[rules-dev] Drools Core Error?

[Michael Neale]

Hi Nestor - that is a tough one.

I have a suspicion this is related to another issue I have seen with
deserliasation of rulebases when the MVEL JIT kicks in... (from that
strack trace it isn't getting the TypeDeclaration back...) - its a
stretch, but might be related to:
https://jira.jboss.org/jira/browse/JBRULES-2253

As there are a few moving parts, if you could create a unit test that
starts up a agent and shows this behaviour, that would be appreciated
(confused about the interaction with entry points).

Thanks,

Michael.



On Mon, Aug 31, 2009 at 8:38 PM, nestabur<nestabur at gmail.com> wrote:
>
> Any suggestions? I have my project in stand-by due to that problem ...
>
> Nestor
>
>
> 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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-- 
Michael D Neale
home: www.michaelneale.net
blog: michaelneale.blogspot.com