@Override
public void execute(OperationContext context, ModelNode operation) throws OperationFailedException {
PathAddress ourAddress = PathAddress.pathAddress(operation.require(OP_ADDR));
final Resource subsystemRootResource = context.getRootResource().navigate(ourAddress.subAddress(0, ourAddress.size() - 1));
if (subsystemRootResource.hasChildren(CommonAttributes.GROUPING_HANDLER)) {
throw new OperationFailedException(new ModelNode().set(String.format("A child resource of type %s already exists; " +
"the messaging subsystem only allows a single resource of type %s",
CommonAttributes.GROUPING_HANDLER, CommonAttributes.GROUPING_HANDLER)));
}