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Enhancement
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Resolution: Done
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Critical
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6.2.0.CR4
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None
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None
When you hit NullPointerException with LHS constraint during runtime, the error message is not very helpful for users to detect the root cause.
For example,
rule 'hello person'
when
Person( address.street == 'abbey' )
then
end
If Person.address is null, the error message is:
[Error: null pointer: address.street]
[Near : {... address.street == "abbey" ....}]
^
[Line: 1, Column: 1]
at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.compileGetChain(ReflectiveAccessorOptimizer.java:427)
at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.optimizeAccessor(ReflectiveAccessorOptimizer.java:140)
at org.mvel2.ast.ASTNode.optimize(ASTNode.java:159)
at org.mvel2.ast.ASTNode.getReducedValueAccelerated(ASTNode.java:115)
at org.mvel2.ast.BinaryOperation.getReducedValueAccelerated(BinaryOperation.java:117)
at org.mvel2.MVELRuntime.execute(MVELRuntime.java:86)
at org.mvel2.compiler.CompiledExpression.getDirectValue(CompiledExpression.java:123)
at org.mvel2.compiler.CompiledExpression.getValue(CompiledExpression.java:119)
at org.mvel2.compiler.CompiledExpression.getValue(CompiledExpression.java:113)
at org.mvel2.MVEL.executeExpression(MVEL.java:930)
at org.drools.core.util.MVELSafeHelper$RawMVELEvaluator.executeExpression(MVELSafeHelper.java:481)
at org.drools.core.rule.constraint.MvelConditionEvaluator.evaluate(MvelConditionEvaluator.java:77)
at org.drools.core.rule.constraint.MvelConditionEvaluator.evaluate(MvelConditionEvaluator.java:62)
at org.drools.core.rule.constraint.MvelConstraint.evaluate(MvelConstraint.java:226)
at org.drools.core.rule.constraint.MvelConstraint.isAllowed(MvelConstraint.java:183)
at org.drools.core.reteoo.AlphaNode.assertObject(AlphaNode.java:138)
at org.drools.core.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:60)
at org.drools.core.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:290)
at org.drools.core.reteoo.EntryPointNode.assertObject(EntryPointNode.java:253)
at org.drools.core.common.NamedEntryPoint.insert(NamedEntryPoint.java:281)
at org.drools.core.common.NamedEntryPoint.insert(NamedEntryPoint.java:241)
at org.drools.core.impl.StatefulKnowledgeSessionImpl.insert(StatefulKnowledgeSessionImpl.java:1481)
at org.drools.core.impl.StatefulKnowledgeSessionImpl.insert(StatefulKnowledgeSessionImpl.java:1436)
at org.drools.compiler.integrationtests.Misc2Test.testMvelConstraintErrorMessage(Misc2Test.java:7086)
...
Caused by: java.lang.NullPointerException
at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.compileGetChain(ReflectiveAccessorOptimizer.java:393)
... 46 more
Users cannot identify which rule is associated with the constraint when they have many similar rules. Also users cannot identify which fact (Person) caused the issue when they insert many facts.
I'm not sure if it's really possible to provide a better message in this case. But I filed this as an enhancement request.