There are two solutions: 1.delete the Janino compiler in Seam lib and use Eclipse compiler. You can get the Eclipse compiler after downloading the Drools 4.0 binary. In the drools/lib, you see a core-xxxx.jar. That is Eclipse compiler. Drop it into your Seam lib folder, edit your build.xml, edit your application.xml. 2. Drools 4.0 uses Eclipse compiler by default. You can use Janino compiler, but you need to provide a conf file. Example please see here: http://anonsvn.labs.jboss.com/labs/jbossrules/trunk/drools-compiler/src/m... Regards, Ellen View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4068565#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...