Spring Boot vs Spring Framework: Key Differences and When to Use Each

Spring Framework is a comprehensive Java framework for building applications with flexible configuration, while Spring Boot is a tool built on top of it that simplifies setup by providing defaults and auto-configuration to quickly start projects.

Quick Comparison

Here is a quick side-by-side comparison of Spring Boot and Spring Framework based on key factors.

Factor	Spring Framework	Spring Boot
Setup Complexity	Manual configuration of beans and dependencies	Auto-configuration with sensible defaults
Project Initialization	Requires manual setup of dependencies and XML or Java config	Starter templates and opinionated defaults for fast start
Configuration Style	Flexible XML, annotations, or Java config	Convention over configuration with minimal setup
Embedded Server	Requires external server setup (e.g., Tomcat)	Includes embedded servers like Tomcat or Jetty
Use Case	Full control for complex, customized apps	Rapid development of microservices and standalone apps
Learning Curve	Steeper due to manual setup	Gentler with simplified conventions

Key Differences

Spring Framework is the core framework that provides the foundation for dependency injection, aspect-oriented programming, and transaction management. It requires developers to manually configure beans, application contexts, and often external servers. This flexibility allows fine-grained control but can be time-consuming for setup.

Spring Boot builds on top of Spring Framework to reduce boilerplate and speed up development. It uses auto-configuration to guess and set up components based on included libraries, and provides starter dependencies to simplify build files. It also embeds servers like Tomcat, so you can run applications standalone without external server installation.

In essence, Spring Boot is designed to get you running quickly with Spring Framework’s power, while Spring Framework alone gives you full control but requires more manual work.

Code Comparison

This example shows a simple REST controller setup in plain Spring Framework requiring manual configuration.

java

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@Configuration
@EnableWebMvc
public class AppConfig implements WebMvcConfigurer {

    @Bean
    public HelloController helloController() {
        return new HelloController();
    }
}

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

Output

When running with a configured servlet container, accessing /hello returns: Hello from Spring Framework!

Spring Boot Equivalent

The same REST controller in Spring Boot requires minimal setup and runs with an embedded server.

java

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

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

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

Output

Running this Spring Boot app and accessing /hello returns: Hello from Spring Boot!

When to Use Which

Choose Spring Boot when you want to quickly start a project with minimal configuration, especially for microservices or standalone applications that benefit from embedded servers and auto-configuration.

Choose Spring Framework when you need full control over configuration, want to integrate deeply with existing infrastructure, or build complex applications where manual setup and customization are necessary.

Key Takeaways

Spring Boot simplifies Spring Framework by providing auto-configuration and embedded servers.

Spring Framework offers full control but requires manual setup and configuration.

Use Spring Boot for rapid development and microservices.

Use Spring Framework for complex, highly customized applications.

Spring Boot reduces boilerplate and speeds up project startup.