07_ZkClient提供的API使用

1. ZkClient API简介

zkclient是Github上一个开源的ZooKeeper客户端，在原生ZooKeeper API接口上进行包装，同时在内部实现了session超时重连，Watcher反复注册等功能

2. Maven工程方式导入ZkClient API

通过POM.xml方式，指定依赖的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 创建和zookeeper集群间的连接

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!");

    }
}

 核心代码分析：

1）和zookeeper原生API不同，通过zkclient API创建会话，需要提供session timout, connection timeout两个定时器

2）同时要提供1个序列化器实例，原因在于后续创建znode节点时，写入的数据（java对象）会自动通过序列化器来转换为byte[]

3）同理，读取出的byte[]的数据，也会自动通过序列化器直接转换为Java对象

3.2 创建znode节点

/**
 * 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); //直接将实例u写入，自动通过序列化为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 修改节点数据

/**
 * 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);  //直接写入实例，自动通过连接创建时创建的序列化实例，转换为byte[]
        
    }
}

3.4 获取节点数据

/**
 * 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 获取子节点列表

/**
 * 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());  //打印子节点列表

    }
}

 3.6 删除节点

/**
 * 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 判断节点是否存在

/**
 * 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 订阅子节点列表发生变化

/**
 * 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 订阅数据变化

/**
 * 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命令行写入的数据才能被检测
        ZkClient zc = new ZkClient("192.168.179.101:2181", 5000, 5000, new BytesPushThroughSerializer()); //写入什么直接当做byte[]进行存储
        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 { //覆写方法1
            System.out.println("Path Data Changed: " + s);
            System.out.println("Current Data: " + o.toString());
        }
        public void handleDataDeleted(String s) throws Exception { //覆写方法2
            System.out.println("Data Deleted: " + s);
        }
    }//ZkDataListener
}