Re: Modernizing Green Screen Was: Re: IBM HATS vs. ?

The primary problem with moving from green screen to web is the impedance mismatch. RPG applications are a page at a time, and most RPG programmers think that way and thus most tools follow that path. And if you use Web 1.0 thin-client designs you can match up relatively closely. Some of the more sophisticated tools allow you to merge multiple green screens into one page, but at the end of the day you end up writing applications that are very much web counterparts of green screen: a table rather than a subfile, a form rather than a record format.

If you're willing to go this route, JavaServer Faces (JSF) is very powerful and allows you to avoid a lot of the plumbing. Tools such as those from Rational make it even easier.

But if you want real Web 2.0 applications (the ones that don't make web users "queasy" <grin>), then you need to change your paradigm completely and start thinking of services and sending small bits of data back and forth. You'll need a solid JavaScript framework to implement the UI - without it you'll be as lost trying to manually code pages as you would be if you had to program the 5250 data stream yourself.

I disagree a bit with Nathan about throwing out your existing RPG code. Depending on how far along the road you are to modularization and things like called programs and service programs, you should be able to use that code almost immediately n a good web application.

Anyway, that's probably more than enough for Midrange-Tech; any more discussion of web architectures belongs best in the WEB400 list.

Joe

Nathan,
Very interesting. I must have missed that one somehow. I will definitely
have to take a look for that. If I can find something that works like that I
will write something for it and be happy to share the source.

I like the data structure idea even more because like you said it could
generate any type of structure. I used XML because it has better support
than JSON, but JSON is becoming more popular for sure.
--
James R. Perkins
http://twitter.com/the_jamezp


On Tue, Oct 6, 2009 at 14:43, Nathan Andelin <nandelin@xxxxxxxxx> wrote:

James,

I have no idea what kind of support we might get from IBM in converting
5250 output to XML, but that idea reminded me of something that Niels
Liisberg of Denmark shared on the Web400 list.

Niels wrote an ILE C service program that used IBM's virtual terminal
interface to expose 5250 data streams as simple data structures, which could
subsequently be formatted in any way a developer might chose. He then wrote
an RPG utility that converted 5250 output to JSON formats - used by a
JavaScript client - apparently written by one of his colleagues at System &
Method.

It was good to see an ILE (server based) approach to screen scrapping,
which performed a lot better than anything else I've seen.

-Nathan.