Did you try using: AlarmFailureEvent( btsNumber == $BTS.number, $ID : ID ) Note that btsNumber starts with a lowercase letter. Best, On Sun, May 30, 2010 at 9:04 PM, Djerir Smail <1983djerir(a)gmail.com <mailto:1983djerir@gmail.com>> wrote: Hello everybody, *I need help please **I am new in drools, to start I am trying to write some simple examples with drools fusion . I wrote a rule which print a message when an alarm is received multiple times during 20 minutes but i get this error * [java] Unable to create Field Extractor for 'BtsNumber' of '[ClassObjectType event=com.mfe.casestudy.pojo.AlarmFailureEvent]' in rule 'MaxBtsAlarmrule' : [Rule name='MaxBtsAlarmrule'] [java] java.lang.IllegalArgumentException: Could not parse knowledge. [java] at com.mfe.casestudy.test.Tester.prepareKnowledgeBase(Tester.java:73) [java] at com.mfe.casestudy.test.Tester.setUp(Tester.java:43) [java] at com.mfe.casestudy.test.Tester.main(Tester.java:87) [java] Exception in thread "main" java.lang.NullPointerException [java] at com.mfe.casestudy.test.Tester.prepareStatefulKnowledgeSession(Tester.java:58) [java] at com.mfe.casestudy.test.Tester.setUp(Tester.java:44) [java] at com.mfe.casestudy.test.Tester.main(Tester.java:87) [java] Java Result: 1 main: *This is my rule it calculates the number of alarms received from one BTS and if this number exceeds the threshold it prints a warning message * rule "MaxBtsAlarmrule" dialect "mvel" no-loop true salience 100 when $BTS : BTS() # check if the number of alarms of last 20 minutes exceeds # the BTS threshold $numOfAlarms : Number( intValue > $BTS.threshold ) from accumulate( AlarmFailureEvent( BtsNumber == $BTS.number, $ID : ID ) over window:time(3) from entry-point BTSAlarmStream, count($ID) ) then System.out.println("BTS should be restarted..."); end Finally this is the alarm event class public class AlarmFailureEvent implements Serializable { /** * */ private static final long serialVersionUID = 1L; public String BtsNumber = ""; private int code = 0; private int ID=0; public AlarmFailureEvent(String BtsNumber, int code ,int ID) { this.BtsNumber = BtsNumber; this.ID=ID; this.code=code; } public void setID(int iD) { this.ID = iD; } public int getID() { return this.ID; } public void setCode(int code) { this.code = code; } public int getCode() { return this.code; } public void setBtsNumber(String btsNumber) { this.BtsNumber = btsNumber; } public String getBtsNumber() { return BtsNumber; } } *Thank you * _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org <mailto:rules-users@lists.jboss.org> https://lists.jboss.org/mailman/listinfo/rules-users -- XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX Esteban Aliverti ------------------------------------------------------------------------ _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users