I need to call a java function in the LHS (When part of the DRL) like so: When eval(DataComparator.compare("key1", "key2")) where key1 and key2 are keys into a Map encapsulated by DataComparator class. How do I pass the Map to the DataComparator class in the first place. Do I have to do like so: eval(DataComparator.init(Map<String, String> map) eval(DataComparator.compare("key1", "key2") This all seems like a bad hack to me. What are the standard best practice to achieve what I need? Also eval are slow why? is eval the only way to call a function in the When part? thx! -- View this message in context: http://drools.46999.n3.nabble.com/calling-a-function-in-When-of-DRL-tp402... 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