Drools Java更新

Question

I am new to drool, please help me understand if I update the object after I call fire all rules, will it fire the rules as it does in the drools file?

like

rule "Hello World"
no-loop true
when
    message:Message (type=='Hello')
then
    modify(message){
        setType("Hi")//Fires other rule below
    }
    message.setMsgtext("Msg: Hello World, Drools");
    System.out.println("Hello World, Drools!");
end

rule "Hi World"
when
    message:Message (type=='Hi')
then
    modify(message){
        setType("Hello")
    }
    System.out.println("Hi World, Drools!");
end

whereas in JAVA code,

Message msg = new Message();
msg.setType("Hello");
//sessionObject = rbase.newStatefulSession();
sessionObject.insert(msg);
sessionobject.fireAllrules();
msg.setType("Hi"); //Here can it fire the rule? for me its not doing it

If it doesn't fire, does drool engine keep a msg as entirely different session object from Java runtime object, so its its not affected. If its not the concept behind, please help me understand

Thanks Chakri

Answer 1

The rules are not going to react upon your change. Drools will not keep a different 'copy' of the object, it just will not evaluate the rules. If you want to make drools aware of your modification you must use sessionObject.update(). And then don't forget to fireAllRules() again. Your code should look something similar to this:

Message msg = new Message();
msg.setType("Hello");
//sessionObject = rbase.newStatefulSession();
FactHandle handle = sessionObject.insert(msg);
sessionobject.fireAllrules();
msg.setType("Hi");
sessionObject.update(handle, msg) // rules are re-evaluated here
session.fireAllRules(); // fire any pre-activated rule

Hope it helps,