07_ZkClient提供的API使用

1. ZkClient API簡介

zkclient是Github上一個開源的ZooKeeper客戶端，在原生ZooKeeper API接口上進行包裝，同時在內部實現了session超時重連，Watcher反復注冊等功能

 

2. Maven工程方式導入ZkClient API

通過POM.xml方式，指定依賴的zookeepr包以及zkclient包

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.newforce</groupId>
    <artifactId>testzkclient</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
            <version>3.4.5</version>
        </dependency>
        <dependency>
            <groupId>com.101tec</groupId>
            <artifactId>zkclient</artifactId>
            <version>0.5</version>
        </dependency>
    </dependencies>


</project>

 

 3. ZkClient API使用

 3.1  create session 創建和zookeeper集群間的連接

import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.serialize.SerializableSerializer;

/**
 * ZkClient library usage
 */
public class CreateSession {
    public static void main(String args[]){
        ZkClient zc = new ZkClient("192.168.179.101:2181", 5000, 5000, new SerializableSerializer());
        System.out.println("Connection OK!");

    }
}

 

 核心代碼分析：

1）和zookeeper原生API不同，通過zkclient API創建會話，需要提供session timout, connection timeout兩個定時器

2）同時要提供1個序列化器實例，原因在於后續創建znode節點時，寫入的數據（java對象）會自動通過序列化器來轉換為byte[]

3）同理，讀取出的byte[]的數據，也會自動通過序列化器直接轉換為Java對象

 

3.2 創建znode節點

/**
 * ZkClient library usage
 */

import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.serialize.SerializableSerializer; import org.apache.zookeeper.CreateMode;

 public class CreateNode { public static void main(String args[]){  ZkClient zc = new ZkClient("192.168.179.101:2181", 5000, 5000, new SerializableSerializer());
 User u = new User();
        String actual_path = zc.create("/node_zkclient", u, CreateMode.PERSISTENT); //直接將實例u寫入，自動通過序列化為byte[]

        System.out.println("Create path is: " + actual_path);
    }

　　private class User{
　　　　private Integer id;
       private String name;

       public Integer getId(){
　　　　　　return this.id;
       }
       public String getName(){
          return this.name;
       }
       public String getInfo(){
          return this.name + this.id;
       }
   }//User
}

 

3.3 修改節點數據

/**
 * ZkClient library usage
 */
import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.serialize.SerializableSerializer;
import org.apache.zookeeper.CreateMode;

public class SetData {
    public static void main(String args[]){
        ZkClient zc = new ZkClient("192.168.179.101:2181", 5000, 5000, new SerializableSerializer());

        User u = new User();
        u.setId(1);
        u.setName("shayzhang");

        String actual_path = zc.create("/node_zkclient", u, CreateMode.PERSISTENT);
        
 
        u.setId(2);
        u.setName("zhangjin");
        zc.writeData(actual_path, u); //直接寫入實例，自動通過連接創建時創建的序列化實例，轉換為byte[]
        
    }
}

 

3.4 獲取節點數據

/**
 * ZkClient library usage
 */
import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.serialize.SerializableSerializer;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.data.Stat;

public class GetData {
    public static void main(String args[]){
        ZkClient zc = new ZkClient("192.168.179.101:2181", 5000, 5000, new SerializableSerializer()); 
        User u = new User();
        u.setId(1);
        u.setName("shayzhang");

        String actual_path = zc.create("/node_zkclient", u, CreateMode.PERSISTENT);
        System.out.println("Create path is: " + actual_path);

        Stat stat = new Stat();
       u = zc.readData(actual_path, stat); if (u == null){
            System.out.println("Node doesn't exist!");
        }else{
            System.out.println(u.getInfo()); System.out.println(stat);
        }
    }
}

 

3.5 獲取子節點列表

/**
 * ZkClient library usage
 */
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;


public class GetChildren {
    public static void main(String args[]){
        ZkClient zc = new ZkClient("192.168.179.101:2181", 5000, 5000, new SerializableSerializer());

        User u = new User();
        u.setId(1);
        u.setName("shayzhang");

        String actual_path = zc.create("/node_zkclient", u, CreateMode.PERSISTENT);
        System.out.println("Create path is: " + actual_path);
 List<String> children_list = zc.getChildren(actual_path);
        System.out.println("Children list of /node_zkclient is : " + children_list.toString());  //打印子節點列表

    }
}

 

 3.6 刪除節點

/**
 * ZkClient library usage
 */
import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.serialize.SerializableSerializer;

public class DeleteNode {
    public static void main(String args[]){
        ZkClient zc = new ZkClient("192.168.179.101:2181", 5000, 5000, new SerializableSerializer());

        String delete_node = "/node_zkclient";

        //delete node without children
        boolean e1 = zc.delete(delete_node);
        System.out.println("Delete node without children: " + e1);

        // delete node and all children
        boolean e2 = zc.deleteRecursive(delete_node);
        System.out.println("Delete node and children: " + e2);

    }
}

 

3.7 判斷節點是否存在

/**
 * ZkClient library usage
 */
import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.serialize.SerializableSerializer;

public class NodeExist {
    public static void main(String args[]){
        ZkClient zc = new ZkClient("192.168.179.101:2181", 5000, 5000, new SerializableSerializer()); 
        String check_node = "/node_zkclient";
        boolean exist = zc.exists(check_node);
        System.out.println("Node exist status is: " + exist);

    }
}

 

3.8 訂閱子節點列表發生變化

/**
 * ZkClient library usage
 */
import org.I0Itec.zkclient.IZkChildListener;
import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.serialize.SerializableSerializer;
import java.util.List;

public class SubscribeChildren {
    public static void main(String args[]){
       ZkClient zc = new ZkClient("192.168.179.101:2181", 5000, 5000, new SerializableSerializer());
        System.out.println("Connected to zk server!");

        // subscribe children change event, multiple subscribe
      List<String> results = zc.subscribeChildChanges("/node_zkclient", new ZkChildListener()); // sleep until receive event notify
        try {
            Thread.sleep(Integer.MAX_VALUE);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }//main

    private static class ZkChildListener implements IZkChildListener{
        public void handleChildChange(String s, List<String> list) throws Exception {
            //print parent path
            System.out.println("Parent path: " + s);
            //print current children
            System.out.println("Current children: " + list.toString());
        }
    }//ZkChildListener
}

 

3.9 訂閱數據變化

/**
 * ZkClient library usage
 */
import org.I0Itec.zkclient.IZkDataListener;
import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.serialize.BytesPushThroughSerializer;

public class SubscribeData {
    public static void main(String args[]){
        //使用了新的序列化器, zk命令行寫入的數據才能被檢測
        ZkClient zc = new ZkClient("192.168.179.101:2181", 5000, 5000, new BytesPushThroughSerializer()); //寫入什么直接當做byte[]進行存儲
        System.out.println("Connected to zk server!");

        // subscribe data change event, multiple subscribe
       zc.subscribeDataChanges("/node_zkclient", new ZkDataListener()); // sleep until receive event notify
        try {
            Thread.sleep(Integer.MAX_VALUE);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

    }

    private static class ZkDataListener implements IZkDataListener{
        public void handleDataChange(String s, Object o) throws Exception { //覆寫方法1
            System.out.println("Path Data Changed: " + s);
            System.out.println("Current Data: " + o.toString());
        }
        public void handleDataDeleted(String s) throws Exception { //覆寫方法2
            System.out.println("Data Deleted: " + s);
        }
    }//ZkDataListener
}