Zookeeper客戶端java代碼操作

Zookeeper客戶端java代碼操作

上篇博客記錄了shell命令操作zookeeper集羣的方式，這次嘗試採用java代碼來操作。通過查閱API，發現並不困難。

1. 首先獲得客戶端與服務器的連接

    //zookeeper客戶端
    private ZooKeeper zkCli;
    //連接地址
    private static final String CONNECT_STRING = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
    //session過期時間
    private static final int SESSION_TIMEOUT = 2000;

    /**
     * 創建客戶端實例對象
     *
     * @throws IOException
     */
    @Before
    public void before() throws IOException {
        zkCli = new ZooKeeper(CONNECT_STRING, SESSION_TIMEOUT, (event) -> {
            System.out.println("默認的回調函數");
        });
    }

2. 列出根節點下的子節點(非遞歸)

    @Test
    public void ls() throws KeeperException, InterruptedException {
        List<String> children = zkCli.getChildren("/", e -> {
            System.out.println("自定義回調函數");
        });

        System.out.println("---------------------");
        for (String child : children) {
            System.out.println(child);
        }
        System.out.println("+++++++++++++++++++++");

        Thread.sleep(Long.MAX_VALUE);

    }

3. 在一個節點下創建子節點

    @Test
    public void create() throws KeeperException, InterruptedException {

        //parameter1：創建的節點路徑  parameter2：節點的數據 parameter3：節點權限  parameter4：節點類型
        String str = zkCli.create("/idea", "idea2019".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        System.out.println(str);
        Thread.sleep(Long.MAX_VALUE);
    }

4. 獲取指定節點的內容

    @Test
    public void get() throws KeeperException, InterruptedException {
        byte[] data = zkCli.getData("/simon", true, new Stat());
        String str = new String(data);
        System.out.println(str);
    }

5. 給指定節點設置值

    @Test
    public void set() throws KeeperException, InterruptedException {
        Stat stat = zkCli.setData("/simon", "abcd".getBytes(), 1);
        System.out.println(stat.getDataLength());
    }

6. 獲取指定節點的狀態信息

    @Test
    public void stat() throws KeeperException, InterruptedException {

        Stat exists = zkCli.exists("/ideaa", false);
        if (exists == null) {
            System.out.println("節點不存在");
        } else {
            System.out.println(exists.getDataLength());
        }
    }

7. 刪除指定節點

    @Test
    public void delete() throws KeeperException, InterruptedException {
        Stat exists = zkCli.exists("/idea", false);
        if (exists != null) {
            zkCli.delete("/idea", exists.getVersion());
        }
    }

8. 循環註冊，動態獲取節點的信息。

也就是當節點有任何變化時，就會調用回調函數，動態的顯示節點的變化信息。

    @Test
    public void register() throws KeeperException, InterruptedException {
        byte[] data = zkCli.getData("/simon2", new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {
                try {
                    register();//發生事件，通知的時候在註冊一遍，實現了循環調用
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, null);
        System.out.println(new String(data));
    }


    @Test
    public void testRegister() {
        try {
            register(); //調用register()方法,將進程卡住，循環執行register
            Thread.sleep(Long.MAX_VALUE);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

代碼很簡單易懂，只是有些內部原理還是有些模糊，例如：Stat是什麼？zookeeper是怎麼監聽到節點發生變化的？又是如何將變化通知給客戶端的？在之後的博客中將會詳細記錄。~