RE: Defining System.out.println in RPG

Ah... I didn't realise that the RPG interface didn't support directly
accessing public data members... 
I hadn't checked out the V5R2 programmer's guide either - there's a lot more
in there than the V5R1 version...

I can see now how I could go about getting hold of the System.out object -
although I don't think that using the lower level JNI calls looks to be a
viable way forward for the kind of 'Hello World' example code I am putting
together... It will be much simpler to code a wrapper class that will
provide a getter method for this... 

As a slight aside, are there any plans to support RPG access to public data
members/fields in future releases? 

Thanks for your help. 

Stu

-----Original Message-----
From: Barbara Morris [mailto:bmorris@xxxxxxxxxx] 
Sent: Thursday 04 March 2004 21:52
To: rpg400-l@xxxxxxxxxxxx
Subject: Re: Defining System.out.println in RPG


"Bramley, Stu" wrote:
> 
> I'm trying to put together some 'Hello World' code that will call the Java
> method System.out.println(String) from RPG - however I'm struggling to get
> this defined correctly in the RPG..
> 
> I have tried the following :
> 
> D println         PR                  EXTPROC(*JAVA :
> D                                     'java.lang.System.out':
> D                                     'println')
> D                                     STATIC

Stu, "out" isn't part of the class; it's a PrintStream field in the
Static class.  'println' is an instance method in the PrintStream
class.  http://java.sun.com/j2se/1.4.2/docs/api/java/lang/System.html

D println         PR                  EXTPROC(*JAVA :
D                                     'java.io.PrintStream':
D                                     'println')                     
D  inString                       O   CLASS(*JAVA : 'java.lang.String')

To make this call, you need to get hold of the System field "out".  

D out             S               O   CLASS(*JAVA :
'java.io.PrintStream')
...
         println (out : string)

I think you might have to write a little Java method to return it; RPG
can only access methods, not fields (at least using the EXTPROC(*JAVA)
support).  The ILE RPG programmer's guide does have an example of doing
the JNI calls to access fields, so you could try that to get the "out"
field from System.

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