Re: JCA Library usage

["David Dudley" <DavidDu@cctexas.com>]

This is useful as a workaround, however if I want to use this to drive
an applet on a WEB page, for instance, I don't want to have to hardcode
into the applet the address of where to get data.  I'd much rather
create a properties file on the server, and somehow tell the package
that it needs to get it's properties from a particular stream.

That way, if I have a page with 50 applets on it, I could pass a
parameter to the applet as to where to get the properties from.

Just a thought-
David

>>> Kay-Uwe Kasemir <kasemirk@ornl.gov> 5/11/2007 12:02 PM >>>
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


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