Consider this test: --- package tests; import java.lang.reflect.Method; dialect "mvel" rule "Rule #1" when then Class clazz = Class.forName("java.lang.Class"); System.out.println("clazz = " + clazz); Method m = clazz.getDeclaredMethod("forName", new Class [] { java.lang.String.class }); System.out.println("m = " + m); end -- (which runs correctly when dialect "java" is given), fails in Drools 4.0.4/MVEL 1.4 with: org.mvel.CompileException: could not create constructor: java.lang.Class.<init>() at org.mvel.optimizers.impl.refl.ReflectiveAccessorOptimizer.optimizeObjectCreation(ReflectiveAccessorOptimizer.java:688) at org.mvel.ast.NewObjectNode.getReducedValueAccelerated(NewObjectNode.java:191) at org.mvel.MVELRuntime.execute(MVELRuntime.java:88) at org.mvel.CompiledExpression.getValue(CompiledExpression.java:111) at org.mvel.CompiledExpression.getValue(CompiledExpression.java:106) at org.mvel.optimizers.impl.refl.ReflectiveAccessorOptimizer.getMethod(ReflectiveAccessorOptimizer.java:521) at org.mvel.optimizers.impl.refl.ReflectiveAccessorOptimizer.compileGetChain(ReflectiveAccessorOptimizer.java:260) at org.mvel.optimizers.impl.refl.ReflectiveAccessorOptimizer.optimizeAccessor(ReflectiveAccessorOptimizer.java:109) at org.mvel.ast.VariableDeepPropertyNode.getReducedValueAccelerated(VariableDeepPropertyNode.java:29) at org.mvel.ast.PropertyASTNode.initializePropertyNode(PropertyASTNode.java:77) at org.mvel.ast.PropertyASTNode.getReducedValueAccelerated(PropertyASTNode.java:26) at org.mvel.ExecutableAccessor.getValue(ExecutableAccessor.java:45) at org.mvel.ast.TypedVarNode.getReducedValueAccelerated(TypedVarNode.java:43) at org.mvel.MVELRuntime.execute(MVELRuntime.java:88) at org.mvel.CompiledExpression.getValue(CompiledExpression.java:111) at org.mvel.MVEL.executeExpression(MVEL.java:235) at org.drools.base.mvel.MVELConsequence.evaluate(MVELConsequence.java:47) at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:550) at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:514) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:471) at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:433) at org.libx.autodetect.DroolsDriver$Host.fireAllRules(DroolsDriver.java:63) at org.libx.autodetect.DroolsDriver.main(DroolsDriver.java:136) It appears to be looking for a constructor for "new java.lang.Class()" rather than constructing an array.) Similarly, "o.method(new String [] { ... })" fails because it looks for a method taking a String, rather than String[]. - Godmar