Re: RPG Web Service Architecture

I guess I shouldn't totally blame the .NET developers. Rather, the
designers of the page. It is a client search screen and for some reason
they didn't want to implement it using paging. I tried to tell them it
was a bad design, but nobody wanted to listen.

By the way, I do have the XML for RPG Programmers training course you
wrote. It has taught me a few things already. I'm still concerned about
security for a CGI based web service. The method presented in the
training course isn't secure enough for us. We want to avoid any user
id's and passwords on the .NET side. From the reading I've done, it
sounds like digital certificates is what we need to use. Do you know if
this can be done with a CGI based web service?

Dean Eshleman,
MMA, Inc.



Aaron Bartell <aaronbartell@xxxxxxxxx>
Sent by: web400-bounces@xxxxxxxxxxxx
12/10/2008 02:30 PM
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Web Enabling the AS400 / iSeries <web400@xxxxxxxxxxxx>


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Re: [WEB400] RPG Web Service Architecture

but the web developers don't want to callthe web service multiple

times, so I'm stuck with finding a solution.

Did they give a reason *why* they don't want to call it multiple times?
They might have a good reason, but more than likely they are ignorant or
lazy. Returning 10k of records for each listing request wont scale real
well if you have a lot of users hitting that web service. Instead they
should be making multiple requests and stating which page of a result
set they would like returned along with a page count.

Note that for blackbox applications where you own both ends of the
spectrum, XML is quite the bloated middle-ware technology - though it
does provide insulation from bad technology decisions (i.e. today your
front end is .NET, but when it is realized that was a bad decision then
they will try Java, and then PHP, and then RoR, etc). Just think of how
many bytes of data would be required for 10k of records and then add on
top of that the CPU cost to serialize and parse it - ouch.

You are right to question them Dean,
Aaron Bartell
http://mowyourlawn.com

p.s. if you are looking for a commercial solution check out
www.rpg-xml.com (of which I am the lead developer)




Dean.Eshleman@xxxxxxxxxxxxxx wrote:

Hi,

I have some questions about web services and how we are designing them.

We

are using web services to provide data from our system i to our .NET web

application. These web services are not intended to be used outside of

our

own application. One of our reasons for using web services was to avoid
storing a user id and password on the .NET side.

Our current approach has been to create the RPG program to return the

data

and then use the functionality in WDSC to create the web service front

end

for the RPG program. Overall, this approach works pretty well for most
situations. The only thing we don't like about this approach is when we

are returning multiple records from the RPG. We set the size of the

output

multiple occurrence data structure to be large enough to handle what we
think is the highest number we will run into. In one case it needs to
handle close to 10,000 records. Personally, I think that is to large of

a

number to return at one time, but the web developers don't want to call
the web service multiple times, so I'm stuck with finding a solution.

The generated Java code from WDSC will return an XML document matching

the

number of occurrences output from the RPG. We would like it to only

return

the number of occurrences that actually contain data.

Since I don't know Java, my initial thought solve this problem was to
create an RPG program to replace the Java in this situation. The RPG

would

receive the input XML document, parse it and then call the RPG data
retrieval program. Next it would build the XML response document and
return that result. I thought I could do this using CGIDEV2 and Scott
Klement's port of the Expat parser (thanks Scott). This way, I can

control

the XML document that is output. Does this seem like a reasonable
solution?

I was able to test out the XML parsing and that seems to work okay.

Right

now, I'm trying to use CGIDEV2 to read the input XML and I'm not sure

how

to do that. All the examples I see involve reading input from a web

page.

Does anyone know what field would contain the XML after using the
zhbgetinput procedure?

One concern I have about the CGIDEV2 approach is how will I secure the

web

service? Only our application should be authorized to call it.

We are on V5R3 and won't be going to V5R4 until sometime next year and
this needs to be solved before then.

Dean Eshleman,
MMA, Inc.

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