[rules-dev] Throwing runtimeException 4.0.7 not supposed

[Edson Tirelli]

   Wolfgang is right, as usual. Also, if I am not mistaken, if you are using
the MVEL you can use ? to prevent the NPE. Something like:

person?.name?.firstName

   But this needs to be double checked. I never used it myself.

   []s
   Edson

2009/6/13 Wolfgang Laun <wolfgang.laun at gmail.com>

> You have answered your question yourself: evaluation of patterns is
> done whenever a fact is added; salience will only order firings. Thus,
> the access person.name.firstName runs into the NPE.
>
> One way to cope with this would be to introduce a Name object which
> represents "no name", available as a public static object in Name; use
> this to initialize Person objects. This will still let you detect the
> absence of a name (name == Name.noName) but it won't run into the NPE
> in your second rule.
>
> -W
>
> On 6/12/09, surya_n2007 <surya_n2007 at yahoo.co.in> wrote:
> >
> > Throwing runtime exception in this example inserted person object as
> person
> > name is null. Ideally need to add error
> > "P01" and in second rule checks for precondition "P01" exist and skip
> rule.
> > But i am getting the below error.
> > Please let me know this is bug, i dont want to check again "Second Rule"
> > name object is not null.
> >  I think this is happening since drools frist try to run all rules before
> > start execution.
> >
> > please let me know whether anything wrong on my end.
> >
> >
> > Rule Engine COde :
> >
> >    Person person = test.new Person();
> > // Name name = person.new Name();
> > // person.setName(name);
> >    workingMemory.insert(person);
> >
> >
> > rule "First Rule" salience 100 lock-on-active true
> > when
> >         person : Person()
> >         eval(person.name == null)
> > then
> >         person.errors.add("P01");
> >         System.out.println("Rule 1 invoked"+person.errors);
> >         update(person);
> > end
> >
> > rule "Second Rule" salience 99 lock-on-active true
> > when
> >         person : Person()
> >         eval(!person.errors.contains("P01"))
> >         eval(person.name.firstName=="Bob")
> > then
> >         person.name.suffix="Mr";
> >         System.out.println("Rule 2 invoked");
> > end
> >
> >
> >
> >
> > org.drools.RuntimeDroolsException:
> > com.sample.Rule_Second_Rule_0Eval1Invoker at 4b42aa1e :
> > java.lang.NullPointerException
> >         at org.drools.rule.EvalCondition.isAllowed(EvalCondition.java:82)
> >         at
> >
> org.drools.reteoo.EvalConditionNode.assertTuple(EvalConditionNode.java:148)
> >         at
> >
> org.drools.reteoo.SingleTupleSinkAdapter.propagateAssertTuple(SingleTupleSinkAdapter.java:29)
> >         at
> >
> org.drools.reteoo.EvalConditionNode.assertTuple(EvalConditionNode.java:157)
> >         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:162)
> >         at org.drools.reteoo.Rete.assertObject(Rete.java:175)
> >         at
> > org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:192)
> >         at
> >
> org.drools.reteoo.ReteooWorkingMemory.doInsert(ReteooWorkingMemory.java:71)
> >         at
> >
> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:911)
> >         at
> >
> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:883)
> >         at
> >
> org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:684)
> >         at com.sample.DroolsTest.main(DroolsTest.java:36)
> > Caused by: java.lang.NullPointerException
> >         at
> com.sample.Rule_Second_Rule_0.eval1(Rule_Second_Rule_0.java:14)
> >         at
> >
> com.sample.Rule_Second_Rule_0Eval1Invoker.evaluate(Rule_Second_Rule_0Eval1Invoker.java:20)
> >         at org.drools.rule.EvalCondition.isAllowed(EvalCondition.java:77)
> >         ... 14 more
> > --
> > View this message in context:
> >
> http://www.nabble.com/Throwing-runtimeException-4.0.7-not-supposed-tp24005070p24005070.html
> > Sent from the drools - dev mailing list archive at Nabble.com.
> >
> > _______________________________________________
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> >
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-- 
 Edson Tirelli
 JBoss Drools Core Development
 JBoss, a division of Red Hat @ www.jboss.com
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