Spring Boot Hello World Example (Beginner Friendly)

Starting with a “Hello World” application is the simplest and most effective way to understand how Spring Boot works.
This guide walks you through creating, running, and understanding your first Spring Boot application, while also explaining what happens behind the scenes in real-world systems.

This post is designed for:

Beginners learning Spring Boot
Developers moving from Spring Framework
Engineers preparing for production-grade applications

What Is a Spring Boot Hello World Application?

A Spring Boot Hello World application is the smallest possible Spring Boot project that:

Starts an embedded web server
Exposes a REST endpoint
Returns a simple response like "Hello World"

Even though it looks simple, this application demonstrates:

Auto-configuration
Embedded server startup
Component scanning
REST API handling

These same mechanisms power large production systems.

Prerequisites

Before starting, make sure you have:

Java 17 or later installed
Maven or Gradle
Basic Java knowledge
An IDE like IntelliJ IDEA, Eclipse, or VS Code

No prior Spring experience is required.

Creating a Spring Boot Project

The easiest way to create a Spring Boot project is using Spring Initializr.

Choose the following options:

Project: Maven
Language: Java
Spring Boot version: Stable default
Packaging: Jar
Java version: 17+
Dependencies: Spring Web

Once generated, import the project into your IDE.

Project Structure Explained

After creating the project, you will see a structure similar to this:

src
 └── main
     ├── java
     │   └── com.example.demo
     │       └── DemoApplication.java
     └── resources
         └── application.properties

This structure is standard across Spring Boot projects and scales well into production systems.

For a deeper understanding of how this structure evolves in real projects, see:
spring boot project structure explained beginner to production guide

Main Application Class

The entry point of a Spring Boot application looks like this:

@SpringBootApplication
public class DemoApplication {

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

What `@SpringBootApplication` Does

This single annotation combines:

@Configuration
@EnableAutoConfiguration
@ComponentScan

Together, they tell Spring Boot to:

Load configuration
Auto-configure components
Scan your project for beans

Creating a Hello World REST Controller

Now let’s expose a simple API endpoint.

@RestController
public class HelloController {

    @GetMapping("/hello")
    public String hello() {
        return "Hello World";
    }
}

This creates an HTTP GET endpoint available at /hello.

Running the Application

Run the application using:

Your IDE’s Run button
or
The command line:

mvn spring-boot:run

Once started, open your browser and visit:

http://localhost:8080/hello

You should see:

Hello World

What Happens When the Application Starts?

When you run the app, Spring Boot:

Starts the JVM
Initializes the Spring context
Creates beans
Starts the embedded web server (Tomcat by default)
Maps controllers to URLs

To fully understand this startup flow, read: how spring boot application starts startup flow explained

Common Beginner Issues and Fixes

Port 8080 Already in Use

If you see an error saying port 8080 is already in use, it means another process is using that port.

You can fix it by:

Stopping the conflicting process
Or changing the server port

Full guide:
how to fix port 8080 already in use error in spring boot

Application Starts but URL Not Working

Common reasons:

Wrong endpoint path
Controller package outside component scan
Missing @RestController

Understanding how beans are created helps here:
how spring boot creates beans bean lifecycle simplified for production

Why Hello World Matters Beyond Beginners

Although this example is simple, it teaches core concepts used everywhere in Spring Boot:

Dependency Injection
Auto-configuration
REST APIs
Embedded servers

Every advanced feature—profiles, security, databases, cloud deployment—builds on this foundation.

To see how configuration changes across environments, read:
spring boot configuration and profiles explained beginner to production guide

Summary

In this guide, you learned:

What a Spring Boot Hello World app is
How to create and run it
How REST endpoints work
What happens during startup
Common beginner issues and fixes

This is your foundation for all future Spring Boot topics.

Frequently Asked Questions

Is Spring Boot Hello World used in real projects?

Yes. Real projects start with this structure and evolve with more components.

Can I use Gradle instead of Maven?

Yes. Spring Boot fully supports both.

Why does Spring Boot start a server automatically?

Spring Boot includes an embedded server so applications are self-contained and production-ready.

What should I learn next?

Dependency Injection, bean lifecycle, profiles, and REST API design.