Hi Wolfgang, Can you please open a JIRA for this. It seems the consequence is not properly managing the scope of $m. I.e., it must either cache it locally or queue the WMA until it executes completely. Thanks, Edson On Fri, Feb 10, 2012 at 6:52 AM, Wolfgang Laun <wolfgang.laun(a)gmail.com&gt;wrote: > 5.3.0 Final. > > KnowledgeBase using STREAM, running a stateful session in one thread, > inserting events from another fact. > > class Event{ String name; } > class Monitor{ Event event; String name; } > > rule "start monitoring" > when > $e: Event($name: name) > not Monitor( name == $name ) > then > insert( new Monitor( $e, $name ) ); > end > > rule "timeout" > timer( int: 10s ) > when > $m: Monitor( name == $name ) > $e: Event($name: name) > then > retract( $m ); // ======================= > retract( $m.getEvent() ); // ======================== > end > > This order of retracts results in a NPE, see the dump below. > > Reversing these two works correctly. > > Exception in thread "main" Exception executing consequence for rule > "start monitoring" in hashcode: java.lang.NullPointerException > at > org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39) > at > org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1101) > at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1029) > at > org.drools.common.DefaultAgenda.fireUntilHalt(DefaultAgenda.java:1229) > at > org.drools.common.AbstractWorkingMemory.fireUntilHalt(AbstractWorkingMemory.java:753) > at > org.drools.common.AbstractWorkingMemory.fireUntilHalt(AbstractWorkingMemory.java:729) > at > org.drools.impl.StatefulKnowledgeSessionImpl.fireUntilHalt(StatefulKnowledgeSessionImpl.java:234) > at hashcode.Main.execute(Main.java:148) > at hashcode.Main.main(Main.java:206) > Caused by: java.lang.NullPointerException > at > org.drools.base.hashcode.StateEvent42211789$getItemName.getValue(Unknown > Source) > at org.drools.base.ClassFieldReader.getValue(ClassFieldReader.java:87) > at org.drools.rule.Declaration.getValue(Declaration.java:219) > at > hashcode.Rule_start_monitoringDefaultConsequenceInvoker.evaluate(Unknown > Source) > at > org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1091) > ... 7 more > > > _______________________________________________ > rules-dev mailing list > rules-dev(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-dev > > -- Edson Tirelli JBoss Drools Core Development JBoss by Red Hat @ www.jboss.com _______________________________________________ rules-dev mailing list rules-dev(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-dev