Re: Parsing JSON data into a data structure without knowing variable's names

Yes, this seems like the most straightforward approach, Jon. Kind of like
a web service generator that builds code based on a WSDL. Sure,
THEORETICALLY you could map the data dynamically by looking at an
externally described data structure, and done properly you'd only have to
do it once, but the overhead of parsing an FFD every time could be
significant.

I like the generated adapter technique. A good balance between
flexibility and performance. As long as you can avoid the temptation to
tweak the generated code... :)


I concur with the others that in a language such as RPG this is not

readily done. However, by constraining the problem space it can be done. I
wrote up this technique some 10 years ago http://ibmsystemsmag.com/ibmi/
developer/rpg/how-flexible-are-your-calculations-/ <
http://ibmsystemsmag.com/ibmi/developer/rpg/how-flexible-
are-your-calculations-/> and this followup article which took it one
step further.
http://ibmsystemsmag.com/ibmi/developer/rpg/even-more-flexib
le-calculations/ <http://ibmsystemsmag.com/ibmi
/developer/rpg/even-more-flexible-calculations/> providing you know the
names of all fields involved, then this could work but I don't think t is
the best solution.

Instead in your case I would suggest writing a simple code generator
would be a more practical way of handling the multiple parameter sets that
you have. Rather than try and write a completely generic program write a
generic generator that spits out the RPG to do the JSON to DS mapping for
each of your DS. If the parameter set changes regen the code.

Nested structures would be harder to handle but by no means impossible.


Jon Paris

www.partner400.com
www.SystemiDeveloper.com

On Aug 12, 2017, at 3:12 AM, Maria Lucia Stoppa <mlstoppa@xxxxxxxxx>

wrote:

Hello,

I am new to this forum, but I have done some research related to JSON and
couldn't find anything similar to my issue.

I am working on a proof of concept to code new programs in order to parse
the only received parameter formed as a JSON object into a data
structure.

I explain it better: previously, all our programs received a single
parameter defined as an external data structure, so as soon as *entry
plist
operation code is executed the data structure and all the fields in it
were
filled in and made available for programs to use them (quite common
solution). External data structure are defined as PF without member and
can
be used by any program that need to call the one which received it as a
parameter to perform a specific function.

Now we are moving our ERP's graphic interface to web: it means that a
program call can be executed by a store procedure called either by web
applications or by RPG programs. To serve the purpose of having a quick
UI
response, parameters are passed coded in a JSON object and new programs
have been coded to parse JSON input parameter field by field using SK's
JSON APIs (thanks!).

I am guessing whether I can expand and generalize this behavior by
coding a
general routine which takes an external definition of JSON (even nested)
structure and assigns each object's name found into JSON parameter to its
corresponding variable name's value.

My nightmares are: firstly, today's external DS are one level only and I
can't figure out how to represent nested levels; secondly how to
dynamically associate the value of JSON pair to its corresponding
variable's value according to its type.

One general idea might be to code some external D specifications to be
used
through /COPY option, which represent JSON structure in terms of
qualified
names and types, array included. Then JSON objects can be read element by
element but how can I address the right DS variable without explicitly
write its name?

Can you suggest me some technique I haven't explored yet or any other way
to approach the problem?

Thank you

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