吴裕雄--天生自然 Zookeeper学习笔记--Zookeeper Java 客户端搭建

使用的 IDE 为 IntelliJ IDEA，创建一个 maven 工程，命名为 zookeeper-demo，并且引入如下依赖，可以自行在maven中央仓库选择合适的版本，介绍原生 API 和 Curator 两种方式。

<dependency>
  <groupId>junit</groupId>
  <artifactId>junit</artifactId>
  <version>4.11</version>
  <scope>test</scope>
</dependency>
<dependency>
  <groupId>org.apache.zookeeper</groupId>
  <artifactId>zookeeper</artifactId>
  <version>3.4.8</version>
</dependency>
<dependency>
  <groupId>org.apache.curator</groupId>
  <artifactId>curator-framework</artifactId>
  <version>4.0.0</version>
</dependency>
<dependency>
  <groupId>org.apache.curator</groupId>
  <artifactId>curator-recipes</artifactId>
  <version>4.0.0</version>
</dependency>

一、客户端的 zookeeper 原生 API
使用 zookeeper 原生 API,连接上一教程搭建的三台服务组成的集群，因为连接需要时间，用 countDownLatch 阻塞，等待连接成功，控制台输出连接状态！
实例
public static void main(String[] args) {
    try {
        final CountDownLatch countDownLatch=new CountDownLatch(1);
        ZooKeeper zooKeeper=
            new ZooKeeper("192.168.3.33:2181," +
                    "192.168.3.35:2181,192.168.3.37:2181",
                    4000, new Watcher() {
                @Override
                public void process(WatchedEvent event) {
                    if(Event.KeeperState.SyncConnected==event.getState()){
                        //如果收到了服务端的响应事件，连接成功
                        countDownLatch.countDown();
                    }
                }
            });
        countDownLatch.await();
        //CONNECTED
        System.out.println(zooKeeper.getState());
    
    }
}

简单示例添加节点 API:

zooKeeper.create("/runoob","0".getBytes(),ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);

二、客户端的curator连接
Curator 是 Netflix 公司开源的一套 zookeeper 客户端框架，解决了很多 Zookeeper 客户端非常底层的细节开发工作，包括连接重连、反复注册 Watcher 和 NodeExistsException 异常等。

Curator 包含了几个包：

curator-framework：对 zookeeper 的底层 api 的一些封装。
curator-client：提供一些客户端的操作，例如重试策略等。
curator-recipes：封装了一些高级特性，如：Cache 事件监听、选举、分布式锁、分布式计数器、分布式 Barrier 等。

实例
public class CuratorDemo {
 
    public static void main(String[] args) throws Exception {
        CuratorFramework curatorFramework=CuratorFrameworkFactory.
                builder().connectString("192.168.3.33:2181," +
                "192.168.3.35:2181,192.168.3.37:2181").
                sessionTimeoutMs(4000).retryPolicy(new
                ExponentialBackoffRetry(1000,3)).
                namespace("").build();
        curatorFramework.start();
        Stat stat=new Stat();
        //查询节点数据
        byte[] bytes =        curatorFramework.getData().storingStatIn(stat).forPath("/runoob");
        System.out.println(new String(bytes));
        curatorFramework.close();
    }
}

curator 相关参考链接: http://curator.apache.org/。

package com.runoob.zookeeper;

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;

import java.io.IOException;
import java.util.concurrent.CountDownLatch;


public class ConnectionDemo {

    public static void main(String[] args) {
        try {
            final CountDownLatch countDownLatch=new CountDownLatch(1);
            ZooKeeper zooKeeper=
                    new ZooKeeper("192.168.3.33:2181," +
                            "192.168.3.35:2181,192.168.3.37:2181",
                            4000, new Watcher() {
                        @Override
                        public void process(WatchedEvent event) {
                            if(Event.KeeperState.SyncConnected==event.getState()){
                                //如果收到了服务端的响应事件，连接成功
                                countDownLatch.countDown();
                            }
                        }
                    });
            countDownLatch.await();
            //CONNECTED
            System.out.println(zooKeeper.getState());
            //添加节点
            zooKeeper.create("/runoob","0".getBytes(),ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (KeeperException e) {
           e.printStackTrace();
        }
    }
}

package com.runoob.zookeeper;

import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.zookeeper.data.Stat;


public class CuratorDemo {

    public static void main(String[] args) throws Exception {
        CuratorFramework curatorFramework=CuratorFrameworkFactory.
                builder().connectString("192.168.3.33:2181," +
                "192.168.3.35:2181,192.168.3.37:2181").
                sessionTimeoutMs(4000).retryPolicy(new
                ExponentialBackoffRetry(1000,3)).
                namespace("").build();
        curatorFramework.start();
        Stat stat=new Stat();
        byte[] bytes = curatorFramework.getData().storingStatIn(stat).forPath("/runoob");
        System.out.println(new String(bytes));
        curatorFramework.close();
    }
}