpath, embeds a web server, and removes XML and boilerplate via sensible defaults — so you can run a production-ready app with one command. It exists because raw Spring, while powerful, required significant manual configuration and an external servlet container to deploy, which slowed development and made onboarding hard. The pieces I anchor on are auto-configuration, which inspects the classpath and creates beans you'd otherwise write — if Tomcat's present it configures an embedded server, if a DataSource is present it configures one — and you override only what differs. Starters, which are curated, tested dependency sets that prevent version conflicts. The embedded server, which runs inside the jar so the app is self-contained and runnable with java -jar. And the fact that it's still Spring underneath — every Boot behavior is Spring beans, so I can override any auto-config by defining my own bean, and actuator's /beans endpoint lists what's there. The tension I'm honest about is convention versus control: the auto-configuration can feel like magic, but every auto-config has a conditional and is overridable, so the control is always there when I need it.