5:53 a.m.
Version 5.5.0.Final (Guvnor and libraries)
We are seeing the NPE with the stack trace given below, but only when
loading rules through Guvnor. Same rules file and code runs fine without
Guvnor, but error with Guvnor.
*With Guvnor:* KnowlegdeBase from KnowledgeAgent using changeset.xml,
scanner running for on-the-fly rule updates in Guvnor.
*Without Guvnor:* kbuilder.add(new ClassPathResource("Rules.drl",
getClass()), ResourceType.DRL);
I have only little experience with Drools and would appreciate advice on how
to approach this problem.
Could it be something in the rules file itself?
But why would it make a difference whether the rules came from Guvnor or a
file?
Could the error point to something missing from the POJO model in Guvnor? I
am still in the process of determining what should go in the JAR file
exported from Eclipse and what not. The rules validate OK in Guvnor though,
and the package can be built.
What else to consider?
A similar problem was discussed here
<http://thread.gmane.org/gmane.comp.java.drools.user/15285> , but the
solution seems to have been an upgrade to version 5.
Unexpected exception caught: null
java.lang.NullPointerException
at
org.drools.base.evaluators.AfterEvaluatorDefinition$AfterEvaluator.evaluateCachedRight(AfterEvaluatorDefinition.java:322)
at
org.drools.rule.constraint.EvaluatorConstraint.isAllowedCachedRight(EvaluatorConstraint.java:80)
at
org.drools.common.TripleBetaConstraints.isAllowedCachedRight(TripleBetaConstraints.java:101)
at org.drools.reteoo.JoinNode.propagateFromRight(JoinNode.java:156)
at org.drools.reteoo.JoinNode.assertObject(JoinNode.java:148)
at
org.drools.reteoo.CompositeObjectSinkAdapter.doPropagateAssertObject(CompositeObjectSinkAdapter.java:497)
at
org.drools.reteoo.CompositeObjectSinkAdapter.propagateAssertObject(CompositeObjectSinkAdapter.java:382)
at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:235)
at org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:240)
at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:350)
at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:311)
at
org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:903)
at
org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:847)
at
org.drools.impl.StatefulKnowledgeSessionImpl.insert(StatefulKnowledgeSessionImpl.java:269)
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9:52 a.m.
Environment: Windows 7 PC with Java 1.7.0_09, Drools 5.5.0.Final.
I have carefully cleaned up the POJO model loaded into the Guvnor: The model
now has no external dependencies except for "org.drools..." and
"java..."
packages. Everything validates perfectly in Guvnor, but this did not solve
the problem.
In the debugger I can see that the line in bold in the Drools source code
below is where the NPE happens: "this.getOperator()" returns null (unless
the debugger is misleading me somehow). I have included the stack trace
right /before/ the NPE happens.
I have also found out that the problem is caused by a single specific rule.
I have removed it in Guvnor and that made the problem go away. (The event
declaration was not removed, I have included it to show that events are
involved).
The problem disappears if this rule is removed
declare TicketKaufEvent
@role(event)
@timeStamp(timestamp)
end
/rule "Kundenbelohnung"
when
$tk1 : TicketKaufEvent( $k : kunde )
$tk2 : TicketKaufEvent( kunde == $k, produktinformation.preis >=
2*($tk1.produktinformation.preis), this != $tk1, this after[0, 2m] $tk1)
not KundeRewarded( kunde == $k )
then
service.notifyKunde($k.vorname + " " + $k.name + " hat innerhalb
von
2 Minuten zwei Tickets gekauft, wobei das zweite Ticket mind. doppelt so
teuer wie das erste war und erhaelt deshalb einmalig einen Kaffeegutschein")
insert(new KundeRewarded( $k ));
end/
Source: org.drools.base.evaluators.AfterEvaluatorDefinition
It looks like "this.getOperator()" on the bold line returns null...
public boolean evaluateCachedRight(InternalWorkingMemory
workingMemory,
final VariableContextEntry
context,
final Object left) {
if ( context.rightNull ) {
return false;
}
long rightTS;
if( this.unwrapRight ) {
if( context instanceof ObjectVariableContextEntry ) {
if( ((ObjectVariableContextEntry) context).right
instanceof Date ) {
rightTS = ((Date)((ObjectVariableContextEntry)
context).right).getTime();
} else {
rightTS = ((Number)((ObjectVariableContextEntry)
context).right).longValue();
}
} else {
rightTS = ((LongVariableContextEntry) context).right;
}
} else {
rightTS = ((EventFactHandle) ((ObjectVariableContextEntry)
context).right).getStartTimestamp();
}
long leftTS = this.unwrapLeft ?
context.declaration.getExtractor().getLongValue( workingMemory,
left ) : ((EventFactHandle) left).getEndTimestamp();
long dist = rightTS - leftTS;
*return this.getOperator().isNegated() ^ (dist >= this.initRange
&& dist <= this.finalRange);*
}
Stack Trace right before NPE is triggered
Thread [pool-2-thread-1] (Suspended (breakpoint at line 322 in
AfterEvaluatorDefinition$AfterEvaluator))
AfterEvaluatorDefinition$AfterEvaluator.evaluateCachedRight(InternalWorkingMemory,
VariableRestriction$VariableContextEntry, Object) line: 322
EvaluatorConstraint.isAllowedCachedRight(LeftTuple, ContextEntry) line: 80
TripleBetaConstraints.isAllowedCachedRight(ContextEntry[], LeftTuple) line:
101
JoinNode.propagateFromRight(RightTuple, LeftTuple, BetaMemory,
PropagationContext, InternalWorkingMemory) line: 156
JoinNode.assertObject(InternalFactHandle, PropagationContext,
InternalWorkingMemory) line: 148
CompositeObjectSinkAdapter.doPropagateAssertObject(InternalFactHandle,
PropagationContext, InternalWorkingMemory, ObjectSink) line: 497
CompositeObjectSinkAdapter.propagateAssertObject(InternalFactHandle,
PropagationContext, InternalWorkingMemory) line: 382
ObjectTypeNode.assertObject(InternalFactHandle, PropagationContext,
InternalWorkingMemory) line: 235
EntryPointNode.assertObject(InternalFactHandle, PropagationContext,
ObjectTypeConf, InternalWorkingMemory) line: 240
NamedEntryPoint.insert(InternalFactHandle, Object, Rule, Activation,
ObjectTypeConf) line: 350
NamedEntryPoint.insert(Object, Object, boolean, boolean, Rule, Activation)
line: 311
ReteooStatefulSession(AbstractWorkingMemory).insert(Object, Object,
boolean, boolean, Rule, Activation) line: 903
ReteooStatefulSession(AbstractWorkingMemory).insert(Object) line: 847
StatefulKnowledgeSessionImpl.insert(Object) line: 269
EventHub.receive(AbstractEvent) line: 85
EventFeeder$FeedJob.execute(JobContext) line: 90
DefaultTimerJobInstance.call() line: 51
DefaultTimerJobInstance.call() line: 14
FutureTask$Sync.innerRun() line: 314
ScheduledThreadPoolExecutor$ScheduledFutureTask<V>(FutureTask<V>).run()
line: 149
ScheduledThreadPoolExecutor$ScheduledFutureTask<V>.access$301(ScheduledThreadPoolExecutor$ScheduledFutureTask)
line: 109
ScheduledThreadPoolExecutor$ScheduledFutureTask<V>.run() line: 218
ThreadPoolExecutor$Worker.runTask(Runnable) line: 897
ThreadPoolExecutor$Worker.run() line: 919
Thread.run() line: 736
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7:14 a.m.
We were able to narrow it down a bit further: It is sufficient to remove this
part of the rule to make the problem go away:
*, this after[0, 2m] $tk1*
In the meantime I have also used "New Declarative Model" to declare our
events in Guvnor. Now the events are available in the guided rule editor.
But the additional declarative model did not solve the NullPointerException.
Of course, the event declarations have always been in the rules file that
was pushed to Guvnor from Eclipse.
Am I right in assuming that the declarative model in Guvnor is not required
for execution, but only for guided rule editing?
Having narrowed down the problem to the above time restriction clause: Does
anybody have an idea what could cause the NPE? Should we state the rule
differently?
rule "Kundenbelohnung"
when
$tk1 : TicketKaufEvent( $k : kunde )
$tk2 : TicketKaufEvent( kunde == $k, produktinformation.preis >=
2*($tk1.produktinformation.preis), this != $tk1*, this after[0, 2m] $tk1*)
not KundeRewarded( kunde == $k )
then
service.notifyKunde($k.vorname + " " + $k.name + " hat innerhalb
von
2 Minuten zwei Tickets gekauft, wobei das zweite Ticket mind. doppelt so
teuer wie das erste war und erhaelt deshalb einmalig einen Kaffeegutschein")
insert(new KundeRewarded( $k ));
end
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