Re: call Java program from RPG

[Richard Shaler <rshaler@xxxxxxxxxxx>]

If your system is at V5R1 you should be able to do this by usingn the new RPG 
object data type and defining RPG prototypes for the Java objects and methods 
you want to use. I've included the source code for a simple working example 
where the Java class accepts a string from the RPG program and returns a 
modified string. 
/**
 * @author shaler
 *
*/
public class TestHello {

    public String getResponse (String pMessage) {
          String message = "Hello " + pMessage + "! ...from Java";
          return (message);
       }
}

Figure 1: The Java TestHello Class


h DftActGrp(*NO) ActGrp(*Caller)
 *********************************************************************
 * Prototype for a Java String object
 *********************************************************************
d crtString       PR              O   EXTPROC(*JAVA:
d                                             'java.lang.String':
d                                             *CONSTRUCTOR)
d  RPGBytes                     30A   Const Varying
 *********************************************************************
 * Prototype for TestHello object creation (instantiation)
 *********************************************************************
d crtTestHello    PR              O   EXTPROC(*JAVA:
d                                             'TestHello':
d                                             *CONSTRUCTOR)
 *********************************************************************
 * Prototype for TestHello's getResponse method
 *********************************************************************
d getResponse     PR              O   EXTPROC(*JAVA:
d                                             'TestHello':
d                                             'getResponse')
d                                     Class(*JAVA:
d                                           'java.lang.String')
d String                          O   Class(*JAVA:
d                                           'java.lang.String')
d                                     Const
 *********************************************************************
 * Prototype for Java String's getBytes method
 *********************************************************************
d cvtToBytes      PR            30A   EXTPROC(*JAVA:
d                                             'java.lang.String':
d                                             'getBytes')
d                                     Varying 
 * Create TestHello object field
d TestHelloObj    S               O   Class(*Java:
d                                           'TestHello')
 * Create message String object field to contain RPG message
d sendMsg         S               O   Class(*Java:
d                                           'java.lang.String')
 * Create message String object field to contain Java message
d rcvMsg          S               O   Class(*Java:
d                                           'java.lang.String')
 * Create constant to load into sendMsg String object
d msg             C                   CONST('RPG')

d DisplayMsg      S             30A   Varying 
 *********************************************************************
 * Create Java String object to contain sending message
 *********************************************************************
c                   eval      sendMsg = crtString(msg)
 *********************************************************************
 * Create TestHello object to access its getResponse method
 *********************************************************************
c                   eval      TestHelloObj = crtTestHello()
 *********************************************************************
 * Call the getResponse method of the TestHello object
 *********************************************************************
c                   eval      rcvMsg = getResponse(TestHelloObj:sendMsg)
 *********************************************************************
 * Convert the Java rcvMsg String to RPG bytes (Varying alpha field)
 *********************************************************************
c                   eval      DisplayMsg = cvtToBytes(rcvMsg)

c     DisplayMsg    Dsply

c                   EVAL      *INLR = *ON
Figure 2: The CALLJAVA RPG Program
For more information in Chapter 11 "RPG and the eBusiness World" of the ILE RPG 
Programmers Guide (V5R1 or greater) or see see an article I wrote "Hello 
RPG!... from Java" at: http://www.lab400.com/newsletter.html#HelloRPG 

Yildiray Ozen <yildirayo@xxxxxxxxxxxxxxxxxxx> wrote:

Hi,

I have a Java program on 400 and it takes some parameters and returns a
value. It should be called from some RPG programs.
Has anybody tried something similar?

Yildiray Ozen





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