JavaFX service examples for executing service tasks in parallel or sequentially.

FirstLineSequentialVsParallelService.java

import java.io.*;
import java.net.URL;
import java.util.concurrent.*;
import java.util.concurrent.atomic.AtomicInteger;
import javafx.application.Application;
import javafx.beans.property.*;
import javafx.concurrent.*;
import javafx.event.EventHandler;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.layout.*;
import javafx.stage.Stage;
 
public class FirstLineSequentialVsParallelService extends Application {
  private static final String[] URLs = {
    "http://www.google.com", 
    "http://www.yahoo.com", 
    "http://www.microsoft.com", 
    "http://www.oracle.com" 
  };
 
  private ExecutorService sequentialFirstLineExecutor;
  private ExecutorService parallelFirstLineExecutor;
 
  @Override public void init() throws Exception {
    sequentialFirstLineExecutor = Executors.newFixedThreadPool(
      1, 
      new FirstLineThreadFactory("sequential")
    );  
 
    parallelFirstLineExecutor = Executors.newFixedThreadPool(
      URLs.length, 
      new FirstLineThreadFactory("parallel")
    );  
  }
 
  @Override
  public void stop() throws Exception {
    parallelFirstLineExecutor.shutdown();
    parallelFirstLineExecutor.awaitTermination(3, TimeUnit.SECONDS);
 
    sequentialFirstLineExecutor.shutdown();
    sequentialFirstLineExecutor.awaitTermination(3, TimeUnit.SECONDS);
  }
  
  public static void main(String[] args) { launch(args); }
  @Override public void start(Stage stage) throws Exception {
    final VBox messages = new VBox();
    messages.setStyle("-fx-background-color: cornsilk; -fx-padding: 10;");
 
    messages.getChildren().addAll(
      new Label("Parallel Execution"), 
      new Label("------------------"), 
      new Label()
    );
    fetchFirstLines(messages, parallelFirstLineExecutor);
 
    messages.getChildren().addAll(
      new Label("Sequential Execution"), 
      new Label("--------------------"), 
      new Label()
    );
    fetchFirstLines(messages, sequentialFirstLineExecutor);
    
    messages.setStyle("-fx-font-family: monospace");
 
    stage.setScene(new Scene(messages, 600, 800));
    stage.show();
  }
 
  private void fetchFirstLines(final VBox monitoredLabels, ExecutorService executorService) {
    for (final String url: URLs) {
      final FirstLineService service = new FirstLineService();
      service.setExecutor(executorService);
      service.setUrl(url);
 
      final ProgressMonitoredLabel monitoredLabel = new ProgressMonitoredLabel(url);
      monitoredLabels.getChildren().add(monitoredLabel);
      monitoredLabel.progress.progressProperty().bind(service.progressProperty());
      
      service.setOnSucceeded(new EventHandler<WorkerStateEvent>() {
        @Override public void handle(WorkerStateEvent t) {
          monitoredLabel.addStrings(
            service.getMessage(),
            service.getValue()
          );
        }
      });
      service.start();
    }
  }
  
  public class ProgressMonitoredLabel extends HBox {
    final ProgressBar progress;
    final VBox labels;
            
    public ProgressMonitoredLabel(String initialString) {
      super(20);
      
      progress = new ProgressBar();
      labels   = new VBox();
      labels.getChildren().addAll(new Label(initialString), new Label());
      
      progress.setPrefWidth(100);
      progress.setMinWidth(ProgressBar.USE_PREF_SIZE);
      HBox.setHgrow(labels, Priority.ALWAYS);
      setMinHeight(80);
      
      getChildren().addAll(progress, labels);
    }
    
    public void addStrings(String... strings) {
      for (String string: strings) {
        labels.getChildren().add(
          labels.getChildren().size() - 1, 
          new Label(string)
        );
      }
    }
  }
  
  public static class FirstLineService extends Service<String> {
    private StringProperty url = new SimpleStringProperty(this, "url");
    public final void setUrl(String value) { url.set(value); }
    public final String getUrl() { return url.get(); }
    public final StringProperty urlProperty() { return url; }
    protected Task createTask() {
      final String _url = getUrl();
      return new Task<String>() {
        protected String call() throws Exception {
          updateMessage("Called on thread: " + Thread.currentThread().getName());
          URL u = new URL(_url);
          BufferedReader in = new BufferedReader(
                  new InputStreamReader(u.openStream()));
          String result = in.readLine();
          in.close();
          
          // pause just so that it really takes some time to run the task 
          // so that parallel execution behaviour can be observed.
          for (int i = 0; i < 100; i++) {
            updateProgress(i, 100);
            Thread.sleep(50); 
          }
          
          return result;
        }
     };
    }
  }
  
  static class FirstLineThreadFactory implements ThreadFactory {
    static final AtomicInteger poolNumber = new AtomicInteger(1);
    private final String type;
    
    public FirstLineThreadFactory(String type) {
      this.type = type;
    }
            
    @Override public Thread newThread(Runnable runnable) {
      Thread thread = new Thread(runnable, "LineService-" + poolNumber.getAndIncrement() + "-thread-" + type);
      thread.setDaemon(true);
 
      return thread;
    }
  }  
}

Answer to Oracle JavaFX forum question: Creating multiple parallel tasks by a single service

Also related to StackOverflow question: How to reset progress indicator between tasks in JavaFX2?

Hi, why are you using multiple Services rather than just multiple Tasks?

Hi 'John';

First of all I apologize for asking the question under this heading, I tried to reach you directly, but I could not access your mail.

https://community.oracle.com/message/14486835#14486835 as I explained under the title, I want to use progress when loading a new scene.

How can I do this, share your suggestions, Could you come back if you are available ?

Best Regards,
omernaci