[rules-users] Verify if an objects attribute exists

I'm having difficulty writing this rule. Background information: A User can have a supervisor but it's not required. When viewing User information I want to verify that the logged in user is either the current user or the currentUser's supervisor but I throw an exception when the supervisor object is null on the currentUser. The target is the User being viewed and I have a global object that is the current user. How can I check to see if the supervisor exists before evaluating if the currentUser and the supervisor are equal? rule 'CanViewUserData' dialect 'mvel' when $user : User() $supervisor : User( ) from $user.userProfile.supervisor $check: PermissionCheck(target == $user, action == "viewUserData") eval(isUserMatching($user)) || eval (isUserMatching($supervisor)) then System.out.println("The currentUser CanViewUserData"); $check.grant(); end -- View this message in context: http://drools-java-rules-engine.46999.n3.nabble.com/Verify-if-an-objects-... Sent from the Drools - User mailing list archive at Nabble.com.