Thanks for the insight, br, Els --- On Wed, 11/9/11, Wolfgang Laun <wolfgang.laun(a)gmail.com&gt; wrote: From: Wolfgang Laun <wolfgang.laun(a)gmail.com&gt; Subject: Re: [rules-users] variables confusion Java/MVEL To: "Rules Users List" <rules-users(a)lists.jboss.org&gt; Date: Wednesday, November 9, 2011, 3:35 PM You cannot create variables on the Left Hand Side; there you can only bind (!) variable names (!) to matched facts or their attributes. -W On 9 November 2011 15:14, elsdestickere <elsdestickere(a)yahoo.com&gt; wrote: Hi, I'm confused about when en where to use Java or MVEL in a rule. In the example below I want to replace  " openRes.getMasterExemplaar().getBruikbareExemplaren()" with a variable. RHD: works with JAva expression:        List<Exemplaar> bruikEx = openRes.getMasterExemplaar().getBruikbareExemplaren(); but I prefer to create the variable in the LHS, but Java doesn't work here. Should this be a MVEL expression or should JAVA allways be possible? rule "GarandeerReservaties"    when        garRes : GarandeerReservatieTaak();        openRes : Reservatie() from repFact.getReservatieRepository().findVandaagOpenstaandeReservaties();     List<Exemplaar> bruikEx =openRes.getMasterExemplaar().getBruikbareExemplaren();       eval(Reservatie.getVandaagOpenstaandeReservaties().size() > 0 && openRes.getMasterExemplaar().getBruikbareExemplaren().size() != 0)    then        //List<Exemplaar> bruikEx = openRes.getMasterExemplaar().getBruikbareExemplaren();        bruikEx.get(0).setStatus(ExemplaarStatus.MOMENTEEL_GERESERVEERD);        openRes.setStatus(ReservatieStatus.GEGARANDEERD);        System.out.println( "Drools "+drools.getRule().getName()+": ocr: "+openRes.getAantalVandaagOpenstaandeConcurReservaties() + " bruikex: " +bruikEx.size() ); end (written in Dutch, but I think it will be ok to understand) br, Els -- View this message in context: http://drools.46999.n3.nabble.com/variables-confusion-Java-MVEL-tp3493632... Sent from the Drools: User forum mailing list archive at Nabble.com. _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users -----Inline Attachment Follows----- _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users