Custom configuration properties in Spring Boot - Mini Project: Build & Apply

Custom Configuration Properties in Spring Boot

📖 Scenario: You are building a Spring Boot application that needs to read custom settings from an external configuration file. These settings will control how your app behaves in different environments.

🎯 Goal: Create a custom configuration properties class to load specific settings from application.properties. Bind these properties to a Java class and use them in your application.

📋 What You'll Learn

Create a Java class to hold custom properties with prefix app.settings

Add properties app.settings.name and app.settings.timeout in application.properties

Use Spring Boot's @ConfigurationProperties annotation to bind properties

Enable configuration properties scanning in the main application class

💡 Why This Matters

🌍 Real World

Custom configuration properties let you easily manage app settings for different environments without changing code.

💼 Career

Many jobs require configuring Spring Boot apps with external settings for flexibility and maintainability.

1

Create application.properties with custom properties

Create a file named application.properties in src/main/resources and add these exact properties:
app.settings.name=MyApp
app.settings.timeout=30

Spring Boot

# Your code here to create application.properties with the specified properties

Need a hint?

Put the properties exactly as shown in the application.properties file.

2

Create a Java class to hold the custom properties

Create a Java class named AppSettings in package com.example.demo with private fields String name and int timeout. Add public getters and setters for both fields.

Spring Boot

package com.example.demo;

// Your code here to create AppSettings class with name and timeout fields and getters/setters

Need a hint?

Make sure the class has private fields and public getter and setter methods for both name and timeout.

3

Bind the properties using @ConfigurationProperties

Annotate the AppSettings class with @ConfigurationProperties(prefix = "app.settings") and add @Component annotation to make it a Spring bean.

Spring Boot

package com.example.demo;

// Add @Component and @ConfigurationProperties annotations to AppSettings class

public class AppSettings {
    private String name;
    private int timeout;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getTimeout() {
        return timeout;
    }

    public void setTimeout(int timeout) {
        this.timeout = timeout;
    }
}

Need a hint?

Import and use @Component and @ConfigurationProperties with the correct prefix.

4

Enable configuration properties scanning in main application

In the main application class DemoApplication in package com.example.demo, add the annotation @EnableConfigurationProperties(AppSettings.class) above the class declaration.

Spring Boot

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

// Add @EnableConfigurationProperties(AppSettings.class) annotation here

@SpringBootApplication
public class DemoApplication {

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

Need a hint?

Import and add @EnableConfigurationProperties(AppSettings.class) above the main application class.