In order to make writing drl files easy and not requiring writers to be developers, I have written some JavaAssist code that dynamically creates a subclass and new methods in memory. If for example there is a REAL java class called 'com.foo.Instance'. Via javasssist, I create a new in-memory subclass called 'com.foo.InstanceEx'. The new class dynamically creates a new getter called getFoo(). The drl writer would like to directly reference 'foo' in the drl file like so: when i : Instance(foo == 'fee') The problem is, in order to reference foo, I would need the drl file to do this: import com.rrd.xspace.drools.InstanceEx; But I cannot do that because InstanceEx does not exist at runtime. The error I get, which is an obvious one, is "Unable to create Field Extractor for 'foo' of '[ClassObjectType class=com.foo.Instance]' in rule 'Test' : [Rule name='Test']" Is there a way to include a dynamic import of a JavaAssist class while I am constructing the KnowledgeBase instances to run the rules so that I can reference that new method? I would hope to have something similar to: KnowledgeBuilder kbuilder = .... kbuilder.addImport("com.foo.InstanceEx") or kbuilder.addClass(Class.forName("com.foo.InstanceEx")) Any help GREATLY appreciated. -- View this message in context: http://drools-java-rules-engine.46999.n3.nabble.com/Challenge-Using-javas... Sent from the Drools - User mailing list archive at Nabble.com.