@Override
public boolean input(JIDContext context, Protocol protocol) {
GroupItem item = protocol.cast(Roster.class).first();
JID to = super.build(item.getJid());
item.addOnEmpty(this.group).setAsk(this.ask()).setSubscription(this.subscription(context.jid(), to)).setJid(to.asStringWithBare());
// Roster Set/Remove From必须=null
super.broadcast(context.jid(), protocol.parent().setFrom((String) null));
return true;
}