There is a problematic cast in org.jboss.jmx.connector.invoker.AuthenticationInterceptor.invoke(Invocation invocation) on line 110:

String opname = (String) obj[1];

When Twiddling to get a particular attribute, the following code is used in org.jboss.console.twiddle.command.GetCommand.execute(String[] args) on line 165:

attributeNames.toArray(names);
(...)
AttributeList attrList = server.getAttributes(objectName, names);

So obj[1] ends up holding a String[] of attribute names (even if there is only one) and the cast fails:

14:14:44,760 ERROR [Twiddle] Exec failed
java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to java.lang.String
at org.jboss.jmx.connector.invoker.AuthorizationInterceptor.invoke(AuthorizationInterceptor.java:107)
at org.jboss.jmx.connector.invoker.AuthenticationInterceptor.invoke(AuthenticationInterceptor.java:108)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:88)
at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:264)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:659)
at org.jboss.invocation.jrmp.server.JRMPProxyFactory.invoke(JRMPProxyFactory.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:589)
at org.jboss.mx.interceptor.ReflectedDispatcher.invoke(ReflectedDispatcher.java:155)
at org.jboss.mx.server.Invocation.dispatch(Invocation.java:94)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:86)
at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:264)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:659)
at org.jboss.invocation.jrmp.server.JRMPInvoker$MBeanServerAction.invoke(JRMPInvoker.java:819)
at org.jboss.invocation.jrmp.server.JRMPInvoker.invoke(JRMPInvoker.java:420)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:589)
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:305)
at sun.rmi.transport.Transport$1.run(Transport.java:159)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:155)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:535)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:790)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:649)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:679)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:704)
at java.lang.Thread.run(Thread.java:637)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(StreamRemoteCall.java:255)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:233)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:142)
at org.jboss.invocation.jrmp.server.JRMPInvoker_Stub.invoke(Unknown Source)
at org.jboss.invocation.jrmp.interfaces.JRMPInvokerProxy.invoke(JRMPInvokerProxy.java:133)
at org.jboss.invocation.InvokerInterceptor.invokeInvoker(InvokerInterceptor.java:331)
at org.jboss.invocation.InvokerInterceptor.invoke(InvokerInterceptor.java:194)
at org.jboss.jmx.connector.invoker.client.InvokerAdaptorClientInterceptor.invoke(InvokerAdaptorClientInterceptor.java:66)
at org.jboss.proxy.SecurityInterceptor.invoke(SecurityInterceptor.java:70)
at org.jboss.proxy.ClientMethodInterceptor.invoke(ClientMethodInterceptor.java:74)
at org.jboss.proxy.ClientContainer.invoke(ClientContainer.java:100)
at $Proxy0.getAttributes(Unknown Source)
at org.jboss.console.twiddle.command.GetCommand.execute(GetCommand.java:168)
at org.jboss.console.twiddle.Twiddle.main(Twiddle.java:305)