Java calls to RPG functions

[Anthony_Castillon]

How can I call a function written in RPG for AS/400 from my Java application? I think JNI cannot be used because it can only handle C/C++ functions. What other options are there?

[James Swan]

IBM has produced a ToolBox for calling/accessing AS/400 specific objects.
Check out this link: http://publib.boulder.ibm.com/pubs/html/as400/v5r1/ic2924/index.htm?info/rzahh/page1.htm
In particular, you probably want to look at the ServiceProgramCall class:
http://publib.boulder.ibm.com/pubs/html/as400/v5r1/ic2924/info/rzahh/javadoc/com/ibm/as400/access/ServiceProgramCall.html
James.

[Anthony_Castillon]

Thanks for the tips, James. However, the ServiceProgramCall class API says that a max. of 7 parameters may be passed to the service program. In my program, I may have to pass more params. Have any idea how to handle that?

[James Swan]

Well that kind of sucks doesn't it ;-)
How about using ProgramCall object then, it apparently allows 35 parameters to be passed to the program.
The only catch being now, the main entry/exit point would be the main line of code in the RPG program (*ENTRY and *PARMLIST part), rather than just a specific method.
James.

[Dave Vick]

Anthony_Castillon
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[Anthony Castillon]

Thanx for the tips, James. Have a question though: Do I have to do any configuration of my system (I'm running a java app from Windows 2000 connected to an AS400 machine) to make the connection. The ProgramCall API and samples I've seen so far looks deceivingly simple or has IBM really abstracted away the fine details of the connection (given that the fully integrated file name has been provided) that I just have to use the setProgram() and run() on the AS400 object?

Originally posted by james swan:
Well that kind of sucks doesn't it ;-)
How about using ProgramCall object then, it apparently allows 35 parameters to be passed to the program.
The only catch being now, the main entry/exit point would be the main line of code in the RPG program (*ENTRY and *PARMLIST part), rather than just a specific method.
James.

[James Swan]

Hi Anthony,
yeah it is pretty simple to set up the client (Windows 2000 side).
Just have the jt400.jar in your classpath, and so long as you can see the AS400 on the network (and have a valid AS400 user profile), you should be fine.
From the AS400 side, somebody might have to install some of the IBM java support programs (but don't quote me on this).
check out this link for more info: http://publib.boulder.ibm.com/html/as400/v5r1/ic2924/info/rzahh/rzahnm05.htm#HDRRZAHNRE2-RE2RF
here is a simple example of a CL program call to get you started.
the CL program (get someone to compile it for you, or maybe you can just do it yourself)

pgm parm(&jobDate)
    dcl &jobDate *CHAR 6
    rtvJobA date(&jobDate)
endPgm

the java class that calls it

import java.io.*;
import java.util.*;
import com.ibm.as400.access.*;
public class CallAS400Pgm {
    public static void main(String[] args) {
        try  {
            // Create an AS400 object
            AS400 as400 = new AS400("myAS400");
        
            // Create a parameter list
            ProgramParameter[] parmList = new ProgramParameter[1];
        
            // A six-byte character is returned.
            parmList[0] = new ProgramParameter(6);
            QSYSObjectPathName programName = new QSYSObjectPathName("/QSYS.LIB/MYLIB.LIB/MYPGM.PGM");
        
            // Create a program object
            // specifying the name of the
            // program and the parameter list.
            ProgramCall pgm = new ProgramCall(as400);
            
            pgm.setProgram(programName.getPath(),parmList);
            
            // Run the program.
            if (!pgm.run()) {
                // If the AS/400 cannot run the
                // program, look at the message list
                // to find out why it didn't run.
                AS400Message[] messageList = pgm.getMessageList();
            } else {
                // Else the program ran. Process the
                // second parameter, which contains
                // the returned data.
                int textLength = 6;
            
                // Create a converter for the AS/400
                // data type. Note a default
                // converter is being built.  This
                // converter assumes the AS/400
                // EBCDIC code page matches the
                // client's locale.  If this is not
                // true the Java program can
                // explicitly specify the EBCDIC
                // ccsid to use.
                byte[] data = parmList[0].getOutputData();
                AS400Text textConverter = new AS400Text(textLength);
            
                // Convert the data from EBCDIC to
                // unicode.
                String time = (String) textConverter.toObject(data);
                System.out.println("time is " +  time);
            }
        
            // Disconnect since I am done running programs
            as400.disconnectAllServices();
        } catch (Exception e) {
            e.printStackTrace();
        }
    
        System.exit(0);
    }
}

You might need to adjust these slightly for your environment, in particular the name of the AS/400 you want to connect to, and the library and program name of the CL program.
I don't work on the AS/400 platform anymore, so that's about my limit of being able to help you.
Basically (after maybe program/class compile issues), if you can't run this successfully then the AS/400 might not have the necessary supporting software installed (see the above url).
Hope this helps,
James.

[Anthony Castillon]

I created a class and patterned it after the sample code in the ProgramCall API. I also created a client that populates an array of AS400Parameter(which I created) and called on my program. It worked. Thanx again for the tips.