Springboot hello app - demo project

Here’s a complete beginner-friendly guide to create a simple Spring Boot application step-by-step — using only annotations, no XML, and designed for learning key Spring Boot concepts like:

• @SpringBootApplication
  
  

• @RestController
  
  

• @GetMapping
  
  

• @Autowired with @Service
  
  

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✅ Project: springboot-helloapp

This app exposes an API:

GET http://localhost:8080/hello

Response:

{ "message": "Hello, Spring Boot!" }

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🔧 Step-by-Step Setup

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🔹 Step 1: Go to Spring Initializr

🌐 Visit: https://start.spring.io

Fill these:

Field	Value
Project	Maven
Language	Java
Spring Boot	3.2.x (latest stable)
Group	com.example
Artifact	springboot-helloapp
Name	springboot-helloapp
Packaging	Jar ✅
Java	17 or 21

Add Dependencies:

• ✅ Spring Web
  
  

Then click "Generate"
Unzip the project and open it in VSCode or IntelliJ

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🔹 Step 2: Project Structure

src/

 └── main/

     ├── java/

     │   └── com.example.springboothelloapp/

     │       ├── SpringbootHelloappApplication.java

     │       ├── controller/HelloController.java

     │       └── service/HelloService.java

     └── resources/

         └── application.properties

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🔹 Step 3: Main Application Class

📄 SpringbootHelloappApplication.java

package com.example.springboothelloapp; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication public class SpringbootHelloappApplication {     public static void main(String[] args) {         SpringApplication.run(SpringbootHelloappApplication.class, args);     } }

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🔹 Step 4: Create HelloService

📄 service/HelloService.java

package com.example.springboothelloapp.service; import org.springframework.stereotype.Service; @Service public class HelloService {     public String getMessage() {         return "Hello, Spring Boot!";     } }

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🔹 Step 5: Create HelloController

📄 controller/HelloController.java

package com.example.springboothelloapp.controller; import com.example.springboothelloapp.service.HelloService; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; import java.util.Collections; import java.util.Map; @RestController public class HelloController {     private final HelloService helloService;     // Constructor injection (recommended)     public HelloController(HelloService helloService) {         this.helloService = helloService;     }     @GetMapping("/hello")     public Map<String, String> sayHello() {         return Collections.singletonMap("message", helloService.getMessage());     } }

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🔹 Step 6: Run the App

In terminal:

./mvnw spring-boot:run

Or in VSCode/IntelliJ:
Right-click → Run SpringbootHelloappApplication.main()

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🔹 Step 7: Test the Endpoint

Go to:
http://localhost:8080/hello

Response:

{ "message": "Hello, Spring Boot!" }

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✅ Summary of Concepts Used

Concept	Usage
@SpringBootApplication	Main application class
@RestController	Exposes HTTP endpoints
@Service	Business logic class
@GetMapping	Maps HTTP GET request
@Autowired (implicit via constructor)	Injects service

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