Spring Framework vs Spring Boot — What's the Difference?

Q: Spring Framework vs Spring Boot — What's the Difference?

Spring Boot is **not a replacement** for Spring Framework — it's an opinionated layer on top that eliminates boilerplate configuration. Spring provides the ecosystem (**IoC, AOP, MVC, Data, Security**), while Spring Boot provides **auto-configuration, embedded servers, starter dependencies**, and production-ready defaults so you can go from zero to running application in minutes instead of hours. Every Spring Boot app is still a Spring app — the same `ApplicationContext`, the same `BeanPostProcessor`s, the same proxies — Boot just stops you from writing the configuration that wires it together.

Intermediate·2 min read·

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Core answer

Spring Boot is not a replacement for Spring Framework — it's an opinionated layer on top that eliminates boilerplate configuration. Spring provides the ecosystem (IoC, AOP, MVC, Data, Security), while Spring Boot provides auto-configuration, embedded servers, starter dependencies, and production-ready defaults so you can go from zero to running application in minutes instead of hours. Every Spring Boot app is still a Spring app — the same ApplicationContext, the same BeanPostProcessors, the same proxies — Boot just stops you from writing the configuration that wires it together.

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Interview answer

Spring Boot is not a different framework — it is Spring Framework with decisions already made for you. The same ApplicationContext, the same IoC container, the same AOP proxies. What Spring Boot adds is conventions, auto-configuration, embedded servers, and starter POMs that wire everything together automatically.

What Spring Boot adds

Auto-configuration: reads @ConditionalOnClass, @ConditionalOnMissingBean conditions at startup and registers beans only when the right dependencies are on the classpath and you have not already defined your own
Embedded server: Tomcat, Jetty, or Netty ships inside the JAR — no deployment to an external container required
Starter POMs: spring-boot-starter-web pulls in exactly the right set of dependencies at compatible versions

What stays the same

The IoC container is identical — ApplicationContext, BeanPostProcessor, @Autowired, @Transactional all work exactly as in raw Spring
Debugging an auto-configuration issue requires understanding raw Spring: which BeanPostProcessor runs, what condition failed, why two beans of the same type conflict

When to use raw Spring

Embedding Spring into a non-Boot environment (legacy app servers, custom tooling)
Writing a Spring Boot starter or auto-configuration itself

@SpringBootApplication is three annotations composed: @Configuration (this class defines beans), @EnableAutoConfiguration (activate auto-config), @ComponentScan (scan this package). Understanding the composition means you can decompose it when you only need part of it.

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