Re: Error checking when calling Java classes from RPG/Advantage Plex

I have used both of these technologies extensively, although never 
together in the way that you have.  My first recommendation, since I think 
it would just be an overall better solution would be to use data queues. 
In other words, put a layer of Java code in that waits on messages to a 
data queue, then executes your Java code and puts some return code on a 
data queue.  Your Plex RPG code could then just be modified to call the 
QSNDDTAQ and QRCVDTAQ API's.  This is a better architecture because your 
Java code stays running and you do not have incur the overhead of starting 
and tearing down the JVM.  A single Java process could probably serve 
many, many RPG server jobs in this manner, and you could always just start 
up more Java server jobs listening on the same data queue because the data 
queue code handles all of that for you nicely.

My second suggestion would be to write a small CL program that runs the 
Java.  This could then trap any errors and return them in a variable.  You 
would then just define this CL program as an API function in your Plex 
model and call it from your RPG.

Good luck.

Mark

PS - I think you would get better answers on the Plex forums at the Edge 
UserGroup.

http://edgeusergroup.pugmarks.net/

java400-l-bounces+markp=softlanding.com@xxxxxxxxxxxx wrote on 01/14/2004 
01:14:52 PM:

> Hi,
> 
> I am doing calls to Java classes from Advantage Plex programs which
> generate and then compile RPG code.  I'm doing this by using Format 
Message
> to put the Java command into CommandString, e.g. JAVA 
CLASS(com.my.class)
> CLASSPATH('/My.jar') and then using the ExecuteCommand API to run it. 
This
> all works fine, except that I haven't found a way to get some sort of
> success or error code back from the Java program, so the Java program 
may
> throw an exception which gets caught and want to return some sort of 
error
> code back to the Plex/RPG program to say what went wrong but it cannot 
do
> this.  Also you can get more serious situations such as if the JAR file 
is
> missing, or the Java program tries to access a class not on the 
classpath,
> which throws a JVA0122 message back to the Plex program, which again 
cannot
> be detected and the Plex program carries on happily assuming the Java
> program worked fine.
> 
> So far my best idea on how to handle this is to:
> 1) In Plex, use a numerator table to allocate a unique number, lets call 
it
> Java Call Number, to the function call (just allocate the number, don't
> write out a record with this number anywhere yet)
> 2) Do the call to Java, passing in the Java Call Number as a parameter
> 3) The Java program runs and at the very end must at the very end write 
out
> a record using JDBC to a 'Java Call' table, writing out the Java Call
> Number and we can also put a return status field on the table which we
> would write out as zero/empty if the Java program worked, or
> non-zero/not-blank if there was an exception or some other error 
condition.
> 4) After the line which calls the Java program, the Plex program 
attempts
> to read the record back from the 'Java Call' table.  If the record is 
there
> then the Java program must have ran successfully and we can read the 
return
> status out to know if there were any problems, and then delete the 
record
> from the 'Java Call' table.  If there was no record written out, the 
call
> to the Java program must have failed due to a missing class/JAR, or the
> Java program ran but something fundamental failed e.g. the Java program
> could not connect to the database.
> 
> This seems completely overkill, surely there must be a better way to 
handle
> this?  Has anybody else had this situation?  Is there a better way to be
> calling Java programs from Plex/RPG than using the JAVA OS/400 command? 
I
> know there are extensions in RPGLE to allow declaring Java classes as
> native methods, but Plex unfortunately uses RPG and not RPGLE.  I'm by 
no
> means an RPG expert but I gather the two are not compatible?
> 
> Thanks very much,
> 
> Nigel Gay,
> Computer Patent Annuities.
> 
> 
> 
> 
> 
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