How to implemented an scheduled service using ScheduledExecutorService

Question

Hi, everybody
I have a case that need retrieve data periodically from server. And I used the ScheduledExecutorService and javafx.concurrent.Service to implemented this case. But the trick thing is that ScheduledExecutorService schedule method aleady need a Runnable parameter. And Service setExecutor method set the ScheduledExecutorService. But the result is the Runnable is implemented run periodically but not the Service's call method(Which is I want). The Service is not extends from Runnable or Callable, how it can be used by the ScheduledExecutorService to implemented the periodical task?
Please see my example:
public class ScheduledService extends Application{
     * @param args
     *            the command line arguments
    public static void main(String[] args) {
        launch(args);
    @Override
    public void start(Stage primaryStage) throws Exception {
        primaryStage.setTitle("Test");
        Parent root = new Label("abc");
        Scene scene = new Scene(root, 800, 600);
        primaryStage.setScene(scene);
        primaryStage.show();
        test();
    public static void test() {
        ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(1);
        scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                System.out.println("ScheduledServiceTest.main(...).new Runnable() {...}.run()");
        }, 0, 2, TimeUnit.SECONDS);
        CustomService service = new CustomService();
        service.setExecutor(scheduledExecutorService);
        service.start();
class CustomService extends Service<Void> {
    @Override
    protected Task<Void> createTask() {
        return new Task<Void>() {
            @Override
            protected Void call() throws Exception {
                System.out.println("CustomService.createTask().new Task() {...}.call()");
                return null;
}The result is:
ScheduledServiceTest.main(...).new Runnable() {...}.run()
CustomService.createTask().new Task() {...}.call()
ScheduledServiceTest.main(...).new Runnable() {...}.run()
ScheduledServiceTest.main(...).new Runnable() {...}.run()
ScheduledServiceTest.main(...).new Runnable() {...}.run()
ScheduledServiceTest.main(...).new Runnable() {...}.run()
ScheduledServiceTest.main(...).new Runnable() {...}.run()
{code}
Edited by: Owen on May 20, 2012 12:05 AM
Edited by: Owen on May 20, 2012 12:07 AM                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

Answer 1

You are not allowed to call "restart" on a different thread, it must be from the JavaFX application thread. You don't see the Exception for it because it is encapsulated in the ScheduledFuture that "executor.scheduleWithFixedDelay" returns.
Let's forget about this ScheduledExecutorService, that is not the way to do it when you want to work with a Service. Here's a fully working example that uses standard JavaFX:
package hs.mediasystem;
import javafx.animation.Animation;
import javafx.animation.KeyFrame;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.concurrent.Service;
import javafx.concurrent.Task;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.stage.Stage;
import javafx.util.Duration;
public class Test extends Application {
  public static void main(String[] args) {
    launch(args);
  public static class MyService extends Service<Void> {
    @Override
    protected Task<Void> createTask() {
      return new Task<Void>() {
        @Override
        protected Void call() throws Exception {
          System.out.println("Begin task");
          return null;
  @Override
  public void start(Stage paramStage) throws Exception {
    final MyService myService = new MyService();
    Timeline timeline = new Timeline(new KeyFrame(Duration.seconds(5), new EventHandler<ActionEvent>() {
      @Override
      public void handle(ActionEvent event) {
        myService.restart();   // automatically on JavaFX thread, so can call restart directly
    timeline.setCycleCount(Animation.INDEFINITE);
    timeline.playFrom("end"); // can also play from start but you will have an initial 5 second delay
}