java zookeeper客户端 zookeeper java使用

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mob64ca14017c37 2023-08-21 06:34:51

文章标签 java zookeeper客户端 zookeeper System 子节点 文章分类 Java 后端开发

一、简介

在文章 zookeeper使用（一）--简介与安装中，我们介绍了zookeeper相关知识及安装方法。

在文本，将介绍zookeeper的常用命令，以及在java中的基本操作（包括原生的zookeeper和包装后的ZkClient）。

二、常用命令

1、启动、停止服务

./zkServer.sh start[stop]

2、连接服务

./zkCli.sh -server ip:port

3、清理历史数据、包括事务日志谁的和快照数据文件

./zkCleanup.sh

4、设置zookeeper的环境变量

./zkEnv.sh

5、创建节点

create [-s] [-e] path data acl

其中，-s指顺序节点，-e指临时节点，不添加-s和-e时，创建的是持久节点。acl是权限控制，不添加时，无权限控制。

6、查看子节点

ls path

7、获取指定节点的数据内容和属性信息

get path

8、更新节点数据内容

set path data

9、删除节点

delete path

10、递归删除节点

rmr path

三、原生zookeeper的java客户端使用

1、添加maven依赖

<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.4.6</version>
</dependency>

2、代码实例

public class ZookeeperMain {
    public static void main(String[] args) throws Exception {
        String connectStr = "127.0.0.1:2181"; //连接地址，后可跟目录，如127.0.0.1:2181/mydata
        Watcher watcher = new SimpleWatcher(); //事件监听器
        int sessionTimeout = 10000; //会话超时时间，单位是毫秒
        ZooKeeper zookeeper = new ZooKeeper(connectStr,sessionTimeout,watcher);  //创建会话
        System.out.println("zookeeper state: "+ zookeeper.getState());

        long sessionId = zookeeper.getSessionId();  //会话id ,用于重连
        byte[] sessionPasswd = zookeeper.getSessionPasswd(); //会话密码,用于重连

        TimeUnit.SECONDS.sleep(8);
        System.out.println("zookeeper state : "+zookeeper.getState());
        zookeeper = new ZooKeeper(connectStr,sessionTimeout,watcher,sessionId,sessionPasswd);  //重新连接
        System.out.println("zookeeper state : "+zookeeper.getState());


        //同步创建节点
        String m1 = zookeeper.create("/m1","mv1".getBytes("utf-8"), ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);
        //异步创建节点
        zookeeper.create("/m2", "mv2".getBytes("utf-8"), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT
                , new AsyncCallback.StringCallback() {
                    public void processResult(int rc, String path, Object ctx, String name) {
                        System.out.println("异步创建节点成功 rc:"+rc+ "  path:"+path+" ctx:"+ctx+" name:"+name);
                    }
                },"context");


        //同步获取子节点
        List<String> children = zookeeper.getChildren("/",watcher);
        System.out.println("同步获取子节点:"+children);
        //异步获取子节点
        zookeeper.getChildren("/", watcher, new AsyncCallback.Children2Callback() {
            public void processResult(int rc, String path, Object ctx, List<String> children, Stat stat) {
                System.out.println("异步获取子节点:"+children);
            }
        },null);


        //同步获取节点的值
        Stat stat = new Stat();
        byte[] dataByte = zookeeper.getData("/m1",watcher,stat);
        String data = new String(dataByte,"utf-8");
        System.out.println("同步获取节点的值 m1 :"+data);
        //异步获取节点的值
        zookeeper.getData("/m1", watcher, new AsyncCallback.DataCallback() {
            public void processResult(int rc, String path, Object ctx, byte[] data, Stat stat) {
                try {
                    System.out.println("异步获取节点的值 m1 :"+new String(data,"utf-8"));
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                }
            }
        },null);


        //同步更新值
        zookeeper.setData("/m1","nm1".getBytes("utf8"),-1);
        //异步更新值
        zookeeper.setData("/m1", "nnm1".getBytes("utf8"), -1, new AsyncCallback.StatCallback() {
            public void processResult(int rc, String path, Object ctx, Stat stat) {
                if(rc==0){
                    System.out.println("异步更新值成功 ");
                }
            }
        },null);

        //删除节点
        zookeeper.delete("/m1",-1);

        //检测节点是否存在
        Stat existStat = zookeeper.exists("/m1",watcher);
        if(null== existStat){
            System.out.println("节点不存在");
        }


        //权限控制
        ZooKeeper zk = new ZooKeeper(connectStr,sessionTimeout,watcher);
        zk.addAuthInfo("digest","pass".getBytes("utf8"));
        String m6 = zk.create("/m6","mv6".getBytes("utf-8"), ZooDefs.Ids.CREATOR_ALL_ACL,CreateMode.PERSISTENT); //创建有权限的节点
        byte[] byteResult = zk.getData("/m6",watcher,stat);  //有权限读取
        String result = new String(byteResult,"utf-8");
        System.out.println("result with auth:"+result);
        try{
            byteResult = zookeeper.getData("/m6",watcher,stat);  //无权限读取
            result = new String(byteResult,"utf-8");
            System.out.println("result without auth:"+result);
        }catch (Exception e){
            e.printStackTrace();
        }

        TimeUnit.HOURS.sleep(1);
    }

    static class SimpleWatcher implements Watcher{  //事件监听器，客户端注册后，当事件发生时，会通知客户端
        public void process(WatchedEvent event) {
            System.out.println("event is :"+event);
        }
    }
}

输出：

zookeeper state: CONNECTING
event is :WatchedEvent state:SyncConnected type:None path:null
zookeeper state : CONNECTED
zookeeper state : CONNECTING
event is :WatchedEvent state:SyncConnected type:None path:null
同步获取子节点:[ m6]
异步获取子节点:[ m6]
同步获取节点的值 m1 :mv1
异步获取节点的值 m1 :mv1
event is :WatchedEvent state:SyncConnected type:NodeDataChanged path:/m1
异步更新值成功
event is :WatchedEvent state:SyncConnected type:NodeChildrenChanged path:/
节点不存在
event is :WatchedEvent state:SyncConnected type:None path:null
result with auth:mv6

四、基于开源zookeeper的java客户端ZkClient使用

ZkClient是对Zoookeeper客户端的包装，包装自动序列化和反序列化、通过Listener进行监听等。

1、添加maven依赖

<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.4.6</version>
</dependency>
<dependency>
    <groupId>com.github.sgroschupf</groupId>
    <artifactId>zkclient</artifactId>
    <version>0.1</version>
</dependency>

2、代码实例

public class ZkClientMain {
    public static void main(String[] args) throws Exception {
        ZkClient zkClient = new ZkClient("127.0.0.1:2181",5000);  //创建会话

        zkClient.subscribeChildChanges("/", new IZkChildListener() {  //监听子节点变化
            public void handleChildChange(String s, List<String> list) throws Exception {
                System.out.println("parent path: "+ s+ "  now children is:"+list);
            }
        });
        
        zkClient.create("/c1","cd1", CreateMode.PERSISTENT);  //创建节点

        List<String> children = zkClient.getChildren("/");//读取子节点
        System.out.println("children : "+children);

        String cv = zkClient.readData("/c1");  //读取节点数据
        System.out.println("value of c1 :"+cv);

        zkClient.subscribeDataChanges("/c1", new IZkDataListener() {  //监听节点变化
            public void handleDataChange(String s, Object o) throws Exception {
                System.out.println(s+" data change :"+o);
            }
            public void handleDataDeleted(String s) throws Exception {
                System.out.println(s+" data delete");
            }
        });

        zkClient.writeData("/c1","nncv1");  //更新节点数据
        System.out.println("value of c1 :"+zkClient.readData("/c1"));

        zkClient.delete("/c1"); //删除节点数据

        boolean existFlag = zkClient.exists("/c1");  //判断节点是否存在
        if(!existFlag){
            System.out.println("/c1 节点不存在");
        }

        TimeUnit.HOURS.sleep(1);
    }
}

输出：

children : [c1]
 parent path: /  now children is:[c1]
 value of c1 :cd1
 value of c1 :nncv1
 /c1 data change :nncv1
 /c1 节点不存在
 /c1 data delete
 parent path: /  now children is:[]

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