Jess likes to work with JavaBeans properties, and your 'Message' class
isn't very Bean-like, so it will be somewhat awkward to work with. I
think what you want your rule to do is print "valid" whenever a
RoutingMessage with a non-nil "EBID" property is asserted, right? So
your rule could look like
(defrule valid-message
(RoutingMessage (OBJECT ?o&:(neq (?o getProperty "EBID") nil)))
=>
(printout t "valid " crlf))
The lines on the left-hand-side of the rule -- i.e., before the "=>
-- are "patterns" that match facts in working memory. They are not
function calls. In the "{}" syntax you were using (but that I have not
used here) the left-hand-side of each expression is the name of a
property (a "slot") in a fact; since your object has no JavaBeans
properties of interest, this syntax is basically useless (see, I told
you your class would be awkward to work with.)
The syntax I've used here is a color followed by a function call that
returns boolean; it's called a "predicate constraint" and you can read
about that in the manual.
On Feb 17, 2010, at 11:59 AM, Kumar, Amitesh wrote:
Hi guys ,
I new to Jess rules and im struggling on the syntax
What im trying to do is execute a function on an object added to the
rete engine
Object been added
engine.getEngine().add(message);
engine.getEngine().run();
CLP file
1 (import com.standardbank.cibi.infra.zippy.dataobject.*)
2 (import com.standardbank.cibi.infra.zippy.jess.functions.*)
3
4 (deftemplate RoutingMessage (declare (from-class
RoutingMessage)))
5 (load-function GetProperties)
6
7 (defrule valid-message
8 ?ebid<- ( get-property OBJECT "EBID" )
9 (RoutingMessage {?ebid <> nil})
10 =>
11 (printout t "valid " crlf)
12 )
I get an exception
Caused by: Jess reported an error in routine Jesp.parsePattern.
Message: Bad slot name at token '?ebid'.
Program text: ( defrule valid-message ?ebid <- ( get-property
OBJECT "EBID" ) ( RoutingMessage { ?ebid at line 9 in file zippy.clp.
If I remove line 9) then it compiles but the rule doesn’t fire
Can anyone help me out
All my Function does Is
public class GetProperties implements Userfunction
{
public String getName() {
return "get-property";
}
public Value call(ValueVector valueVector, Context context)
throws JessException
{
String key = valueVector.get(2).stringValue(context);
RoutingMessage routingMessage = (RoutingMessage)
valueVector.get(1).externalAddressValue(context);
try {
return new Value(routingMessage.getProperty(key));
} catch (JMSException e) {
e.printStackTrace();
}
return null;
}
}
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Sandia National Labs
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