class AbstractClusterInvoker implements Invoker<T> {

    protected List<Invoker<T>> list(Invocation invocation) throws RpcException {
        List<Invoker<T>> invokers = directory.list(invocation);
        return invokers;
    }

    public  AbstractClusterInvoker(Directory<T> directory);
    public  AbstractClusterInvoker(Directory<T> directory, URL url);

}