Zookeeper实例原生API--创建一个基本的Zookeeper会话

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import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Created with IntelliJ IDEA.
 * Description: TODO(Java API -> 创建连接 -> 创建一个最基本的ZooKeeper对象实例)
 * User: zhubo
 * Date: 2018-01-09
 * Time: 20:58
 */
public class ZooKeeper_Constructor_Usage_Simple implements Watcher{

    /** 定义原子变量 */
    AtomicInteger seq = new AtomicInteger();

    private static CountDownLatch countDownLatch = new CountDownLatch(1);
    public static void main(String[] args) throws Exception{
        ZooKeeper zooKeeper = new ZooKeeper("centos4:2181",5000,new ZooKeeper_Constructor_Usage_Simple());
        try{
            countDownLatch.await();
        }catch (Exception e){
            e.printStackTrace();
        }
        System.out.println("ZooKeeper session established.");

        if(zooKeeper != null){
            zooKeeper.close();
        }
        Thread.sleep(1000L);
    }

    @Override
    public void process(WatchedEvent event) {
        System.out.println("进入 process 。。。。。event = " + event);
        try {
            Thread.sleep(200);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        if (event == null) {
            return;
        }
        // 连接状态
        Event.KeeperState keeperState = event.getState();
        // 事件类型
        Event.EventType eventType = event.getType();
        // 受影响的path
        String path = event.getPath();

        String logPrefix = "【Watcher-" + this.seq.incrementAndGet() + "】";

        System.out.println(logPrefix + "收到Watcher通知");
        System.out.println(logPrefix + "连接状态:\t" + keeperState.toString());
        System.out.println(logPrefix + "事件类型:\t" + eventType.toString());

        if (Event.KeeperState.SyncConnected == keeperState) {
            // 成功连接上ZK服务器
            if (Event.EventType.None == eventType) {
                System.out.println(logPrefix + "成功连接上ZK服务器");
                countDownLatch.countDown();
            }
            //创建节点
            else if (Event.EventType.NodeCreated == eventType) {
                System.out.println(logPrefix + "节点创建");
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                //this.exists(path, true);
            }
            //更新节点
            else if (Event.EventType.NodeDataChanged == eventType) {
                System.out.println(logPrefix + "节点数据更新");
                System.out.println("我看看走不走这里........");
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                //System.out.println(logPrefix + "数据内容: " + this.readData(PARENT_PATH, true));
            }
            //更新子节点
            else if (Event.EventType.NodeChildrenChanged == eventType) {
                System.out.println(logPrefix + "子节点变更");
                try {
                    Thread.sleep(3000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                //System.out.println(logPrefix + "子节点列表：" + this.getChildren(PARENT_PATH, true));
            }
            //删除节点
            else if (Event.EventType.NodeDeleted == eventType) {
                System.out.println(logPrefix + "节点 " + path + " 被删除");
            }
            else{}
        }
        else if (Event.KeeperState.Disconnected == keeperState) {
            System.out.println(logPrefix + "与ZK服务器断开连接");
        }
        else if (Event.KeeperState.AuthFailed == keeperState) {
            System.out.println(logPrefix + "权限检查失败");
        }
        else if (Event.KeeperState.Expired == keeperState) {
            System.out.println(logPrefix + "会话失效");
        }
        else {}
        System.out.println("--------------------------------------------");
    }
}

 

注意：

Zookeeper客户端和服务器端会话的建立是一个异步的过程，也就是说，在程序中构造方法会在处理完客户端初始化工作后立即返回，大多数情况下会话的生命周期处于CONNECTING状态，当该会话真正创建完毕后，Zookeeper服务端会向会话对应的客户端发送一个事件通知，已告知客户端，客户端之后在获取这个通知之后，才算真正建立了会话。

实现Watcher接口，重写process方法，该方法负责处理来自Zookeeper服务端的Watcher通知。 

 

转载于:https://my.oschina.net/LucasZhu/blog/1605022