If you're creating those "shadow facts" using "assert", as you've
shown here, then the OBJECT slot is empty, of course. They're not
really shadow facts if you create them that way, since there are no
objects for them to "shadow". Jess will never create the Java object
for you. You must create the Java object, give it to Jess (using
"definstance" or "add") and then Jess creates the shadow fact from
that, setting the OBJECT slot to point to the object.
On Nov 4, 2009, at 7:03 AM, Marco Zappatore wrote:
Thanks for your suggestion.
The modified JESS code snippet now looks like the following one:
(defrule myRule
?fA <- (factA (slotA_name...) (slotB_name...))
?fB <- (factB (slotC_name...) (slotD_name...))
=>
(bind ?fC (assert
(factC
(slotE_name (?fA getSlotValue OBJECT))
(slotF_name...)
)
))
)
(call-my-java-method (?fc getSlotValue OBJECT)))
I've used getSlotValue method two times in order to show you the
following
behaviour:
The first one getSlotValue call works correctly and the actual ?fA
fact is
stored into slotE_name.
The second call (?fc getSlotValue OBJECT) returns NIL both if used
into
the JESS side (as shown above) and if used in Java with
val.factValue(context).getSlotValue("OBJECT").
What's wrong in the binding operation?
Thanks in advance
Marco Zappatore
Ernest Friedman-Hill wrote:
Nothing wrong with that, if that's what you need to do. Every shadow
fact also has a slot named OBJECT which contains the actual object,
and so if you wanted to match that, you could call "getClass()" on it
rather than using Class.forName().
Note if you use getShadowClassName() as suggested below, then you'll
get the name of the class used to define the template, which might be
an interface (in which case you can't instantiate it, of course.) If
you use the OBJECT slot, as I suggest, then you'll get the actual
class of the object behind the fact, and that may or may not be what
you actually want.
On Nov 3, 2009, at 7:26 AM, Marco Zappatore wrote:
I think that a possible solution could be the following
val.factValue(context).getDeftemplate().getShadowClassName()
and then instantiate a new instance starting from the string that
the above
method returns...
In any case, I'd like to know your opinion...
Marco Zappatore wrote:
Dear Jess users,
I have a rule "myrule" that fires whenever two facts with specific
slot
contents are found within the working memory.
These facts are shadow facts.
Then I have a java user function "myUserFunction" that passes those
two
facts (using their pointers, let's say ?f1 and ?f2) to a Java
program.
My question is: is it possible to get those facts and instantiate
them
again in Java?
In other words the procedure is:
1) define a java bean
2) assert shadow facts from that java bean with different slot
contents
each time
3) find a given fact with a given content using a proper rule
4) pass the fact to a java program
5) create a new instance of the java bean with the content just
retrieved
the problem resides at point n°5 because actually I'm using
Value val = vv.get(1).resolveValue(context);
Using val.factValue(context)) I can verify that the content is
correct but
how can I use val to instantiate a new Java Bean?
Any help is appreciated, thanks in advance.
Marco Zappatore
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Informatics & Decision Sciences, Sandia National Laboratories
PO Box 969, MS 9012, Livermore, CA 94550
http://www.jessrules.com
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