Helpful error message for MvelConstraint ---------------------------------------- Key: DROOLS-687 URL: https://issues.jboss.org/browse/DROOLS-687 Project: Drools Issue Type: Enhancement Affects Versions: 6.2.0.CR4 Reporter: Toshiya Kobayashi Assignee: Mario Fusco Priority: Critical Fix For: 6.2.0.Final 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, {noformat} rule 'hello person' when Person( address.street == 'abbey' ) then end {noformat} If Person.address is null, the error message is: {noformat} [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 {noformat} 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.