I had an issue while creating a download manager in JavaFX. I raised my concern in JavaFX OTN Community (https://forums.oracle.com/message/11279428) but the issue is not yet resolved .



Problem :

Calling a thread from ExecutorService which executes a thread which download file from the given URL. Code was working fine and I used it to download some sample files.
Then I added code to find rate of download in the Thread run and print the output(rate=(1024/(end-start))). After adding that code the task is not even running .

Code :

FXMLDocumentController.java


package try3;

import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ResourceBundle;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.TextField;
import javafx.scene.control.cell.ProgressBarTableCell;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.stage.DirectoryChooser;

/**
 *
 * @author Lijo Jose
 */
public class FXMLDocumentController implements Initializable {
    
    @FXML
    private Label comment;
    
    
    @FXML private TextField addr;
    
    @FXML TableView <Worker> table;
    
    @FXML TableColumn<Worker,String> colname;
    @FXML TableColumn<Worker,String> colstatus;
    @FXML TableColumn<Worker,Double> colprogress;
    
    private final ObservableList<Worker> list=FXCollections.observableArrayList();
    private String path=new String("");
    
    
    
    @FXML
    private void addButtonAction(ActionEvent event) throws MalformedURLException {
        
         String name=addr.getText().substring(addr.getText().lastIndexOf("/")+1);
        
              
        
         if(!name.isEmpty()){
            list.add(new Worker(name,new URL(addr.getText()),path));
            System.out.println("Added..."+list.size());
            comment.setText("Added...");
         }
         else
             comment.setText("Not Added...");
       
       
        
        
        
        
       
        addr.clear();
        
//// boolean b=list.add(new Worker(new SimpleStringProperty("ABCD"), new URL("http://ww.goole.co")));
//
//
//
// comment.setText("Added...");
//
        
       
        
        
        
    }
    
     @FXML
    private void startButtonAction (ActionEvent event){
     
// ExecutorService service= Executors.newFixedThreadPool(3);
      ExecutorService service= Executors.newFixedThreadPool(2, new ThreadFactory() {

            @Override
            public Thread newThread(Runnable r) {
                Thread t=new Thread(r);
                t.setDaemon(true);
                return t;
                
            }
        });
// Worker selected=table.getSelectionModel().getSelectedItem();
         
        
// System.out.println("Selected :"+selected.getName()+" "+selected.getUrl());
         
        
        
        
        for(Worker w:table.getItems())
            service.execute(w);
         
          
         
         
    }
    @FXML
    private void stopButtonAction (ActionEvent event){
      Worker selected=table.getSelectionModel().getSelectedItem();
      int index=table.getSelectionModel().getSelectedIndex();
      
      selected.stopTask();
      
     
      
      
      list.set(index, selected);
      
// table.setItems(list);
      
      table.getColumns().get(0).setVisible(false);
      table.getColumns().get(0).setVisible(true);
      
      System.out.println("Index.."+index);
      
      for(Worker entry:list)
            System.out.println(entry.getName()+" "+entry.getProgress()+" "+entry.getMessage());
      
      
    }
    
    
    
    @FXML
    private void removeButtonAction(ActionEvent e){
     Worker selected=table.getSelectionModel().getSelectedItem();
      
      list.remove(selected);
      System.out.println("Removed...");
      
      
    }
    
    @FXML
    private void pathButtonAction(ActionEvent e){
        DirectoryChooser chooser= new DirectoryChooser();
        File showDialog = chooser.showDialog(null);
        String temp;
        
        if(showDialog!=null)
        {
             temp=showDialog.getPath();
             
             if(temp.endsWith("\\")){
               comment.setText(temp);
               path=temp;
             }
             else{
               comment.setText(temp+"\\");
               path=temp+"\\";
             }
            
        }
    }
    
    
    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
        
        colname.setCellValueFactory(new PropertyValueFactory<Worker,String>("name"));
        
        
        colprogress.setCellValueFactory(new PropertyValueFactory<Worker,Double>("progress"));
        colprogress.setCellFactory(ProgressBarTableCell.<Worker>forTableColumn());
        
        colstatus.setCellValueFactory(new PropertyValueFactory<Worker,String>("message"));
        
        
        
        
        
        table.setItems(list);
    }
    
}

---------------------------
Worker.java

/*
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 */

package try3;

import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.concurrent.Task;
import javafx.scene.control.ProgressIndicator;


/**
 *
 * @author Lijo Jose
 */
public class Worker extends Task{

    private String name;
    private URL url;
    
    
    
    private int downloaded=0;
    private RandomAccessFile file;
    private InputStream stream;
    private int size=-1;
    private int status;
    private final int DOWNLOADING=0;
    private final int COMPLETED=1;
    private final int MAX_BUFFER_SIZE=1024*1024;
    private String path;
    private long start,end;
    private float rate;
    

    public Worker(String fname, URL url) {
        this.name = fname;
        this.url = url;
        updateMessage("Not Started..");
    }

    Worker(String fname, URL url, String path) {
        this.name = fname;
        this.url = url;
        this.path=path;
        updateMessage("Not Started..");
     }
    
    
    
    
    @Override
    protected Object call() throws Exception {
        
        
        updateProgress(ProgressIndicator.INDETERMINATE_PROGRESS, 100);
// Thread.sleep(100);
         
         
// String temp=url.getFile().substring(url.getFile().lastIndexOf("/")+1);
         System.out.println("Path :"+path+",File Name:"+name);
// System.out.println("Temp: "+temp);
        try {
            HttpURLConnection connection=(HttpURLConnection) url.openConnection();
            connection.setRequestProperty("Range", "bytes="+downloaded+"-");
            
            connection.connect();
            if(connection.getResponseCode()/100!=2){
                error("Respose Code :"+String.valueOf(connection.getResponseCode()));
            }
                    
            int contentLength=connection.getContentLength();
            
            if(contentLength<1){
                error("Content Length :"+String.valueOf(contentLength));
            }
            size=contentLength;
            
            System.out.println("Size :"+size);
            
            
            
            file= new RandomAccessFile(path+this.name, "rw");
            file.seek(downloaded);
            
            System.out.println("path :"+path+this.name);
            stream=connection.getInputStream();
            
            while(status==DOWNLOADING){
                byte[] buffer;
                if(size-downloaded>MAX_BUFFER_SIZE){
                    buffer=new byte[MAX_BUFFER_SIZE];
                }
                else{
                    buffer=new byte[size-downloaded];
                }
                
                start=System.currentTimeMillis();
                
                int read=stream.read(buffer);
                
                end=System.currentTimeMillis();
                
                if(read==-1)
                    break;
       
                
                file.write(buffer,0,read);
                downloaded+=read;
                

                
                
                System.out.println("Start:"+start+" End :"+end+" Diff :"+(end-start));

                
                rate=(1024/(end-start));
                System.out.println("Rate :"+rate+" KBps");
                
                updateMessage("In Progress");
                updateProgress(downloaded, size);
            }
            
            
            status=COMPLETED;
            
                
            System.out.println("Downloaded...");
            updateMessage("Completed..");
            updateProgress(100, 100);
                    
        } catch (IOException ex) {
            System.out.println("Error :"+ex.toString());
        }
        finally{
            try {
                file.close();
            } catch (IOException ex) {
                Logger.getLogger(Worker.class.getName()).log(Level.SEVERE, null, ex);
                System.out.println("Error: "+ex.toString());
            }
            
            if(stream!=null){
                try {
                    stream.close();
                } catch (IOException ex) {
                    System.out.println("Error :"+ex.toString());
                }
            }
        }
        return null;
        
        
        
    }

    public void setName(String fileName){
        name=fileName;
    }
      
    public String getName(){
        return name;
    }

    /**
     * @return the url
     */
    public URL getUrl() {
        return url;
    }

    /**
     * @param url the url to set
     */
    public void setUrl(URL url) {
        this.url = url;
    }

    void stopTask() {
        updateMessage("Stopped..");
        try {
            Thread.sleep(100);
        } catch (InterruptedException ex) {
            Logger.getLogger(Worker.class.getName()).log(Level.SEVERE, null, ex);
        }
        
    }
    private void error(String err) {
        System.out.println("Error...."+err);
    }
    
}
-----------------------------

Try3.java

package try3;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

/**
 *
 * @author Lijo Jose
 */
public class Try3 extends Application {
    
    @Override
    public void start(Stage stage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));
        
        Scene scene = new Scene(root);
        
        stage.setScene(scene);
        stage.show();
    }

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

FXMLDocument.fxml


<?xml version="1.0" encoding="UTF-8"?>

<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<AnchorPane id="AnchorPane" prefHeight="411.0" prefWidth="387.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/2.2" fx:controller="try3.FXMLDocumentController">
  <children>
    <Button fx:id="button" layoutX="239.0" layoutY="23.0" onAction="#addButtonAction" text="Add" />
    <Label id="label" fx:id="comment" layoutX="14.0" layoutY="381.0" minHeight="16.0" minWidth="69.0" prefWidth="186.0" />
    <TextField fx:id="addr" layoutX="14.0" layoutY="23.0" prefWidth="200.0" promptText="Address :" />
    <TableView fx:id="table" layoutX="14.0" layoutY="124.0" prefHeight="220.0" prefWidth="333.0">
      <columns>
        <TableColumn maxWidth="5000.0" minWidth="10.0" prefWidth="130.0" text="Name" fx:id="colname" />
        <TableColumn maxWidth="5000.0" minWidth="10.0" prefWidth="118.0" text="Progress" fx:id="colprogress" />
        <TableColumn maxWidth="5000.0" minWidth="10.0" prefWidth="83.0" text="Status" fx:id="colstatus" />
      </columns>
    </TableView>
    <HBox id="HBox" alignment="CENTER" layoutX="17.0" layoutY="76.0" spacing="20.0">
      <children>
        <Button mnemonicParsing="false" onAction="#startButtonAction" text="Start" />
        <Button disable="true" mnemonicParsing="false" onAction="#stopButtonAction" text="Stop" />
        <Button mnemonicParsing="false" onAction="#removeButtonAction" text="Remove" />
        <Button mnemonicParsing="false" onAction="#pathButtonAction" text="Path" />
      </children>
    </HBox>
  </children>
</AnchorPane>