Java Threading Issues

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gibboda - 30 Aug 2006 22:55 GMT

I am working on trying to use a thread to spawn a class I call to run
in a seperate thread but it has failed. I have a class called
ConnectDir for opening a vpn connection to a server. But what happens
is the Cisco VPN connects but does to give screen control back. I have
to open a seperate session of xterm or alt+F2 for another window. This
does not work very well with automation. I have used vpncommand >
vpn.log 2>&1 & in a java program which works if I am using simple
methods. But I want to create individual classes to be able to read
from text files certain information and be able to integrate with other
classes I develop. Therefore this does not work very well either.
Below is what I have attempted.

The program structure I have is:

public class myconnect
{
    public static void main(String[] args)
    {
        ConnectDir dc = new ConnectDir();

        try
        {
            dc.open();
        }
        catch(expectj.ExpectJException error1)
        {
            System.out.println(error1)
        }

    }
}

What I have tried but it failed to put in seperate thread:

public class myconnect2 extends Thread
{
    public void run()
    {
        ConnectDir dc = new ConnectDir();

        try
        {
            dc.open();
        }
        catch(expectj.ExpectJException error1)
        {
            System.out.println(error1)
        }

    }

    public static void main(String[] args)
    {
        Thread mytest = new myconnect2();
        mytest.start();

    }
}

It may just be that I do not fully understand what threads are suppose
to do. Thank you for your advice and wisdom.

Reply to this Message

Ben - 31 Aug 2006 03:00 GMT

> I am working on trying to use a thread to spawn a class I call to run
> in a seperate thread but it has failed. I have a class called
[quoted text clipped - 57 lines]
> It may just be that I do not fully understand what threads are suppose
> to do. Thank you for your advice and wisdom.

You don't need to extend Thread to use threads...instead try this:

public class myconnect2 implements Runnable
{
    public void run()     {
         ConnectDir dc = new ConnectDir();

         try
         {
             dc.open();
         }
         catch(expectj.ExpectJException error1)
         {
             System.out.println(error1)
         }

     }

    public static void main(String[] args)
     {
        myconnect2 threadTest = new myconnect2() /*or however you construct
this class*/

         Thread mytest = new Thread(threadTest);
         mytest.start();

     }

Good luck,
Ben

Reply to this Message

Chris Smith - 31 Aug 2006 04:58 GMT

> It may just be that I do not fully understand what threads are suppose
> to do. Thank you for your advice and wisdom.

Perhaps. You wrote:

> What I have tried but it failed to put in seperate thread:
>
> public class myconnect2 extends Thread
> {
> public void run()
> {

[...]

> }
>
[quoted text clipped - 5 lines]
> }
> }

That definitely does run the code in a new thread. However, the
difference won't be observable here, because you let the main thread
exit immediately without doing anything else. Threads all your program
to do two things at once (or, at least, interleaved so tightly that they
apparently happen at once); so if you want to get that benefit, your
program will need to do two things. Add the code for that second thing
onto the end of main, and (if your tasks run long enough) you'll be able
to see that they both occur at about the same time.

If all you wanted was to run your program in the background, then you
don't need to change your code to do that. Just tell the operating
system that you want that. For example, on UNIX (at least in common
shells), it's done by adding an ampersand (&) to the end of the command.

Signature

Chris Smith

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