Re: Converting programs

[Pluta@xxxxxxxxxxxxxxxxxx]

    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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