RE: Calling JAVA from RPG ( passing string variable )

[pekrzyz@xxxxxxxxxxxxxxx]

I have had to write several RPG to JAVA programs for our group, and wanted 
to minimize
the programming impact for the RPG programmers would have when using the 
Java programs.
Many of them don't like change and keeping the interfaces simple made it 
more likely that
they would use them. :)

I often have to pass strings back and forth between RPG and JAVA. 
What I found that worked best for us was to use the same old strings 
within
RPG but declare them as varying.

eg (sample Dspec for string server):
D  server         S             255    varying

Then when I need to pass strings to the Java program, I would
receive them within the Java method as a byte array.  I would then convert 
them within
the Java method to a string.

eg (sample Java method which accepts a string from RPG):

public void IBMsetOracleServer(byte[] sserver) {
        String str = new String(sserver);
        server = str;
    }

When I needed to return a string from Java back to RPG, i would return it 
as a byte array.
eg(sample Java method returning a string to RPG)

public byte[] IBMgetOracleServer() {  // needed for IBM iseries
        return server.getBytes();    //getBytes() is a String object 
method
    }

(Note: The Java String object has overloaded constructors, and one of the 
constructors
             accepts byte arrays when creating the String object.  Since 
RPG passes byte arrays,
             this makes it easy for Java to automatically convert the byte 
arrays to strings.) 


RPG code which passes a string to Java was:
    // initialize the Oracle Server name
    setServer(objOraCon:server); 
(objOraCon was the object that pointed to the Java class that contained 
the methods)

RPG code accepting a string from Java was:
//get the Oracle server name
server=getServer(objOraCon);


By using byte arrays in JAVA, you don't have to worry about strings in 
RPG.
Calls to and from the Java methods are converted automatically within the 
Java method(s), without having to 
deal with converting the Java strings back to RPG strings everytime you 
need to call
the Java method.  The JVM automatically takes care of converting the 
character set between the AS400
and Java as the data is being passed into and from the Java application.

When declaring your prototypes, ensure that the string paramaters your 
passing to and from JAVA are
also declared as varying

eg:
        D getServer       PR           255A   EXTPROC(*JAVA: 
        D 'as400Orcle': 
        D 'IBMgetOracleServer') VARYING 

                D setServer       PR                        EXTPROC(*JAVA: 
 
                D 'as400Orcle': 
                D 'IBMsetOracleServer')
                D    parm                             255A   CONST VARYING 
 


...Paul
(pekrzyz@xxxxxxxxxxxxxxx)