Yeah,
I'd second that. Mark's approach actually had me all dazed right from the second line. I need to use Drools to accomplish a rather simple task, however the suggestions made by Mark had me all lost.
My requirement is that I have an input XML which my application should parse and output another XML. The output XML will have tags and values capturing the required business model. The structure of the
input XML is something like this:
<parent name="aaaaaaa">
<child value="sdfsdfsdf"/>
<child value="sdfsdfsdf"/>
<child value="sdfsdfsdf"/>
<child value="sdfsdfsdf"/>
</parent>
Now the transformation of this input XML has to be done condition to certain rules which our client will provide us. I thought Drools would fit in very well. However after reading and acquiring a basic understanding I came across this particular limitation.
My problem arises since, the input bean's parent tag can have varying number of child tags. As a consequence, I can't define a single Bean class to capture this XML data. I can capture the data in a HashMap, but then I can't access the
key-value pairs from the "when" block of a rule.
Arjun, as you suggested,
- can you tell me whether I can really utilize
DynaBeans to meet my ends in this particular case?
- Can you also let me know a simple approach I can adopt?
- also, if eval can be used in this case, can you pass across an example to show how to access say, the
key-values from a HashMap set in the asserted Bean object.
Amongst the other Rule Engines, I still think that Drools fits in best. A little help perhaps?
Thanks a lot!
Anirvan
On 5/15/07, Arjun Dhar <dhar_ar@yahoo.com> wrote:
Mark Proctor <mproctor <at> codehaus.org> writes:
>
>
> You need to alter the parser and the Extractor api, you also need to be
> able to deal with ShadowFacts, where we need to know the previous and
> current value.Further to that nested value should not change without
> notifying the parent fact in the network - i.e. correct network state
> must always been maintained. It's a complex area, we are looking at a
> work around that allows this declarative language, but rewrites it as
> an eval - so you don't get the performance advantages - but it's a
> quick work around for now.
> Mark
If what you want is the ability to extend the use of the class beyond what it
was designed for (like a Dyna Bean, I think it is that!), then as a work around
you could use 'eval' over your object methods also, but this practice is
discouraged for a few reasons.
The other more sophisticated approach is already given by Mark!
regards,
Arjun
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