RPG Calling a Java main method

["Mike Silvers" <msilvers@xxxxxxxxxxx>]

I finally figured this one out.  As you know, the main method of a Java
class is a special method.  It is always defined as "public static void"
with an argument of a string array.  This provides some special
circumstances for calling this method from within an RPG program.  After
referencing the RPG Programmers manual and some trial and error, I have come
up with the resolution.  Why the importance of the main method you ask?
Well, when I develop classes, and other Java programmers I have spoken to, I
code the main method to test all aspects of the class.  Normally I print the
results out to System.out.  Well, enough babble.  Lets look at the example
and the explanation.

Calling the main method -- and the appropriate definitions

first, define the parameter array:

D  args           S               O    Class(*JAVA:'java.lang.String')
D                                           DIM(1)

Next, define the main method prototype:

D main            PR                  ExtProc(*JAVA:
D                                          'com.shipley.ssl.CRD001J':
D                                          'main')
D                                          STATIC
D                                    O   Class(*JAVA:'java.lang.String')
D                                         CONST
D                                         DIM(1)
D                                         OPTIONS(*VARSIZE)


Note on the prototype - the array definition must be the same size as the
definition of the "args" variable.  Remember, this is a static method, so it
must be prototyped as such.

Next, define the prototype to create a String object:

D string          PR              O   ExtProc(*JAVA:
D                                               'java.lang.String':
D                                               *CONSTRUCTOR)
D   value                      100A   CONST VARYING

Finally, add an element to the array & call the method:

/Free
    args(1) = string('Test Value');
    main(args);
/End-Free

Remember that RPG arrays are based on 1 where Java arrays are zero based.
The main method in the class I am testing does not require any parameters.
Actually, the class will not reference any parameters passed in to the
method.  You MUST pass a valid array to the method on the call.  I tried
passing *NULL without any luck.  I tried to pass an empty array with no
luck.

Hope this helps someone out there!

Mike