RPG Web Service Architecture

[Dean.Eshleman@xxxxxxxxxxxxxx]

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.