You can create a rule that initializes your global, preferrably with a high salience so it gets executed first: rule "InitializeGlobal" salience 100 when then ArrayList objectList = new ArrayList(); objectList.add("1"); objectList.add("2"); drools.getWorkingMemory().setGlobal("objectList", objectList); end Kris ----- Original Message ----- From: "drools_user" <jkraemer(a)cs.tufts.edu&gt; To: <rules-users(a)lists.jboss.org&gt; Sent: Wednesday, October 24, 2007 7:35 PM Subject: [rules-users] Initialize Global > > How do I initialize a global fact in the drl file? I want use the JSR94 > API > and avoid using the Drools API inside the Java code. I would like to > access > the same variable every execution of a stateful session without having to > reinstantiate the variable after each execution? > > Basically I want to define a global like this: > # Define global variable > global List objectList ; > > # Part that does not work > objectList = new ArrayList() ; > objectList.add("1"); > objectList.add("2"); > > > Thanks > -- > View this message in context: > http://www.nabble.com/Initialize-Global-tf4685186.html#a13388685 > Sent from the drools - user mailing list archive at Nabble.com. > > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users

> That initialized my global but the rule still runs every execution. > Can I > disable the rule after the first execution? What do you mean by "every execution". A rule should only be executed once, unless it gets reactivated (which should not be the case in this situation). > I would like to use (if (objectList==null)). My list is not > immutable. Can > I make a similar rule for the LHS? You can test whether the global is null using eval( objectList == null ) in the LHS of the rule. Kris _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users

It's normal. Globally, the rule engine works in two steps : - first : the activation (the "when" statement) - second : the execution (the "then" statement) with salience, ruleflow ... In your test, you have in the first step objectList = null and in the second step objectList = [1, 2]. If you want to re-activate your rule, you have to do an update/insert/remove action... But you can't do that with globals. So you need to use the WM facts. Waruzjan Shahbazian-2 wrote: > I have the same "problem", but eval(objectList == null) doesn't work. If > I don't execute "drools.getWorkingMemory().setGlobal()" it "works fine", > as if the rule activates and the object is null. > > global List objectList; > > rule "Start" > salience 101 > when > #conditions > then > objectList = new ArrayList() ; > objectList.add("1"); > objectList.add("2"); > System.out.println("Start objectList:"+objectList); > //drools.getWorkingMemory().setGlobal("objectList", objectList); > end > > rule "end" > salience 97 > when > eval (objectList == null) > then > System.out.println("End objectList: "+objectList); > end > > gives: > > Start objectList:[1, 2] > End objectList: null > > Next I uncomment the "drools.getWorkingMemory().setGlobal("objectList", > objectList);" and run the rule again an get: > > Start objectList:[1, 2] > End objectList: [1, 2] > > so the objectList isn't null, but the rule still activates... > > Kris Verlaenen schreef: > >>> That initialized my global but the rule still runs every execution. >>> Can I >>> disable the rule after the first execution? >>> >> What do you mean by "every execution". A rule should only be executed >> once, unless it gets reactivated (which should not be the case in this >> situation). >> >> >>> I would like to use (if (objectList==null)). My list is not >>> immutable. Can >>> I make a similar rule for the LHS? >>> >> You can test whether the global is null using eval( objectList == null >> ) in the LHS of the rule. >> >> Kris >> _______________________________________________ >> rules-users mailing list >> rules-users(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/rules-users >> > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users > > >

This is in essence already catered for - you need a LHS fact. A global is just a holder for some (immutable) set of values\functions to make life easier for common (immutable) values\functions your rule may need. If you want to start making the global mutable for RETE to "use" the changes they become facts. >> rule "Start" >> salience 101 >> when >> then >> MyGlobalObject myGlobal = new MyGlobalObject(); >> ArrayList objectList = new ArrayList() ; >> objectList.add("1"); >> objectList.add("2"); >> myGlobal.setList(objectList); >> System.out.println("Start objectList:" + objectList); >> insert(myGlobal); >> end >> >> rule "end" >> salience 97 >> when >> $g : MyGlobalObject( list != null ) >> then >> System.out.println("End objectList: " + $g.getList()); >> end >> -----Original Message----- From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Waruzjan Shahbazian Sent: 30 October 2007 09:31 To: Rules Users List Subject: Re: [rules-users] Initialize Global Thanks, that sounds logical to me. I guess I just have to "trust" that the rule where the array gets initialised activates earlier than the rule where I need the array. That shouldn't be a problem since I use salience and to avoid nullpoint exceptions I can use the if(objectList != null) in the "Then" part of the rule where I need the array. Maybe an idea for the drools developers to create an "update" function for the globals so we can eval on them too...in the future. vdelbart schreef: > It's normal. > > Globally, the rule engine works in two steps : > - first : the activation (the "when" statement) > - second : the execution (the "then" statement) with salience, ruleflow > ... > In your test, you have in the first step objectList = null and in the > second > step objectList = [1, 2]. > > If you want to re-activate your rule, you have to do an > update/insert/remove > action... But you can't do that with globals. So you need to use the WM > facts. > > > > Waruzjan Shahbazian-2 wrote: > > >> I have the same "problem", but eval(objectList == null) doesn't work. If >> I don't execute "drools.getWorkingMemory().setGlobal()" it "works fine", >> as if the rule activates and the object is null. >> >> global List objectList; >> >> rule "Start" >> salience 101 >> when >> #conditions >> then >> objectList = new ArrayList() ; >> objectList.add("1"); >> objectList.add("2"); >> System.out.println("Start objectList:"+objectList); >> //drools.getWorkingMemory().setGlobal("objectList", objectList); >> end >> >> rule "end" >> salience 97 >> when >> eval (objectList == null) >> then >> System.out.println("End objectList: "+objectList); >> end >> >> gives: >> >> Start objectList:[1, 2] >> End objectList: null >> >> Next I uncomment the "drools.getWorkingMemory().setGlobal("objectList", >> objectList);" and run the rule again an get: >> >> Start objectList:[1, 2] >> End objectList: [1, 2] >> >> so the objectList isn't null, but the rule still activates... >> >> Kris Verlaenen schreef: >> >> >>>> That initialized my global but the rule still runs every execution. >>>> Can I >>>> disable the rule after the first execution? >>>> >>>> >>> What do you mean by "every execution". A rule should only be executed >>> once, unless it gets reactivated (which should not be the case in this >>> situation). >>> >>> >>> >>>> I would like to use (if (objectList==null)). My list is not >>>> immutable. Can >>>> I make a similar rule for the LHS? >>>> >>>> >>> You can test whether the global is null using eval( objectList == null >>> ) in the LHS of the rule. >>> >>> Kris >>> _______________________________________________ >>> rules-users mailing list >>> rules-users(a)lists.jboss.org >>> https://lists.jboss.org/mailman/listinfo/rules-users >>> >>> >> _______________________________________________ >> rules-users mailing list >> rules-users(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/rules-users >> >> >> >> > > _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users ------------------------------------------------------------------------ _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users

You can test whether the global is null using eval( objectList == null ) in the LHS of the rule.

> That initialized my global but the rule still runs every execution. Can > I > disable the rule after the first execution? What do you mean by "every execution". A rule should only be executed once, unless it gets reactivated (which should not be the case in this situation). > I would like to use (if (objectList==null)). My list is not immutable. > Can > I make a similar rule for the LHS? You can test whether the global is null using eval( objectList == null ) in the LHS of the rule. Kris _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users

Thanks. That initialized my global but the rule still runs every execution. Can I disable the rule after the first execution? I would like to use (if (objectList==null)). My list is not immutable. Can I make a similar rule for the LHS? Kris Verlaenen wrote: > > You can create a rule that initializes your global, preferrably with a > high > salience so it gets executed first: > > rule "InitializeGlobal" salience 100 > when > then > ArrayList objectList = new ArrayList(); > objectList.add("1"); > objectList.add("2"); > drools.getWorkingMemory().setGlobal("objectList", objectList); > end > > Kris > > ----- Original Message ----- > From: "drools_user" <jkraemer(a)cs.tufts.edu&gt; > To: <rules-users(a)lists.jboss.org&gt; > Sent: Wednesday, October 24, 2007 7:35 PM > Subject: [rules-users] Initialize Global > > >> >> How do I initialize a global fact in the drl file? I want use the JSR94 >> API >> and avoid using the Drools API inside the Java code. I would like to >> access >> the same variable every execution of a stateful session without having >> to >> reinstantiate the variable after each execution? >> >> Basically I want to define a global like this: >> # Define global variable >> global List objectList ; >> >> # Part that does not work >> objectList = new ArrayList() ; >> objectList.add("1"); >> objectList.add("2"); >> >> >> Thanks >> -- >> View this message in context: >> http://www.nabble.com/Initialize-Global-tf4685186.html#a13388685 >> Sent from the drools - user mailing list archive at Nabble.com. >> >> _______________________________________________ >> rules-users mailing list >> rules-users(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/rules-users > > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users > >

How do I initialize a global fact in the drl file? I want use the JSR94 API and avoid using the Drools API inside the Java code. I would like to access the same variable every execution of a stateful session without having to reinstantiate the variable after each execution? Basically I want to define a global like this: # Define global variable global List objectList ; # Part that does not work objectList = new ArrayList() ; objectList.add("1"); objectList.add("2"); Thanks