Re: [rules-users] [droolsflow] Code-based constraints for EventWait nodes - is this possible?

Kris, I've attached a simple test case (transaction manager, data source, etc. are configured via Spring). The error is thrown on line: ksession.insert(new SimpleFact()); If this line is commented out, the rule flow executes without error. Many thanks for looking at this. Regards, Alan Kris Verlaenen <kris.verlaenen(a)cs.kuleuven.be&gt; 28/10/2009 10:40 To Alan.Gairey(a)tessella.com cc Rules Users List <rules-users(a)lists.jboss.org&gt; Subject Re: [rules-users] [droolsflow] Code-based constraints for EventWait nodes - is this possible? Alan, Could you send me the entire output / stack trace (as the rollback of the transaction is usually caused by another exception)? Or a simple test case that shows the error, so I can take a look? Thx, Kris Quoting Alan.Gairey(a)tessella.com: > Kris, > > After posting my last question, I quickly came to the same conclusion > as > you, so I'm now using a rule-based constraint in my EventWait node. > > This however has presented a different problem. If I create my > session > from JPAKnowledgeService, then when I try to insert my fact into the > > session, I get the following error: > > bitronix.tm.internal.BitronixRollbackException: transaction was > marked as > rollback only and has been rolled back > at > bitronix.tm.BitronixTransaction.commit(BitronixTransaction.java:153) > at >

> at >

> at >

> (Everything works fine if I create my session from the knowledge base > - > i.e. with no state persistence.) > Prior to using a rule-based constraint (with no call to > CommandBasedStatefulKnowledgeSession.insert), the session created > from > JPAKnowledgeService worked OK. > I'm using the default JPA configuration from the Drools documentation > > (persisting to H2 database, etc.). > Any ideas what might be causing the problem? > Many thanks, > Alan > > > > > Kris Verlaenen <kris.verlaenen(a)cs.kuleuven.be&gt; > 23/10/2009 03:00 > > To > Rules Users List <rules-users(a)lists.jboss.org&gt;, > Alan.Gairey(a)tessella.com > cc > Rules Users List <rules-users(a)lists.jboss.org&gt; > Subject > Re: [rules-users] [droolsflow] Code-based constraints for EventWait > nodes > - is this possible? > > > > > > > No, the constraint of an EventWait node (or the State node in Drools > 5.1) can only be rule-based. The reason for this is that the rule > engine knows when to re-evaluates rules (based on the evailable > input). > If you would use a code-based constraint, the engine would have no > idea > when this code constraint might become true (if it was false at the > start). Only constant re-evaluation of the code constraint could > achieve this (which would be tremendously inefficient). Could you > explain why you would like to have this behaviour? Maybe there is > an > alternative way to model this. > > To change the value of a variable from inside the process (using an > action), simply use kcontext.setVariable(name, value). We do not > recommend manually changing the value of a process variable from > outside > the engine. Again, could you explain why you would like to have > this > functionality? > > Kris > > Quoting Alan.Gairey(a)tessella.com: > > > Can the constraint for an EventWait node in a flow be code-based > > (rather > > than rule-based)? The Eclipse plug-in (v 5.0.1) doesn't allow this > to > > be > > specified, unlike say for a Split node, although the relevant XML > can > > of > > course be edited. > > Trying to load such a process flow results in a > NullPointerException, > > > > because the constraint is always interpreted as a rule. > > > > Ideally what I'd like to do is have an EventWait node where the > > constraint > > tests the value of a process variable. This then leads me to > another > > > > question; is there a way of setting the value of a process > variable > > via > > the Drools Flow API? > > > > Thanks in advance for any help, > > > > Alan > > Tessella plc > > 26 The Quadrant, Abingdon Science Park, Abingdon, Oxfordshire, > OX14 > > 3YS > > E: Alan.Gairey(a)tessella.com, T: +44 (0)1235 555511, F: +44 (0)1235 > > 553301 > > www.tessella.com Registered in England No. 1466429 > > > > This message is commercial in confidence and may be privileged. It > is > > > > intended for the addressee(s) only. Access to this message by > anyone > > else > > is unauthorized and strictly prohibited. If you have received this > > message > > in error, please inform the sender immediately. Please note that > > messages > > sent or received by the Tessella e-mail system may be monitored > and > > stored > > in an information retrieval system. > > > > > > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm