Prevent dialog from closing

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Dialog;
import javafx.scene.control.DialogEvent;
import javafx.stage.Stage;

public class DialogTest extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        Dialog<Void> dialog = new Dialog<>();
        dialog.setOnCloseRequest(new EventHandler<DialogEvent>() {
            @Override
            public void handle(DialogEvent event) {
                event.consume();
                System.out.println("Consumed event: " + event.isConsumed());
            }
        });
        dialog.getDialogPane().getButtonTypes().addAll(ButtonType.OK, ButtonType.CANCEL);
        dialog.show();
    }
}