RE: what is Java bytecodes? was a contentious ILE vs CLI debate.

Yes, calling Java from RPG, no problem!

I have done this to access the JAVA mail APIs, to send formatted HTML emails
directly from RPG. Much simpler than using the OS400 sendmail API's.

If you understand running procedures in RPG, you will have no problem
calling Java from RPG, one you figure out

        1. Setting up your classpath
        2. Sending output to Stdout/Stderr so that you can view errors
        3. Creating objects such as String, so that you can pass a string
object to the class you want to call 

Once you figure these out, which is a bit of a learning process, its
actually pretty straight-forward.
First call seems to be slow, presumably creating the JVM, after that its
pretty nippy

Cheers
Colin.W

-----Original Message-----
From: McCallion, Martin [mailto:martin.mccallion@xxxxxxxxx] 
Sent: 04 November 2003 14:32
To: 'Midrange Systems Technical Discussion'
Subject: RE: what is Java bytecodes? was a contentious ILE vs CLI debate.


> >> Basically, the question is, what does Java bytecodes
> provide in terms of
> the
> >> inter language use of classes?  That is, can the Java
> bytecodes generated
> by
> >> the compiling of code in one language be referenced at the
> source code
> level
> >> by a programmer in another language.

Well, you can call Java classes from RPG: there is a source-level interface.

> What I am interested in is mixing Java and RPG  without the need of a 
> cumbersome interface barrier.

I haven't done it, (calling Java from RPG) but from what I've seen of it,
the interface appears to be just an extension of the RPG procedure interface
(PR and PI specs, basically).

> So what prevents the RPG compiler from translating RPG to
> Java ByteCodes?

Probably just that IBM hasn't seen a cost/benefit-justifiable business
reason for doing so; but perhaps Hans could comment on this?

> Esp if VisualAge RPG possibly does.  The thinking being that
> if RPG can
> translate to ByteCodes, then the programmer can also natively 
> reference Java
> classes contained in the Java ByteCode stream emitted by the 
> compiling of
> Java code.

Well, as I said above, the (RPG) programmer _can_ reference Java classes;
the fact that what you call by doing so is bytecode rather than
'conventional' OS/400 objects is neither here nor there, really.  Even if
RPG could compile to bytecode natively, there would still have to be a
syntax for calling Java classes.  And it would probably be the syntax we
already have.

Cheers,

Martin.

-- 
Martin McCallion
Senior Technical Consultant
Misys Wholesale Banking Systems
1 St George's Road, London, SW19 4DR, UK
T +44 (0)20 8486 1951
F +44 (0) 20 8947 3373
martin.mccallion@xxxxxxxxx
www.misys.com

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