Later on I found out that it was caused by the mvel-x-x.jar Drools 5.x depends on. I previously had a different version under the lib directories on glassfish server and it got picked up. Double check your lib folders under $GLASSFISH_HOME to make sure you don't have any .jar from previous versions of Drools. It might resolve the problem. Good luck. On Wed, May 26, 2010 at 7:21 AM, Dinesh kumar [via Drools - Java Rules Engine] <ml-node+844751-2092748442-80491@n3.nabble.com&lt;ml-node%2B844751-2092748442-80491(a)n3.nabble.com&gt; -- View this message in context: http://drools-java-rules-engine.46999.n3.nabble.com/Problem-using-Oracle-... Sent from the Drools - User mailing list archive at Nabble.com.