RE: RPG, Java and Classpath practices

["DeLong, Eric" <EDeLong@xxxxxxxxxxxxxxx>]

That would only be used the first time Java was invoked for a job.  Once the JVM has started, it will not look at classpath again, afaik...

Eric

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx]On Behalf Of Bradley V. Stone
Sent: Thursday, June 12, 2008 9:43 AM
To: RPG programming on the AS400 / iSeries
Subject: RE: RPG, Java and Classpath practices


Quick question.

I noticed on the JAVA command you can specify a classpath.  Would using this
be a bad idea?  Does it start a new JVM every time it runs?  Or how exactly
does this work?

For example, if another application used the JAVA command and specified a
classpath, if I use it afterward it start a new JVM and use my classpath, or
will the first call have started it's own JVM and again be in the situation
where you can't change the classpath?



Bradley V. Stone
BVSTools - www.bvstools.com
eRPG SDK - www.erpgsdk.com

> -----Original Message-----
> From: rpg400-l-bounces@xxxxxxxxxxxx
> [mailto:rpg400-l-bounces@xxxxxxxxxxxx]On Behalf Of David Gibbs
> Sent: Thursday, June 12, 2008 8:34 AM
> To: RPG programming on the AS400 / iSeries
> Subject: Re: RPG, Java and Classpath practices
>
>
> Bradley V. Stone wrote:
> > So, looking for ideas on handling this.  In a nutshell, you have a
> > standalone app that uses Java inside of RPG and you want to ensure the
> > classpath is set properly when your application runs, no matter
> what else
> > they are running or if the JVM is already running for that job.
>
> Brad:
>
> FWIW, I'm not a big fan of invoking Java directly from RPG.  I know it
> can be done but, for the same reasons you mention, I don't think it's a
> great idea.
>
> Personally I would suggest you start the java process up in a daemon job
> and communicate to it with data queues.  Simply have the java process
> monitor a queue for commands and have your RPG send the command requests
> through the queue.
>
> That way you only have the JVM startup penalty once ... and the job is
> running in batch.  Your RPG program suffers no performance impact
> because the data queue api is relatively light weight.
>
> Obviously all ther java code would have to be in your daemon job's
> classpath.
>
> JMO, obviously.... but I've been using this kind of technique for quite
> a while with great success (using sockets though, not data queues ...
> given a chance to rework the implementation, I would probably use a data
> queue).
>
> david
>
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