application.yml alternative in Spring Boot - Mini Project: Build & Apply

Using application.properties as an application.yml Alternative in Spring Boot

📋 What You'll Learn

💡 Why This Matters

🌍 Real World

Many Spring Boot projects use application.properties files for configuration because they are simple and widely supported. This project shows how to switch from YAML to properties format.

💼 Career

Understanding how to configure Spring Boot applications with properties files is essential for backend developers working with Java and Spring frameworks in real-world projects.

1

Create application.properties file with app.title

Create a file named application.properties and add the property app.title=My Spring App inside it.

Spring Boot

# Create application.properties file
# Add the property app.title=My Spring App

Need a hint?

The application.properties file uses key=value pairs. Write app.title=My Spring App exactly.

2

Create a Spring component to read app.title property

Create a Spring component class named AppConfig with a field title that reads the app.title property using @Value("${app.title}") annotation.

Spring Boot

app.title=My Spring App

// Create AppConfig class with @Component and @Value annotation
// Add private String title field
// Add getter for title
# Your code here

Need a hint?

Use @Component on the class and @Value("${app.title}") on the title field. Add a getter method.

3

Inject AppConfig into main application and print title

In the main Spring Boot application class named DemoApplication, inject AppConfig using constructor injection. Add a CommandLineRunner bean that prints the title property value from AppConfig.

Spring Boot

app.title=My Spring App

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class AppConfig {

    @Value("${app.title}")
    private String title;

    public String getTitle() {
        return title;
    }
}

import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class DemoApplication {

    private final AppConfig appConfig;

    public DemoApplication(AppConfig appConfig) {
        this.appConfig = appConfig;
    }

    // Add CommandLineRunner bean to print appConfig.getTitle()
    // Your code here

Need a hint?

Use a @Bean method returning CommandLineRunner that prints appConfig.getTitle(). Include the main method to run the app.

4

Complete the Spring Boot application setup

Ensure the DemoApplication class has the @SpringBootApplication annotation and the main method to start the application.

Spring Boot

app.title=My Spring App

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class AppConfig {

    @Value("${app.title}")
    private String title;

    public String getTitle() {
        return title;
    }
}

import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class DemoApplication {

    private final AppConfig appConfig;

    public DemoApplication(AppConfig appConfig) {
        this.appConfig = appConfig;
    }

    @Bean
    public CommandLineRunner run() {
        return args -> System.out.println(appConfig.getTitle());
    }

    // Ensure main method is present
    // Your code here

Need a hint?

Make sure the DemoApplication class has @SpringBootApplication and a main method that calls SpringApplication.run.