// Component with requirements and lifecycle management.
@Component @Instantiate
public class FooComponent {
    @Requires private LogService log;

    @Validate private void start () {
        // Called when all instance requirements become available.
        ...
    }

    @Invalidate private void stop () {
        // Called when some instance requirement ceases being available.
        ...
    }

    // Setting controller field to false disables component instance.
    @Controller private boolean enabled;
}

// Example adjusted from documentation, see references.