[rules-users] NullPointerException while inserting Facts

[Swindells, Thomas]

The most likely reason for this is that one of your rules is trying to evaluate a value which is null.   The when part of a rule is evaluated as the fact is inserted and may be evaluated even if the then part will never be reached.

Looking at your stack trace it looks like the rule involved may have a NOT in it.  Have a careful look through your rules and see if there is a case where a null pointer may occur and/or try removing them one by one until it stops breaking, if that doesn’t work can you post your rules as well.

Thomas

From: rules-users-bounces at lists.jboss.org [mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Sebastian Furth
Sent: 23 March 2010 13:11
To: rules-users at lists.jboss.org
Subject: [rules-users] NullPointerException while inserting Facts

Hi,

we are currently trying to integrate DROOLS 5.1 in our project.
In our Project we have two different kinds of Facts, called Values and Inputs. We don't have any problems with inserting Input instances but sometimes when we try to insert an instance of the Value class (@see: http://www.pastie.org/private/juv7hh7rxahpluo5agu3q) we get the following NullPointerException:

java.lang.NullPointerException
    at org.drools.reteoo.LeftTuple.get(LeftTuple.java:265)
    at org.drools.reteoo.LeftTuple.get(LeftTuple.java:300)
    at org.drools.rule.VariableRestriction$ObjectVariableContextEntry.updateFromTuple(VariableRestriction.java:320)
    at org.drools.common.SingleBetaConstraints.updateFromTuple(SingleBetaConstraints.java:119)
    at org.drools.reteoo.NotNode.assertLeftTuple(NotNode.java:98)
    at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:117)
    at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:34)
    at org.drools.reteoo.NotNode.assertLeftTuple(NotNode.java:123)
    at org.drools.reteoo.CompositeLeftTupleSinkAdapter.doPropagateAssertLeftTuple(CompositeLeftTupleSinkAdapter.java:145)
    at org.drools.reteoo.CompositeLeftTupleSinkAdapter.createAndPropagateAssertLeftTuple(CompositeLeftTupleSinkAdapter.java:57)
    at org.drools.reteoo.LeftInputAdapterNode.assertObject(LeftInputAdapterNode.java:142)
    at org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:42)
    at org.drools.reteoo.AlphaNode.assertObject(AlphaNode.java:147)
    at org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateAssertObject(CompositeObjectSinkAdapter.java:360)
    at org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:344)
    at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:185)
    at org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:146)
    at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:1046)
    at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:1001)
    at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:788)
    at org.drools.impl.StatefulKnowledgeSessionImpl.insert(StatefulKnowledgeSessionImpl.java:216)
    at de.d3web.we.drools.DroolsAction.addFacts(DroolsAction.java:296)
    at de.d3web.we.drools.DroolsAction.createKnowledgeSession(DroolsAction.java:268)
    at de.d3web.we.drools.DroolsAction.execute(DroolsAction.java:67)

The weird thing is that we don't get this exception with all instances of the Value class - some of them can be inserted, others not. The objects are created correctly - we've already debugged this. The crash happens somewhere deeper in the drools api.

It would be really great if you could give us a hint how we could fix this problem.

Thank you in advance.

Best regards

Sebastian Furth

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