当事实不再匹配时，从Drools获取一些事件

Question

Please have a look at the two code settings below.

Setting 1:

public class DroolsAnotherTest {
    private static KieSession kSession;
    private static Building building;
    private static FactHandle buildingFact;
    public static final void main(String[] args) {
        try {
            // load up the knowledge base
            KieServices ks = KieServices.Factory.get();
            KieContainer kContainer = ks.getKieClasspathContainer();
            kSession = kContainer.newKieSession("ksession-rules");
            building = new Building();
            building.setRooms(2);
            buildingFact = kSession.insert(building);
            kSession.fireAllRules();
        } catch (Throwable t) {
            t.printStackTrace();
        }
    }

    public static void fireAgain(){
        System.out.println("inside fireAgain method");
        kSession.fireAllRules(); // firing the rules second time
    }
public static class Building {

        public int rooms;
        public int getRooms() {
            return this.rooms;
        }
        public void setRooms(int rooms) {
            this.rooms = rooms;
        }
    }
}

And the .drl file

package com.sample

import com.sample.DroolsAnotherTest.Building;
import com.sample.DroolsAnotherTest;

rule "Building"
    when
        Building( rooms <3 )
    then
        System.out.println( "Building rule fired" );
        DroolsAnotherTest.firingAgain();
end

Upon running, the output is : Building rule fired

inside fireAgain method

---

Setting 2: Here I just changed the fireAgain() method to:

public static void fireAgain(){
                System.out.println("inside fireAgain method");
        kSession.delete(buildingFact);
        building.setRooms(4);
        kSession.insert(building);
        kSession.fireAllRules(); // firing the rule second time
}

everything else is same. Upon running, the output is same again : Building rule fired

inside fireAgain method

---

As per my understanding,

in Setting 1, the rule did not get fired second time because the fact has not changed in the working memory.

in Setting 2, the rule did not get fired second time because now the fact has updated and it does not match with the rule condition.

My question is, does Drools generate any event for the setting 2 ( the rule fired once but now is not fired again because fact has updated ?) In that way I can distinguish between : a rule did not get fired because the fact are unchanged and it did not get fired because now the fact does not match with rule condition ?

Answer 1

There is no way you can determine why a rule isn't put on the agenda.

You know when you update a fact, so if this interesting for some reason, register it in the fact or elsewhere.

And DO NOT, repeat: DO NOT, call fireAllRules while another such call on the same session is still executing. There may be all kind of unexpected effects.