RE: (no subject) -- WDSCI-L

> From: Mike Troxclaire
> 
> Large part of our AS400 shop will still stay in RPG but we will be
> using Java mostly on the intranet and internet side for the outside
world.
> I will be needing to take some/lots of applications in RPG and make
Java
> versions of it so that I can make them work as servlets and JSP pages.

First off, let me make clear that I write articles and books and teach
seminars on this subject, and I also sell a tool that does exactly what
you are asking, so I am somewhat biased in my opinions.

The idea of putting a JSP front end on an existing RPG program is called
"refacing", and is a subject that has been covered extensively both in
the midrange.com mailing lists and pretty much everywhere else in the
iSeries community, including magazines and online publications.  It is
part of a larger issue called "application modernization", which covers
all the ways you can use the Web to get data into and out of your legacy
application.  I wrote an extensive article on the subject:

http://www.mcpressonline.com/mc?1@xxxxxxxxxxxxxxxxxxxxx@.6ae97856

I'm sure others on the list can point you to other articles, and the
vendors can all pipe in with their recommendations. You might even want
to post a message to WEB400-L to get some more input.


> May be I could easily convert them into Java beans and call those
> beans from JSP
> pages. In order to do this I will be needing to understand RPG and may
be
> write my own RPG modifications to suit my needs and that is why I want
to
> learn RPG so desperately.

The biggest problem has to do with where you want to interface to the
existing system.  If you simply want to put the existing user interface
out on the web, there are many ways to do it.  The problem is that most
of them do not allow the program to be encapsulated in a bean; instead,
the legacy program runs basically the same way it used to, only in a
browser (or in a thick client on the PC).  Some products, like mine,
will allow you to simulate a user through APIs and thus you can
encapsulate the user interaction, but in most cases the program simply
runs in the browser.

If you are trying to encapsulate business logic in a bean, that is much
more difficult.  Depending on how your programs were written, there is a
distinct likelihood that the I/O code and the business logic are
inextricably linked, and trying to extract the business logic is a
difficult proposition.  I'd be willing to go out on a limb here and say
that a good 80% or more of typical iSeries programs are not designed to
separate business logic into callable modules.  This is changing,
especially with the advent of RPG IV and ILE, but older systems still
have that "monolithic" approach.

I'll plug one of my books here: "e-Deployment: The Fastest Path to the
Web" was written specifically to outline a staged approach to migrating
existing legacy applications to the Web.  It assumes knowledge of RPG,
but it may also help you to understand what parts of a legacy program
need to change.  The ideas in that book eventually became a successful
web enabling product, so they work.

Joe

By the way, here's the required plug for PSC/400, my web-enabling suite:

http://www.plutabrothers.com/PBDWeb/p1.html