RE: Calling JAVA from RPG ( passing string variable )

An RPG string is not compatible with a Java String object.  To pass a string
from RPG to Java, you must do one of two things:
1.      In the RPG, create a prototype to call the Java String constructor
to create a Java String object and then pass that object to your Java
method.
2.      In the Java, define that field as a byte array and then create a
Java String object from the byte array in the Java method.
The latter is much more efficient, and you don't leave any Java String
objects about that the Java garbage collector can not collect.  Also,
convert any String objects being returned from Java to RPG to a byte array
before returning.  That way the String object can be garbage collected.  If
you pass the String object back, you have to send the object back into the
Java getBytes method to convert it into a byte array, which RPG can use.
I have implemented this byte array usage, and volume tested the process with
hundreds of thousands of repetitions and there was no slow down.  Making
three calls into Java, the first to call the String constructor, the second
to call your method, and finally to use getBytes to convert the String back,
will slow down very quickly.
Bill


        -----Original Message-----
        From: Roman Prigozhin [mailto:Roman.Prigozhin@xxxxxxxxxxxxxxx] 
        Sent: Tuesday, March 30, 2004 7:51 PM
        To: 'java400-l@xxxxxxxxxxxx'
        Subject: Calling JAVA from RPG ( passing string variable )

        I'm trying to call my java methods from RPG, everything works but
passing
        string variables. 
        Probably I have some issues with data conversion. 
        Error I'm getting is : 
        Message . . . . : Java exception received when calling Java method
(C G D 
        F). 
        Cause . . . . . : RPG procedure TEST in program ROMAN/TEST received
Java 
        exception "java.lang.NoSuchMethodError: testStuff" when calling
method 
        "testStuff" with signature "([B)I" in class "MyClass". 
        But prototype of the java function is correct : 
        Compiled from MyClass.java 
        public class MyClass extends java.lang.Object 
        public MyClass(); 
        /* ()V */ 
        public static int testStuff(byte[]); 
        /* ([B)I */ 
        Here is my java class : 
        public class MyClass {

        public static int testStuff( byte[] test ){
        int size =0;
        size = test.length;
        return size; 
        } 
        } 
        Here is the Prototype :
         
        D testStuff PR 10i 0 ExtProc(*JAVA:
        D 'MyClass':
        D 'testStuff')
        D Static
        D teststr 30A
         
        And here is the RPG programm :
        H DftActGrp(*NO) ActGrp(*CALLER)
        /Copy *LibL/RPGSRC,TEST1PR
        D first S 10i 0 Inz(23)
        D second S 10i 0 Inz(18)
        D sum S 10i 0
        D testStr S 30A
        /Free
        // call my home grown method
        testStr = 'roman';
        sum = testStuff(testStr);
        Dsply testStr;
        /End-Free 
        Thanks, 
        Roman 
        www.aadt.com