[rules-users] Getting facts from external source using 'from' and parametrized method call

[Jaroslaw Kijanowski]

Did you set the global on your session?

http://downloads.jboss.com/drools/docs/4.0.7.19894.GA/html_single/index.html#d0e948

Cheers

Przemysław Różycki wrote:
> Sorry for responsing myself, but I'm still working on it and found that 
> when factSource is a fact, not global, the rule works very well. I mean, 
> this rule works fine:
> 
> rule "My Rule"
>   when
>     $factSrc : FactSource(  )
>     $fact : Fact(  ) from $factSrc.getSomeFacts("a","b","c")
>   then
>     // do something
> end
> 
> so what's the difference between invocation on global object and 
> invocation on fact object? Why the first one doesn't work and the second 
> one works?
> 
> Best regards,
> Przemek
> 
> 
> Przemysław Różycki pisze:
>> Hi,
>>
>> could I ask for some advice, please, how to use a parametrized method 
>> call to get some data using 'from' element in LHS.
>>
>> To be more precise, I would like to do something like this:
>>
>> rule "My Rule"
>>   when
>>     $fact : Fact(  ) from factSource.getSomeFacts("a","b","c")
>>   then
>>     // do something
>> end
>>
>> where factSource is for example some global and 
>> getSomeFacts(String,String,String) is a parametrized method that 
>> returns some array of Fact objects.
>>
>> Unfortunately, when I try to launch the following rule I have an error:
>>
>> Exception in thread "main" org.mvel.PropertyAccessException: unable to 
>> resolve property: factSource.getSomeFacts("a","b","c")
>>     at 
>> org.mvel.optimizers.impl.refl.ReflectiveAccessorOptimizer.compileGetChain(ReflectiveAccessorOptimizer.java:295) 
>>
>>     at 
>> org.mvel.optimizers.impl.refl.ReflectiveAccessorOptimizer.optimizeAccessor(ReflectiveAccessorOptimizer.java:110) 
>>
>>     at 
>> org.mvel.ast.VariableDeepPropertyNode.getReducedValueAccelerated(VariableDeepPropertyNode.java:26) 
>>
>>     at 
>> org.mvel.ast.PropertyASTNode.initializePropertyNode(PropertyASTNode.java:70) 
>>
>>     at 
>> org.mvel.ast.PropertyASTNode.getReducedValueAccelerated(PropertyASTNode.java:24) 
>>
>>     at org.mvel.MVELRuntime.execute(MVELRuntime.java:90)
>>     at org.mvel.CompiledExpression.getValue(CompiledExpression.java:111)
>>     at org.mvel.MVEL.executeExpression(MVEL.java:252)
>>     at 
>> org.drools.base.dataproviders.MVELDataProvider.getResults(MVELDataProvider.java:55) 
>>
>>     at org.drools.reteoo.FromNode.assertTuple(FromNode.java:68)
>>     at 
>> org.drools.reteoo.SingleTupleSinkAdapter.createAndPropagateAssertTuple(SingleTupleSinkAdapter.java:55) 
>>
>>     at 
>> org.drools.reteoo.LeftInputAdapterNode.assertObject(LeftInputAdapterNode.java:116) 
>>
>>     at 
>> org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:22) 
>>
>>     at 
>> org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:162)
>>     at org.drools.reteoo.Rete.assertObject(Rete.java:175)
>>     at 
>> org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:192)
>>     at 
>> org.drools.reteoo.ReteooWorkingMemory$WorkingMemoryReteAssertAction.execute(ReteooWorkingMemory.java:181) 
>>
>>     at 
>> org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:1312) 
>>
>>     at 
>> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:915) 
>>
>>     at 
>> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:883) 
>>
>>     at 
>> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:684) 
>>
>>     at com.sample.DroolsTest6.main(DroolsTest6.java:29)
>> Caused by: java.lang.NullPointerException
>>     at 
>> org.mvel.optimizers.impl.refl.ReflectiveAccessorOptimizer.getMethod(ReflectiveAccessorOptimizer.java:530) 
>>
>>     at 
>> org.mvel.optimizers.impl.refl.ReflectiveAccessorOptimizer.compileGetChain(ReflectiveAccessorOptimizer.java:261) 
>>
>>     ... 21 more
>>
>> Documentation says:
>>
>> "The from Conditional Element allows users to specify a source for 
>> patterns to reason over. This allows the engine to reason over data 
>> not in the Working Memory. This could be a sub-field on a bound 
>> variable or the results of a method call."
>>
>> so I assume that it is possible to do what I want. If not, could I ask 
>> for an advice of some workaround, please?
>>
>> Best regards,
> 
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>