@Override
    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException
    {
		if ( ExternalizableUtil.getInstance().readBoolean( in ) ) {
		    uniqueIdentifier = (Node.UniqueIdentifier) ExternalizableUtil.getInstance().readSerializable( in );
		} else {
			this.uniqueIdentifier = null;
        }
	}
Instantiates a flush task for a system-wide flush of pending changes.
xmppserver/src/main/java/org/jivesoftware/openfire/pubsub/cluster/FlushTask.java