Zookeeper之建立組，加入組，列出組成員和刪除組

public class CreateGroup implements Watcher {
    private static final int SESSION_TIMEOUT=5000;
    //ZooKeeper類是客戶端API的主要類，用於維護客戶端和ZooKeeper服務之間的鏈接
    private ZooKeeper zk;
    //鎖存器(latch)此計數器爲1，表示在釋放全部等待線程以前須要發生的事件數，
    private CountDownLatch connectedSignal= new CountDownLatch(1);

    public void connect(String hosts) throws InterruptedException, IOException {
        //參數this表示一個Watcher對象接收來自於Zookeeper的回調，以得到各類事件的通知，在此表示CreateGroup對象
        zk = new ZooKeeper(hosts, SESSION_TIMEOUT, this);
        connectedSignal.await();
    }

    public void process(WatchedEvent watchedEvent) { // Watcher interface
        if (watchedEvent.getState()==Event.KeeperState.SyncConnected){
            //在調用這個方法表示計數器遞減1，若計數器的值變爲0，則await()方法返回
            connectedSignal.countDown();
        }
    }

    //建立組
    public void create(String groupName) throws KeeperException, InterruptedException {
        String path="/"+groupName;
        String createPath = zk.create(path, null/*data*/, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);// 持久化的 znode
        System.out.println("Created "+createPath);
    }

    //加入組
    public  void join(String groupName,String memberName) throws KeeperException, InterruptedException {
        String path = "/" + groupName + "/" + memberName;
        String createPath = zk.create(path, null/*data*/, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);// 持久化的 znode
        System.out.println("Created "+createPath);
    }

    //列出組成員
    public  void ListGroup(String groupName){
        String path="/"+groupName;
        try {
            List<String> children = zk.getChildren(path, false);
            if (children.isEmpty()){
                System.out.println(String.format("No members in group %s",groupName));
                System.exit(1);
            }
            for (String child:children){
                System.out.println(child);
            }
        } catch (KeeperException.NoNodeException e) {
            System.out.println(String.format("Group %s does not exist\n",groupName));
            System.exit(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (KeeperException e) {
            e.printStackTrace();
        }
    }
    //刪除組成員
    public void deleteGroup(String groupName){
        String path="/"+groupName;
        try {
            List<String> children = zk.getChildren(path, false);
            for (String child:children){
                //節點路徑和版本號  將版本號設置爲-1 能夠繞過版本檢測機制
                zk.delete(path+"/"+child,-1);
            }
            zk.delete(path,-1);
        } catch (KeeperException.NoNodeException e) {
            System.out.println(String.format("Group %s does not exist\n",groupName));
            System.exit(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (KeeperException e) {
            e.printStackTrace();
        }
    }

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



    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
        CreateGroup createGroup = new CreateGroup();
        createGroup.connect("192.168.1.132:2181");
        //createGroup.join("a","b");
        //createGroup.ListGroup("a");
        createGroup.deleteGroup("a");
        createGroup.close();
    }
}