Zk学习笔记——ZkClient

ZkClient是开源的zk客户端，对Zookeeper原生的java api进行了封装，实现了诸如session超时重连，watcher反复注册等功能。

依赖的话有

<dependency>
    <groupId>com.101tec</groupId>
    <artifactId>zkclient</artifactId>
    <version>0.10</version>
</dependency>

和

<dependency>
    <groupId>com.github.sgroschupf</groupId>
    <artifactId>zkclient</artifactId>
    <version>0.1</version>
</dependency>

前者使用较为广泛，使用其的项目包括kafka，dubbo等

1.创建，获取和删除节点

依赖

        <!-- zookeeper -->
        <dependency>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
            <version>3.4.5-cdh5.16.2</version>
        </dependency>
        <dependency>
            <groupId>com.101tec</groupId>
            <artifactId>zkclient</artifactId>
            <version>0.10</version>
        </dependency>

 代码

package com.bigdata.zookeeper;

import org.I0Itec.zkclient.ZkClient;

public class ZkClientExample {

    public static void main(String[] args) throws Exception {

        ZkClient zkClient = new ZkClient("master:2181", 5000);
        System.out.println("Zookeeper session established");
        String path = "/app4/app4-1";
        // true表示可以递归创建节点，重复节点不会报错
        zkClient.createPersistent(path, true);
        // 获取
        System.out.println(zkClient.getChildren("/app4"));

        // 删除节点
//        zkClient.delete(path);
        // 递归删除
        zkClient.deleteRecursive("/app4");
    }

}

2.zkClient引入了listener，客户端可以通过注册相关的事件监听来实现对ZooKeeper服务端事件的订阅

listener是异步的，可能触发会有延迟

代码，chiild listener，监听子节点是否发生变化

package com.bigdata.zookeeper;

import org.I0Itec.zkclient.IZkChildListener;
import org.I0Itec.zkclient.ZkClient;

import java.util.List;

public class ZkClientExample {

    public static void main(String[] args) throws Exception {

        ZkClient zkClient = new ZkClient("master:2181", 5000);
        System.out.println("Zookeeper session established");
        String path = "/app4/app4-1";

        // listener
        zkClient.subscribeChildChanges("/app4", new Listerner());

        // true表示可以递归创建节点，重复节点不会报错
        zkClient.createPersistent(path, true);
        // 如果注释的话，listener的执行可能会在删除节点执行之后，所以输出可能是空的子节点
        Thread.sleep(10000);
        // 获取
        System.out.println(zkClient.getChildren("/app4"));


        // 删除节点
        zkClient.delete(path);

        Thread.sleep(10000);
        // 递归删除
//        zkClient.deleteRecursive("/app4");


    }

}

class Listerner implements IZkChildListener {

    @Override
    public void handleChildChange(String s, List<String> list) throws Exception {
        System.out.println("parent path: " + s + " changed, current children: " + list);
    }
}

输出

3.代码，data listener，监听节点的data是否发生变化

ZkClient的默认序列化类是org.I0Itec.zkclient.serialize.SerializableSerializer

在zkui上查看会有乱码，比如

所以重写了序列化类，并且使用writeData和readData修改和读取节点数据

package com.bigdata.zookeeper;

import org.I0Itec.zkclient.IZkChildListener;
import org.I0Itec.zkclient.IZkDataListener;
import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.exception.ZkMarshallingError;
import org.I0Itec.zkclient.serialize.ZkSerializer;
import org.apache.commons.io.Charsets;

import java.util.List;

public class ZkClientExample {

    public static void main(String[] args) throws Exception {

        ZkClient zkClient = new ZkClient("master:2181", 5000);
        zkClient.setZkSerializer(new MyZkSerializer());
        System.out.println("Zookeeper session established");
        String path = "/app4/app4-1";

        // child listener
        zkClient.subscribeChildChanges("/app4", new ChildListerner());
        // data listener
        zkClient.subscribeDataChanges(path, new DataListerner());

        // true表示可以递归创建节点，重复节点不会报错
        zkClient.createPersistent(path, true);
        // 设置data
        zkClient.writeData(path, "12345");
        System.out.println(zkClient.readData(path).toString());
        // 如果注释的话，listener的执行可能会在删除节点执行之后，所以输出可能是空的子节点
        Thread.sleep(10000);
        // 获取
        System.out.println(zkClient.getChildren("/app4"));


        // 删除节点
        zkClient.delete(path);

        Thread.sleep(10000);
        // 递归删除
//        zkClient.deleteRecursive("/app4");


    }

}

class MyZkSerializer implements ZkSerializer {
    public Object deserialize(byte[] bytes) throws ZkMarshallingError {
        return new String(bytes, Charsets.UTF_8);
    }

    public byte[] serialize(Object obj) throws ZkMarshallingError {
        return String.valueOf(obj).getBytes(Charsets.UTF_8);
    }
}


class ChildListerner implements IZkChildListener {

    @Override
    public void handleChildChange(String s, List<String> list) throws Exception {
        System.out.println("parent path: " + s + " changed, current children: " + list);
    }
}

class DataListerner implements IZkDataListener {


    @Override
    public void handleDataChange(String s, Object o) throws Exception {
        System.out.println("data path: " + s + " changed, current data: " + o);
    }

    @Override
    public void handleDataDeleted(String s) throws Exception {
        System.out.println("data path: " + s + " deleted");
    }
}

输出