Spring vs Spring Boot | Learn Code With Durgesh

First, the Basics

Spring Framework (a.k.a Spring):
A comprehensive framework for building Java applications.
It provides dependency injection, aspect-oriented programming, data access, web MVC, security, etc.
But it requires a lot of manual configuration.
Spring Boot:
A framework built on top of Spring that makes development faster, easier, and less error-prone by removing configuration overhead.
It comes with auto-configuration, starter dependencies, embedded servers, and production-ready features.

Spring = Buying raw ingredients and cooking everything yourself.

Spring Boot = Ordering a ready-made meal kit that comes pre-measured, half-cooked, and ready in 10 minutes.

Key Differences

Feature / Aspect	Spring Framework	Spring Boot
Configuration	Manual XML/Java config needed	Auto-configuration (smart defaults)
Setup Time	Long (set up Tomcat, DataSource, beans manually)	Short (starters + embedded server)
Server	Requires external server (Tomcat, Jetty, etc.)	Comes with embedded Tomcat/Jetty/Undertow
Dependencies	Must specify each library	Uses starter dependencies (bundled)
Deployment	Typically WAR file deployment	Run as a standalone JAR (`java -jar app.jar`)
Production Features	Must integrate manually (monitoring, metrics)	Built-in via Spring Boot Actuator
Learning Curve	Steeper (more boilerplate)	Easier (opinionated defaults)
Focus	Flexibility & modularity	Productivity & convention-over-configuration
Use Case	Large enterprise apps needing fine-grained control	Microservices, REST APIs, cloud-native apps

Example — Building a Simple REST API

(A) Using Spring Framework

Steps:

Configure DispatcherServlet in web.xml.
Set up Spring Beans in applicationContext.xml.
Configure Tomcat/Jetty server.
Create Controller.

<!-- web.xml -->
<web-app>
  <servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>
</web-app>

<!-- web.xml -->
<web-app>
  <servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>
</web-app>

@Controller
public class HelloController {
    @RequestMapping("/hello")
    @ResponseBody
    public String sayHello() {
        return "Hello from Spring!";
    }
}

Needs external Tomcat, WAR deployment.

(B) Using Spring Boot

Steps:

Add spring-boot-starter-web dependency.
Write Controller.
Run the app.

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

@RestController
public class HelloController {
    @GetMapping("/hello")
    public String sayHello() {
        return "Hello from Spring Boot!";
    }
}

Just run → http://localhost:8080/hello works immediately. No XML. No server setup.

When to Use What?

Use Spring Framework when:
- You need fine-grained control over every bean and configuration.
- You’re working on large legacy enterprise systems that still follow WAR deployment.
- You want flexibility over conventions.
Use Spring Boot when:
- You want rapid development (REST APIs, microservices).
- You’re deploying to cloud-native environments (Docker, Kubernetes).
- You want production-ready features out of the box.

Conclusion

Spring = Foundation (powerful but configuration-heavy).
Spring Boot = Accelerator (removes boilerplate, adds auto-magic).
Spring Boot saves time, reduces errors, and is ideal for modern cloud-based apps.
Example proves: Boot = 5 lines of code vs. Spring = multiple XMLs + configs.

Think of Spring as the “engine” and Spring Boot as the “car”. You can build your own car from scratch with just the engine (Spring), but Boot gives you a ready-to-drive car.