ZooKeeper（四）ZooKeeper客户端Java zkClient和Curator

• zkClient：开源的zk客户端，在原生API基础上封装，是一个更易于使用的zookeeper客户端
  1. 创建会话（同步，重试）
  2. 创建节点（同步，递归创建）
  3. 删除节点（同步，递归删除）
  4. 代码示例

    import net.lc7.model.User;
    import net.lc7.util.ZkPropertiesUtil;
    import org.I0Itec.zkclient.IZkChildListener;
    import org.I0Itec.zkclient.IZkDataListener;
    import org.I0Itec.zkclient.ZkClient;
    import org.I0Itec.zkclient.serialize.SerializableSerializer;
    import org.apache.zookeeper.CreateMode;
    import org.apache.zookeeper.data.Stat;
  
    import java.util.List;
  
    /**
     * @Description:
     * @Author: Jason.zhu
     * @Create: 2019/05/22 17:37
     */
  
    public class ZkClientMain {
        private static ZkClient zkClient;
  
  
        public static void main(String[] args) throws Exception{
            String ip_port = ZkPropertiesUtil.getZkServerIp();
            int sessionTimeout = 10000;
            int connetionTimeout = ZkPropertiesUtil.getZktimeout();
            zkClient = new ZkClient(ip_port,sessionTimeout,connetionTimeout,new SerializableSerializer());
  
            updateNodeData();
        }
  
        /**
         * 新建节点
         */
        private static void createNode(){
            User user = User.builder().age(18).id(1).name("jason").build();
            String node = zkClient.create("/user",user,CreateMode.PERSISTENT);
            System.out.println(node);
        }
  
        //获取节点
        private static void getNodeData(){
            Stat stat = new Stat();
            User user1 = zkClient.readData("/user", stat);
            System.out.println("name : " + user1.getName() );
            System.out.println("stat : " + stat);
        }
  
        /**
         * 创建子节点
         */
        private static void createChildrenNode(){
            String node = zkClient.create("/user/1","user1",CreateMode.PERSISTENT);
            System.out.println(node);
            node = zkClient.create("/user/2","user2",CreateMode.PERSISTENT);
            System.out.println(node);
            node = zkClient.create("/user/3","user3",CreateMode.PERSISTENT);
            System.out.println(node);
        }
  
        /**
         * 获取子节点
         */
        private static void getChildNode(){
            String node = "/user";
            boolean exist = zkClient.exists(node);
            if(exist){
                List childNodes = zkClient.getChildren(node);
                childNodes.stream().forEach(System.out::println);
            }
        }
  
        private static void delNode(){
            String node = "/user";
            boolean exist = zkClient.exists(node);
            if(exist){
    //           zkClient.delete(node);//删除当前节点，有子节点无法删除
                zkClient.deleteRecursive(node);//删除当前节点，有子节点删除子节点
            }
        }
  
        /**
         * 更新节点数据
         */
        private static void updateNodeData(){
            User user = User.builder().age(11).name("wangwu").id(12).build();
            String node = "/user";
            zkClient.writeData(node, user);
  
        }
  
        /**
         * 监控子节点
         */
        private static void watchChildChange() throws InterruptedException {
            String node = "/user";
            zkClient.subscribeChildChanges(node, (str,strs) -> {
                System.out.println(str);
                System.out.println(strs);
            });
            Thread.sleep(Long.MAX_VALUE);
        }
  
        /**
         *监控节点
         */
        private static void watchNode(){
            String node ="/user";
            zkClient.subscribeDataChanges(node, new IZkDataListener() {
                @Override
                public void handleDataChange(String s, Object o) throws Exception {
                    System.out.println("node name : " + s + ",updated !!");
                    User user = (User)o;
                    System.out.println("node new value : " + user);
                }
  
                @Override
                public void handleDataDeleted(String s) throws Exception {
                    System.out.println("node name : " + s + ", deleted !!");
                }
            });
  
            try {
                Thread.sleep(Long.MAX_VALUE);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
  
    }
  
  import lombok.Builder;
  import lombok.Data;
  
  import java.io.Serializable;
  
  @Data
  @Builder
  public class User implements Serializable {
        private int id;
        private int age;
        private String name;
  
        @Override
        public String toString(){
            return "id=" + id + ", age="+age + ",name="+name;
       }
  }
  

• curator：开源的zk客户端，在原生API基础上封装，apache顶级项目
  1. Curator采用Fluent风格API
  2. Curator对zk进行基本操作代码示例：

  import net.lc7.util.ZkPropertiesUtil;
  import org.apache.curator.framework.CuratorFramework;
  import org.apache.curator.framework.CuratorFrameworkFactory;
  import org.apache.curator.retry.RetryNTimes;
  
  /**
    * @Description: Curator对zk进行基本操作，Curator采用流式风格API
    * @Author: Jason.zhu
    * @Create: 2019/05/24 17:55
    */
  public class CuratorClient {
  private static CuratorFramework curatorFramework = CuratorFrameworkFactory.newClient(
                ZkPropertiesUtil.getZkServerIp(),
                new RetryNTimes(10, 5000));
  
  private static String path = "/curator_node";
  
  public static void main(String[] args) throws Exception {
            curatorFramework.start();
  
            //create node
            String data = "curator_data";
            curatorFramework.create().creatingParentsIfNeeded().forPath(path,data.getBytes());
  
  
            //get Node and Data
            print("ls", "/");
            print(curatorFramework.getChildren().forPath("/"));
  
            print("get", path);
            print(curatorFramework.getData().forPath(path));
  
            //update node data
  
            String dataNew = "curator_data_new";
            print("set", path, dataNew);
            curatorFramework.setData().forPath(path, dataNew.getBytes());
  
            print("get", path);
            print(curatorFramework.getData().forPath(path));
  
            //remove node
            print("delete", path);
            curatorFramework.delete().forPath(path);
            print("ls", "/");
            print(curatorFramework.getChildren().forPath("/"));
  
            curatorFramework.close();
        }
  
        private static void print(String... cmds) {
            StringBuilder text = new StringBuilder("$ ");
            for (String cmd : cmds) {
                text.append(cmd).append(" ");
            }
            System.out.println(text.toString());
        }
  
        private static void print(Object result) {
            System.out.println(
                    result instanceof byte[]
                            ? new String((byte[]) result)
                            : result);
        }
  
    }
  
    public class ZkPropertiesUtil {
  
    private static Properties zkProperties = new Properties();
  
    static {
  
        InputStream is = ZkPropertiesUtil.class.getResourceAsStream("/zk.properties");
        try {
            zkProperties.load(is);
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            try {
                if (is != null) {
                    is.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
  
    public static String getZkServerIp(){
        return zkProperties.getProperty("zk.zkServerIps");
    }
  
    public static int getZktimeout(){
        return Integer.valueOf(zkProperties.getProperty("zk.timeout"));
    }
  
    public static void main(String[] args) {
       String source = "0101888";
  
        System.out.println(source.substring(0, source.length() - 2));
    }
  }
  

  3. Curator操作zk实现分布式锁

    import net.lc7.util.ZkPropertiesUtil;
    import org.apache.curator.framework.CuratorFramework;
    import org.apache.curator.framework.CuratorFrameworkFactory;
    import org.apache.curator.framework.recipes.locks.InterProcessMultiLock;
    import org.apache.curator.framework.recipes.locks.InterProcessMutex;
    import org.apache.curator.retry.RetryNTimes;
  
    import java.util.concurrent.TimeUnit;
  
    /**
     * @Description: Curator操作zk实现分布式锁
     * @Author: Jason.zhu
     * @Create: 2019/05/27 11:28
     */
  
    public class CuratorDistributeLock {
        private static String lockPath = "/lockPath";
  
        public static void main(String[] args) throws Exception{
            CuratorFramework curatorFramework = CuratorFrameworkFactory.newClient(ZkPropertiesUtil.getZkServerIp(),
                                                            new RetryNTimes(10,5000));
            curatorFramework.start();
            System.out.println("zk client start successfully!!");
            Thread.sleep(1000L);
  
  
            Thread t1 = new Thread(() -> {
               doWithLock(curatorFramework);
            }, "t1");
  
            Thread t2 = new Thread(() -> {
                doWithLock(curatorFramework);
            }, "t2");
  
            t1.start();
            t2.start();
  
  
    //        curatorFramework.close();
        }
  
        private static void doWithLock(CuratorFramework curatorFramework){
            System.out.println("Client state : " + curatorFramework.getState());
            InterProcessMutex lock = new InterProcessMutex(curatorFramework, lockPath);
  
            try {
                if(lock.acquire(10*1000, TimeUnit.SECONDS)){
                    System.out.println(Thread.currentThread().getName() + "hold lock!!");
                    Thread.sleep(5000L);
                    System.out.println(Thread.currentThread().getName() + "release lock!!");
                }
            }catch (Exception e){
                e.printStackTrace();
            }finally {
                try {
                    lock.release();
                }catch (Exception e){
                    e.printStackTrace();
                }
  
            }
        }
    }
  

  4. Curator操作zk实现Leader选举

    import net.lc7.util.ZkPropertiesUtil;
    import org.apache.curator.framework.CuratorFramework;
    import org.apache.curator.framework.CuratorFrameworkFactory;
    import org.apache.curator.framework.recipes.leader.LeaderSelector;
    import org.apache.curator.framework.recipes.leader.LeaderSelectorListener;
    import org.apache.curator.framework.state.ConnectionState;
    import org.apache.curator.retry.RetryNTimes;
    import org.apache.curator.utils.EnsurePath;
  
    /**
     * @Description: Leader选举
     * 当集群里的某个服务down机时，我们可能要从slave结点里选出一个作为新的master，这时就需要一套能在分布式环境中自动协调的Leader选举方法。
     * Curator提供了LeaderSelector监听器实现Leader选举功能。同一时刻，只有一个Listener会进入takeLeadership()方法，说明它是当前的Leader。
     * 注意：当Listener从takeLeadership()退出时就说明它放弃了“Leader身份”，这时Curator会利用Zookeeper再从剩余的Listener中选出一个新的Leader。
     * autoRequeue()方法使放弃Leadership的Listener有机会重新获得Leadership，如果不设置的话放弃了的Listener是不会再变成Leader的。
     * @Author: Jason.zhu
     * @Create: 2019/05/27 11:49
     */
  
    public class CuratorLeaderClient {
        private static String path = "/ensurePath";
  
        public static void main(String[] args) throws InterruptedException {
            LeaderSelectorListener listener = new LeaderSelectorListener() {
                @Override
                public void takeLeadership(CuratorFramework curatorFramework) throws Exception {
                    System.out.println(Thread.currentThread().getName() + " take leadership !!");
                    Thread.sleep(5000L);
                    System.out.println(Thread.currentThread().getName() + " relinquish leadership !!");
                }
  
                @Override
                public void stateChanged(CuratorFramework curatorFramework, ConnectionState connectionState) {
                    System.out.println(connectionState.name() + " state changed !! " + connectionState.isConnected());
                }
            };
  
            new Thread(() -> {
                registerListener(listener);
            }).start();
  
            new Thread(() -> {
                registerListener(listener);
            }).start();
  
  
            new Thread(() -> {
                registerListener(listener);
            }).start();
  
  
            new Thread(() -> {
                registerListener(listener);
            }).start();
  
            new Thread(() -> {
                registerListener(listener);
            }).start();
  
            Thread.sleep(Integer.MAX_VALUE);
        }
  
        public static void registerListener(LeaderSelectorListener listener){
            CuratorFramework curatorFramework = CuratorFrameworkFactory.newClient(ZkPropertiesUtil.getZkServerIp()
                                                                        ,new RetryNTimes(10, 5000));
  
            curatorFramework.start();
  
            //ensure path
            try {
                new EnsurePath(path).ensure(curatorFramework.getZookeeperClient());
            } catch (Exception e) {
                e.printStackTrace();
            }
  
            //register listener
            LeaderSelector selector = new LeaderSelector(curatorFramework, path, listener);
            selector.autoRequeue();
            selector.start();
        }
  
    }
  

  5. Curator操作ZK实现监听功能

    import net.lc7.util.ZkPropertiesUtil;
    import org.apache.curator.framework.CuratorFramework;
    import org.apache.curator.framework.CuratorFrameworkFactory;
    import org.apache.curator.framework.recipes.cache.ChildData;
    import org.apache.curator.framework.recipes.cache.PathChildrenCache;
    import org.apache.curator.retry.RetryNTimes;
  
    /**
     * @Description:  Curator实现监听功能
     *
     * Path Cache：监视一个路径下1）孩子结点的创建、2）删除，3）以及结点数据的更新。产生的事件会传递给注册的PathChildrenCacheListener。
     * Node Cache：监视一个结点的创建、更新、删除，并将结点的数据缓存在本地。
     * Tree Cache：Path Cache和Node Cache的“合体”，监视路径下的创建、更新、删除事件，并缓存路径下所有孩子结点的数据。
     *
     * @Author: Jason.zhu
     * @Create: 2019/05/27 11:10
     */
  
    public class CuratorWatchClient {
  
        private static String watcherNode = "/watcherNode";
  
        public static void main(String[] args) throws Exception {
            CuratorFramework curatorFrameworkClient = CuratorFrameworkFactory.newClient(
                                                            ZkPropertiesUtil.getZkServerIp(),
                                                            new RetryNTimes(10, 5000));
            curatorFrameworkClient.start();
  
            System.out.println("zk client start successfully!!");
  
  
            //register watcher
            PathChildrenCache pathChildrenCache = new PathChildrenCache(curatorFrameworkClient, watcherNode, true);
            pathChildrenCache.getListenable().addListener((client, event) -> {
                ChildData data = event.getData();
                if(null == data){
                    System.out.println("no data in event [" + event +"]");
                }else {
                    System.out.println(
                            "Receive event :" +
                                    "type=["+ event.getType() +"], " +
                                    "path=[" + data.getPath() + "]," +
                                    "data=["+ data.getData() +"]," +
                                    "state=[" + data.getStat() + "]"
                    );
                }
            });
            pathChildrenCache.start(PathChildrenCache.StartMode.BUILD_INITIAL_CACHE);
            System.out.println(" Register zookeeper watcher successfully!! Please operate in terminal to show the listener function");
            Thread.sleep(Integer.MAX_VALUE);
  
        }
    }