Calling java methods from RPG in batch -- RPG400-L

Help!

Prompted the excellent article by Geert Van Landeghem,I've been tinkering 
(fumbling blindly would be more accurate) around with calling Java methods 
from 
RPG to generate / update Excel spreadsheets (using the classes provided by 
the Jakarta Poi APIs - 
http://jakarta.apache.org/poi/hssf/index.html). Has anyone used this with 
some degree of success?
I've managed to write programs (batch and interactive) that will create 
spreadsheets from scratch 
and write them out to the IFS (which are then emailed out to users), but 
I'm having a problem when 
I try to open up an existing spreadsheet for updating ( I only need to 
change the contents of 
particular cells & re-save the file, plus it means I can use charts & 
other bits and pieces).

I can call my program interactively with no problems at all (having first 
set my CLASSPATH to point to 
where the .jar file is within the IFS) and get an updated spreadsheet at 
the end of it that is persisted to 
the IFS, but if I try to run it with a SBMJOB I get the error message:

*****
Message . . . . :   Java exception received when calling Java method.  
Cause . . . . . :   RPG procedure JAVAXLS8 in program DHWORKLIB/JAVAXLS8  
  received Java exception "java.io.IOException:" when calling method 
"<init>"
  with signature "(Ljava.io.InputStream;)V" in class  
  "org.apache.poi.poifs.filesystem.POIFSFileSystem". Recovery  . . . :  
  Contact the person responsible for program maintenance to determine the  
 
  cause of the problem. Technical description . . . . . . . . :   If the  
  exception indicates that the Java class was not found, ensure the class 
for
  the method is in the class path. If the exception indicates that the 
Java 
  method was not found, check the method name and signature. If the 
signature
  is not correct, change the RPG prototype for the method, or change the 
Java
  method, so that the return type and parameter types match. You can 
determine
  the signatures for all the methods in class XYZ using command QSH 
CMD('javap
  -s XYZ').  
*****

Not much help to the uninitiated ....



Here's a code snippet from the program in question:


0006.00 D jInStream       S               O   CLASS(*JAVA: 
0007.00 D                                     'java.io.FileInputStream') 

0029.00 D inFile          S                   LIKE( jInStream) 


0089.00    // Get pointer to JNI Environment 
0090.00    JNIEnv_P = getJNIEnv2(); 
0091.00    If JNIEnv_P = *NULL; 
0092.00       *INLR = *ON; 
0093.00       Return; 
0094.00    EndIf; 
0095.00 
0096.00    // Create a new local reference frame so we can clear all the 
0097.00    // java objects in one go 
0090.00    JNIEnv_P = getJNIEnv2(); 
0091.00    If JNIEnv_P = *NULL; 
0092.00       *INLR = *ON; 
0093.00       Return; 
0094.00    EndIf; 
0095.00 
0096.00    // Create a new local reference frame so we can clear all the 
0097.00    // java objects in one go 
0098.00 
0099.00    pushFrame( JNIEnv_P: capacity); 
0100.00 
0101.00    // Create a string object to contain the filename    
0102.00    wrkString = createString( %trim(IFSFile)); 
0103.00    // Trim filename (50A). 
0104.00    filename = trimString( wrkString); 
0105.00    // Create FileInputStream. 
0106.00    inFile = openFile( filename); 

                // a FileInputStream is passed into the poi method so that 
the
                // workbook can be opened and loaded 

0107.00    fs = createPOIFSFileSystemForInput( inFile);
0108.00    // Load the workbook  
0109.00    wb = openWorkbook( fs);  


(It's probably not relevant, but) I'm using the JNI to create/destroy JVM 
and do 
garbage collection thanks to some really useful articles posted by Barbara 
Morris.


The error occurs when statement 0107.00 is executed. The batch job doesn't 
seem
to have any problems coping with calling other Java methods (to create 
String
objects, numbers etc), and I don't think it's a CLASSPATH problem?. Is 
there
some issue with using a FileInputStream in a batch job or something??
Apologies in advance, but as you've probably already deduced, I don't have 
any 
Java experience at all.

I'm on V5R2 of the O/S and using JDK 1.3 if that helps any ?


FYI

Here's my FileInputStream contructor prototype

0017.00  * // FileInputStream CONSTRUCTOR  
0018.00  * // openHandle = openFile( fileName)  
0019.00 D openFile        PR              O   EXTPROC(*JAVA:  
0020.00 D                                     'java.io.FileInputStream':   
 
0021.00 D                                     *CONSTRUCTOR)  
0022.00 D fileName                        O   CLASS(*JAVA:  
0023.00 D                                     'java.lang.String')  
0024.00  


And here is my POIFSFileSytem prototype (if it helps)

0021.00  * // createPOIFSFileSystemForInput( java.io.InputStrean)  
0022.00  * // Creates a POI FileSystem object from a java input stream,   
0023.00  * // required for reading exising xls files.  
0024.00 D createPOIFSFileSystemForInput...  
0025.00 D                 PR              O   EXTPROC(*JAVA:  
0026.00 D 'org.apache.poi.poifs.filesystem-
0027.00 D                                     .POIFSFileSystem':  
0028.00 D                                     *CONSTRUCTOR)  
0029.00 D                                     CLASS( *JAVA:  
0030.00 D 'org.apache.poi.poifs.filesystem-
0031.00 D                                     .POIFSFileSystem')  
0032.00 D  inputStream                    O   CLASS(*JAVA:  
0033.00 D                                     'java.io.InputStream')  



Sorry if this isn't enough info to be going on yet, I just wanted to get 
my
problem "out there" as it's giving me a real headache.

ps Apologies if this isn't the right forum or format for this as I've not 
posted before & I'm stuck with
using Lotus Notes as my mail agent here at work (don't have a newsgroup 
reader either).


Many thanks,

David Hinselwood


COMPUTACENTER (UK) LTD

The contents of this e-mail are intended for the named addressee only.
It contains information which may be confidential and which may also be 
privileged. 
Unless you are the named addressee (or authorised to receive
for the addressee) you may not copy or use it, or disclose it to anyone
else. If you received it in error please notify us immediately and then
destroy it. 

Computacenter information is available from http://www.computacenter.com

This footnote also confirms that this email message has been swept for the 
presence of computer viruses.

***************************************************************************************************************************