分布式框架Zookeeper?api的使用介紹

更新時(shí)間：2022年09月02日 16:04:22 作者：悠然予夏

Zookeeper作為?個(gè)分布式框架，主要用來解決分布式?致性問題，它提供了簡單的分布式原語，并且對多種編程語?提供了API，所以接下來重點(diǎn)來看下Zookeeper的java客戶端API使用方式

前言

Zookeeper API共包含五個(gè)包，分別為：

org.apache.zookeeper
org.apache.zookeeper.data
org.apache.zookeeper.server
org.apache.zookeeper.server.quorum
org.apache.zookeeper.server.upgrade

其中org.apache.zookeeper，包含Zookeeper類，他是我們編程時(shí)最常?的類文件。這個(gè)類是Zookeeper客戶端的主要類文件。如果要使用Zookeeper服務(wù)，應(yīng)?程序?先必須創(chuàng)建?個(gè)Zookeeper實(shí)例，這時(shí)就需要使用此類。?旦客戶端和Zookeeper服務(wù)端建立起了連接，Zookeeper系統(tǒng)將會(huì)給本次連接會(huì)話分配?個(gè)ID值，并且客戶端將會(huì)周期性的向服務(wù)器端發(fā)送心跳來維持會(huì)話連接。只要連接有效，客戶端就可以使?Zookeeper API來做相應(yīng)處理了

導(dǎo)入依賴

<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.4.14</version>
</dependency>

建立會(huì)話

package com.lagou.api;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import java.io.IOException;
import java.util.concurrent.CountDownLatch;
public class CreateSession implements Watcher {
    private static CountDownLatch countDownLatch = new CountDownLatch(1);
    /**
     * 建立會(huì)話
     */
    public static void main(String[] args) throws IOException, InterruptedException {
        /*
            客戶端可以通過創(chuàng)建?個(gè)zk實(shí)例來連接zk服務(wù)器
            new Zookeeper(connectString,sesssionTimeOut,Wather)
            connectString: 連接地址：IP：端?
            sesssionTimeOut：會(huì)話超時(shí)時(shí)間：單位毫秒
            Wather：監(jiān)聽器(當(dāng)特定事件觸發(fā)監(jiān)聽時(shí)，zk會(huì)通過watcher通知到客戶端)
        */
        ZooKeeper zooKeeper = new ZooKeeper("127.0.0.1:2181", 5000, new CreateSession());
        System.out.println(zooKeeper.getState());
        // 計(jì)數(shù)工具類 CountDownLatch : 不讓main方法結(jié)束，讓線程處于等待阻塞
        countDownLatch.await();
        System.out.println("客戶端與服務(wù)端會(huì)話真正建立了");
    }
    /**
     * 回調(diào)方法：處理來自服務(wù)器端的watcher通知
     */
    // 當(dāng)前類實(shí)現(xiàn)了Watcher接?，重寫了process?法，該?法負(fù)責(zé)處理來?Zookeeper服務(wù)端的watcher通知，在收到服務(wù)端發(fā)送過來的SyncConnected事件之后，解除主程序在CountDownLatch上的等待阻塞，?此，會(huì)話創(chuàng)建完畢
    public void process(WatchedEvent watchedEvent) {
        //當(dāng)連接創(chuàng)建了，服務(wù)端發(fā)送給客戶端SyncConnected事件
        if(watchedEvent.getState() == Event.KeeperState.SyncConnected) {
            // 解除主程序在CountDownLatch上的等待阻塞
            countDownLatch.countDown();
        }
    }
}

注意，ZooKeeper 客戶端和服務(wù)端會(huì)話的建立是?個(gè)異步的過程，也就是說在程序中，構(gòu)造?法會(huì)在處理完客戶端初始化工作后立即返回，在?多數(shù)情況下，此時(shí)并沒有真正建立好?個(gè)可用的會(huì)話，在會(huì)話的生命周期中處于“CONNECTING”的狀態(tài)。當(dāng)該會(huì)話真正創(chuàng)建完畢后ZooKeeper服務(wù)端會(huì)向會(huì)話對應(yīng)的客戶端發(fā)送?個(gè)事件通知，以告知客戶端，客戶端只有在獲取這個(gè)通知之后，才算真正建立了會(huì)話。

創(chuàng)建節(jié)點(diǎn)

package com.lagou.api;
import org.apache.zookeeper.*;
import java.io.IOException;
import java.util.concurrent.CountDownLatch;
public class CreateNote implements Watcher {
    private static ZooKeeper zooKeeper;
    /**
     * 建立會(huì)話
     */
    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
        /*
            客戶端可以通過創(chuàng)建?個(gè)zk實(shí)例來連接zk服務(wù)器
            new Zookeeper(connectString,sesssionTimeOut,Wather)
            connectString: 連接地址：IP：端?
            sesssionTimeOut：會(huì)話超時(shí)時(shí)間：單位毫秒
            Wather：監(jiān)聽器(當(dāng)特定事件觸發(fā)監(jiān)聽時(shí)，zk會(huì)通過watcher通知到客戶端)
        */
        zooKeeper = new ZooKeeper("127.0.0.1:2181", 5000, new CreateNote());
        System.out.println(zooKeeper.getState());
        Thread.sleep(Integer.MAX_VALUE);
    }
    // 創(chuàng)建節(jié)點(diǎn)的方法
    private static void createNoteSync() throws InterruptedException, KeeperException {
        /**
         *	path	：節(jié)點(diǎn)創(chuàng)建的路徑
         *	data[]	：節(jié)點(diǎn)創(chuàng)建要保存的數(shù)據(jù)，是個(gè)byte類型的
         *	acl	：節(jié)點(diǎn)創(chuàng)建的權(quán)限信息(4種類型)
         *	    ANYONE_ID_UNSAFE	: 表示任何?
         *	    AUTH_IDS	：此ID僅可?于設(shè)置ACL。它將被客戶機(jī)驗(yàn)證的ID替換。
         *	    OPEN_ACL_UNSAFE	：這是?個(gè)完全開放的ACL(常?)--> world:anyone
         *	    CREATOR_ALL_ACL	：此ACL授予創(chuàng)建者身份驗(yàn)證ID的所有權(quán)限
         *	createMode	：創(chuàng)建節(jié)點(diǎn)的類型(4種類型)
         *	    PERSISTENT：持久節(jié)點(diǎn)
         *	    PERSISTENT_SEQUENTIAL：持久順序節(jié)點(diǎn)
         *	    EPHEMERAL：臨時(shí)節(jié)點(diǎn)
         *	    EPHEMERAL_SEQUENTIAL：臨時(shí)順序節(jié)點(diǎn)
         String node = zookeeper.create(path,data,acl,createMode);
         */
        // 持久節(jié)點(diǎn)
        String note_persistent = zooKeeper.create("/lg-persistent", "持久節(jié)點(diǎn)內(nèi)容".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        // 臨時(shí)節(jié)點(diǎn)
        String note_ephemeral = zooKeeper.create("/lg-ephemeral", "臨時(shí)節(jié)點(diǎn)內(nèi)容".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        // 持久順序節(jié)點(diǎn)
        String note_sequential = zooKeeper.create("/lg-sequential", "持久順序節(jié)點(diǎn)內(nèi)容".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT_SEQUENTIAL);
        System.out.println("創(chuàng)建的持久節(jié)點(diǎn): " + note_persistent);
        System.out.println("創(chuàng)建的臨時(shí)節(jié)點(diǎn): " + note_ephemeral);
        System.out.println("創(chuàng)建的持久順序節(jié)點(diǎn): " + note_sequential);
    }
    /**
     * 回調(diào)方法：處理來自服務(wù)器端的watcher通知
     */
    public void process(WatchedEvent watchedEvent) {
        // SyncConnected
        if (watchedEvent.getState() == Event.KeeperState.SyncConnected) {
            // 創(chuàng)建節(jié)點(diǎn)
            try {
                createNoteSync();
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
    }
}

獲取節(jié)點(diǎn)數(shù)據(jù)

package com.lagou.api;
import org.apache.zookeeper.*;
import java.io.IOException;
import java.util.List;
public class GetNoteData implements Watcher {
    private static ZooKeeper zooKeeper;
    /**
     * 建立會(huì)話
     */
    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
        /*
            客戶端可以通過創(chuàng)建?個(gè)zk實(shí)例來連接zk服務(wù)器
            new Zookeeper(connectString,sesssionTimeOut,Wather)
            connectString: 連接地址：IP：端?
            sesssionTimeOut：會(huì)話超時(shí)時(shí)間：單位毫秒
            Wather：監(jiān)聽器(當(dāng)特定事件觸發(fā)監(jiān)聽時(shí)，zk會(huì)通過watcher通知到客戶端)
        */
        zooKeeper = new ZooKeeper("127.0.0.1:2181", 5000, new GetNoteData());
        System.out.println(zooKeeper.getState());
        Thread.sleep(Integer.MAX_VALUE);
    }
    /**
     * 回調(diào)方法：處理來自服務(wù)器端的watcher通知
     */
    public void process(WatchedEvent watchedEvent) {
        /*
            子節(jié)點(diǎn)列表發(fā)生改變時(shí)，服務(wù)端會(huì)發(fā)送noteChildrenChanged事件通知
            要重新獲取子節(jié)點(diǎn)列表，同時(shí)注意：通知是一次性的，需要反復(fù)注冊監(jiān)聽
         */
        if (watchedEvent.getType() == Event.EventType.NodeChildrenChanged) {
            List<String> children = null;
            try {
                children = zooKeeper.getChildren("/lg-persistent", true);
            } catch (KeeperException | InterruptedException e) {
                throw new RuntimeException(e);
            }
            System.out.println(children);
        }
        // SyncConnected
        if (watchedEvent.getState() == Event.KeeperState.SyncConnected) {
            // 獲取節(jié)點(diǎn)數(shù)據(jù)的方法
            try {
                getNoteData();
                // 獲取節(jié)點(diǎn)的子節(jié)點(diǎn)列表方法
                getChildren();
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
    }
    /*
        獲取某個(gè)節(jié)點(diǎn)的內(nèi)容
     */
    private void getNoteData() throws Exception {
        /**
         *	path	: 獲取數(shù)據(jù)的路徑
         *	watch	: 是否開啟監(jiān)聽
         *	stat	: 節(jié)點(diǎn)狀態(tài)信息
         *	    null: 表示獲取最新版本的數(shù)據(jù)
         *	zk.getData(path, watch, stat);
         */
        byte[] data = zooKeeper.getData("/lg-persistent", false, null);
        System.out.println(new String(data));
    }
    /*
        獲取某個(gè)節(jié)點(diǎn)的子節(jié)點(diǎn)列表方法
     */
    public static void getChildren() throws InterruptedException, KeeperException {
        /*
            path:路徑
            watch:是否要啟動(dòng)監(jiān)聽，當(dāng)?節(jié)點(diǎn)列表發(fā)?變化，會(huì)觸發(fā)監(jiān)聽
            zooKeeper.getChildren(path, watch);
        */
        List<String> children = zooKeeper.getChildren("/lg-persistent", true);
        System.out.println(children);
    }
}

修改節(jié)點(diǎn)數(shù)據(jù)

package com.lagou.api;
import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import java.io.IOException;
public class UpdateNoteData implements Watcher {
    private static ZooKeeper zooKeeper;
    /**
     * 建立會(huì)話
     */
    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
        /*
            客戶端可以通過創(chuàng)建?個(gè)zk實(shí)例來連接zk服務(wù)器
            new Zookeeper(connectString,sesssionTimeOut,Wather)
            connectString: 連接地址：IP：端?
            sesssionTimeOut：會(huì)話超時(shí)時(shí)間：單位毫秒
            Wather：監(jiān)聽器(當(dāng)特定事件觸發(fā)監(jiān)聽時(shí)，zk會(huì)通過watcher通知到客戶端)
        */
        zooKeeper = new ZooKeeper("127.0.0.1:2181", 5000, new UpdateNoteData());
        System.out.println(zooKeeper.getState());
        Thread.sleep(Integer.MAX_VALUE);
    }
    /**
     * 回調(diào)方法：處理來自服務(wù)器端的watcher通知
     */
    public void process(WatchedEvent watchedEvent) {
        // SyncConnected
        if (watchedEvent.getState() == Event.KeeperState.SyncConnected) {
            // 更新數(shù)據(jù)節(jié)點(diǎn)內(nèi)容的方法
            try {
                updateNoteSync();
            } catch (InterruptedException | KeeperException e) {
                throw new RuntimeException(e);
            }
        }
    }
    /*
        更新數(shù)據(jù)節(jié)點(diǎn)內(nèi)容的方法
     */
    private void updateNoteSync() throws InterruptedException, KeeperException {
        /*
            path:路徑
            data:要修改的內(nèi)容 byte[]
            version:為-1，表示對最新版本的數(shù)據(jù)進(jìn)?修改
            zooKeeper.setData(path, data,version);
        */
        byte[] data = zooKeeper.getData("/lg-persistent", false, null);
        System.out.println("修改前的值：" + new String(data));
        // 修改 /lg-persistent 的數(shù)據(jù)    stat: 狀態(tài)信息對象
        Stat stat = zooKeeper.setData("/lg-persistent", "客戶端修改了節(jié)點(diǎn)數(shù)據(jù)".getBytes(), -1);
        byte[] data2 = zooKeeper.getData("/lg-persistent", false, null);
        System.out.println("修改后的值：" + new String(data2));
    }
}

刪除節(jié)點(diǎn)

package com.lagou.api;
import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
import java.io.IOException;
public class DeleteNote implements Watcher {
    private static ZooKeeper zooKeeper;
    /**
     * 建立會(huì)話
     */
    public static void main(String[] args) throws IOException, InterruptedException, KeeperException {
        /*
            客戶端可以通過創(chuàng)建?個(gè)zk實(shí)例來連接zk服務(wù)器
            new Zookeeper(connectString,sesssionTimeOut,Wather)
            connectString: 連接地址：IP：端?
            sesssionTimeOut：會(huì)話超時(shí)時(shí)間：單位毫秒
            Wather：監(jiān)聽器(當(dāng)特定事件觸發(fā)監(jiān)聽時(shí)，zk會(huì)通過watcher通知到客戶端)
        */
        zooKeeper = new ZooKeeper("127.0.0.1:2181", 5000, new DeleteNote());
        System.out.println(zooKeeper.getState());
        Thread.sleep(Integer.MAX_VALUE);
    }
    /**
     * 回調(diào)方法：處理來自服務(wù)器端的watcher通知
     */
    public void process(WatchedEvent watchedEvent) {
        // SyncConnected
        if (watchedEvent.getState() == Event.KeeperState.SyncConnected) {
            // 刪除節(jié)點(diǎn)
            try {
                deleteNoteSync();
            } catch (InterruptedException | KeeperException e) {
                throw new RuntimeException(e);
            }
        }
    }
    /*
        刪除節(jié)點(diǎn)方法
     */
    private void deleteNoteSync() throws InterruptedException, KeeperException {
        /*
            zooKeeper.exists(path,watch) :判斷節(jié)點(diǎn)是否存在
            zookeeper.delete(path,version) : 刪除節(jié)點(diǎn)
        */
        Stat stat = zooKeeper.exists("/lg-persistent/c1", false);
        System.out.println(stat == null ? "該節(jié)點(diǎn)不存在" : "該節(jié)點(diǎn)存在");
        if (stat != null) {
            zooKeeper.delete("/lg-persistent/c1", -1);
        }
        Stat stat2 = zooKeeper.exists("/lg-persistent/c1", false);
        System.out.println(stat2 == null ? "該節(jié)點(diǎn)不存在" : "該節(jié)點(diǎn)存在");
    }
}

到此這篇關(guān)于分布式框架Zookeeper api的使用介紹的文章就介紹到這了,更多相關(guān)Zookeeper api內(nèi)容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！

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