Experimental Physics and
Industrial Control System

"J. Lewis Muir" <[email protected]> · Tue, 15 May 2007 14:35:53 -0400

David Dudley wrote:

After putting a bunch more comments in my Applet file, what I find is that the call to JCALibrary.getInstance() completes successfully, but the call to jca.createContext() fails.
My code is:
—-------------------------
			try
			{
				URL codebase=this.getCodeBase();
				String host=codebase.getHost();
				// Get the JCALibrary instance
				jca=JCALibrary.getInstance();
				System.out.println("Instance initialization passed");

				System.setProperty("com.cosylab.epics.caj.CAJContext.addr_list",host);
				System.setProperty("com.cosylab.epics.caj.CAJContext.auto_addr_list","false");
				// Create a thread safe context with default configuration values
				ctxt=jca.createContext(JCALibrary.CHANNEL_ACCESS_JAVA);

				System.out.println("Context creation passed");

				System.setProperty("com.cosylab.epics.caj.CAJContext.addr_list",host);
				System.setProperty("com.cosylab.epics.caj.CAJContext.auto_addr_list","false");

			}
			catch(Exception ex)
			{
				System.err.println("Initialization failed for " + dpm.dataSource+":\n" + ex);
				System.exit(1);
			}
—-------------------------
The console outputs:
Instance initialization passed
Initialization failed for Util1:Tot:KW:
java.security.AccessControlException: access denied (java.util.PropertyPermission com.cosylab.epics.caj.CAJContext.addr_list write)
java.security.AccessControlException: access denied (java.lang.RuntimePermission exitVM.1)
	at java.security.AccessControlContext.checkPermission(Unknown Source)
	at java.security.AccessController.checkPermission(Unknown Source)
	at java.lang.SecurityManager.checkPermission(Unknown Source)
	at java.lang.SecurityManager.checkExit(Unknown Source)
	at java.lang.Runtime.exit(Unknown Source)
	at java.lang.System.exit(Unknown Source)
	at Applet1.initDPM(Applet1.java:279)
	at Applet1.init(Applet1.java:61)
	at sun.applet.AppletPanel.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)

Line 279 (the error line) is the line number of the System.exit(1) function call.

ideas??
David Dudley

Hi, David.
It looks like it might be failing because the applet does not have write
permission to *set* the system property
"com.cosylab.epics.caj.CAJContext.addr_list" in the System.setProperty call.
You could try the approach I suggested earlier to see if it might work
instead:
  DefaultConfiguration conf = new DefaultConfiguration("applet");
  conf.setAttribute("class", "com.cosylab.epics.caj.CAJContext");
  ...
  JCALibrary.getInstance().createContext(conf);
-lewis

Kay-Uwe Kasemir <[email protected]> 5/15/2007 12:13 PM >>>

On May 15, 2007, at 12:16 , David Dudley wrote:
OK, all you JCA and CAJ people, here's a problem for you-
I'm setting up JCA/CAJ to run through an applet. How do I prevent
them

from *attempting* to find the JCALibrary.properties file?
When an applet tries to find the file, it creates an access security
exception, since Applets, by nature, can't access the underlying file
system.
I tried doing System.setProperty commands to set
'com.cosylab.epics.caj.CAJContext' to values before the createContext,
but the moment that createContext is accessed, I get an error.

Interesting.
In jca-2.3.0/src/core/gov/aps/jca/JCALibrary.java
there's this code:
 try {

InputStream is = JCALibrary.class.getResourceAsStream
( "JCALibrary.properties" );

if (is == null)

throw new RuntimeException("resource not found.");

_builtinProperties.load( is );

} catch( Throwable ressourceEx ) {

System.out.println( "Unable to load default configuration....);

}
I would think the worst that can happen is a println,
and your System.setProperty calls would actually win.
But maybe that attempt to read a file does worse things
to an applet, something that the catch() doesn't catch?
I'd try to change that code section somewhat to see
what's happening in your case.
-Kay

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System