Zookeeper三個監聽案例

一、監聽某一節點內容

/**
 * @author: PrincessHug
 * @date: 2019/2/25, 14:28
 * @Blog: https://www.cnblogs.com/HelloBigTable/
 * 監聽一個節點內容的變化
 */
public class WatchZoneDemo {
    ZooKeeper zkCli = null;

    public static void main(String[] args) throws IOException, InterruptedException {
        WatchZoneDemo wz = new WatchZoneDemo();
        wz.getConnection();
        Thread.sleep(Long.MAX_VALUE);
    }

    private void getConnection() throws IOException {
        zkCli = new ZooKeeper("192.168.126.128:2181,192.168.126.129:2181,192.168.126.130:2181", 3000, new Watcher() {
            public void process(WatchedEvent watchedEvent) {
                try {
                    byte[] data = zkCli.getData("/Wyh", true, null);
                    System.out.println("監聽類型為：" + watchedEvent.getType());
                    System.out.println("監聽路徑為：" + watchedEvent.getPath());
                    System.out.println("數據被修改為：" + new String(data));
                    System.out.println("=======================================");
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}

二、監聽某節點目錄的變化

/**
 * @author: PrincessHug
 * @date: 2019/2/25, 14:57
 * @Blog: https://www.cnblogs.com/HelloBigTable/
 * 監聽一個節點的子節點的變化
 */
public class WatchChildrenDemo {
    ZooKeeper zkCli = null;

    public static void main(String[] args) throws IOException, InterruptedException {
        WatchChildrenDemo wc = new WatchChildrenDemo();
        wc.getConnction();
        Thread.sleep(Long.MAX_VALUE);
    }

    private void getConnction() throws IOException {
        zkCli = new ZooKeeper("192.168.126.128:2181,192.168.126.129:2181,192.168.126.130:2181", 3000, new Watcher() {
            public void process(WatchedEvent watchedEvent) {
                ArrayList<String> nodes = new ArrayList<String>();
                try {
                    List<String> children = zkCli.getChildren("/", true);
                    for (String c:children){
                        nodes.add(c);
                    }
                    System.out.println(nodes);
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}

三、Zookeeper當太上下線的感知系統

　　1.需求：某分散式系統中，主節點有多台，可以進行動態上下限，當有任何一臺機器發生了動態的上下線， 任何一臺客戶端都能感知得到

　　2.思路：

　　　　(1)創建客戶端與服務端

　　　　(2)啟動client端 並監聽

　　　　(3)啟動server端 並註冊

　　　　(4)當server端發生上下線

　　　　(5)client端都能感知的到

　　3.代碼

public class ZKServer {
    ZooKeeper zk = null;
    private String parentNode = "/Servers";

    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
        String childNode = "hd1-1";
        ZKServer zkServer = new ZKServer();
        //獲取連接
        zkServer.getConnection();
        //註冊信息
        zkServer.regist(childNode);
        //業務邏輯，提示上線
        zkServer.build(childNode);

    }

    private void build(String hostname) throws InterruptedException {
        System.out.println(hostname + "上線了！！");
        Thread.sleep(Long.MAX_VALUE);
    }

    private void regist(String hostname) throws KeeperException, InterruptedException {
        String path = zk.create(parentNode + "/server", hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
        System.out.println(path);
    }

    private void getConnection() throws IOException {
        zk = new ZooKeeper("192.168.126.128:2181,192.168.126.129:2181,192.168.126.130:2181", 3000, new Watcher() {
            public void process(WatchedEvent watchedEvent) {

            }
        });
    }
}

public class ZKClient {
    ZooKeeper zk = null;
    public static void main(String[] args) throws IOException, KeeperException, InterruptedException {
        ZKClient zkClient = new ZKClient();
        zkClient.getConnection();
        zkClient.watching();
    }

    private void watching() throws InterruptedException {
        Thread.sleep(Long.MAX_VALUE);
    }

    private void getConnection() throws IOException {
        zk = new ZooKeeper("192.168.126.128:2181,192.168.126.129:2181,192.168.126.130:2181", 3000, new Watcher() {
            public void process(WatchedEvent watchedEvent) {
                try {
                    List<String> children = zk.getChildren("/Servers", true);
                    ArrayList<String> node = new ArrayList<String>();
                    for (String c:children){
                        byte[] data = zk.getData("/Servers/" + c, true, null);
                        node.add(new String(data));
                    }
                    System.out.println(node);
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
    }
}