Zookeeper之常用API详解

1、创建ZNode

①命令行方式

• 在根目录下创建“FZnode"节点并存储数据”First Znode"：

       create /FZnode "First Znode"

• 在根目录下创建短暂的Znode节点

       create -e /SZnode "Secondary Znode"

• 创建短暂有序列的Znode节点

       create -e -s /EZnode "Ephemeral_SEQUENTIAL"

• 创建持久有序列的Znode节点

       create -s /PZnode "PERSISTENT_SEQUENTIAL"

②JAVA调用API

    /**     * 创建ZNode节点     * @throws Exception     */    @Test    public void create() throws Exception{        //用于停止（等待）主进程，直到客户端与Zookeeper集合连接。        final CountDownLatch cd = new CountDownLatch(1);        ZooKeeper zk = new ZooKeeper("centos75:2181,centos76:2181,centos77:2181",5000,new Watcher(){            //watcher返回Zookeeper连接状态            public void process(WatchedEvent watchedEvent) {                System.out.println(watchedEvent.getState());                //连接建立，回调process接口时，其watchedEvent.getState() 为 Event.KeeperState.SyncConnected                if(watchedEvent.getState() == Event.KeeperState.SyncConnected){                    //唤醒wait中的线程                    cd.countDown();                }            }        });        cd.await();        /**         * 1、Znode节点路径         * 2、Znode节点内容         * 3、Znode创建节点的访问控制列表         * 4、Znode状态，有四种状态         */        zk.create("/APIjava",new String("test API").getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);    }

2、获取ZNode数据

①、命令行方式

      get /FZnode

②、JAVA调用API

    /**     * 获取Znode数据     */    @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、给ZNode设置内容

①、命令行方式

      set /FZnode "Set Data"

②、JAVA调用API

    /**     * 给Znode设置数据     * @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表示当前Znode版本，每当数据更改时，Zookeeper会更新Znode的版本号.         */        zk.setData("/apijava",new String("API SET").getBytes(),1);    }

4、列出ZNode下的的子节点

①、命令行方式

      ls /FZnode

②、JAVA调用API

    /**     * 获取Znode所有的子节点     */    @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、删除ZNode节点

①、命令行方式

       rmr /FZnode

②、JAVA调用API

    /**     * 删除指定Znode,并且该Znode没有子项     * @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、判断ZNode是否存在：

    /**     * 检查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节点不存在");        }else {            System.out.println("Znode节点存在，并且版本是："+stat.getVersion());        }    }

7、总结：

• 梳理笔记，加强记忆及理解。
• 巩固基础，勇攀高峰！！！
• 加油(ง •_•)ง(ง •_•)ง(ง •_•)ง