Zookeeper--05---客户端API操作

Posted 2022-02-03 高高for 循环

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文章目录

客户端API操作

客户端API操作

依赖

<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>

前提：

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

1.创建 ZooKeeper客户端

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();
//                
            
        );

2.创建子节点

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

create 方法

String path, 节点路径
byte data[], 存储内容
List acl, 权限
CreateMode createMode 节点类型 (持久还是临时节点)

acl----- 权限

CreateMode -----节点类型 (持久还是临时节点)

持久节点
持久序号节点
临时节点
临时序号节点
Container节点
TTL节点

3.获取子节点并监听节点变化

    @Before
    public void init() throws IOException 

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

        );
    


    @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);

注意设置的监听,只监听一次,如果重复监听,得设置监听得process再次注册

4.判断 Znode是否存在

    @Test
    public void exist() throws KeeperException, InterruptedException 

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

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