Hello World Program in Spring Boot

1. Setup a Spring Boot Project

You can set up a Spring Boot project using:

• Spring Initializr (Recommended)
• Manually (Maven or Gradle)

Using Spring Initializr

1. Go to Spring Initializr
2. Select the following:
   • Project: Maven or Gradle
   • Language: Java
   • Spring Boot Version: Latest Stable (e.g., 3.x)
   • Dependencies: Add Spring Web
3. Click Generate and download the project.
4. Extract and open it in an IDE (IntelliJ, Eclipse, VS Code).

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2. Create the Main Application Class

Spring Boot applications start with a class annotated with @SpringBootApplication.

Main Class (HelloWorldApplication.java)

package com.example.helloworld;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication

public class HelloWorldApplication {

    public static void main(String[] args) {

        SpringApplication.run(HelloWorldApplication.class, args);

    }

}

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3. Create a REST Controller

Now, create a REST API to return “Hello, World!”.

Controller (HelloController.java)

package com.example.helloworld;

import org.springframework.web.bind.annotation.GetMapping

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RestControll

@RestController

@RequestMapping(“/api”)

public class HelloController {

    @GetMapping(“/hello”)

    public String sayHello() {

        return “Hello, World!”;

    }

}

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4. Run the Application

• Open a terminal in your project folder and run:

mvn spring-boot:run

OR (if using Gradle)

gradle bootRun

• You should see logs indicating the server has started on port 8080.

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5. Test the API

Open a browser or use Postman and visit:

bash

http://localhost:8080/api/hello

Output:

Hello, World!

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Bonus: Running as a JAR

You can package and run your Spring Boot application as a JAR:

mvn clean package

java -jar target/helloworld-0.0.1-SNAPSHOT.jar