Running a Spring Boot application in Spring Boot - Mini Project: Build & Apply

Running a Spring Boot Application

📖 Scenario: You want to create a simple Spring Boot application that starts up and shows a welcome message on the home page. This is like opening a shop and putting a welcome sign on the door.

🎯 Goal: Build a minimal Spring Boot application that runs and displays "Welcome to Spring Boot!" on the home page.

📋 What You'll Learn

Create a Spring Boot main application class with the correct annotation

Add a configuration variable for the welcome message

Create a controller with a method to handle the home page request

Complete the application by running it with the Spring Boot run method

💡 Why This Matters

🌍 Real World

Spring Boot is widely used to build web applications and REST APIs quickly. Knowing how to run a basic app is the first step to creating real services.

💼 Career

Many Java developer jobs require knowledge of Spring Boot to build and maintain backend services. This project teaches the essential startup pattern.

1

Create the Spring Boot main application class

Create a class called DemoApplication in package com.example.demo. Add the @SpringBootApplication annotation and a main method that calls SpringApplication.run(DemoApplication.class, args).

Spring Boot

package com.example.demo;

// Your code here

Need a hint?

Use @SpringBootApplication on the class and a main method that calls SpringApplication.run.

2

Add a configuration variable for the welcome message

Inside the DemoApplication class, add a public static final String variable called WELCOME_MESSAGE and set it to "Welcome to Spring Boot!".

Spring Boot

package com.example.demo;

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);
    }

    // Add the WELCOME_MESSAGE variable below
    // Your code here
}

Need a hint?

Define a public static final String named WELCOME_MESSAGE with the exact text.

3

Create a controller to handle the home page request

Create a new class called HomeController in package com.example.demo. Add the @RestController annotation. Add a method called home that returns the DemoApplication.WELCOME_MESSAGE string. Annotate this method with @GetMapping("/").

Spring Boot

package com.example.demo;

// Add imports and create HomeController class below
// Your code here

Need a hint?

Use @RestController on the class and @GetMapping("/") on the method that returns the welcome message.

4

Run the Spring Boot application

Ensure the DemoApplication class has the main method that calls SpringApplication.run(DemoApplication.class, args). This method starts the application.

Spring Boot

package com.example.demo;

// Confirm the main method is present and runs the application
// Your code here

Need a hint?

The main method must call SpringApplication.run to start the app.