@Override
  public synchronized void nodeDeleted(String path) {
    if (path.equals(node)) {
      try {
        if (ZKUtil.watchAndCheckExists(watcher, node)) {
          nodeCreated(path);
        } else {
          this.data = null;
        }
      } catch (KeeperException e) {
        abortable.abort("Unexpected exception handling nodeDeleted event", e);
      }
    }
  }
Gets the data of the node.
<p>
If the node is currently available, the most up-to-date known version of the data is returned.
If the node is not currently available, null is returned.
@param refresh whether to refresh the data by calling ZK directly.
@return data of the node, null if unavailable
hbase-zookeeper/src/main/java/org/apache/hadoop/hbase/zookeeper/ZKNodeTracker.java