2. Zookeeper的java api

引入maven：

<dependencies>
    <dependency>
        <groupId>org.apache.zookeeper</groupId>
        <artifactId>zookeeper</artifactId>
        <version>{服务器的zk是什么版本这里就引入什么版本}</version>
    </dependency>
</dependencies>

java：

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import java.io.IOException;
import java.util.concurrent.CountDownLatch;
public class TestZookeeperClient {
    static CountDownLatch cd = new CountDownLatch(1);
    static Stat stat=new Stat();
    static ZooKeeper zk;
    static {
        try {
            zk = new ZooKeeper("192.168.235.133:2181,192.168.235.133:2182,192.168.235.133:2183,192.168.235.133:2184",
                        3000, new SessionWatcher() );
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
        System.out.println( "Hello World!" );
        //zk是有session概念的，没有连接池的概念
        //watch:观察，回调
        //watch的注册值发生在 读类型调用，get，exites。。。
        //第一类：new zk 时候，传入的watch，这个watch，session级别的，跟path 、node没有关系。
        System.out.println("程序卡主等待连接zk...");
        cd.await();
        ZooKeeper.States state = zk.getState();
        switch (state) {
            case CONNECTING:
                System.out.println("ing......");
                break;
            case ASSOCIATING:
                break;
            case CONNECTED:
                System.out.println("程序已连接zk......");
                break;
            case CONNECTEDREADONLY:
                break;
            case CLOSED:
                break;
            case AUTH_FAILED:
                break;
            case NOT_CONNECTED:
                break;
        }
        //创建/ooxx的临时目录。存放数据为 "olddata"
        String pathName = zk.create("/ooxx", "olddata".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        //获取/ooxx下的数据，并在数据修改时触发一次new OOXXWatcher()
        byte[] node = zk.getData("/ooxx", new OOXXWatcher() , stat);
        System.out.println("/ooxx下的数据为" + new String(node));
        //触发回调
        Stat stat1 = zk.setData("/ooxx", "newdata".getBytes(), 0);
        //再次在/ooxx的临时目录下设置新的数据
        Stat stat2 = zk.setData("/ooxx", "newdata01".getBytes(), stat1.getVersion());
        System.out.println("-------async start----------");
        zk.getData("/ooxx", false, new GetOOXXCallBack("/ooxx"),"abc");
        System.out.println("-------async over----------");
        //程序阻塞住，防止程序session丢失
        System.in.read();
    }
    /**
     * Session级别的 Watcher
     */
    private static class SessionWatcher implements Watcher{
        //Watch 的回调方法！
        @Override
        public void process(WatchedEvent event) {
            Event.KeeperState state = event.getState();
            Event.EventType type = event.getType();
            String path = event.getPath();
            System.out.println("new zk watch: "+ event.toString());
            switch (state) {
                case Unknown:
                    break;
                case Disconnected:
                    break;
                case NoSyncConnected:
                    break;
                case SyncConnected:
                    System.out.println("SessionWatcher监听到到程序已连接zk......");
                    cd.countDown();
                    break;
                case AuthFailed:
                    break;
                case ConnectedReadOnly:
                    break;
                case SaslAuthenticated:
                    break;
                case Expired:
                    break;
            }
            switch (type) {
                case None:
                    break;
                case NodeCreated:
                    break;
                case NodeDeleted:
                    break;
                case NodeDataChanged:
                    break;
                case NodeChildrenChanged:
                    break;
            }
        }
    }
    /**
     * 目录级别的 Watcher
     */
    private static class OOXXWatcher implements Watcher{
        @Override
        public void process(WatchedEvent event) {
            System.out.println("触发 OOXXWatcher : "+event.toString());
            try {
                //true   default Watch  被重新注册   new zk的那个watch
                System.out.println("再次注册/ooxx下的Watcher为 OOXXWatcher");
                zk.getData("/ooxx",this  ,stat);
            } catch (KeeperException e) {
                e.printStackTrace();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
    /**
     * /OOXX目录下的数据更新 异步回调
     */
    private static class GetOOXXCallBack implements AsyncCallback.DataCallback{
        private String path;
        GetOOXXCallBack(String path){
            this.path = path;
        }
        @Override
        public void processResult(int i, String s, Object ctx, byte[] data, Stat stat) {
            System.out.println("-------async call back----------");
            System.out.println(ctx.toString());
            System.out.println(this.path+"目录下的数据为："+new String(data));
        }
    }
}