Spring vs Spring Boot: What Are the Main Differences Every Java Developer Should Know?

Source: Dev.to

Introduction

If you’ve ever started learning Java programming for backend development, chances are you’ve heard people casually say, “Just use Spring Boot.” But then you wonder—What about Spring? Are they the same thing?

Think of Spring and Spring Boot like cooking at home. Spring is like having raw ingredients and full control over how you cook—powerful, but time‑consuming. Spring Boot, on the other hand, is like a ready‑to‑cook meal kit—it sets things up for you so you can focus on the final dish.

Understanding the Spring vs Spring Boot difference is crucial for beginners because it affects how fast you can build applications, how much configuration you manage, and how production‑ready your app is. In this article we’ll break things down in simple terms, with clear explanations, practical examples, and real‑world use cases to help you learn Java the right way.

Core Concepts

What is Spring?

Spring Framework is a powerful, lightweight framework used to build Java applications. Its main goal is to make Java development easier by handling common concerns like dependency injection, transaction management, and security.

However, Spring gives you freedom with responsibility. You must:

• Configure beans manually
• Set up XML or Java‑based configurations
• Manage dependencies carefully
• Configure servers like Tomcat explicitly

Use case:
Spring is ideal when you need fine‑grained control over every part of your application or when working with legacy systems.

What is Spring Boot?

Spring Boot is built on top of Spring. It doesn’t replace Spring—it enhances it.

Spring Boot focuses on convention over configuration, meaning:

• Sensible defaults are provided
• Embedded servers (Tomcat, Jetty) come built‑in
• Auto‑configuration reduces boilerplate code
• Applications can run with a simple main() method

Use case:
Spring Boot is perfect for microservices, REST APIs, cloud‑native apps, and rapid development.

Key Differences: Spring vs Spring Boot

In short, Spring is the foundation, and Spring Boot is the accelerator 🚀. Most modern Java applications today use Spring Boot because it dramatically improves developer productivity.

Code Examples (Java 21)

Example 1: Simple REST API Using Spring (Traditional Configuration)

// Java 21 compatible
@Configuration
@ComponentScan(basePackages = "com.example.springapp")
public class AppConfig {
}

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

Observation: You must configure component scanning, server setup, and deployment manually (e.g., web.xml or external server configuration).

Example 2: Simple REST API Using Spring Boot

// Java 21 compatible
@SpringBootApplication
public class SpringBootDemoApplication {

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

@RestController
public class HelloController {

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

Observation: No XML, no server configuration, and the app runs with a single command:

mvn spring-boot:run

This simplicity is why Spring Boot dominates modern Java programming.

Best Practices (3–5 Tips)

• Start with Spring Boot if you’re a beginner – avoid unnecessary complexity when learning Spring vs Spring Boot.
• Understand Spring fundamentals first – knowing dependency injection and beans helps you debug Spring Boot better.
• Avoid over‑customizing auto‑configuration – let Spring Boot do its job unless you truly need customization.
• Use Spring Boot Actuator for production apps – it provides health checks, metrics, and monitoring out of the box.
• Keep configurations externalized – use application.yml or application.properties for environment‑specific settings.

Conclusion

The debate around Spring vs Spring Boot becomes simple once you understand their roles. Spring is a powerful framework that gives you full control, while Spring Boot builds on that power by removing unnecessary setup and configuration.

If your goal is to learn Java and build real‑world applications quickly, Spring Boot is the clear winner. It lets you focus on writing business logic instead of plumbing code. That said, Spring knowledge remains essential—it’s the engine running under the hood.

Whether you’re preparing for interviews, building microservices, or starting your backend journey, mastering both Spring and Spring Boot will make you a confident and effective Java developer.