Spring Boot Interview Questions — Easy

• Opinionated framework removing Spring's configuration burden: auto-configuration, starter dependencies, embedded servers (Tomcat/Jetty), production features (Actuator).
• Plain Spring requires explicit XML/Java config for every bean; Boot infers from classpath ("found H2 + JPA → configure datasource").
• Result: java -jar app.jar runnable microservice in minutes vs days of wiring.

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• Boot inspects classpath, beans, properties at startup; @EnableAutoConfiguration loads conditionally-defined configurations (@ConditionalOnClass, @ConditionalOnMissingBean).
• Debug with --debug flag printing the CONDITIONS EVALUATION REPORT (matched/not-matched).
• Exclude via @SpringBootApplication(exclude=DataSourceAutoConfiguration.class) or property. Your bean ALWAYS wins over auto-config (@ConditionalOnMissingBean backs off) - the key extension principle.

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• Curated dependency descriptors: spring-boot-starter-web pulls Spring MVC+Jackson+Tomcat coherently versioned.
• Kill transitive-dependency guesswork; Boot's BOM manages compatible versions across the ecosystem.
• Common set to name: web, data-jpa, security, validation, actuator, test, data-redis.

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Composite of three:

1. @Configuration - class is a bean-definition source.
2. @ComponentScan - pick up @Component/@Service/@Repository/@Controller under package (root scan covers sub-packages - why main class sits at root).
3. @EnableAutoConfiguration - activates conditional config machinery.

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• Inversion of Control: the framework creates and wires objects (beans) instead of classes instantiating their own dependencies.
• ApplicationContext is the advanced container - lifecycle callbacks, events, i18n, resource loading on top of bean factory.
• Beans defined via stereotype annotations, @Bean methods, or imports; retrieved by type mostly - coding to interfaces becomes natural.

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