How can I execute an external program from within a button's event handler?

Question

I am using Tomcat ApacheTomcat 6.0.16 with Netbeans 6.1 (with the latest JDK/J2EE)
I need to execute external programs from an event handler for a button on a JSF page (the program is compiled, and extremely fast compared both to plain java and especially stored procedures written in SQL).
I tried what I'd do in a standalone program (as shown in the appended code), but it didn't work. Instead I received text saying the program couldn't be found. This error message comes even if I try the Windows command "dir". I thought with 'dir' I'd at least get the contents of the current working directory. :-(
I can probably get by with cgi on Apache's httpd server (or, I understand tomcat supports cgi, but I have yet to get that to work either), but whatever I do I need to be able to do it from within the button's event handler. And if I resort to cgi, I must be able to maintain session jumping from one server to the other and back.
So, then, how can I do this?
Thanks
Ted
NB: The programs that I need to run do NOT take input from the user. Rather, my code in the web application processes user selections from selection controls, and a couple field controls, sanitizes the inoputs and places clean, safe data in a MySQL database, and then the external program I need to run gets safe data from the database, does some heavy duty number crunching, and puts the output data into the database. They are well insulated from mischeif.
NB: In the following array_function_test.pl was placed in the same folder as the web application's jsp pages, (and I'd tried WEB-INF - with the same result), and I DID see the file in the application's war file.
        try {
            java.lang.ProcessBuilder pn = new java.lang.ProcessBuilder("array_function_test.pl");
            //pn.directory(new java.io.File("K:\\work"));
            java.lang.Process pr = pn.start();
            java.io.BufferedInputStream bis = (java.io.BufferedInputStream)pr.getInputStream();
            String tmp = new String("");
            byte b[] = new byte[1000];
            int i = 0;
            while (i != -1) {
                bis.read(b);
                tmp += new String(b);
            getSelectionsDisplayTextArea().setText(getSelectionsDisplayTextArea().getText() + "\n\n" + tmp);
        } catch (java.io.IOException ex) {
            getSelectionsDisplayTextArea().setText(getSelectionsDisplayTextArea().getText() + "\n\n" + ex.getMessage());
        }

Answer 1

Hi Fonsi!
One way to execute an external program is to use the System Exec.vi. You find it in the functions pallet under Communication.
/Thomas