Zookeeper之常用API詳解

1、創建ZNode

①命令行方式

• 在根目錄下創建“FZnode"節點並存儲數據”First Znode"：

       create /FZnode "First Znode"

• 在根目錄下創建短暫的Znode節點

       create -e /SZnode "Secondary Znode"

• 創建短暫有序列的Znode節點

       create -e -s /EZnode "Ephemeral_SEQUENTIAL"

• 創建持久有序列的Znode節點

       create -s /PZnode "PERSISTENT_SEQUENTIAL"

②JAVA調用API

    /**
     * 創建ZNode節點
     * @throws Exception
     */
    @Test
    public void create() throws Exception{
        //用於停止（等待）主進程，直到客戶端與Zookeeper集合連接。
        final CountDownLatch cd = new CountDownLatch(1);
        ZooKeeper zk = new ZooKeeper("centos75:2181,centos76:2181,centos77:2181",5000,new Watcher(){
            //watcher返回Zookeeper連接狀態
            public void process(WatchedEvent watchedEvent) {
                System.out.println(watchedEvent.getState());
                //連接建立，回調process接口時，其watchedEvent.getState() 爲 Event.KeeperState.SyncConnected
                if(watchedEvent.getState() == Event.KeeperState.SyncConnected){
                    //喚醒wait中的線程
                    cd.countDown();
                }
            }
        });
        cd.await();
        /**
         * 1、Znode節點路徑
         * 2、Znode節點內容
         * 3、Znode創建節點的訪問控制列表
         * 4、Znode狀態，有四種狀態
         */
        zk.create("/APIjava",new String("test API").getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);
    }

2、獲取ZNode數據

①、命令行方式

      get /FZnode

②、JAVA調用API

    /**
     * 獲取Znode數據
     */
    @Test
    public void getData() throws Exception {
        final CountDownLatch countDownLatch = new CountDownLatch(1);
        ZooKeeper zk = new ZooKeeper("centos75:2181,centos76:2181,centos77:2181", 5000, new Watcher() {
            public void process(WatchedEvent watchedEvent) {
                if(watchedEvent.getState()==Event.KeeperState.SyncConnected){
                    countDownLatch.countDown();
                }
            }
        });
        countDownLatch.await();
        byte[] data = zk.getData("/apijava", false, new Stat());
        System.out.println(new String(data));
    }

3、給ZNode設置內容

①、命令行方式

      set /FZnode "Set Data"

②、JAVA調用API

    /**
     * 給Znode設置數據
     * @throws Exception
     */
    @Test
    public void setData() throws  Exception{
        final CountDownLatch countDownLatch = new CountDownLatch(1);
        ZooKeeper zk = new ZooKeeper("centos75:2181,centos76:2181,centos77:2181", 5000, new Watcher() {
            public void process(WatchedEvent watchedEvent) {
                if(watchedEvent.getState() == Event.KeeperState.SyncConnected){
                    countDownLatch.countDown();
                }
            }
        });
        countDownLatch.await();
        /**
         * 1表示當前Znode版本，每當數據更改時，Zookeeper會更新Znode的版本號.
         */
        zk.setData("/apijava",new String("API SET").getBytes(),1);
    }

4、列出ZNode下的的子節點

①、命令行方式

      ls /FZnode

②、JAVA調用API

    /**
     * 獲取Znode所有的子節點
     */
    @Test
    public void getChild()throws Exception{
        final CountDownLatch countDownLatch = new CountDownLatch(1);
        ZooKeeper zk = new ZooKeeper("centos75:2181,centos76:2181,centos77:2181", 5000, new Watcher() {
            public void process(WatchedEvent watchedEvent) {
                if(watchedEvent.getState() == Event.KeeperState.SyncConnected){
                    countDownLatch.countDown();
                }
            }
        });
        countDownLatch.await();
        List<String> children = zk.getChildren("/apijava", false);
        for (int i = 0; i < children.size(); i++) {
            System.out.println(children.get(i));
        }
    }

5、刪除ZNode節點

①、命令行方式

       rmr /FZnode

②、JAVA調用API

    /**
     * 刪除指定Znode,並且該Znode沒有子項
     * @throws Exception
     */
    @Test
    public void delete() throws  Exception{
        final CountDownLatch countDownLatch = new CountDownLatch(1);
        ZooKeeper zk = new ZooKeeper("centos75:2181,centos76:2181,centos77:2181", 5000, new Watcher() {
            public void process(WatchedEvent watchedEvent) {
                if(watchedEvent.getState() == Event.KeeperState.SyncConnected  ){
                    countDownLatch.countDown();
                }
            }
        });
        countDownLatch.await();
        zk.delete("/APIjava0000000012",0);
    }

6、判斷ZNode是否存在：

    /**
     * 檢查Znode是否存在
     */
    @Test
    public void exists() throws Exception {
        final CountDownLatch  countDownLatch = new CountDownLatch(1);
        ZooKeeper zk = new ZooKeeper("centos75:2181,centos76:2181,centos77:2181", 5000, new Watcher() {
            public void process(WatchedEvent watchedEvent) {
                if(watchedEvent.getState() == Event.KeeperState.SyncConnected){
                    countDownLatch.countDown();
                }
            }
        });
        countDownLatch.await();
        Stat stat = zk.exists("/apijava", false);
        if(stat == null){
            System.out.println("Znode節點不存在");
        }else {
            System.out.println("Znode節點存在，並且版本是："+stat.getVersion());
        }
    }

7、總結：

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