Where can I see if a pattern failed in rule?

问题

I run a rule that contains a few patterns, I want to know which pattern failed:

I've tried to debug the code (drools 7.18.0), and didn't found the relevant place.

rule example:

rule "Trigger"
agenda-group "Trigger"
salience 100
    when
        $pcase : PCaseMgr()

        D1($id: id, type != null, type == "AAA")
        D2(aId == $id)

    then
        $pcase.printAnalyticsRuleLog(">>>>>>>>>>>>>>>>>>> In Trigger");
end

in the example above, if D1 pattern is passed, and D2 pattern is failed, where in the code (of drools 7.18.0) can i see if the pattern was failed?

回答1:

You can't. Because of the algorithm Drools uses internally, patterns are decomposed into nodes and nodes can be shared among multiple rules in your knowledge base. If you really need to know why a rule was not fire, then you can create other rules that will tell you that. In your example, you could create something like this:

rule "No Trigger because of No D2"
agenda-group "Trigger"
salience 100
    when
        $pcase : PCaseMgr()

        D1($id: id, type != null, type == "AAA")
        not D2(aId == $id)

    then
        $pcase.printAnalyticsRuleLog(">>>>>>>>>>>>>>>>>>> No Trigger because no D2");
end

Hope it helps,

来源：https://stackoverflow.com/questions/57593723/where-can-i-see-if-a-pattern-failed-in-rule