Pritam wrote: As I understood it, a stateless session behaves as if the only object known to it is the one you just inserted. Personally, I look at it like: stateless -> propositional logic stateful -> first-order logic I'm not sure that's 100% true though. In any case, it depends on the kind of questions you like to ask. If you're not sure, test it. Cheers, Simon

Wolfgang Laun wrote: Thanks for the clarification. So stateless _uses_ state but just doesn't have it bound to the session? If that's true, is there a deeper sense behind StatelessSession not supporting agenda arbitration? IOW, should I reasonably be able to cook up a "SomewhatStatelessSessionWithAgendaSupport", or would I end up with a half-arsed StatefulSession ?

Is there plan to support work items in Stateless sessions as well? It seems I had a POC using stateless and had to convert it to stateful in order to use a simple "send email" work item. Thanks Barry -----Original Message----- From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Mark Proctor Sent: Wednesday, January 27, 2010 8:18 AM To: Rules Users List Subject: Re: [rules-users] Stateless Vs Stateful Sessions in Webtier On 27/01/2010 13:09, Simon Thum wrote: you can use agenda and ruleflow from within the stateless session. Mark _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail.

On 20/01/2010 11:41, Simon Thum wrote: I prefer to look at it as turning a drools session into a function. It can do eveything a normal stateful session can do, just you have to do it all within the scope of a single execute call. Mark

I'm planning to use the following approach in my webtier: High level design: Each http request for a page on our site has an average of 5 separate requests to process rules before finally rendering. Each time, servlet handler calls runRule(<some context object>). Essentially, rules is serving as a filtering process and while Stateless ksession would have done the trick, I needed to control the execution of rules based on agenda-order and salience, hence the stateful ksession. The rules themselves are pretty st forward and I don't see the need to insert facts "dynamically" during a long web conversation (at least for now). protected void runRule(MyContect context) { try { KnowledgeBase kbase = loadKnowledgeBase(context); StatefulKnowledgeSession kSession = kbase.newStatefulKnowledgeSession(); // set some globals here // pop groups into agenda's stack for controlling execution order kSession.getAgenda().getAgendaGroup("<page-id>").setFocus(); kSession.getAgenda().getAgendaGroup("<section-id>).setFocus(); kSession.getAgenda().getAgendaGroup("site-global").setFocus(); kSession.insert(context); kSession.fireAllRules(); // at this point context is updated by rules for the servlet to handle after the call; kSession.dispose(); } catch (Exception e) { e.printStackTrace(); throw new RuntimeException("Error occured in processing Drools rules", e); } } public KnowledgeBase loadKnowledgeBase() throws DroolsParserException, IOException { if(kbase != null) { // singleton instance return kbase; } KnowledgeBuilder knowledgeBuilder = KnowledgeBuilderFactory.newKnowledgeBuilder(); knowledgeBuilder.add(ResourceFactory.newClassPathResource("dsl/global.dsl"), ResourceType.DSL); knowledgeBuilder.add(ResourceFactory.newClassPathResource("rules/"), ResourceType.DSLR); if (knowledgeBuilder.hasErrors()) { throw new RuntimeException(knowledgeBuilder.getErrors().toString()); } kbase = KnowledgeBaseFactory.newKnowledgeBase(); kbase .addKnowledgePackages(knowledgeBuilder.getKnowledgePackages()); return kbase ; } Michael Bali's book has an entire chapter on Stateful Session in which it recommended to create a StatefulSession Service with a dedicated writeObject and readObject and "warns" about thread safety. I'm still not clear about the unsafe threading issues with using a stateful ksession inside a webtier. And would the approach 1 in the above work, assuming multiple users are executing the same rules at the same time? Thanks public class DroolsService implements Serializable { private static final long serialVersionUID = 6623448115053519253L; private transient KnowledgeBase knowledgeBase; private transient StatefulKnowledgeSession statefulSession; public DroolsService(KnowledgeBase knowledgeBase) { this.knowledgeBase = knowledgeBase; statefulSession = createKnowledgeSession(); } private StatefulKnowledgeSession createKnowledgeSession() { StatefulKnowledgeSession session = knowledgeBase .newStatefulKnowledgeSession(); return session; } public void insertOrUpdate(Object fact) { if (fact == null) { return; } FactHandle factHandle = statefulSession.getFactHandle(fact); if (factHandle == null) { statefulSession.insert(fact); } else { statefulSession.update(factHandle, fact); } } public void executeRules() { statefulSession.fireAllRules(); } public void terminate() { statefulSession.dispose(); } private void writeObject(ObjectOutputStream out) throws IOException { out.defaultWriteObject(); DroolsObjectOutputStream droolsOut = new DroolsObjectOutputStream( (OutputStream) out); droolsOut.writeObject(knowledgeBase); Marshaller marshaller = createSerializableMarshaller(knowledgeBase); marshaller.marshall(droolsOut, statefulSession); } private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException { in.defaultReadObject(); DroolsObjectInputStream droolsIn = new DroolsObjectInputStream( (InputStream) in); this.knowledgeBase = (KnowledgeBase) droolsIn.readObject(); Marshaller marshaller = createSerializableMarshaller(knowledgeBase); statefulSession = marshaller.unmarshall(droolsIn); } private Marshaller createSerializableMarshaller(KnowledgeBase knowledgeBase) { ObjectMarshallingStrategyAcceptor acceptor = MarshallerFactory .newClassFilterAcceptor(new String[] { "*.*" }); ObjectMarshallingStrategy strategy = MarshallerFactory .newSerializeMarshallingStrategy(acceptor); Marshaller marshaller = MarshallerFactory.newMarshaller(knowledgeBase, new ObjectMarshallingStrategy[] { strategy }); return marshaller; } } -- View this message in context: http://n3.nabble.com/Stateless-Vs-Stateful-Sessions-in-Webtier-tp130284p1... Sent from the Drools - User mailing list archive at Nabble.com.