Re: [rules-users] Drools Bug: Custom Operator with Maps results in Mvel Error

Uday, The short answer is: Drools supports pluggable evaluators only for direct fact attributes, with direct values as a second parameter. It is not possible to use nested access or map access when using pluggable operators. The workaround for now is to extract the value from the map before using your operator. MyValue( myField myoperator xxx ) from $myMap["someKey"] The long answer is: Drools process all direct attributes by himself, and delegates any nested access and map/collection access to MVEL. This is just a quick solution to avoid forcing users to wrap nested property access in eval() blocks. The problem with that is that it causes inconsistencies like this, between what drools processes natively and what it delegates to MVEL. As I mentioned in my previous e-mail, we had a team meeting last week and defined solving these inconsistencies in corner cases as one of our top goals for the next version of Drools. The idea is to eliminate these differences by always delegating constraint resolution to MVEL, while adding support in MVEL for any non-existing feature, like pluggable operators. Also, we want to add support to free form expressions in constraints, eliminating the requirement to have a field access on the left, operator in the center and value or parenthesized expression on the right, etc. Hope this helps, Edson 2010/10/28 Uday Kodukula <ukodukula(a)synacor.com&gt;: --   Edson Tirelli   JBoss Drools Core Development   JBoss by Red Hat @ www.jboss.com