Help with security error

[ChrisMacPherson]

Hi,
I am getting this error when trying to run a few different examples taken from the net which create simple applets and try to create a thread.

java.security.AccessControlException: access denied (java.lang.RuntimePermission modifyThreadGroup)


code is as below

private Thread th = null;
    public void start() {
        if (th == null) {
           
                 th = new Thread(this); << error hits here
            
            th.start();
        }
    }

I took these examples from good tutorials so am stumped why they dont work. Have also been searching for answers for ages so any help would be great.

I am running netbeans 4, j2se 1.5

Chris MacPherson

 

[Diancecht]

It's curious.

I suppose that the Security Manager fails at allocating the new thread on the current ThreadGroup.

I'd try instantiating a new Runnable object instead of this.

Cheers,

Dian

 

[idarke]

Here are some things to try:

If you're trying to do this in an applet, try doing it in an application instead. The permissions in a browser may be limited.

It seems to me that this construction will result in a loop that will consume all memory quickly. Since th isn't static, each time a new Thread is created, it has it's own copy of th that starts as null. Then when start() is called, th == null will trigger another Thread created. You may be getting an erroneous Exception simply because resources have been used up.

 

[ChrisMacPherson]

Thanks for your replies,

I have tried out some more applets and have been running in to the same message. If I try running an applet from a website in my browser it works. If I then download the source and try and run it in netbeans, then it come up with the error message in my first post.

Is this something to do with netbeans then I guess?

I am trying to learn java, this is really putting me off!

Chris MacPherson

 

[sedj]

The applet sandbox will not allow you to create new threads explicitly on the client machine, unless the applet is signed and has an appropriate security policy.

--------------------------------------------------
Free Database Connection Pooling Software

http://www.primrose.org.uk

 

[ChrisMacPherson]

Thanks, that sounds like a pretty certain answer. So how do I go about doing that? The examples on the net that I was viewing did not mention anything about these issues. Any links to appropriate guides or tutorials would be greatly appreciated.

Chris MacPherson

 

[sedj]

This example talks about signing an applet for access to the local file system, but the principle is the same for your problem.

http://java.sun.com/developer/technicalArticles/Security/Signed/

--------------------------------------------------
Free Database Connection Pooling Software

http://www.primrose.org.uk

 

[ChrisMacPherson]

Thanks sedj, I will try that out.

Initially I was trying to run my applet in the netbeans ide and was getting the errors, I tried to run it in my browser and it worked. I think I will forget the ide for the moment.

cheers again..


Chris MacPherson

 

[Diancecht]

Am I wrong or the default security policy allows and unsigned applet to create threads inside the same ThreadGroup as the applet?

Cheers,

Dian