Experimental Physics and
Industrial Control System

"David Dudley" <[email protected]> · Wed, 16 May 2007 07:42:49 -0500

I forgot about signing the jar!  Completely slipped my mind (a lot of
stuff does that lately ;-)

I know I've got a bunch too much stuff in the applet program.  Once I
get it operating correctly, I'm going to go through and straighten it
all out (for instance, I'm not going to print a message every 2 lines in
the initialization code for one).  I'm not taking a lot of time to do
things too right for a program I'm using just for a test, but need to
demonstrate things to my boss without having to 'interpret' things for
her.  Stack traces she wouldn't understand, but a simple message would
at least distract her.

Maybe I can talk her into more Java training now ;-)

David Dudley

>>> Matej Sekoranja <[email protected]> 5/16/2007 4:35 AM
>>>
Hi, all!

Igor notified me that there is a JCA/CAJ debate going on... :)

Note that applets are run in a "sanbox" and do not have the same  
permissions like any ordinary java application, simple reasion: you  
do not want an applet to delete your local files.
Calls as IO/file calls are restricted, some system calls call and  
also making TCP/UDP connections to the other-than-originating server  
(from where applet was loaded) are not allowed, so this will
not work for for JCA (I guess this is the problem here). Still there  
is a simple solution. You must sign the JAR file. Signed JARs  
(accepted by user) will gain more permissions.

Just a note:

			catch(Exception ex)
			{
				System.err.println("Initialization
failed for " + dpm.dataSource 
+":\n" + ex + "\n");
				System.exit(1);
			}

Exception handling is one of the things that 99% of (java)  
programmers do not do right.
Just to be short (not to write the whole essay): if you cannot handle 

the exception, stack it (and provide any context information) and  
rethrow, or at least (not really nice solution) dump the whole stack  
trace (this will show you the source of the problems). Still it is  
safer to catch Throwable than Exception.
So add line "ex.printStackTrace()" after println.

Matej

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System