RE: RPG, Java and Classpath practices

Brad,

I don't know if this would help you, but I tell you what I have (and it
works for me):

From an RPG program I run RUNJVA command (using QCMDEXC); this command

has a parameter named CLASS where I put the "tool" I need (I perform a
PDF file compression) and, also, another parameter named CLASSPATH where
I put the path for the .jar file (residing in IFS folder) where the
"tool" is.

I noticed that the first time is slower, but after that it improves.
Hopefully this it helps...


Florin Todor



-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Bradley V. Stone
Sent: Thursday, June 12, 2008 10:43 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

--
IBM System i - For when you can't afford to be out of business

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