You’ve probably configured your system to be using persistence? In which case what you are persisting needs to be serializable so that it can be persisted Thomas *From:* rules-users-bounces(a)lists.jboss.org [mailto: rules-users-bounces(a)lists.jboss.org] *On Behalf Of *Wolfgang Laun *Sent:* 23 August 2010 12:17 *To:* Rules Users List *Subject:* [rules-users] counting facts of a kind As simple as it gets: rule countHigh when $n : Number() from accumulate ( $sgc : StartGoalConn() count( $sgc ) ) then System.out.println( "plain routes: " + $n ); end And yet, it fails: Exception in thread "main" org.drools.RuntimeDroolsException: java.lang.ClassCastException: rss.ixl.route.TrainStartGoalConn cannot be cast to java.io.Serializable Sure, adding "implements Serializable" to StartGoalConn fixes this. But why is this necessary? FYI, StartGoalConn is abstract superclass of TrainStartGoalConn - just in case this has some bearing on this issue. Best -W ------------------------------ ************************************************************************************** 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 ************************************************************************************** _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users

Wolfgang, The requirement for serializable classes even when not using persistence was a "mistake" made several versions ago and I believed it was fixed. What version of Drools are you using? If that is trunk, we need to fix it. The latest official release 5.1.

Anyway, workaround: for count(), you can simply write "count(1)" instead of using the actual variable,

Edson 2010/8/23 Wolfgang Laun <wolfgang.laun(a)gmail.com&gt; No, not knowingly :-) I'm using the simplest possible setup for > KnowledgeBase, KnowledgeBuilder, StatefulKnowledgeSession. > > Why should accumulate/count effect persistence? > > -W > > > 2010/8/23 Swindells, Thomas <TSwindells(a)nds.com&gt; > >> You’ve probably configured your system to be using persistence? >> >> In which case what you are persisting needs to be serializable so that it >> can be persisted >> >> >> >> Thomas >> >> >> >> *From:* rules-users-bounces(a)lists.jboss.org [mailto: >> rules-users-bounces(a)lists.jboss.org] *On Behalf Of *Wolfgang Laun >> *Sent:* 23 August 2010 12:17 >> *To:* Rules Users List >> *Subject:* [rules-users] counting facts of a kind >> >> >> >> As simple as it gets: >> >> rule countHigh >> when >> $n : Number() from accumulate ( $sgc : StartGoalConn() count( $sgc ) >> ) >> then >> System.out.println( "plain routes: " + $n ); >> end >> >> And yet, it fails: >> >> Exception in thread "main" org.drools.RuntimeDroolsException: >> java.lang.ClassCastException: rss.ixl.route.TrainStartGoalConn cannot be >> cast to java.io.Serializable >> >> Sure, adding "implements Serializable" to StartGoalConn fixes this. But >> why is this necessary? >> >> FYI, StartGoalConn is abstract superclass of TrainStartGoalConn - just in >> case this has some bearing on this issue. >> >> Best >> -W >> >> ------------------------------ >> >> >> ************************************************************************************** >> 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 >> >> ************************************************************************************** >> >> _______________________________________________ >> rules-users mailing list >> rules-users(a)lists.jboss.org >> https://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