[rules-users] Re: Is this scenario suitable for using Drools?

[Steven Williams]

change DBUtils to return a Collection and it should work I think.

On Wed, Apr 23, 2008 at 5:50 PM, Anstis, Michael (M.) <manstis1 at ford.com>
wrote:

>  So, in my usual helpful manner I thought Drools would be a perfect match
> and put together what I thought would be a simple example:-
>
> package com.sample
>
> global com.sample.DBUtils dbutils;
> rule "a1"
>     when
>         $max : Integer() from accumulate( Integer( $v : intValue ) from
> dbutils.getNumbers(), max($v) )
>     then
>         System.out.println($max);
> end
>
>
> public class DBUtils {
>
>     public Integer[] getNumbers() {
>
>         Integer[] numbers = new Integer[10];
>         for (int i = 0; i < numbers.length; i++) {
>             numbers[i] = (int) (Math.random() * 100);
>         }
>         return numbers;
>     }
> }
>
> However this led to some errors:-
>
> org.drools.RuntimeDroolsException: java.lang.ClassCastException:
> [Ljava.lang.Integer; incompatible with java.lang.Integer
>  at org.drools.rule.Accumulate.accumulate(Accumulate.java:131)
>  at org.drools.reteoo.AccumulateNode.assertTuple(AccumulateNode.java:127)
>  at
> org.drools.reteoo.CompositeTupleSinkAdapter.createAndPropagateAssertTuple(CompositeTupleSinkAdapter.java:73)
>  at
> org.drools.reteoo.LeftInputAdapterNode.assertObject(LeftInputAdapterNode.java:116)
>  at
> org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:22)
>  at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:153)
>  at org.drools.reteoo.Rete.assertObject(Rete.java:177)
>  at org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:192)
>  at
> org.drools.reteoo.ReteooWorkingMemory$WorkingMemoryReteAssertAction.execute(ReteooWorkingMemory.java:179)
>  at
> org.drools.common.AbstractWorkingMemory.executeQueuedActions(AbstractWorkingMemory.java:1292)
>  at
> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:891)
>  at
> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:858)
>  at
> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:659)
>  at com.sample.DroolsTest.main(DroolsTest.java:36)
> Caused by: java.lang.ClassCastException: [Ljava.lang.Integer; incompatible
> with java.lang.Integer
>  at
> org.drools.base.java.lang.Integer968047027$intValue.getIntValue(Unknown
> Source)
>  at
> org.drools.base.ClassFieldExtractor.getIntValue(ClassFieldExtractor.java:197)
>  at org.drools.rule.Declaration.getIntValue(Declaration.java:230)
>  at
> com.sample.Rule_a1_0AccumulateExpression0Invoker.evaluate(Rule_a1_0AccumulateExpression0Invoker.java:16)
>  at
> org.drools.base.accumulators.JavaAccumulatorFunctionExecutor.accumulate(JavaAccumulatorFunctionExecutor.java:74)
>  at org.drools.rule.Accumulate.accumulate(Accumulate.java:123)
>  ... 13 more
> Have I done something really stupid and is Drools a fit?
>
> Cheers,
>
> Mike
>
>  ------------------------------
> *From:* rules-users-bounces at lists.jboss.org [mailto:
> rules-users-bounces at lists.jboss.org] *On Behalf Of *Cheng Wei Lee
> *Sent:* 22 April 2008 17:27
> *To:* rules-users at lists.jboss.org
> *Subject:* [rules-users] Re: Is this scenario suitable for using Drools?
>
> I've 2 algorithms to calculate the cost of a product. At any one time,
> there is only 1 algorithm in use. Initially algorithm 1 will be the default.
> Subsequently, the decision to use which algorithm will depend on customers
> feedback. The algorithms are:
>
> Algorithm 1:
> Cost = MAX(P1, T1, P2, T2, P3, T3, ...)
>
> Algorithm 2:
> Cost = MIN(P1, P2, P3, ...) + MIN(T1, T2, T3, ...)
>
> The values of P1, P2, ... are stored within a database. The number of Ps &
> Ts are unknown but can be determined by querying the database, Would drools
> be a good option to use to store the algorithms? If so, how could I be able
> to retrieve the values of P1, P2, etc from the database from within drools?
>
> Thanks!
>
>
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>


-- 
Steven Williams

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