xstream.alias("protocol", Y.class);
qnameMap.registerMapping(new QName(getDefaultNS(Handler.class)+1, "handler", "h"), "handler");
qnameMap.registerMapping(new QName(getDefaultNS(Protocol.class)+2, "protocol", "p"), "innerObj");
X x = new X();
x.aStr = "foo";
x.anInt = 42;
x.innerObj = new Y();
x.innerObj.yField = "YField";