Java - 当使用ForkJoinPool时，Applet在Firefox上不起作用（在Eclipse中工作时）

Question

when I run the following code on Eclipse (Luna, java vers=8), the code runs and pops-up the two errors messages. On the other hand, when I embed the code in a html page the code shows only the first error message. It seems that calling the ForkJoinPool class crushes the applet on firefox. Do you know why? Here is the code.

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.concurrent.ForkJoinPool;

import javax.swing.JApplet;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class ProvaVera extends JApplet
{
    public void start() 
    {

        SwingUtilities.invokeLater(new Runnable(){
        public void run() 
            {
                MainPanel panel = new MainPanel();      
                // Add Swing components to content pane
                Container c = getContentPane();
                c.add(panel, BorderLayout.CENTER);
            }
        });

    }

}
class MainPanel extends JPanel
{

    public MainPanel()
    {
        JLabel label1 = new JLabel("label1");
        this.add(label1);
        JButton btn1 = new JButton("button1");
        this.add(btn1);

        btn1.addActionListener  (
                new ActionListener() 
                {
                    public void actionPerformed(ActionEvent e)
                    {
                        metodo();
                    }
                }

                );
    }



    public void metodo()
    {
        JOptionPane.showMessageDialog(new JFrame(), "test1", "Dialog", JOptionPane.ERROR_MESSAGE);
        ForkJoinPool pool = new ForkJoinPool();
        JOptionPane.showMessageDialog(new JFrame(), "test2", "Dialog", JOptionPane.ERROR_MESSAGE);
    }
}

Answer 1

You are probably getting a security exception because ForkJoinPool requires the 'modifyThread' runtime permission.

When you run in Eclipse there is no security manager installed so you don't get security exceptions. When you run in a browser there is a strict security manager.

Answer 2

I have enabled the Java console from the java control panel. And the error was: java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "modifyThread")

So I went to my java.policy file located in java.home/lib/security/ and I wrote the following

grant codeBase "url or file where the applet is" {
permission java.lang.RuntimePermission "modifyThread";
};

And now the applet is working.

Again, thank you for your support.