zookeeper快速入门四：在java客户端中操作zookeeper

先启动zookeeper服务端。

在maven引入zookeeper依赖。

<dependency> <groupId>org.apache.hadoop</groupId> <artifactId>zookeeper</artifactId> <version>3.3.1</version> </dependency>

org.apache.zookeeper.Zookeeper是客户端入口主类，负责建立与server的会话。它提供了以下 所示几类主要方法。 

 

在java中启动客户端，注册一个watcher监听链接的建立。

import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooKeeper; public class ZookeeperClient { private static final String connectString = "127.0.0.1:2181"; private static final int sessionTimeout = 2000; private static ZooKeeper zkClient = null; public void init() throws Exception { zkClient = new ZooKeeper(connectString, sessionTimeout, new Watcher() { @Override public void process(WatchedEvent event) { // 收到事件通知后的回调函数（应该是我们自己的事件处理逻辑） System.out.println("zookeeper链接建立"); } }); } }

在main方法里测试我们的init方法，用Thread.sleep方法等待zookeeper连接创建，不然在zookeeper客户端建立连接之前主线程就已经退出。

public static void main(String[] args)throws Exception{ new ZookeeperClient().init(); Thread.sleep(5000); }

控制台输出：

接下来我们创建一个名为“/java”的节点，节点数据为“data”，ZooDefs.Ids.OPEN_ACL_UNSAFE的意思是不节点能被所有人访问，CreateMode.PERSISTENT：节点的类型为持久节点。

public void createZnode()throws Exception{ zkClient.create("/java", "data".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); }

判断节点是否存在，false代表不注册监听事件，如果是true，则注册我们在new zookeeper方法里面传递的watcher。

public void testExist() throws Exception{ Stat stat = zkClient.exists("/java", false); System.out.println(stat==null?"节点不存在":"节点存在"); }

测试一下我们的方法。

public static void main(String[] args)throws Exception{ new ZookeeperClient().init(); Thread.sleep(5000); new ZookeeperClient().createZnode(); new ZookeeperClient().testExist(); }

 

 获取节点的数据。false和上面exists方法参数含义一样，表示不注册连接建立时的watcher，第三个stat对象则存储了除了节点数据之外的其他信息，如czxid、mzxid等。如果为null则表示不保存节点的这些信息。

public void getNodeData()throws Exception{ byte[] res = zkClient.getData("/java",false,new Stat()); System.out.println(new String(res)); }

同样测试我们的方法。

public static void main(String[] args)throws Exception{ new ZookeeperClient().init(); Thread.sleep(3000); new ZookeeperClient().getNodeData(); }

 获取ACL控制列表

public void getACl()throws Exception{ List<ACL> res = zkClient.getACL("/java",new Stat()); for(ACL acl : res){ System.out.println(acl.getId().toString()+acl.getPerms()); } }

测试：

public static void main(String[] args)throws Exception{ new ZookeeperClient().init(); Thread.sleep(3000); new ZookeeperClient().getACl(); }

在/java下创建子节点，获取子节点列表。

public void createChildZnode()throws Exception{ zkClient.create("/java/child", "child data".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); zkClient.create("/java/child2", "child2 data".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); } public void getChildNode()throws Exception{ List<String> res = zkClient.getChildren("/java",false); for(String s : res){ System.out.println(s); } }

测试：

public static void main(String[] args)throws Exception{ new ZookeeperClient().init(); Thread.sleep(3000); new ZookeeperClient().createChildZnode(); new ZookeeperClient().getChildNode(); }

全部代码如下：

import org.apache.zookeeper.*; import org.apache.zookeeper.data.ACL; import org.apache.zookeeper.data.Stat; import java.util.List; public class ZookeeperClient { private static final String connectString = "127.0.0.1:2181"; private static final int sessionTimeout = 2000; private static ZooKeeper zkClient = null; public void init() throws Exception { zkClient = new ZooKeeper(connectString, sessionTimeout, new Watcher() { @Override public void process(WatchedEvent event) { // 收到事件通知后的回调函数（应该是我们自己的事件处理逻辑） System.out.println("zookeeper链接建立"); } }); } public void createZnode()throws Exception{ zkClient.create("/java", "data".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); } public void createChildZnode()throws Exception{ zkClient.create("/java/child", "child data".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); zkClient.create("/java/child2", "child2 data".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); } public void getChildNode()throws Exception{ List<String> res = zkClient.getChildren("/java",false); for(String s : res){ System.out.println(s); } } public void testExist() throws Exception{ Stat stat = zkClient.exists("/java", false); System.out.println(stat==null?"节点不存在":"节点存在"); } public void getNodeData()throws Exception{ byte[] res = zkClient.getData("/java",false,new Stat()); System.out.println(new String(res)); } public void getACl()throws Exception{ List<ACL> res = zkClient.getACL("/java",new Stat()); for(ACL acl : res){ System.out.println(acl.getId().toString()+acl.getPerms()); } } public static void main(String[] args)throws Exception{ new ZookeeperClient().init(); Thread.sleep(3000); new ZookeeperClient().createChildZnode(); new ZookeeperClient().getChildNode(); } }