Spring Framework vs Spring Boot

Introduction

Newcomers often blur the line. Spring Framework is the core library (container, MVC, AOP, data, security modules). Spring Boot is a thin layer on top that adds auto-configuration, starter dependencies and an embedded server, so a new project runs in minutes instead of days.

Boot does not replace the framework — it preconfigures it. Every Boot feature ultimately calls Framework APIs you can use directly. That is why this course teaches the Framework: it is the foundation under everything Boot does.

Understanding the topic

The differences in one table-like list:

• Wiring: Framework → you write config classes. Boot → opinionated defaults already wired.
• Dependencies: Framework → pick versions yourself. Boot → curated starters (e.g. spring-boot-starter-web).
• Server: Framework → deploy a WAR to Tomcat/Jetty. Boot → embedded server, java -jar and you're live.
• Properties: Framework → load yourself. Boot → unified application.yml with profiles.
• Observability: Framework → add libraries. Boot → Actuator endpoints out of the box.

Syntax reference

The smallest possible Boot app:

@SpringBootApplication
public class App {
    public static void main(String[] args) {
        SpringApplication.run(App.class, args);
    }
}

@RestController
class Ping {
    @GetMapping("/ping") String ping() { return "pong"; }
}

Six lines and you have an HTTP server. The same setup in pure Framework takes a web.xml, a DispatcherServlet bean, a server configuration, dependency management — easily 50+ lines and several files.

Real-world use

Almost every new Spring project today is a Boot project — but the moment something breaks, you debug inside the Framework. Knowing the layer below Boot is what separates a tutorial follower from an engineer who can fix production incidents at 3 AM.

Best practices

• Use Boot for new projects. Use your Framework knowledge to understand and override Boot's defaults.
• Read the auto-configuration report (--debug flag) to see what Boot wired for you.
• Override defaults by declaring your own bean — Boot backs off when it sees one.

Common mistakes

• Believing Boot is its own framework — it isn't, and that belief slows your learning.
• Fighting Boot's defaults instead of overriding them with a single @Bean.

Hands-on exercise

Compare: bootstrap the same "hello world" REST endpoint twice — once as a pure Spring Framework project (with explicit DispatcherServlet wiring), once with Spring Boot. Count the lines of configuration in each. Reflect on what Boot did for you.