> 动态监视服务器上下线的过程

public class Server {
    private static String connectString = "hadoop151:2181,hadoop152:2181,hadoop153:2181";
    private static int sessionTimeout = 2000;
    private ZooKeeper zk = null;
    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
        args = new String[]{"hadoop153"};
        Server server = new Server();
        server.getConnect();
        server.regist(args[0]);
        server.business();
    }
  //连接ZooKeeper集群
    private void getConnect() throws IOException {
        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {
            }
        });
    }
  //注册服务器，将主机名写入ZooKeeper中
    private void regist(String hostname) throws KeeperException, InterruptedException {
        String create = zk.create("/servers/server", hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
        System.out.println(hostname + " is online" + create);
    }
  //业务代码
    private void business() throws InterruptedException {
    //保持代码不结束，监控整个过程
        Thread.sleep(Long.MAX_VALUE);
    }
}

public class Client {
    private static String connectString = "hadoop151:2181,hadoop152:2181,hadoop153:2181";
    private static int sessionTimeout = 2000;
    private ZooKeeper zk = null;
    public static void main(String[] args) throws InterruptedException, IOException, KeeperException {
        Client client = new Client();
        client.getConnect();
        client.getServerList();
        client.business();
    }
  //连接ZooKeeper，并实现方法
    private void getConnect() throws IOException {
        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {
                try {
                    getServerList();
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
    }
  //获取文件子目录文件
    private void getServerList() throws KeeperException, InterruptedException {
        List<String> children = zk.getChildren("/servers", true);
        ArrayList<String> servers = new ArrayList<>();
        for (String child : children) {
            byte[] data = zk.getData("/servers/" + child, false, null);
            servers.add(new String(data));
        }
        System.out.println(servers);
    }
    private void business() throws InterruptedException {
        Thread.sleep(Long.MAX_VALUE);
    }
}