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Eric Orilla wrote:

> 
> How to implement a single instance application?
> 

I don't think that's possible in Java.  You need access to
operating-system specific calls to get to the task list and switch to
your currently-running instance.

If you're running under UNIX, a shell script that starts your
application will do the job quite nicely.  Under Windows, there's no
easy way I can think of.

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"Eric Orilla" <eorilla@hotmail.com> wrote in message
news:421c464c$1@newsgroups.borland.com...
>
Here's how I would do it to ensure XPlatform.

When the application starts, read from a configuration file (XML, Properties
file, whatever you wish). Look for a runtime value (call it AppRunning,
Running, IsRunning, etc). If the value of the param is true, create a
message starting that the application is currently running. You might want
to add an override feature just in case the application/OS locked up or
crashed.

If, on startup, the value is null, false, etc. set the parameter/entity to
true, once the application has launched. This would ensure that only one
instance is running.

Other than this, as Kevin stated, there is no other way to do this and
ensure XPlatform. If that is not important to you, and let's say you need to
support Windows and not MAC or Unix, then you will need to call a Windows
API.

Here is some information on creating a single instance app using C++Builder.
You could create this app and use it to run your Java application, or use
JNI in the program and in your Java code. However, if you use this as a
wrapper for your Java code, you will have to ensure that the jar file is not
runnable and you will need to create a custom class loader mechanism.

Hope this helps ya!!

Eric Orilla wrote:

> How to implement a single instance application?
> 
> Thank you!

JBuilder does this.  It opens a socket on a particular port (8888).  If 
another instance attempts to starts and detects this port is open, I 
believe it just does an RMI call to force the running instance to the 
front, and then ends.

I'm sure if you do some web searches along those lines you can find more 
information.  I'd also look into the Java Desktop site 
(http://community.java.net/javadesktop/), look into the JDIC project 
there, and ask some questions in their forum.

-- 

Regards,

Lori Olson [TeamB]

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