This article explains the differences between Spring and Spring Boot from the perspective of “what gets easier” and “what you still configure yourself,” breaking it down clearly so beginners can choose with confidence.
This article first gives you the conclusion up front, then walks through a comparison table, concrete code examples, and finally how to choose in real-world projects. Feel free to just read the parts you’re interested in.
What is Spring?
Spring is the “foundation (framework)” for building applications in Java. It’s especially well known for its design centered on DI (Dependency Injection) and IoC (Inversion of Control), which loosens the coupling between classes and makes code easier to test and more resilient to change.
The term “Spring” is a bit broad — in practice it often refers to the “Spring Framework.” Inside the Spring Framework there are many features, including Spring MVC for web development, Spring JDBC for data access, and transaction management.
What is Spring Boot?
Spring Boot is a “mechanism (extension) that lets you get started quickly” with Spring-based development.
While the Spring Framework offers a high degree of freedom, that often means there’s a lot to do up front (configuration and adjusting dependencies). Spring Boot addresses this by providing common configurations out of the box, dramatically reducing tedious initial setup.
There are three keywords that come up often with Spring Boot:
- Auto Configuration: automatically configures things based on “you probably want this, right?” by looking at your dependencies
- Starter: lets you add a complete set of required libraries at once
- Embedded Server: can bundle a server like Tomcat, letting your app start on its own
The short answer
With this “conclusion” in mind, if you’re wondering “when exactly is a Bean managed by DI initialized, and when does it get destroyed?”, it’s worth reading Understanding the Spring Boot Bean Lifecycle - How to Use @PostConstruct, @PreDestroy, and InitializingBean, which will give you a clearer picture of how Spring and Spring Boot connect.
In a nutshell, it’s cleanest to think of it this way:
- Spring: the feature-rich, highly flexible “framework itself”
- Spring Boot: a “convenience package” that makes Spring development easier (streamlining startup, configuration, and dependencies)
Rather than thinking “Spring Boot is something separate from Spring,” the correct way to see it is “something built on top of Spring to improve the development experience.”
Understanding the differences through concrete examples
Let’s start by covering the differences in a table. You can save the detailed explanations for later — this table alone should give you a sense of the overall picture.
| Aspect | Spring (Spring Framework) | Spring Boot |
|---|---|---|
| Positioning | The framework itself, providing DI, MVC, and more | A development-support mechanism built on top of the Spring Framework |
| Configuration | You assemble it yourself with Java Config or XML | Auto Configuration automatically configures things based on your dependencies |
| Dependencies | You choose each library individually and align versions yourself | Added together via Starters, with Boot managing versions |
| Startup | Often deployed as a WAR to an external server like Tomcat | Can start as a standalone app via java -jar, thanks to the embedded server |
| Externalizing configuration | You build the mechanism yourself | Can be overridden from the start via application.properties or environment variables |
| Best suited for | Maintaining existing setups, or when you want to deeply learn the internal mechanisms | New development, quick launches, and as an entry point for learning |
Note that this article assumes Spring Boot 3.x or later (Spring Framework 6.x or later) and Java 17 or above. Java 17 became mandatory starting with Spring Boot 3.0, and this requirement remains unchanged in Spring Boot 4.0, released in November 2025. If you’re running an older combination, be sure to also check out the migration topics introduced later.
With this table in mind, let’s go through each point one by one with concrete examples.
Here are the points where the differences stand out most clearly, ordered by where beginners tend to stumble first.
The amount of configuration differs
To run Spring MVC without Boot, you typically have to write an initializer class yourself to register the DispatcherServlet, like this:
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
public class WebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
@Override
protected Class<?>[] getRootConfigClasses() {
return null;
}
@Override
protected Class<?>[] getServletConfigClasses() {
return new Class<?>[] { WebConfig.class };
}
@Override
protected String[] getServletMappings() {
return new String[] { "/" };
}
}On top of this, you also need a WebConfig class annotated with @Configuration and @EnableWebMvc, configuration for JSON conversion and views, and a deployment-target external Tomcat set up. There are a lot of files to touch before anything runs, which is exactly where beginners tend to get stuck.
When building a web app with just the Spring Framework, the configuration can grow depending on your environment (XML, Java Config, server setup, and so on).
With Spring Boot, you add a dependency (Starter) and write minimal configuration, and things often just work. For a web app, for example, this is basically enough to get started:
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}@SpringBootApplication is actually a convenient bundle — roughly speaking, it’s a signal that says “scan for components, and also enable Spring Boot’s auto configuration.”
The way you add dependencies differs
With Spring Boot, the basic approach is to use “Starters.” For example, if you want to build a web API, with Maven it looks like this:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>With just this one dependency, you get everything typically needed for a web API bundled together — Spring MVC, an embedded Tomcat, JSON conversion, and more. With Spring (without Boot), you’ll more often find yourself selecting each required library individually and aligning the versions yourself.
The way you start the application differs
Thanks to the embedded server, Spring Boot can be “started as a Java application”:
./mvnw spring-boot:run- or
java -jar xxx.jar
On the other hand, when using Spring MVC in the traditional way, it’s common to deploy a WAR to an external application server (like Tomcat), which adds a bit more environment setup.
If you find that your app feels slow to start after switching to Spring Boot, we cover how to track down the cause and shorten startup time in How to Speed Up Spring Boot Application Startup - Reducing Time with CDS, AOT, and Lazy Initialization.
Common misconceptions
”If I use Spring Boot, I don’t need to learn Spring”?
No. While Spring Boot does hide Spring in some respects, in real-world work you’ll be far more effective the better you understand Spring’s fundamentals (DI, transactions, Beans, and how configuration works).
Spring Boot makes things “easier,” not “unnecessary."
"Does Spring Boot magically do everything for you”?
Auto configuration is convenient, but treating it as a complete black box can easily trip you up.
It’s a good idea to gradually learn the role of application.properties / application.yml, so you can trace which setting is taking effect and from where.
server.port=8081
spring.application.name=demo-appThis design — being able to configure things “from outside the app” — is also part of what makes Spring Boot easy to use.
Which should beginners start with?
Starting with Spring Boot is generally easier to learn.
- Things work right away, which makes it easy to build a sense of accomplishment
- You get to touch common real-world patterns quickly, like web APIs and DB connections
- Dependencies and startup are simple, so there are fewer obstacles to learning
From there, as you get more comfortable, gradually come to understand what auto configuration is actually doing — that will deepen your understanding of Spring as a whole.
How to choose in real-world projects (by use case)
In actual projects, the decision is usually not “which should I learn” but “which setup should I use to start development.” When in doubt, judging by the following criteria will keep you consistent:
| Case | Recommendation | Reason |
|---|---|---|
| Launching a new business API in a short timeframe | Spring Boot | Lets you build the initial setup and operational foundation the fastest |
| Quickly iterating on a small proof of concept | Spring Boot | Fewer steps to get running, so you can validate faster |
| Maintaining an existing legacy Spring setup | Spring (existing setup) | Safer to prioritize consistency with the existing design |
| Learning purposes, to deeply understand framework internals | Spring + Spring Boot | Lets you follow the underlying concepts while using it |
In practice, the most reliable approach is “choose Spring Boot, while also deepening your understanding of Spring fundamentals.”
Points to decide up front when migrating
When migrating from Spring (without Boot) to Spring Boot, deciding the following in advance reduces the chance of failure:
- Pin down the Java version and Spring Boot version
- Unify your policy for managing configuration files (
application.yml, environment variables, secrets) - Introduce logging and monitoring (Actuator, metrics) early on
- Decide your testing strategy (unit, integration, startup tests) ahead of time
- Template out initial security settings (authentication, CORS, CSRF)
Deciding these things at project kickoff, rather than “after it’s up and running,” keeps operational costs down.
When it comes to pinning down versions, two things deserve special attention: Java 17 becoming mandatory from Spring Boot 3.x onward, and the package shift from javax to jakarta. We cover the concrete steps in Migration Guide: Spring Boot 2.x to 3.x - Java 17 Required, with Checklist. We also cover introducing and exposing Actuator, which is a great first step toward monitoring, in Getting Started with Spring Boot Actuator.
Common judgment mistakes
Thinking you don’t need to think about design once you use Spring Boot
Spring Boot reduces initial configuration, but it doesn’t reduce the design decisions themselves. Dependencies, exception design, transaction boundaries, and logging policy all still require their own design work.
Disabling auto configuration too aggressively
Turning off all auto configuration “for the sake of understanding” can actually hurt maintainability. It’s safer to make use of the defaults first, and only explicitly adjust the parts you specifically need.
Summary
- Spring is the foundational framework for Java development
- Spring Boot is a mechanism that lets you get started quickly with Spring-based development
- The differences show up in how easy “configuration,” “dependencies,” and “startup” are
- Beginners find it easier to start with Spring Boot
For your next step, we recommend building a simple REST API with Spring Boot and getting comfortable with DI, @RestController, and the role of @Service.
If you’d like to take your understanding of DI a step further, check out Introduction to Spring’s @Bean “Name” - When Should You Set One? How Does It Affect Behavior? What’s the Priority?, which breaks down how Bean names are determined and which Bean gets selected when there are multiple Beans of the same type.
