# Spring vs Spring Boot

## **About**

**Spring Framework** and **Spring Boot** are closely related, but they serve different purposes. While both are part of the larger Spring ecosystem, understanding their difference is key to building efficient applications.

Think of **Spring** as the foundational toolkit, and **Spring Boot** as a modern accelerator built on top of that toolkit to make development faster and more automatic.

## **Spring Framework**

The **Spring Framework** is a comprehensive and modular framework for building Java-based enterprise applications. It offers the foundational building blocks for dependency injection, aspect-oriented programming, transaction management, web development, and integration with data sources.

However, **Spring requires a lot of configuration**, either in XML or Java-based annotations. We must manually define beans, set up application contexts, configure servlet containers, etc.

So while Spring provides flexibility and control, it can feel heavy and complex, especially for newcomers or small projects.

## **Spring Boot**

**Spring Boot** is an extension of the Spring Framework that **eliminates the need for most boilerplate configuration**. It offers:

* Opinionated defaults
* Automatic configuration
* Production-ready features (e.g., metrics, health checks)
* Embedded servers (like Tomcat, Jetty)
* No need for external XML files
* Minimal setup to get started

Spring Boot focuses on **convention over configuration**, helping developers create Spring-based applications quickly.

It doesn’t replace the Spring Framework but builds on top of it and simplifies its use.

## **Comparison**

<table data-full-width="true"><thead><tr><th width="168.52081298828125">Feature</th><th>Spring</th><th>Spring Boot</th></tr></thead><tbody><tr><td><strong>Setup</strong></td><td>Manual configuration of application context, beans, web servers</td><td>Auto-configuration and prebuilt project structure</td></tr><tr><td><strong>Complexity</strong></td><td>More complex and verbose setup</td><td>Simpler, faster, and less configuration</td></tr><tr><td><strong>Embedded Server</strong></td><td>Requires external server (Tomcat, Jetty) setup</td><td>Has embedded servers (Tomcat, Jetty, etc.)</td></tr><tr><td><strong>Deployment</strong></td><td>Usually packaged as WAR and deployed to server</td><td>Usually packaged as JAR and self-contained</td></tr><tr><td><strong>Dependencies</strong></td><td>Manual inclusion and version management</td><td>Uses "starters" for dependencies and auto-manages versions</td></tr><tr><td><strong>Learning Curve</strong></td><td>Steeper, but flexible for large enterprise setups</td><td>Easier for beginners and quick development</td></tr><tr><td><strong>Focus</strong></td><td>Flexibility, extensibility</td><td>Rapid development, ease of use, defaults</td></tr></tbody></table>

## **When to Use What ?**

* **Use Spring** when:
  * We want full control over configuration
  * We are working in an existing enterprise system that doesn’t use Spring Boot
  * We need fine-grained tuning or custom frameworks on top of Spring
* **Use Spring Boot** when:
  * We want to quickly build standalone applications
  * We need rapid prototyping or MVPs
  * We prefer convention over configuration
  * We want production-ready defaults with minimal code

## **Example**

### **Spring Approach**

```java
@Configuration
@ComponentScan("com.example")
public class AppConfig {
    // Define beans manually
}

public class AppInitializer implements WebApplicationInitializer {
    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        // Set up dispatcher servlet
    }
}
```

### **Spring Boot Approach**

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

With Spring Boot, we just annotate and run. Everything else is auto-configured behind the scenes.


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