[rules-users] Null Pointer Exception in "org.drools.reteoo.RuleTerminalNode.retractTuple"

[Anstis, Michael (M.)]

Ok, JIRA-749 created (assigned to default; Mark)

Happy (bug) hunting.

-----Original Message-----
From: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Edson Tirelli
Sent: 23 March 2007 12:35
To: Rules Users List
Subject: Re: [rules-users] Null Pointer Exceptionin
"org.drools.reteoo.RuleTerminalNode.retractTuple"


   Michael,

   Yes, this is certainly a bug. May I ask you please to open a JIRA for

that and attach your sample code?

   A comment about "no-loop": it only prevents the rule activating 
itself... it does not prevent the rule from activating other rules that 
already fired. You must add an explicit constraint to avoid the 
activation of the rules you don't want to activate when modifying 
objects that are part of the matching pattern.

   Thank you in advance.

    Edson


Anstis, Michael (M.) wrote:

> Hi - me again :-(
>
> Unfortunately I receive a NPE (3.1-M1) as follows (a complete JAR 
> illustrating the problem is available):-
>
> **Java
>
> Man man=*new* Man();
> Machine machine=*new* Machine();
> Process p =* new* Process();
> wm.assertObject(man);
> wm.assertObject(machine);
> wm.assertObject(p);
>
> **Rules
>
> *package* drools.debug
>
> *rule* "Rule-1"
> *no-loop** true*
> *when*
>         $p : Process()
> *then*
>         System.out.println("DEBUG [Rule-1]---> Add ProcessAlternative 
> to Process");
>         ProcessAlternative pa =* new* ProcessAlternative();
>         $p.addProcessAlternative(pa);
>        * assert*(pa);
>        * modify*($p);
> *end*
>
> *rule* "Rule-2"
> *no-loop** true*
> *when*
>         $m : Machine()
> *then*
>         System.out.println("DEBUG [Rule-2]---> Add Machine to 
> MachineEntry");
>         MachineEntry me =* new* MachineEntry();
>         me.setMachine($m);
>        * assert*(me);
> *end*
>
> *rule* "Rule-3"
> *no-loop** true*
> *when*
>         $me : MachineEntry()
>         $pa : ProcessAlternative()
> *then*
>         System.out.println("DEBUG [Rule-3]---> Add MachineEntry to 
> ProcessAlternative");
>         $pa.addMachineEntry($me);
>        * modify*($pa);
> *end*
>
> //rule "Rule-4 (Null Pointer Exception)"
> //no-loop true
> //when
> //      $h : Man ( )
> //      $m : Machine ( )
> //      $mte : MachineEntry ( machine == $m )
> //then
> //      System.out.println("DEBUG [Rule 4]---> Assigned resource");
> //      $m.setManualResource($h);
> //      modify($m);
> //end
>
> **Output
>
> DEBUG [Rule-1]---> Add ProcessAlternative to Process
> DEBUG [Rule-2]---> Add Machine to MachineEntry
> DEBUG [Rule-3]---> Add MachineEntry to ProcessAlternative
>
> This is what I'd expect. If however rule "Rule-4" is uncommented the 
> output is:-
>
> DEBUG [Rule-1]---> Add ProcessAlternative to Process
> DEBUG [Rule-2]---> Add Machine to MachineEntry
> DEBUG [Rule-3]---> Add MachineEntry to ProcessAlternative
> DEBUG [Rule 4]---> Assigned resource
> DEBUG [Rule-2]---> Add Machine to MachineEntry          <-- Why 
> activated? no-loop is true
> DEBUG [Rule 4]---> Assigned resource                    <-- Presumably

> activated as a consequence of above
>
> And I receive a NPE with the following stack trace:-
>
> _java.lang.NullPointerException_
>         at 
>
org.drools.reteoo.RuleTerminalNode.retractTuple(_RuleTerminalNode.java:2
67_) 
>
>         at 
>
org.drools.reteoo.SingleTupleSinkAdapter.propagateRetractTuple(_SingleTu
pleSinkAdapter.java:38_) 
>
>         at
org.drools.reteoo.JoinNode.retractTuple(_JoinNode.java:217_)
>         at 
>
org.drools.reteoo.SingleTupleSinkAdapter.propagateRetractTuple(_SingleTu
pleSinkAdapter.java:38_) 
>
>         at
org.drools.reteoo.JoinNode.retractObject(_JoinNode.java:183_)
>         at 
>
org.drools.reteoo.CompositeObjectSinkAdapter.propagateRetractObject(_Com
positeObjectSinkAdapter.java:369_) 
>
>         at 
>
org.drools.reteoo.ObjectTypeNode.retractObject(_ObjectTypeNode.java:189_
)
>         at org.drools.reteoo.Rete.retractObject(_Rete.java:171_)
>         at 
>
org.drools.reteoo.ReteooRuleBase.retractObject(_ReteooRuleBase.java:215_
)
>         at 
>
org.drools.reteoo.ReteooWorkingMemory.doRetract(_ReteooWorkingMemory.jav
a:76_) 
>
>         at 
>
org.drools.common.AbstractWorkingMemory.modifyObject(_AbstractWorkingMem
ory.java:940_) 
>
>         at 
>
org.drools.base.DefaultKnowledgeHelper.modifyObject(_DefaultKnowledgeHel
per.java:95_) 
>
>         at 
>
drools.debug.Rule_Rule_4__Null_Pointer_Exception__0.consequence(_Rule_Ru
le_4__Null_Pointer_Exception__0.java:8_)
>
>         at 
>
drools.debug.Rule_Rule_4__Null_Pointer_Exception__0ConsequenceInvoker.ev
aluate(_Rule_Rule_4__Null_Pointer_Exception__0ConsequenceInvoker.java:24
_)
>
>         at 
>
org.drools.common.DefaultAgenda.fireActivation(_DefaultAgenda.java:467_)
>         at 
> org.drools.common.DefaultAgenda.fireNextItem(_DefaultAgenda.java:431_)
>         at 
>
org.drools.common.AbstractWorkingMemory.fireAllRules(_AbstractWorkingMem
ory.java:360_) 
>
>
> I have also encountered NPE in 
> "org.drools.reteoo.AlphaNode.retractObject" when using my actual rules

> other than these simplifications put together to demonstrate the error

> (both are caused by a call to "final Activation activation = 
> tuple.getActivation();" returning NULL so I suspect the root cause to 
> be common). Is this a case for a new JIRA entry or have I done 
> something idiotic?
>
> With kind regards,
>
> Mike
>
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>
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>  
>


-- 
 Edson Tirelli
 Software Engineer - JBoss Rules Core Developer
 Office: +55 11 3124-6000
 Mobile: +55 11 9218-4151
 JBoss, a division of Red Hat @ www.jboss.com


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