Re: [rules-users] Help debugging NPE

The problem seems not related to shadow facts, but to constraint resolution and fact data extraction. It might be a bug or not... need more info.

In any case, the offending rule is not the one you showed. The offending rule contains a double beta constraint in a join:

Can you narrow it down? Did you tried with Drools 5.0.1?

2009/6/24 Dirk Bergstrom <dirk(a)juniper.net <mailto:dirk@juniper.net>> I'm running into an NPE using Drools 4.0.7, and I'm stumped by it (stacktrace below). I made some changes to seemingly unrelated code, and this error started showing up. It would help me to understand what's going on if someone could tell me roughly what's going on here. Since the error is thrown by generated code (in what I assume is a shadow proxy), I can't tell what the offending null pointer is. I'm not even entirely sure what's triggering the bug (it happens half an hour into the run of big multi-threaded application with about 40K objects in the working memory). Is this happening because: *) getRli_nums() in one of my PRRecord objects is returning a null value? *) There is a null PRRecord object backing the shadow proxy? *) Some other thing is null? *) I'm running into a bug in Drools? I stuck in this rule: when $pr : PRRecord( rli_nums == null ) then System.out.println($pr.getId()); end And it didn't print anything, so I'm inclined to think that this is not a simple matter of something returning a null value... I'll be most appreciative of any help I can get. Here's the stacktrace: java.lang.NullPointerException at org.drools.base.net.juniper.dash.data.PRRecord13409648$getRli_nums.getValue(Unknown Source) at org.drools.base.ClassFieldExtractor.getValue(ClassFieldExtractor.java:127) at org.drools.base.evaluators.BaseMemberOfEvaluator.evaluateCachedRight(BaseMemberOfEvaluator.java:45) at org.drools.rule.VariableRestriction.isAllowedCachedRight(VariableRestriction.java:89) at org.drools.rule.VariableConstraint.isAllowedCachedRight(VariableConstraint.java:81) at org.drools.common.DoubleBetaConstraints.isAllowedCachedRight(DoubleBetaConstraints.java:164) at org.drools.reteoo.JoinNode.retractObject(JoinNode.java:189) at org.drools.reteoo.CompositeObjectSinkAdapter.propagateRetractObject(CompositeObjectSinkAdapter.java:375) at org.drools.reteoo.ObjectTypeNode.retractObject(ObjectTypeNode.java:189) at org.drools.reteoo.Rete.retractObject(Rete.java:215) at org.drools.reteoo.ReteooRuleBase.retractObject(ReteooRuleBase.java:211) at org.drools.reteoo.ReteooWorkingMemory.doRetract(ReteooWorkingMemory.java:79) at org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1250) at org.drools.common.AbstractWorkingMemory.update(AbstractWorkingMemory.java:1203) at net.juniper.dash.data.DataSource.reconcileAssertedRecords(DataSource.java:409)