[rules-users] Simple rulebase not behaving as expected

[Edson Tirelli]

   Well, I'm not sure why are you constraining your rule using the class
Object. What is happening is that the engine always inserts a fact into the
engine known as InitialFact, that as all objects in java, is a subclass of
Object, and that is why the rule fires.
   If instead of Object, you use a different class, like Integer for
instance, to constrain your rule, you will get the behavior you are looking
for.

   []s
   Edson

2007/8/22, Dean Jones <dean.m.jones at gmail.com>:
>
> Hi,
>
> I have the following simple rulebase:
>
> package org.drools.examples
> rule "Hello World"
>         when
>             o : Object( )
>         then
>             System.out.println("Hello world (o=" + o + ")");
> end
> rule "Goodbye World"
>         when
>             not Object( )
>         then
>             System.out.println("Goodbye cruel world");
> end
>
> and the following code:
>
> public class TestReadRuleFile {
>
> public static void main(String[] args) throws Exception {
>   PackageBuilder builder = new PackageBuilder();
>   builder.addPackageFromDrl(
>     new InputStreamReader(
>         TestReadRuleFile.class.getResourceAsStream("test.drl")));
>   Package pkg = builder.getPackage();
>   RuleBase rulebase = RuleBaseFactory.newRuleBase();
>   rulebase.addPackage(pkg);
>   StatefulSession session = rulebase.newStatefulSession();
>   session.fireAllRules();
> }
>
> }
>
> which produces the following output:
>
> Hello world (o=org.drools.reteoo.InitialFactImpl at 4dde85f0)
>
> I expected the "Goodbye World" rule to fire, as there should not be
> any Objects in the working memory. If I change my code to insert an
> object into the working memory as follows:
>
>   session.insert(new Object());
>
> I now get the following output:
>
> Hello world (o=org.drools.reteoo.InitialFactImpl at 4dde85f0)
> Hello world (o=java.lang.Object at 17ba38f)
>
> In this case, I expected the "Hello World" rule to fire only once. Any
> thoughts on what I'm doing wrong here?
>
> Thanks,
>
> Dean.
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>



-- 
  Edson Tirelli
  Software Engineer - JBoss Rules Core Developer
  Office: +55 11 3529-6000
  Mobile: +55 11 9287-5646
  JBoss, a division of Red Hat @ www.jboss.com
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