[rules-users] how to use Array type in Drools

package org.drools.examples.test; import org.drools.examples.HelloWorldExample.Message; rule "check.array" dialect "java" when m:Message( arr[0] == "1" ) then System.out.println( "===check array ok===" ); end

Exception in thread "main" org.drools.RuntimeDroolsException: Exception executing predicate eval( arr[0] == "1" ) at org.drools.rule.PredicateConstraint.isAllowed(PredicateConstraint.java:216) at org.drools.reteoo.AlphaNode.assertObject(AlphaNode.java:137) at org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:22) at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:162) at org.drools.reteoo.Rete.assertObject(Rete.java:175) at org.drools.reteoo.ReteooRuleBase.assertObject(ReteooRuleBase.java:192) at org.drools.reteoo.ReteooWorkingMemory.doInsert(ReteooWorkingMemory.java:71) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:911) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:883) at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:684) at org.drools.examples.HelloWorldExample.main(HelloWorldExample.java:69) Caused by: org.mvel.CompileException: illegal use of []: unknown type: [I at org.mvel.optimizers.impl.refl.ReflectiveAccessorOptimizer.getCollectionProperty(ReflectiveAccessorOptimizer.java:482) at org.mvel.optimizers.impl.refl.ReflectiveAccessorOptimizer.compileGetChain(ReflectiveAccessorOptimizer.java:274) at org.mvel.optimizers.impl.refl.ReflectiveAccessorOptimizer.optimizeAccessor(ReflectiveAccessorOptimizer.java:110) at org.mvel.ASTNode.getReducedValueAccelerated(ASTNode.java:186) at org.mvel.ast.BinaryOperation.getReducedValueAccelerated(BinaryOperation.java:21) at org.mvel.MVELRuntime.execute(MVELRuntime.java:90) at org.mvel.CompiledExpression.getValue(CompiledExpression.java:111) at org.mvel.MVEL.executeExpression(MVEL.java:234) at org.drools.base.mvel.MVELPredicateExpression.evaluate(MVELPredicateExpression.java:45) at org.drools.rule.PredicateConstraint.isAllowed(PredicateConstraint.java:209) ... 10 more