Understanding @ConfigurationProperties and @PropertySources in Spring

In modern software development, configuration management is essential, and Spring provides powerful annotations such as @ConfigurationProperties and @PropertySources to simplify handling of configuration data.

What are @ConfigurationProperties and @PropertySources? @ConfigurationProperties binds external property values to a Java bean, typically used with @Configuration or @Component . @PropertySources (or its singular form @PropertySource ) declares one or more property files that Spring should load.

Using @ConfigurationProperties

@Configuration
@ConfigurationProperties(prefix = "myapp")
public class MyAppProperties {
    private String name;
    private String version;
    // getters and setters
}

After defining the bean, enable it in a configuration class:

import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Configuration;

@Configuration
@EnableConfigurationProperties(MyAppProperties.class)
public class AppConfig {
}

Add matching entries to application.properties or application.yml :

myapp.name=My Spring Boot App
myapp.version=1.0

Inject the bean into a service:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class MyService {
    private final MyAppProperties myAppProperties;

    @Autowired
    public MyService(MyAppProperties myAppProperties) {
        this.myAppProperties = myAppProperties;
    }

    public void doSomething() {
        System.out.println("App Name: " + myAppProperties.getName());
        System.out.println("App Version: " + myAppProperties.getVersion());
    }
}

Using @PropertySources

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.context.annotation.PropertySources;

@Configuration
@PropertySources({
    @PropertySource("classpath:default.properties"),
    @PropertySource("classpath:custom.properties")
})
public class AppConfig {
}

Define the property files (e.g., default.properties and custom.properties ) under src/main/resources and inject values with @Value :

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

@Service
public class MyService {
    @Value("${app.name}")
    private String appName;

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

    public String getAppInfo() {
        return "App Name: " + appName + ", App Version: " + appVersion;
    }
}

Difference between the two annotations – @PropertySources focuses on declaring multiple property files, while @ConfigurationProperties binds the loaded properties to a strongly‑typed Java bean. They can be used together to achieve modular and maintainable configuration management.