[rules-users] Drool Rule Error with "or not" condition

[Wolfgang Laun]

Binding a variable to a fact in a branch of an 'or' (as you are doing with
EtsExecutionOrderXref_core00) is not useful, since you cannot use this
binding in the consequence. (The rule might just as well fire due to the 2nd
term (the "or not...") being true, and then the variable would not be bound,
causing NPE.

If you do need this binding to access the fact in the consequence, you
should splt the rule.

-W

2009/12/2 Shah, Malay <Malay.Shah at morganstanley.com>

>  Thanks Mark. I removed the binding and the rule is compiled now, but
> while firing the rule over set of objects, I get a Null pointer exception.
> Here is the updated Drool rule:
>
> dialect "mvel"
> rule "Legacy ETSDB Rule"
> when
>
> EtsExecutionOrderHist_core0:EtsExecutionOrderHist_core(customerOrFirm !=
> "0")
>         EtsExecutionOrderXref_core00:EtsExecutionOrderXref_core
>         (
>             entityOID == EtsExecutionOrderHist_core0.entityOID,
>             entityRID == EtsExecutionOrderHist_core0.entityRID,
>             entityVID == EtsExecutionOrderHist_core0.entityVID,
>             referenceID != "2" && referenceIDType == "orderSubCapacity"
>         )
>         or
>         not(EtsExecutionOrderXref_core
>                 (
>                     entityOID == EtsExecutionOrderHist_core0.entityOID,
>                     entityRID == EtsExecutionOrderHist_core0.entityRID,
>                     entityVID == EtsExecutionOrderHist_core0.entityVID,
>                     referenceIDType == "orderSubCapacity"
>                 )
>             )
> then
>     System.out.println("Rule fired");
> end
>
> and here is the stack trace:
>
> Exception in thread "main" org.drools.runtime.rule.ConsequenceException:
> java.lang.NullPointerException
>  at
> org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:23)
>  at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:943)
>  at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:885)
>  at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1086)
>  at
> org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:660)
>  at
> org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:637)
>  at
> org.drools.reteoo.ReteooStatelessSession.execute(ReteooStatelessSession.java:203)
>  at com.ms.ruleutils.RuleProcessor.process(RuleProcessor.java:142)
>  at com.ms.ruleutils.RuleProcessor.process(RuleProcessor.java:73)
>  at
> com.ms.ieddata.dataQuality.dqWithRR.DQCommandLineMain.performDQ(DQCommandLineMain.java:291)
>  at
> com.ms.ieddata.dataQuality.dqWithRR.DQCommandLineMain.runEngine(DQCommandLineMain.java:196)
>  at
> com.ms.ieddata.dataQuality.dqWithRR.DQCommandLineMain.main(DQCommandLineMain.java:170)
> Caused by: java.lang.NullPointerException
>  at
> org.drools.base.mvel.DroolsMVELFactory.getTupleObjectFor(DroolsMVELFactory.java:182)
>  at
> org.drools.base.mvel.DroolsMVELFactory.setContext(DroolsMVELFactory.java:176)
>  at org.drools.base.mvel.MVELConsequence.evaluate(MVELConsequence.java:57)
>  at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:934)
>  ... 10 more
>
> After debugging through, DroolMVELFactory class object is looking for
> Declaration definition for "EtsExecutionOrderXref_core00", not finding it,
> and hence giving a null pointer exception. I am using Drools 5.0.1. Any idea
> about why this would happen? Does the rule seem right now?
> Thanks
>
> Malay Shah
>
>
>  ------------------------------
> *From:* rules-users-bounces at lists.jboss.org [mailto:
> rules-users-bounces at lists.jboss.org] *On Behalf Of *Mark Proctor
> *Sent:* Tuesday, December 01, 2009 6:56 PM
> *To:* Rules Users List
> *Subject:* Re: [rules-users] Drool Rule Error with "or not" condition
>
> You are binding the result of the 'or' to EtsExecutionOrderXref_core00 as
> the second part is a 'not' which returns nothing, how would it be bound to?
>
> Shah, Malay wrote:
>
>  Hi All,
>
> I have the following drool rule that has "or not" under Entity Block.
> Basically, the rule tries to check if there either exists an entity object
> EtsExecutionOrderXref_core00 with the given conditions, or the entity does
> not exist at all with some other conditions.
>
> dialect "mvel"
> rule "Legacy ETSDB Rule"
> when
> EtsExecutionOrderHist_core0:EtsExecutionOrderHist_core(customerOrFirm !=
> "0")
> EtsExecutionOrderXref_core00:
> (
>  EtsExecutionOrderXref_core
>  (
>   entityOID == EtsExecutionOrderHist_core0.entityOID , entityRID ==
> EtsExecutionOrderHist_core0.entityRID , entityVID ==
> EtsExecutionOrderHist_core0.entityVID , referenceID != "2" &&
> referenceIDType == "orderSubCapacity"
>  )
>  or not(EtsExecutionOrderXref_core
>  (
>   entityOID == EtsExecutionOrderHist_core0.entityOID , entityRID ==
> EtsExecutionOrderHist_core0.entityRID , entityVID ==
> EtsExecutionOrderHist_core0.entityVID , referenceIDType ==
> "orderSubCapacity"
>  ))
> )
> then
> end
>
> But, while compiling the rule, I am getting the following errors:
>
> org.drools.compiler.DroolsParserException: [ERR 101] Line 22:16 no viable
> alternative at input 'entityOID' in rule "Legacy ETSDB Rule" in pattern
> not,
>
> org.drools.compiler.DroolsParserException: [ERR 102] Line 22:68 mismatched
> input ',' expecting '(' in rule "Legacy ETSDB Rule" in pattern
> EtsExecutionOrderHist_core0.entityOID,
>
> org.drools.compiler.DroolsParserException: [ERR 102] Line 22:122 mismatched
> input ',' expecting '(' in rule "Legacy ETSDB Rule" in pattern
> EtsExecutionOrderHist_core0.entityOID in pattern
> EtsExecutionOrderHist_core0.entityRID,
>
> org.drools.compiler.DroolsParserException: [ERR 102] Line 22:176 mismatched
> input ',' expecting '(' in rule "Legacy ETSDB Rule" in pattern
> EtsExecutionOrderHist_core0.entityOID in pattern
> EtsExecutionOrderHist_core0.entityRID in pattern
> EtsExecutionOrderHist_core0.entityVID]
> I think the rule is correct, but am not able to figure out these
> compilation errors. Could anybody please comment on why this would happen?
>
> Thanks
>
> Malay Shah
>  ------------------------------
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