Why configuration matters in Spring Boot - See It in Action

Why configuration matters

📋 What You'll Learn

💡 Why This Matters

🌍 Real World

In real applications, configuration lets you change messages, URLs, or feature flags without changing code. This makes apps easier to maintain and deploy.

💼 Career

Understanding configuration in Spring Boot is essential for backend developers to build flexible and maintainable applications.

1

Create the greeting property in application.properties

Create a file named src/main/resources/application.properties and add a property called app.greeting with the value Hello, Spring Boot!.

Spring Boot

# Create src/main/resources/application.properties and add the greeting property
# Your code here

Need a hint?

This file holds configuration values. Adding app.greeting=Hello, Spring Boot! sets the greeting message.

2

Create a configuration class to read the greeting

Create a Java class named GreetingConfig in package com.example.demo. Use @ConfigurationProperties(prefix = "app") to bind the app.greeting property to a String greeting field with getter and setter.

Spring Boot

app.greeting=Hello, Spring Boot!

// Create GreetingConfig class with @ConfigurationProperties(prefix = "app")
// Add private String greeting field with getter and setter
// Your code here

Need a hint?

Use @Component and @ConfigurationProperties(prefix = "app") to bind properties. Add a private field greeting with getter and setter.

3

Create a REST controller to return the greeting

Create a class named GreetingController in package com.example.demo. Add @RestController. Inject GreetingConfig via constructor. Create a GET endpoint /greet that returns the greeting from GreetingConfig.

Spring Boot

app.greeting=Hello, Spring Boot!

package com.example.demo;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;

@Component
@ConfigurationProperties(prefix = "app")
public class GreetingConfig {
    private String greeting;

    public String getGreeting() {
        return greeting;
    }

    public void setGreeting(String greeting) {
        this.greeting = greeting;
    }
}

// Create GreetingController with @RestController
// Inject GreetingConfig via constructor
// Add GET mapping for /greet returning greeting
// Your code here

Need a hint?

Use @RestController and constructor injection. Create a method with @GetMapping("/greet") that returns the greeting.

4

Enable configuration properties scanning

In your main application class DemoApplication in package com.example.demo, add @EnableConfigurationProperties(GreetingConfig.class) above the class declaration to enable binding of configuration properties.

Spring Boot

app.greeting=Hello, Spring Boot!

package com.example.demo;

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.properties.EnableConfigurationProperties;

@Component
@ConfigurationProperties(prefix = "app")
public class GreetingConfig {
    private String greeting;

    public String getGreeting() {
        return greeting;
    }

    public void setGreeting(String greeting) {
        this.greeting = greeting;
    }
}

@RestController
public class GreetingController {
    private final GreetingConfig greetingConfig;

    public GreetingController(GreetingConfig greetingConfig) {
        this.greetingConfig = greetingConfig;
    }

    @GetMapping("/greet")
    public String greet() {
        return greetingConfig.getGreeting();
    }
}

@SpringBootApplication
// Add @EnableConfigurationProperties(GreetingConfig.class) here
public class DemoApplication {
    public static void main(String[] args) {
        org.springframework.boot.SpringApplication.run(DemoApplication.class, args);
    }
}

// Your code here

Need a hint?

Add @EnableConfigurationProperties(GreetingConfig.class) above your main application class to enable configuration binding.