Java操作Zookeeper原理及过程详解

ZooKeeper 是一个典型的分布式数据一致性解决方案，分布式应用程序可以基于 ZooKeeper 实现诸如数据发布/订阅、负载均衡、命名服务、分布式协调/通知、集群管理、Master 选举、分布式锁和分布式队列等功能。

Zookeeper 一个最常用的使用场景就是用于担任服务生产者和服务消费者的注册中心。 服务生产者将自己提供的服务注册到Zookeeper中心，服务的消费者在进行服务调用的时候先到Zookeeper中查找服务，获取到服务生产者的详细信息之后，再去调用服务生产者的内容与数据。如下图所示，在 Dubbo架构中 Zookeeper 就担任了注册中心这一角色。

maven依赖

  org.apache.zookeeper
  zookeeper
  3.6.0

程序其它依赖：

  org.apache.logging.log4j
  log4j-core
  2.11.2



  org.apache.logging.log4j
  log4j-1.2-api
  2.11.2



  org.apache.logging.log4j
  log4j-slf4j-impl
  2.11.2



  org.apache.zookeeper
  zookeeper
  3.6.0
  
    
      org.slf4j
      slf4j-log4j12
    
  

API操作代码：

package com.zhi.test;

import java.util.List;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.MethodOrderer;
import org.junit.jupiter.api.Order;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.TestInstance;
import org.junit.jupiter.api.TestInstance.Lifecycle;
import org.junit.jupiter.api.TestMethodOrder;


@TestInstance(Lifecycle.PER_CLASS)
@TestMethodOrder(MethodOrderer.OrderAnnotation.class)
public class ZookeeperTest {
  private final Logger logger = LogManager.getLogger(this.getClass());
  private ZooKeeper zooKeeper;
  private final String path = "/test";

  @BeforeAll
  public void init() throws Exception {
    zooKeeper = new ZooKeeper("192.168.59.131:2181", 60000, new Watcher() {
      public void process(WatchedEvent event) {
 logger.info("事件类型：{}，路径：{}", event.getType(), event.getPath());
      }
    });
  }

  
  @Order(1)
  @Test
  public void create() {
    try {
      String back = zooKeeper.create(path, "这是一个测试".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
      logger.info("添加一条数据成功，实际路径：{}", back);
    } catch (Exception e) {
      logger.error("调用create出错", e);
    }
  }

  
  @Order(2)
  @Test
  public void exists() {
    try {
      Stat stat = zooKeeper.exists(path, false);
      logger.info("路径为{}的节点{}存在", path, stat == null ? "不" : "");
    } catch (Exception e) {
      logger.error("调用exists出错", e);
    }
  }

  
  @Order(3)
  @Test
  public void find() {
    try {
      byte[] bits = zooKeeper.getData(path, false, new Stat()); // 路径不存在时会报错
      String data = new String(bits);
      logger.info("路径{}查询到数据：{}", path, data);
    } catch (Exception e) {
      logger.error("调用getData出错", e);
    }
  }

  
  @Order(3)
  @Test
  public void children() {
    try {
      List list = zooKeeper.getChildren(path, false);
      logger.info("路径{}的子目录有：{}", path, String.join("、", list.toArray(new String[0])));
    } catch (Exception e) {
      logger.error("调用getChildren出错", e);
    }
  }

  
  @Order(4)
  @Test
  public void udpate() {
    try {
      Stat stat = zooKeeper.exists(path, false);
      if (stat != null) {
 stat = zooKeeper.setData(path, "这是一个修改测试".getBytes(), stat.getVersion()); // 版本号为-1时不做版本校验
 logger.info("数据修改成功，原版本号：{}，新版本号：{}", stat.getAversion(), stat.getVersion());
      }
    } catch (Exception e) {
      logger.error("调用setData出错", e);
    }
  }

  
  @Order(5)
  @Test
  public void delete() {
    try {
      zooKeeper.delete(path, -1); // -1表示不做版本校验
      logger.info("根据path删除数据成功");
    } catch (Exception e) {
      logger.error("调用delete出错", e);
    }
  }

  @AfterAll
  public void destory() throws Exception {
    if (zooKeeper != null) {
      zooKeeper.close();
    }
  }
}

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