JavaとZookeeperを始めよう

public class ZKConnection {
    private ZooKeeper zoo;
    CountDownLatch connectionLatch = new CountDownLatch(1);

    // ...

    public ZooKeeper connect(String host)
      throws IOException,
      InterruptedException {
        zoo = new ZooKeeper(host, 2000, new Watcher() {
            public void process(WatchedEvent we) {
                if (we.getState() == KeeperState.SyncConnected) {
                    connectionLatch.countDown();
                }
            }
        });

        connectionLatch.await();
        return zoo;
    }

    public void close() throws InterruptedException {
        zoo.close();
    }
}

public interface ZKManager {
    public void create(String path, byte[] data)
      throws KeeperException, InterruptedException;
    public Object getZNodeData(String path, boolean watchFlag);
    public void update(String path, byte[] data)
      throws KeeperException, InterruptedException;
}

public class ZKManagerImpl implements ZKManager {
    private static ZooKeeper zkeeper;
    private static ZKConnection zkConnection;

    public ZKManagerImpl() {
        initialize();
    }

    private void initialize() {
        zkConnection = new ZKConnection();
        zkeeper = zkConnection.connect("localhost");
    }

    public void closeConnection() {
        zkConnection.close();
    }

    public void create(String path, byte[] data)
      throws KeeperException,
      InterruptedException {

        zkeeper.create(
          path,
          data,
          ZooDefs.Ids.OPEN_ACL_UNSAFE,
          CreateMode.PERSISTENT);
    }

    public Object getZNodeData(String path, boolean watchFlag)
      throws KeeperException,
      InterruptedException {

        byte[] b = null;
        b = zkeeper.getData(path, null, null);
        return new String(b, "UTF-8");
    }

    public void update(String path, byte[] data) throws KeeperException,
      InterruptedException {
        int version = zkeeper.exists(path, true).getVersion();
        zkeeper.setData(path, data, version);
    }
}