Re: Converting programs

[booth@xxxxxxxxxxxx]

"...comes directly from Utopia" wouldn't be exactly the phrase I'd choose. 
 <bg> 

I've done every step that you list but never from RPG all the way through 
to Java.  My experience tells me that the RPG to RPGLE conversion works 
but takes some tweaking and usually includes repairing file definitions 
and replacing a few instances of code that just won't convert. 

The conversion from RPGLE to VARPG is not useful.  It can happen and the 
books are not lying, but the finished product is just too embarrassing to 
show.  It is ugly, the screens are crowded, and it is still cycle-driven, 
not event-driven. 

I've also done the conversion from VARPG to Java and that works, mostly, 
but its still a new product.  There is unsupported code that has to be 
fixed manually. 

All in all the proposed tasks are a lot of work and the end product will 
be unusable in my opinion.  Even if all the conversions of code go 
smoothly you are still faced with the "cycle-driven" vs. "event-driven" 
design base and as long as you avoid event driven programs you have failed 
the goal of the conversion.

It won't be clear to you what I am driving at when I say event driven 
programs until you experience the concept of  event-driven code, but I'd 
bet a sandwich that once experienced you will never willingly code a 
cycle-driven interactive user program again.

_______________________
Booth Martin
Booth@MartinVT.com
http://www.MartinVT.com
_______________________




Pluta@nexgensoftware.com
Sent by: owner-java400-l@midrange.com
06/20/2000 11:49 AM
Please respond to JAVA400-L

 
        To:     JAVA400-L@midrange.com
        cc: 
        Subject:        Re: Converting programs


    Here's  the problem : I have an application running on an AS400e using
RPG400, CL,  CMD programs which are using DSPF and PRTF.  Now my boss 
wants
the whole  application to be cross-platform.  Now since I know that IBM
has
increased considerably the performances of Java language on their  OS400,
it's the language I planned to use for the  application.

     Then my boss talked to me about  some tools that would do the
conversion
from RPG400 to ILE RPG then to VARPG  and to VAJ.  I've been looking for
this
tool at IBM's website, and their  partner's too but still can't find it.

    My question is  simple : Is there a way to do what I mentionned in the
preceding paragraph or  is it an idea that comes directly from Utopia?
---------------------

Before you decide how to go about this, you need to ask yourself a couple
of questions.  First and foremost is, "Why does the boss want the
application to be cross-platform?"  Two possible options:

1. To move off of the AS/400 entirely
2. To move to a graphical user interface but use the AS/400 as a database
server

If you're planning on moving off of the AS/400 completely, I'm not sure
that converting RPG code to Java is a good idea, because it means changing
the native database access to SQL and that's a different animal.  Many
times, you need to completely rethink your database strategy when you go 
to
SQL.  Things like members, multiple-format logicals, recursive databases
(like bills of materials) and so on all cause problems.

If you want option 2, you now need to ask a different question.  What is
your architecture?  There are two basic user interfaces in Java,
browser-based (HTML) and thick client (using the Swing GUI).  Assuming
thick client (the most straightforward), you have the following options:

1. The entire application runs on the workstation, performing remote
database calls to the AS/400
2. The user interface and application logic run on the workstation,
communicating with data servers on the AS/400
3. The user interface runs on the workstation, communicating with a
"modernized" application on the AS/400

In each of these, you can replace the thick client interface with a
browser-based implementation in one of two ways:

1. Move all workstation logic into a servlet, which communicates via
JavaServer Pages to the user
2. Use applets in your HTML

Servlets and JSP are best for Internet access, while applets are best
suited for high-speed intranets.

This is not an exhaustive list by any means, but it gives you a little 
idea
of the concepts.  For a more complete overview, I've got a powerpoint
presentation on my site:

http://www.plutabrothers.com/COMMON/ppts/Moving%20Your%20Legacy%20Systems%20to%20the%20Web.ppt

Apologies if the link is unmanageable.  If so, go to:

http://www.plutabrothers.com/COMMON/index.htm

and then click on "Moving Your Legacy Systems to the Web"

Joe Pluta
www.java400.net


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