Greetings:

Nobody seems to be replying and I'm not really "qualified" to reply but I might be able to point you in the right direction.  Long, long ago in a land far, far away we did a really cool project using Intelligent Agents and employed most of the technology from FIPA, The Foundation for Intelligent Physical Agents; see http://www.fipa.org/ for more information.  

SDG
James Owen
Founder October Rules Fest
Senior Consultant / Architect KBSC
Twitter: OctRulesFest
Blogs:
http://JavaRules.blogspot.com [Rulebased Systems Blog]
http://ORF2009.blogspot.com [October Rules Fest Blog]
http://exscg.blogspot.com/ [Expert Systems Consulting Group Blog]

"If I have seen a little further it is by standing on the shoulders of giants."
Sir Isaac Newton in a letter to Robert Hooke, 5 Feb 1676

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On Aug 26, 2009, at 11:34 AM, nestabur wrote:



Does anyone tried to use the knowledgeAgent with statefulSessions?

I've tried to configure my rule engine obtaining unexpected behaviour.

I configure my statefulSession as follows:

wm = (ReteooStatefulSession) ((KnowledgeBaseImpl) kagent
.getKnowledgeBase()).ruleBase.newStatefulSession(
(SessionConfiguration) sessionConf, env);
ksession = new StatefulKnowledgeSessionImpl(wm, kagent.getKnowledgeBase());

And after updating the KnowledgeBase in the agent I update my ksession:

wm.setRuleBase((InternalRuleBase) ((KnowledgeBaseImpl) kagent
.getKnowledgeBase()).ruleBase);
ksession = new StatefulKnowledgeSessionImpl(wm, kagent.getKnowledgeBase());

Without using entry-points this approach works as expected, but using them
it fails after the first update throwing the error:

Exception while processing message: java.lang.NullPointerException
java.lang.NullPointerException
at
org.drools.reteoo.ReteooFactHandleFactory.newFactHandle(ReteooFactHandleFactory.java:54)
at
org.drools.common.AbstractFactHandleFactory.newFactHandle(AbstractFactHandleFactory.java:79)
at
org.drools.common.AbstractFactHandleFactory.newFactHandle(AbstractFactHandleFactory.java:66)
at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:109)
at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:80)
at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:28)

Browsing the drools core code I found the line that was throwing the
exception and tried to get the same result by implementing:

if (!((InternalRuleBase) ((KnowledgeBaseImpl)
ksession.getKnowledgeBase()).ruleBase)
.getTypeDeclaration(fact.getClass()) == null)
log.info (((InternalRuleBase) ((KnowledgeBaseImpl)
ksession.getKnowledgeBase()).ruleBase)

.getTypeDeclaration(fact.getClass()).getTimestampExtractor().toString());

after updating my ksession. The result was the same, again the same
exception thrown but my logger wrote:
18:01:50,232 INFO [ClassFieldExtractor class=MyPackage.MyFact
field=myTimestampField]

So I dont know why the core is throwing that exception, is that
implementation correct?, any ideas?


Thanks,

Nestor

--
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