It looks like a bug, as it should not raise a NPE no matter what.... which version of Drools are you using? Edson 2011/9/8 Bruno Freudensprung <bruno.freudensprung(a)temis.com&gt; > ** > > Hi Edson, hi all, > > To stick to the subject, I have a strange problem (stack trace in PS) with > a rule containing two accumulate calls, the result of the first one is > re-injected as the input of the second one. Those accumulate functions are > "home made". > The first one (tokenize) returns an ArrayList of Token objects built by > tokenizing the "text" of the Sentence objects. > The second one (build10windows) returns an ArrayList of Window objects, > each one them containing 10 consecutive tokens. > Here is the rule > > when > $budget : ManualAnnotation(text == "something") > *$tokens* : java.util.ArrayList() *from accumulate *($s : > Sentence(), *tokenize*($s)) > $windows : java.util.ArrayList() *from accumulate *($t : Token() > *from $tokens*, *build10windows*($t)) > # removed a part here but the problem occurs even without this > part > then > retract($budget); > > Is there anything else one should be aware of when implementing their own > accumulate function? I mean things related to the fact that "classical" > accumulate functions (sum, average) return an immutable object that does not > share anything with the context object. > Although accumulate, reverse, and getResult methods of my functions are > unit tested, I suspect something that could be related to stateless/stateful > considerations. > What do you think? > > Many thanks, > > Bruno. > > PS : > > The stack trace is: > at > org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39) > at > org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:927) > 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) > at > org.drools.command.runtime.rule.FireAllRulesCommand.execute(FireAllRulesCommand.java:99) > at > org.drools.command.runtime.rule.FireAllRulesCommand.execute(FireAllRulesCommand.java:33) > at > org.drools.command.runtime.BatchExecutionCommandImpl.execute(BatchExecutionCommandImpl.java:159) > at > org.drools.command.runtime.BatchExecutionCommandImpl.execute(BatchExecutionCommandImpl.java:81) > at > org.drools.impl.StatelessKnowledgeSessionImpl.execute(StatelessKnowledgeSessionImpl.java:262) > ... 5 more > Caused by: java.lang.NullPointerException > at > org.drools.reteoo.AccumulateNode.getFirstMatch(AccumulateNode.java:967) > at org.drools.reteoo.AccumulateNode.splitList(AccumulateNode.java:920) > at > org.drools.reteoo.AccumulateNode.removePreviousMatchesForLeftTuple(AccumulateNode.java:874) > at > org.drools.reteoo.AccumulateNode.retractLeftTuple(AccumulateNode.java:205) > at > org.drools.reteoo.CompositeLeftTupleSinkAdapter.doPropagateRetractLeftTuple(CompositeLeftTupleSinkAdapter.java:238) > at > org.drools.reteoo.CompositeLeftTupleSinkAdapter.propagateRetractLeftTupleDestroyRightTuple(CompositeLeftTupleSinkAdapter.java:138) > at > org.drools.reteoo.AccumulateNode.retractLeftTuple(AccumulateNode.java:212) > at > org.drools.reteoo.ObjectTypeNode.retractObject(ObjectTypeNode.java:240) > at > org.drools.reteoo.EntryPointNode.retractObject(EntryPointNode.java:231) > at > org.drools.common.AbstractWorkingMemory.retract(AbstractWorkingMemory.java:1288) > at > org.drools.base.DefaultKnowledgeHelper.retract(DefaultKnowledgeHelper.java:201) > at > org.drools.base.DefaultKnowledgeHelper.retract(DefaultKnowledgeHelper.java:214) > at > defaultpkg.Rule_Display_windows_0.defaultConsequence(Rule_Display_windows_0.java:21) > at > defaultpkg.Rule_Display_windows_0DefaultConsequenceInvoker.evaluate(Rule_Display_windows_0DefaultConsequenceInvoker.java:29) > at > org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:917) > ... 15 more > > > > Bruno. > > Le 24/08/2011 16:21, Edson Tirelli a écrit : > > > Yes, evaluation is incremental, so for every new fact, it will call > accumulate() and getResult(). > > We do want to reduce the calls to getResult(), improving performance, > but it is not easy to figure out a way, as from an engine perspective, it > never knows when the application is done inserting facts and it is time to > calculate the final result. > > Edson > > 2011/8/24 Bruno Freudensprung <bruno.freudensprung(a)temis.com&gt; > >> Hi, >> >> While testing my custom accumulation function I noticed an unexpected >> behavior (th'ats of course a personal point of view). >> It seems that Drools 5.1 calls accumulate(...) and getResult(...) as >> many times as the number of accumulated facts (accumulate, getResult, >> accumulate, getResult, etc...). >> Is it supposed to work like this? >> >> Best regards, >> >> Bruno. >> >> _______________________________________________ >> rules-users mailing list >> rules-users(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/rules-users >> > > > > -- > Edson Tirelli > JBoss Drools Core Development > JBoss by Red Hat @ www.jboss.com > > > _______________________________________________ > rules-users mailing listrules-users@lists.jboss.orghttps://lists.jboss.org/mailman/listinfo/rules-users > > > > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users > > -- Edson Tirelli JBoss Drools Core Development JBoss by Red Hat @ www.jboss.com _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users