I found the problem - noobie mistake! As you suggested there was another rule which was being triggered by the insert and there was a bug in that rule. I was focusing on the insert because this is where the stack-trace was indicating I look. Thanks Thomas! /Ryan. ________________________________ From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Swindells, Thomas Sent: 23 March 2010 13:59 To: Rules Users List Subject: Re: [rules-users] NullPointerException while inserting Facts 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(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Sebastian Furth Sent: 23 March 2010 13:11 To: rules-users(a)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 ________________________________ ************************************************************************************** This message is confidential and intended only for the addressee. If you have received this message in error, please immediately notify the postmaster(a)nds.com and delete it from your system as well as any copies. The content of e-mails as well as traffic data may be monitored by NDS for employment and security purposes. To protect the environment please do not print this e-mail unless necessary. NDS Limited. Registered Office: One London Road, Staines, Middlesex, TW18 4EX, United Kingdom. A company registered in England and Wales. Registered no. 3080780. VAT no. 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My standard "quick guess" is that you should also check for fields that may be subject to unboxing in some CE condition. -W 2010/3/23 Sebastian Furth <sebastian.furth(a)googlemail.com&gt;