[rules-users] variable instance check?

[Eric Miles]

In java, I can check to see if a 2 variables references the same 
instance as such:

Object a = new Object();
Object b = a;

a == b




Is there a way to do this in Drools?  For instance, if there is an 
object in working memory and it is a specific instance, I do not want to 
fire the rule again.  ie:

rule "User Lookup UserKey"
     salience 10000
     when
         com.kronos.taws.model.User(empId == null, $key:empIdKey)
     then
         System.out.println("Firing 2!");
         insert($key);

end

I want to ensure that $key is not already in working memory.  But mind 
you, there might be other $keys that are in working memory that do not 
belong to this particular com.kronos.taws.model.User instance.  I do not 
want this rule to fire because I have subsequent rules that will make 
empId a value other than null.

I attempted to do this:

rule "User Lookup UserKey"
	when
		com.kronos.taws.model.User(empId == null, $key:empIdKey)
		not UserKey(this == $key)
	then
		System.out.println("Firing 2!");
		insert($key);
		
end

However, I still think this is doing an equality check because once the 
$key object is updated in another rule, this rule is fired again!

Thanks in advance!
Eric