Error checking when calling Java classes from RPG/Advantage Plex

[NGay@xxxxxxxxxxxxx]

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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