How to reload a @Value property from application.properties in Spring? [duplicate]

Question

I have a spring-boot application. Under the run folder, there is an additional config file:

dir/config/application.properties

When the applications starts, it uses the values from the file and injects them into:

@Value("${my.property}")
private String prop;

Question: how can I trigger a reload of those @Value properties? I want to be able to change the application.properties configuration during runtime, and have the @Value fields updated (maybe trigger that update by calling a /reload servlet inside the app).

But how?

Answer 1

Use the below bean to reload config.properties every 1 second.

@Component
public class PropertyLoader {

    @Autowired
    private StandardEnvironment environment;

    @Scheduled(fixedRate=1000)
    public void reload() throws IOException {
        MutablePropertySources propertySources = environment.getPropertySources();
        PropertySource<?> resourcePropertySource = propertySources.get("class path resource [config.properties]");
        Properties properties = new Properties();
        InputStream inputStream = getClass().getResourceAsStream("/config.properties");
        properties.load(inputStream);
        inputStream.close();
        propertySources.replace("class path resource [config.properties]", new PropertiesPropertySource("class path resource [config.properties]", properties));
    }
}

Your main config will look something like :

@EnableScheduling
@PropertySource("classpath:/config.properties")
public class HelloWorldConfig {
}

The instead of using @Value, each time you wanted the latest property you would use

environment.get("my.property");

Note

Although the config.properties in the example is taken from the classpath, it can still be an external file which has been added to the classpath.