Re: Help calling java from RPG -- JAVA400-L

Well at this point it is just a Proof of concept, but we would like to encapsulate our database activity in one place that we can be call from anywhere. We currently have a lot of RPG and PHP code, but as a future direction we are looking at Java so we were thinging this may be a good place to start. I welcome any thoughts as to why or why not this is a good idea.

jrperkinsjr@xxxxxxxxx 8/24/2009 11:45:39 AM >>>

Well, from this it's tough to tell you what your error is. I'm don't call
Java from RPG very often, but nothing from this code is jumping out at me.

I am curious to know why you would use JPA form RPG? The reason for JPA in
Java is because there is not native DB interface which RPG has.

I'm not even sure how you would get JPA to properly work in RPG. Using RPG
to create Java objects isn't really a good idea. The JVM doesn't do GC
automatically with these objects. From the manual:

"Normally, Java does its own garbage collection, detecting when an object is
no longer needed. When you create objects by calling Java constructors from
your non-native RPG procedure, Java has no way of knowing that the object
can be destroyed, so it never destroys them. You can enable garbage
collection for several objects at once by calling the JNI functions
described in Telling Java to free several objects at
once<http://publib.boulder.ibm.com/infocenter/iadthelp/v7r0/topic/com.ibm.etools.iseries.pgmgd.doc/c0925076177.htm#wrpsevobj>.
If you know you are not going to need an object any more, you should tell
this to Java by calling the JNI function described in Telling Java you are
finished with a temporary
object<http://publib.boulder.ibm.com/infocenter/iadthelp/v7r0/topic/com.ibm.etools.iseries.pgmgd.doc/c0925076177.htm#wrpfintmp>
."

So, I guess IMHO I wouldn't even try it. It just seems like you would be
doing a lot of work to get something to work that RPG already handles
better.
--
James R. Perkins
http://twitter.com/the_jamezp

On Mon, Aug 24, 2009 at 08:00, Chris Beck <CBeck@xxxxxxxxxxxx> wrote:

Hello,

I am creating a RPG program that calls multiple Java method from RPG and am
having problems with one of them. In the code snippet below I am wondering
how to set the hxplvl6Class field to the propper value? in Java I would just
use the following: "Hxplvl6 hxplvl6 = em.find(Hxplvl6.class, l6number);"

D em...
D S O CLASS(*JAVA:
'javax.persistence.En+
D tityManager' )

D HxpLvl6 S O CLASS(*JAVA : 'java.lang.Object'
)

D hxplvl6Class S O CLASS(*JAVA : 'java.lang.Class' )
D l6Number S O CLASS(*JAVA : 'java.lang.Object'
)

D find PR O CLASS(*JAVA : 'java.lang.Object'
)
D EXTPROC(*JAVA :
'javax.persistence+
D .EntityManager' : 'find' )
D pmClass O CLASS(*JAVA : 'java.lang.Class' )
D pmKey O CLASS(*JAVA : 'java.lang.Object'
)

/Free
HxpLvl6 = find(em:hxplvl6Class:l6Number)

Thanks for any help,

Chris

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