PropertySource in Spring

PropertySource in Spring

The @PropertySource annotation lets you load and register external configuration properties from a file or resource into the Spring Environment.

This helps you externalise configuration settings and keep them separate from your application code, making them easier to manage and maintain.

@PropertySource is commonly used with @Configuration classes. It allows you to load properties from various sources like .properties files, .yml files, or even custom sources.

Here’s how to use @PropertySource:

1. Create a properties file

First, create an external properties file, such as custom-config.properties, and add some key-value pairs:

app.name=My Custom Application
app.version=1.0.0

2. Create a configuration class

Now create a @Configuration class and use the @PropertySource annotation to specify the properties file you want to load:

@Configuration
@PropertySource("classpath:custom-config.properties")
public class CustomConfig {
    // Your configuration code goes here
}

In this example, we’re loading the custom-config.properties file from the classpath.

3. Inject properties

You can now inject the properties from the custom-config.properties file into your beans using the @Value annotation:

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

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

    // Your service code goes here
}

Using Environment

Alternatively, you can inject the Environment object and access the properties using the getProperty method:

@Component
public class MyService {
    private final Environment environment;

    @Autowired
    public MyService(Environment environment) {
        this.environment = environment;
    }

    public void printAppInfo() {
        System.out.println("App Name: " + environment.getProperty("app.name"));
        System.out.println("App Version: " + environment.getProperty("app.version"));
    }
}

@PropertySource can be used multiple times in a @Configuration class to load properties from different sources. If you have a .yml file instead of a .properties file, you can use @PropertySource with a custom PropertySourceFactory to load the .yml file, such as the YamlPropertySourceFactory.