zookeeper常用的方法（四）

创建zookeeper

import java.io.IOException;

import java.util.concurrent.CountDownLatch;

import org.apache.zookeeper.WatchedEvent;

import org.apache.zookeeper.Watcher;

import org.apache.zookeeper.ZooKeeper;

public class ZookeeperDemo {

private static final String CONNECTION_STRING="127.0.0.1:2182";

private static final int SESSION_TIMEOUT = 5000;

private static CountDownLatch latch = new CountDownLatch(1);

public static void main(String[] args) throws IOException, InterruptedException {

ZooKeeper zk = new ZooKeeper(CONNECTION_STRING, SESSION_TIMEOUT, new Watcher(){

@Override

public void process(WatchedEvent event) {

if(event.getState() == Event.KeeperState.SyncConnected){

latch.countDown();

}

}

});

         建立zookeeper会话的过程是异步的，当构造完zk对象后，线程将继续执行后续代码，但此时会话可能尚未建立完毕，所以要用CountDownLatch 工具。

latch.await();

System.out.println(zk);

}

}

 构造函数public ZooKeeper(String connectString, int sessionTimeout, Watcher watcher)

 connectString：连接服务器列表（ip+端口号），如果多个地址用“,”分割，例如："127.0.0.1:3000,127.0.0.1:3001,127.0.0.1:3002"。

    sessionTimeout：心跳检测时间周期，单位毫秒。

    watcher：监视器接口，事件处理通知器。

同步获取节点集合

public List<String> getChildren(final String path, Watcher watcher)

List<String> listNode = zk.getChildren("/", null);

for (String node : listNode) {

System.out.println(node);

}

   //异步获取节点集合

 public void getChildren(final String path, Watcher watcher,

            ChildrenCallback cb, Object ctx)

zk.getChildren("/", null, new ChildrenCallback() {

@Override

public void processResult(int rc, String path, Object ctx, List<String> children) {

System.out.println( "path="+path);

for (String node : children) {

System.out.println(node);

}

}

}, null);

exit()判断节点是否存在

public Stat exists(final String path, Watcher watcher)

        throws KeeperException, InterruptedException

Stat stat = zk.exists("/root", null);

System.out.println(stat);

stat = zk.exists("/root2", null);

System.out.println(stat);

打印信息如下：

4294967298,4294967300,1534486665805,1534486780890,1,0,0,0,11,0,4294967298

null

exit()异步判断节点是否存在

public void exists(final String path, Watcher watcher,

            StatCallback cb, Object ctx)

创建节点create

public String create(final String path, byte data[], List<ACL> acl,

            CreateMode createMode)

CreateMode类型分为4种

1.PERSISTENT--持久型

2.PERSISTENT_SEQUENTIAL--持久顺序型

3.EPHEMERAL--临时型

4.EPHEMERAL_SEQUENTIAL--临时顺序型

zk.create("/root/city", "beijing".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);

获取节点数据getData

public byte[] getData(final String path, Watcher watcher, Stat stat)

        throws KeeperException, InterruptedException

设置节点数据setData

public Stat setData(final String path, byte data[], int version)

        throws KeeperException, InterruptedException

删除节点delete

public void delete(final String path, int version)

        throws InterruptedException, KeeperException