The Three Annotations Inside @SpringBootApplication

@SpringBootApplication is not one mechanism. It is three, combined into a single annotation so a new project starts with one line instead of three.

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SpringBootConfiguration
EnableAutoConfiguration
ComponentScan

SpringBootApplication.class.getAnnotations(), read by reflection — verified

What each one does
Annotation	Job
`@SpringBootConfiguration`	Marks the class as a source of bean definitions — a specialised `@Configuration`
`@EnableAutoConfiguration`	Turns on the classpath-scanning mechanism that creates beans for you
`@ComponentScan`	Finds your own `@Component`-family classes, starting from this class's package

@EnableAutoConfiguration is the one that's actually new here — @Configuration and @ComponentScan both exist in plain Spring already. It's what the next two cards are about.

Spring Boot