Spring Boot is not a new framework. It is Spring plus a set of opinionated defaults that remove most of the XML and boilerplate the older stack required.

What a starter actually does

A starter such as spring-boot-starter-web is a dependency with no code of its own. It pulls in a curated set of libraries that are known to work together, so version alignment stops being your problem.

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
</dependency>

Auto-configuration in one sentence

At startup Boot inspects the classpath and the existing bean definitions, then registers the beans you did not define yourself. Because it backs off whenever you declare your own bean, overriding a default is just a matter of defining it.

Run with --debug to see the full report of what matched and what did not:

./mvnw spring-boot:run -Dspring-boot.run.arguments=--debug

A minimal service

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

@RestController
class HealthController {
  @GetMapping("/health")
  Map<String, String> health() {
    return Map.of("status", "up");
  }
}

That is a running HTTP service with an embedded server, JSON serialization, and sensible error handling already wired.

  • Configuration binding with @ConfigurationProperties instead of scattered @Value
  • Profiles for environment-specific configuration
  • Actuator endpoints, before you need them in production