[rules-users] New in Drools, java.lang.NullPointerException at org.drools.reteoo.AccumulateNode.getFirstMatch(AccumulateNode.java:967)

[Wolfgang Laun]

Manuel,

I have reported this (or a very similar) problem
https://issues.jboss.org/browse/JBRULES-2887  with a small example to
reproduce.

The stack trace is not identical, so please try to reproduce this with a
small test case; it is bound to happen with a rule (Test Negativo Alarma
Acceso Portal Ubicacion UM) that modifies some fact that is used in an
"accumulate" phrase, (If this pattern is different from the one I gave, I'll
raise the issue priority to "critical".)

Cheers
Wolfgang


2011/3/30 Manuel Ortiz <manuel.ortizramos at gmail.com>

> Hello all!
>
> I am new in Drools but day by day, test by test, I think I get a bit more
> knowledge of how the rule engine works from user point of view. I've been
> adding rules to an alarm system, increasing the complexity and functionality
> in several steps. Unfortunately in the last step I found the following
> NullPointerException inside the rule engine...
>
> java.lang.NullPointerException
> at org.drools.reteoo.AccumulateNode.getFirstMatch(AccumulateNode.java:967)
> at
> org.drools.reteoo.AccumulateNode.modifyLeftTuple(AccumulateNode.java:329)
>  at
> org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateModifyChildLeftTuple(SingleLeftTupleSinkAdapter.java:239)
> at
> org.drools.reteoo.AccumulateNode.evaluateResultConstraints(AccumulateNode.java:640)
>  at org.drools.reteoo.AccumulateNode.assertObject(AccumulateNode.java:270)
> at org.drools.reteoo.BetaNode.modifyObject(BetaNode.java:312)
>  at
> org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateModifyObject(CompositeObjectSinkAdapter.java:460)
> at
> org.drools.reteoo.CompositeObjectSinkAdapter.propagateModifyObject(CompositeObjectSinkAdapter.java:428)
>  at org.drools.reteoo.AlphaNode.modifyObject(AlphaNode.java:160)
> at
> org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateModifyObject(CompositeObjectSinkAdapter.java:460)
>  at
> org.drools.reteoo.CompositeObjectSinkAdapter.propagateModifyObject(CompositeObjectSinkAdapter.java:428)
> at org.drools.reteoo.ObjectTypeNode.modifyObject(ObjectTypeNode.java:263)
>  at org.drools.reteoo.EntryPointNode.modifyObject(EntryPointNode.java:172)
> at
> org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1442)
>  at
> org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1349)
> at
> org.drools.base.DefaultKnowledgeHelper.update(DefaultKnowledgeHelper.java:183)
>  at
> org.drools.base.DefaultKnowledgeHelper.update(DefaultKnowledgeHelper.java:196)
> at
> es.simcasva.alarmas.rules.Rule_Test_Negativo_Alarma_Acceso_Portal_Ubicacion_UM_0.defaultConsequence(Rule_Test_Negativo_Alarma_Acceso_Portal_Ubicacion_UM_0.java:18)
>  at
> es.simcasva.alarmas.rules.Rule_Test_Negativo_Alarma_Acceso_Portal_Ubicacion_UM_0DefaultConsequenceInvoker.evaluate(Rule_Test_Negativo_Alarma_Acceso_Portal_Ubicacion_UM_0DefaultConsequenceInvoker.java:44)
>  at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:917)
> at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:856)
>  at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1071)
> at
> org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:785)
>  at
> org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:751)
> at
> org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:218)
>
> I've been trying to find the problem, and found a strange interaction
> between three rules that makes the null pointer to appear. The alarm system
> has many rules now and it is difficult to simplify the scenario, so I just
> would like to know what is the funcion of AccumulateNode object in order to
> have an idea of the NullPointerException possible cause.
>
> Can anyone help me?
>
> Thank you in advance for your time.
>
> Regards,
>
> Manuel Ortiz.
>
>
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