05 | Zookeeper客户端API操作

3.3 客户端 API 操作​

前提:保证 hadoop102、hadoop103、hadoop104 服务器上 Zookeeper 集群服务端启动。

3.3.1 IDEA 环境搭建​

1)创建一个工程:zookeeper

2)添加pom文件

xml

<dependencies>
   <dependency>
        <groupId>junit</groupId> 
        <artifactId>junit</artifactId>
        <version>RELEASE</version>
   </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId> <artifactId>log4j-core</artifactId>
        <version>2.8.2</version>
    </dependency>
    <dependency>
        <groupId>org.apache.zookeeper</groupId> <artifactId>zookeeper</artifactId>
        <version>3.5.7</version>
   </dependency>
</dependencies>

3)拷贝log4j.properties文件到项目根目录

需要在项目的 src/main/resources 目录下，新建一个文件，命名为“log4j.properties”，在文件中填入。

bash

log4j.rootLogger=INFO, stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - %m%n
log4j.appender.logfile=org.apache.log4j.FileAppender
log4j.appender.logfile.File=target/spring.log
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=%d %p [%c] - %m%n

4)创建包名com.atguigu.zk

5)创建类名称zkClient

3.3.2 创建 ZooKeeper 客户端​

java

public class zkClient {

    // 注意：逗号左右不能有空格
    private String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private int sessionTimeout = 2000;
    private ZooKeeper zkClient;

    @Before
    public void init() throws IOException {

        zkClient = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {}
        });
    }
}

3.3.3 创建子节点​

java

public class zkClient {
    @Test
    public void create() throws KeeperException, InterruptedException {
        // 参数 1:要创建的节点的路径; 
        // 参数 2:节点数据 ; 
        // 参数 3:节点权限 ; 
        // 参数 4:节点的类型
        String nodeCreated = zkClient.create("/atguigu", "ss.avi".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
    }
}

测试:在 hadoop102 的 zk 客户端上查看创建节点情况

bash

[zk: localhost:2181(CONNECTED) 16] get -s /atguigu shuaige

3.3.4 获取子节点并监听节点变化​

java

public class zkClient {
    @Test
    public void getChildren() throws KeeperException, InterruptedException {
        List<String> children = zkClient.getChildren("/", true);

        for (String child : children) {
            System.out.println(child);
        }

        // 延时
        Thread.sleep(Long.MAX_VALUE);
    }
}

(1)在 IDEA 控制台上看到如下节点:

zookeeper
sanguo
atguigu

(2)在 hadoop102 的客户端上创建再创建一个节点/atguigu1，观察 IDEA 控制台

bash

[zk: localhost:2181(CONNECTED) 3] create /atguigu1 "atguigu1"

(3)在 hadoop102 的客户端上删除节点/atguigu1，观察 IDEA 控制台

bash

[zk: localhost:2181(CONNECTED) 4] delete /atguigu1

3.3.5 判断 Znode 是否存在​

java

public class zkClient {

    @Test
    public void exist() throws KeeperException, InterruptedException {

        Stat stat = zkClient.exists("/atguigu", false);

        System.out.println(stat==null ? "not exist " : "exist");
    }
}

完整代码

java

package com.atguigu.zk;

import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.util.List;

public class zkClient {

    // 注意：逗号左右不能有空格
    private String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private int sessionTimeout = 2000;
    private ZooKeeper zkClient;

    @Before
    public void init() throws IOException {

        zkClient = new ZooKeeper(connectString, sessionTimeout, new Watcher() {
            @Override
            public void process(WatchedEvent watchedEvent) {

                System.out.println("-------------------------------");
                List<String> children = null;
                try {
                    children = zkClient.getChildren("/", true);

                    for (String child : children) {
                        System.out.println(child);
                    }

                    System.out.println("-------------------------------");
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
    }

    @Test
    public void create() throws KeeperException, InterruptedException {
        String nodeCreated = zkClient.create("/atguigu", "ss.avi".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
    }

    @Test
    public void getChildren() throws KeeperException, InterruptedException {
        List<String> children = zkClient.getChildren("/", true);

        for (String child : children) {
            System.out.println(child);
        }

        // 延时
        Thread.sleep(Long.MAX_VALUE);
    }

    @Test
    public void exist() throws KeeperException, InterruptedException {

        Stat stat = zkClient.exists("/atguigu", false);

        System.out.println(stat==null? "not exist " : "exist");
    }
}

3.4 客户端向服务端写数据流程​

写流程之写入请求直接发送给Leader节点

写流程之写入请求发送给follower节点