I also was getting this error. I brought out package building logic to execute once, and KnowledgeSession realted logic to repeat the required number of times. Seems there required some delay in preparing rules related classes into one package during iteration. Above step was working fine for me. Pseudo code: KnowledgeBuilder kbuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); // this will parse and compile in one step // get the compiled packages (which are serializable) Collection<KnowledgePackage> pkgs = null; // add the packages to a knowledgebase (deploy the knowledge packages). KnowledgeBase kbase = null; StatefulKnowledgeSession ksession = null; // constructor to be called once public RuleEngine (byte[] rules) { kbuilder.add(ResourceFactory.newByteArrayResource(rules),ResourceType.DRL); // Check the builder for errors if (kbuilder.hasErrors()) { System.out.println(kbuilder.getErrors().toString()); throw new RuntimeException("Unable to compile drl."); } pkgs = kbuilder.getKnowledgePackages(); // add the packages to a knowledgebase (deploy the knowledge packages). kbase = KnowledgeBaseFactory.newKnowledgeBase(); kbase.addKnowledgePackages(pkgs); } // this method will be called required number of times public void fire(Object obj) { ksession = kbase.newStatefulKnowledgeSession(); ksession.addEventListener(new DebugAgendaEventListener()); ksession.addEventListener(new DebugWorkingMemoryEventListener()); // setup the audit logging //KnowledgeRuntimeLogger logger = KnowledgeRuntimeLoggerFactory.newFileLogger(ksession, "log/drools.log"); ksession.insert(obj); ksession.fireAllRules(); //logger.close(); ksession.dispose(); } Check this out. Thanks & Regards Santhosh From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Wolfgang Laun Sent: Tuesday, September 27, 2011 4:10 PM To: Rules Users List Subject: Re: [rules-users] Getting Exception while running rules continuously on the Event Streams from Mule Component. Drools version? Looks like a bug, I've seen similar NPE reports. -W On 27 September 2011 12:23, Hari Kishan <HariKishan.Tammana@pass-consulting.com<mailto:HariKishan.Tammana@pass-consulting.com>> wrote: Please find attached the rule Code (.drl) below. Frequently getting this below Exception while running rules. Exception caught while executing action: org.drools.reteoo.PropagationQueuingNode$PropagateAction@41c317<mailto:org.drools.reteoo.PropagationQueuingNode$PropagateAction@41c317> java.lang.NullPointerException at org.drools.util.LeftTupleList.toArray(LeftTupleList.java:106) at org.drools.util.LeftTupleList.toArray(LeftTupleList.java:11) at org.drools.reteoo.CollectNode.assertObject(CollectNode.java:256) at org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:42) at org.drools.reteoo.RightInputAdapterNode.assertLeftTuple(RightInputAdapterNode.java:135) at org.drools.reteoo.SingleLeftTupleSinkAdapter.doPropagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:117) at org.drools.reteoo.SingleLeftTupleSinkAdapter.propagateAssertLeftTuple(SingleLeftTupleSinkAdapter.java:28) at org.drools.reteoo.FromNode.evaluateAndPropagate(FromNode.java:156) at org.drools.reteoo.FromNode.assertLeftTuple(FromNode.java:104) at org.drools.reteoo.CompositeLeftTupleSinkAdapter.doPropagateAssertLeftTuple(CompositeLeftTupleSinkAdapter.java:145) at org.drools.reteoo.CompositeLeftTupleSinkAdapter.propagateAssertLeftTuple(CompositeLeftTupleSinkAdapter.java:39) at org.drools.reteoo.JoinNode.assertObject(JoinNode.java:175) at org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:42) at org.drools.reteoo.PropagationQueuingNode$AssertAction.execute(PropagationQueuingNode.java:326) at org.drools.reteoo.PropagationQueuingNode.propagateActions(PropagationQueuingNode.java:221) at org.drools.reteoo.PropagationQueuingNode$PropagateAction.execute(PropagationQueuingNode.java:394) at org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:1486) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:158) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:122) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:80) at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:28) at org.mule.module.drools.Drools.assertEvent(Drools.java:165) at org.mule.module.bpm.Rules.handleEvent(Rules.java:131) at org.mule.module.bpm.RulesComponent.doInvoke(RulesComponent.java:84) at org.mule.component.AbstractComponent.invokeInternal(AbstractComponent.java:120) at org.mule.component.AbstractComponent.access$000(AbstractComponent.java:56) at org.mule.component.AbstractComponent$1$1.process(AbstractComponent.java:234) at org.mule.processor.chain.DefaultMessageProcessorChain.doProcess(DefaultMessageProcessorChain.java:88) at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:89) at org.mule.processor.chain.InterceptingChainLifecycleWrapper.doProcess(InterceptingChainLifecycleWrapper.java:63) at org.mule.processor.chain.AbstractMessageProcessorChain.process(AbstractMessageProcessorChain.java:89) at org.mule.processor.chain.InterceptingChainLifecycleWrapper.process(InterceptingChainLifecycleWrapper.java:94) at org.mule.component.AbstractComponent.process(AbstractComponent.java:154) at org.mule.processor.AbstractInterceptingMessageProcessor.processNext(AbstractInterceptingMessageProcessor.java:93) at org.mule.interceptor.AbstractEnvelopeInterceptor.process(AbstractEnvelopeInterceptor.java:55) at org.mule.processor.AsyncInterceptingMessageProcessor.processNextTimed(AsyncInterceptingMessageProcessor.java:118) at org.mule.processor.SedaStageInterceptingMessageProcessor$SedaStageWorker.doWork(SedaStageInterceptingMessageProcessor.java:197) at org.mule.processor.SedaStageInterceptingMessageProcessor$SedaStageWorker.doRun(SedaStageInterceptingMessageProcessor.java:178) at org.mule.work.AbstractMuleEventWork.run(AbstractMuleEventWork.java:43) at org.mule.work.WorkerContext.run(WorkerContext.java:309) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:619) http://drools.46999.n3.nabble.com/file/n3372189/sensors.drl sensors.drl -- View this message in context: http://drools.46999.n3.nabble.com/Getting-Exception-while-running-rules-c... Sent from the Drools: User forum mailing list archive at Nabble.com. _______________________________________________ rules-users mailing list rules-users@lists.jboss.org<mailto:rules-users@lists.jboss.org> https://lists.jboss.org/mailman/listinfo/rules-users

It may be worth you trying a later version of drools to see whether the issue still exists - there have been quite a few bug fixes since then! In theory it shouldn't be too much work to change - check the release notes for maven group/project id changes, but there are some subtle differences in some of the rule syntax validation in places which may or may not make it painful. Thomas ************************************************************************************** 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. GB 603 8808 40-00 **************************************************************************************

Looking at the rule I see that you don't really need $activeAlarms : ArrayList() except for computing $alarms : ArrayList(). Try doing this by a single collect, putting all constraints into the Alarm() pattern. -W On 27 September 2011 15:55, HariKishan <HariKishan.Tammana(a)pass-consulting.com&gt; wrote:

On 27 September 2011 17:25, Hari Kishan <HariKishan.Tammana(a)pass-consulting.com&gt; wrote: Another alternative is to use an accumulate to compose the List by init - action - reverse - result. Perhaps this isn't as vulnerable as collect appears to be. -W

@wolfgang Yesterday you told me to use accumulate instead of collect. But i could not find the right way to use accumulate here. Please see below my rules when condition [ collect function(Bold & Italic) ] and please tell me how can i use accumulate there. If possible change the conditional element to accumulate with appropriate changes. when // "Sensor Data Idem Stream" is where Mule sends the Sensordata facts // for each Alarm / Sensordata combination that is identified via the vehicle id $sd : SensorDataIdem ($vid : vehicleId) from entry-point "Sensor Data Idem Stream" // Set a references for later on the initial facts $av : AlarmVehicle(vehicleId == $vid) //The Condition to be added to get the active Alarms from the List of Alarms eval($av!=null && $av.getAlarms()!=null && $av.getAlarms().size()>0) /*$alarms : ArrayList(size>0) from collect ( Alarm( ( (activation == AlarmConstants.ALWAYS_ACTIVE) || (activation == AlarmConstants.ACTIVE_ONLY_ONTOUR && $sd.onTour == true) || (activation == AlarmConstants.ACTIVE_ONLY_NOT_ONTOUR && $sd.onTour == false) || (activation == AlarmConstants.ACTIVE_ONLY_ONMOVING && $sd.onMove == true) || (activation == AlarmConstants.ACTIVE_ON_TIME_WINDOW ) ) && ( ( (geofenceCustomer == 0) || (geofenceCustomer == 1 && $sd.inCustomerGeoFence == true) || (geofenceCustomer == 2 && $sd.inCustomerGeoFence == false) ) && ( (geofenceDepot == 0) || (geofenceDepot == 1 && $sd.inDepotGeoFence == true) || (geofenceDepot == 2 && $sd.inDepotGeoFence == false) ) ) ) from $av.getAlarms() )*/ eval($alarms!=null) then ........... -- View this message in context: http://drools.46999.n3.nabble.com/Getting-Exception-while-running-rules-c... Sent from the Drools: User forum mailing list archive at Nabble.com.

The below code which you wrote is very appropriate but where should we mention on which collection we are traversing the conditions on . Like in collect $alarms : ArrayList(size>0) from collect ( Alarm( ...... ) from av.getAlarms() ) -- View this message in context: http://drools.46999.n3.nabble.com/Getting-Exception-while-running-rules-c... Sent from the Drools: User forum mailing list archive at Nabble.com.

Same place: accumulate ( Alarm( ... ) from .... , init(...),... ) -W 2011/9/28 HariKishan <HariKishan.Tammana(a)pass-consulting.com&gt;

@Thomas, Those Drools library is part of the Mule ESB 3.2.0 I think it would be very risky to change the libraries. As there might be some version dependencies (Compatibility issues). If you have any other idea of how to fix it ???? In the mean while I will checking by replacing the drools library and check it. -- View this message in context: http://drools.46999.n3.nabble.com/Getting-Exception-while-running-rules-c... Sent from the Drools: User forum mailing list archive at Nabble.com.