[rules-users] Using KnowledgeAgent with Stateful session

[nestabur]

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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