[rules-users] sequencing by business logic/ classcastexception in consequence
Joost de Vries
drools at ziener.org
Fri Jan 12 10:38:04 EST 2007
no problem. shall I mail it to you?
2007/1/12, Michael Neale <michael.neale at gmail.com>:
>
> Hi Joost. No problems re the names...
>
> I just think its happening there as its the "extractor" generated class
> causing it.
>
> Any chance you can wrap this up as a unit testable unit so we can try it
> out and see what/where the cast is happening?
>
> Ta,
>
> Michael
> (PS I am offline all week, so don't feel ignored !)
>
> On 1/12/07, Joost de Vries < drools at ziener.org> wrote:
> >
> > Hi Michael,
> >
> > The list is defined in terms of the superclass that both classes share.
> > And the previous and next methods both have the superclass as the return
> > type.
> >
> > So I'd expect
> > PreventieveInsluitingsTitel(previous==secondPosition [...]
> > to evaluate to
> > <instance of superclass> == <instance of subclass>
> > I'd expect this check to just fail when the objectreferences do not
> > refer to the same object. Not to cause a classcastexception.
> >
> > But the exception is thrown in the consequence part of the rule during
> > an invocation of modify( ).....
> >
> > So I'm not sure why this construction would be wrong and what would be
> > the right way to do it.
> >
> > oh, by the way; sorry for the dutch classnames. That must make the
> > problem harder to understand. In fact it's about convictions and the
> > subclasses are types of convictions.
> >
> > regards,
> >
> > Joost
> >
> > 2007/1/12, Michael Neale <michael.neale at gmail.com>:
> > >
> > > In terms of your problem, it seems to be to do with:
> > > PreventieveInsluitingsTitel(previous==secondPosition
> > > the secondPosition is not a compatible class with previous?
> > >
> > > I don't have any specific thoughts on computing a sequence in rules,
> > > unfortunately... maybe someone else does ? ;)
> > >
> > >
> > >
> > >
> > > On 1/11/07, Joost de Vries < drools at ziener.org> wrote:
> > >
> > > > Hi,
> > > >
> > > > I'm new to jBoss Rules and I'm hitting a few snags. I appreciate
> > > > your insight.
> > > >
> > > > Among other things I want to use business rules to compute the right
> > > > sequence of actions that conforms to legal business rules.
> > > > The only way I could think of to implement this using rules is to
> > > > use rewriting production rules similar to:
> > > > input: ACCAAAC
> > > > rule: CA -> AC
> > > >
> > > > My first question is: what other ways are there to compute a
> > > > sequence that conforms to sequencing business rules?
> > > >
> > > > My second question concerns the nullpointerexceptions and
> > > > classcastexceptions I'm encountering in my rules.
> > > > I've got a sequence of C's who are either B's or A's. I.e. C is the
> > > > common superclass. This superclass has the methods:
> > > >
> > > > public C getPrevious();
> > > > public C getNext();
> > > >
> > > > Actually it's in dutch so it's
> > > >
> > > > public class Straf extends InsluitingsTitel {}
> > > > and
> > > > public class PreventieveInsluitingsTitel extends InsluitingsTitel {}
> > > >
> > > > and
> > > > public abstract class InsluitingsTitel{
> > > > public C getPrevious();
> > > > public C getNext();
> > > > }
> > > >
> > > > The rule is as follows:
> > > >
> > > > rule "WSV 68.1"
> > > > when
> > > > // any PreventieveInsluitingsTitel should precede all Straf
> > > > secondPosition: Straf ( firstPosition: previous )
> > > > thirdPosition:
> > > > PreventieveInsluitingsTitel(previous==secondPosition, fourthPosition:next)
> > > > then
> > > > System.out.println( "switching wsv 68.1 "+secondPosition+"
> > > > "+thirdPosition);
> > > > thirdPosition.switchWithPrevious();
> > > > if(firstPosition!=null){
> > > > modify(firstPosition);
> > > > }
> > > > modify( secondPosition);
> > > > modify( thirdPosition);
> > > > if(fourthPosition!=null){
> > > > //in the next statement a classcastexception is thrown
> > > > modify(fourthPosition);
> > > > }
> > > > end
> > > >
> > > > results in a classcastexception. The sequence is at that moment {
> > > > Straf, Straf, PreventieveInsluitingsTitel, Straf } and the middle two items
> > > > are matched by the LHS secondPosition and thirdPosition.
> > > >
> > > > Here's the stacktrace.
> > > >
> > > > java.lang.ClassCastException: org.dji.domein.insgro.Straf
> > > > at
> > > > org.drools.base.org.dji.domein.insgro.PreventieveInsluitingsTitel$getPrevious.getValue(Unknown
> > > > Source)
> > > > at org.drools.base.ClassFieldExtractor.getValue (Unknown Source)
> > > > at org.drools.rule.Declaration.getValue(Unknown Source)
> > > > at com.sample.Rule_WSV_68_1_0ConsequenceInvoker.evaluate
> > > > (Rule_WSV_68_1_0ConsequenceInvoker.java:22)
> > > > at org.drools.common.DefaultAgenda.fireActivation (Unknown
> > > > Source)
> > > > at org.drools.common.DefaultAgenda.fireNextItem(Unknown Source)
> > > > at org.drools.common.AbstractWorkingMemory.fireAllRules(Unknown
> > > > Source)
> > > > at org.drools.common.AbstractWorkingMemory.fireAllRules (Unknown
> > > > Source)
> > > > at org.dji.domein.insgro.VolgordeTest.main(VolgordeTest.java:32)
> > > > org.drools.spi.ConsequenceException: java.lang.ClassCastException:
> > > > org.dji.domein.insgro.Straf
> > > > at org.drools.common.DefaultAgenda.fireActivation (Unknown
> > > > Source)
> > > > at org.drools.common.DefaultAgenda.fireNextItem(Unknown Source)
> > > > at org.drools.common.AbstractWorkingMemory.fireAllRules(Unknown
> > > > Source)
> > > > at org.drools.common.AbstractWorkingMemory.fireAllRules (Unknown
> > > > Source)
> > > > at org.dji.domein.insgro.VolgordeTest.main(VolgordeTest.java:32)
> > > > Caused by: java.lang.ClassCastException: org.dji.domein.insgro.Straf
> > > > at
> > > > org.drools.base.org.dji.domein.insgro.PreventieveInsluitingsTitel$getNext.getValue(Unknown Source)
> > > > at org.drools.base.ClassFieldExtractor.getValue(Unknown Source)
> > > > at org.drools.rule.Declaration.getValue(Unknown Source)
> > > > at com.sample.Rule_WSV_68_1_0ConsequenceInvoker.evaluate(Rule_WSV_68_1_0ConsequenceInvoker.java:22)
> > > >
> > > > ... 5 more
> > > >
> > > > Thanks in advance for your insight.
> > > >
> > > > Regards,
> > > >
> > > > --
> > > > Joost de Vries
> > > >
> > > >
> > > > _______________________________________________
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> > > > rules-users at lists.jboss.org
> > > > https://lists.jboss.org/mailman/listinfo/rules-users
> > > >
> > > >
> > > >
> > >
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> > >
> > >
> > >
> >
> >
> > --
> > Joost de Vries
> > 06 22375323
> > werk: joost.de.vries at ordina.nl
> > privé: joost at ziener.org
> >
> > --
> > Joost de Vries
> > 06 22375323
> > werk: joost.de.vries at ordina.nl
> > privé: joost at ziener.org
> > _______________________________________________
> > rules-users mailing list
> > rules-users at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
> >
>
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--
Joost de Vries
06 22375323
werk: joost.de.vries at ordina.nl
privé: joost at ziener.org
--
Joost de Vries
06 22375323
werk: joost.de.vries at ordina.nl
privé: joost at ziener.org
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