NPE in SlidingLengthWindow.assertFact when some event in window expired ----------------------------------------------------------------------- Key: JBRULES-3671 URL: https://issues.jboss.org/browse/JBRULES-3671 Project: JBRULES Issue Type: Bug Security Level: Public(Everyone can see) Components: drools-compiler (fusion) Affects Versions: 5.4.0.Final, 5.5.0.Beta1, 5.5.0.CR1 Reporter: Marek Winkler Assignee: Edson Tirelli Fix For: 6.0.0.Alpha1 Attachments: stackTrace.txt Consider the following DRL (taken from the CepEspTest integration test, the only modification is commenting out the {{@expires}} declaration): {code:title=test_CEP_collectWithWindows.drl} package org.drools; import java.util.List global List timeResults; global List lengthResults; declare OrderEvent @role( event ) //@expires( 2m ) end rule "collect with time window" when $list : List( empty == false ) from collect( $o : OrderEvent() over window:time(30s) ) then timeResults.add( $list.size() ); end rule "collect with length window" when $list : List( empty == false ) from collect( $o : OrderEvent() over window:length(3) ) then lengthResults.add( $list.size() ); end {code} When you insert more than 3 events and advance pseudo clock time such that an event in the length window expires, a NPE at {{org.drools.rule.SlidingLengthWindow.assertFact(SlidingLengthWindow.java:115)}} is thrown. See the attachment for complete stack trace. The original test with the {{@expires}} declaration uncommented passes. The problem seems not to be present in Drools 5.3.3.Final.