Re: JCA Library usage

[Kay-Uwe Kasemir <kasemirk@ornl.gov>]

On May 11, 2007, at 10:45 , David Dudley wrote:
> All is fine and good to be able to use this, -except-, in the case of
> distributing an application, or as an applet, there is no way to  
> provide
> a location of where to get the 'JCALibrary.properties' file.  Can the
> capability of providing a location (preferably being able to use a URL
> Link as well) be added to 'getInstance' (or should I do it?)?

Actually I think you can already put something like this in your code:

     System.setProperty("com.cosylab.epics.caj.CAJContext.addr_list",
	                        ... your value ...);
     System.setProperty 
("com.cosylab.epics.caj.CAJContext.auto_addr_list",
	                        ... "YES" or  "NO" ...);

Meaning:
All that's usually loaded from the JCALibrary.properties
can be initialized in your code.

So you can hardcode it in your application,
or have your application read that info from
some jar file location as you suggest and copy it to  
System.setProperty().

> Also, is there a way to create a channel and then 'add' a connection
> Listener as a separate function?
Maybe not. But not a show stopper:
Just always create the channel with your 'Forwarding Listener',
and then those later listeners register with your 'Forwarding Listener'.
Of course you'll have to implement that 'Forwarding Listener'.

> Or a way to close a channel?
There is a
   Channel.destroy()
as well as a
   Channel.dispose().

I don't know the difference, but I use the 'destroy()' call and
that works nicely.

Beware, though:
If you have listeners, the 'JNI' version will completely remove the
channel and all listener information,
while the 'CAJ' version might still invoke your listener
with another value update, where the status is actually
indicating "channel was destroyed",
so it makes some sense, it's just that most people who've used
the JNI (C/C++) based CA client lib might not expect another
event from the destroyed channel.

-Kay