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:267_)
at
org.drools.reteoo.SingleTupleSinkAdapter.propagateRetractTuple(_SingleTupleSinkAdapter.java:38_)
at org.drools.reteoo.JoinNode.retractTuple(_JoinNode.java:217_)
at
org.drools.reteoo.SingleTupleSinkAdapter.propagateRetractTuple(_SingleTupleSinkAdapter.java:38_)
at org.drools.reteoo.JoinNode.retractObject(_JoinNode.java:183_)
at
org.drools.reteoo.CompositeObjectSinkAdapter.propagateRetractObject(_CompositeObjectSinkAdapter.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.java:76_)
at
org.drools.common.AbstractWorkingMemory.modifyObject(_AbstractWorkingMemory.java:940_)
at
org.drools.base.DefaultKnowledgeHelper.modifyObject(_DefaultKnowledgeHelper.java:95_)
at
drools.debug.Rule_Rule_4__Null_Pointer_Exception__0.consequence(_Rule_Rule_4__Null_Pointer_Exception__0.java:8_)
at
drools.debug.Rule_Rule_4__Null_Pointer_Exception__0ConsequenceInvoker.evaluate(_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(_AbstractWorkingMemory.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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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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