一、zookeeper java api

zookeeper 可以通過java api連接操作，進行ZNode的創建刪除，數據的獲取設置，子節點的獲取已經狀態的觀察，權限的設置。並且zookeeper客戶端提供了異步操作，並有監聽機制，更爲方便的提供對zookeeper數據的監聽和維護。

上一篇文章提到的可以通過控制命令行操作zookeeper數據節點，同樣，zookeeper官方爲我們提供了相應的java api 操作。

https://blog.csdn.net/qq_33513250/article/details/101618808

客戶端連接後我們可以做如下操作：

創建znode、獲取數據、設置數據、獲取子節點、權限設置、節點存在判斷、刪除節點

二、pom 文件

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

三、同步操作

1.創建節點

package com.szwn.zk;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;

import java.util.concurrent.CountDownLatch;

public class CreateNode implements Watcher{
    private static CountDownLatch connectedSemaphore = new CountDownLatch(1);

    public static void main(String[] args) throws Exception {
        // 1.連接zookeeper 客戶端，參數分別爲服務器連接地址，集羣用逗號隔開，sessionTimeout,事件監聽器
        ZooKeeper zookeeper = new ZooKeeper("127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183", 5000, new CreateNode());
        System.out.println(zookeeper.getState());
        // 2.等待連接完成
        connectedSemaphore.await();
        
        // 3.創建節點，節點類型爲persistent
        String path1 = zookeeper.create("/create-test-ephemeral-", "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        System.out.println("Success create znode: " + path1);

        // 4.創建節點，節點類型爲ephemeral-sequential
        String path2 = zookeeper.create("/create-test-ephemeral-", "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
        System.out.println("Success create znode: " + path2);
    }

    /**
     * WatchedEvent 事件監聽
     * 服務器回調監聽器連接成功
     * @param event
     */
    public void process(WatchedEvent event) {
        if (Event.KeeperState.SyncConnected == event.getState()) {
            connectedSemaphore.countDown();
        }
    }
}

2.獲取數據

package com.szwn.zk;

import java.util.concurrent.CountDownLatch;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;

public class GetData implements Watcher {
    private static CountDownLatch connectedSemaphore = new CountDownLatch(1);
    private static ZooKeeper zk = null;
    private static Stat stat = new Stat();

    public static void main(String[] args) throws Exception {
        String path = "/zk-book";
        // 1.連接zookeeper 客戶端，參數分別爲服務器連接地址，集羣用逗號隔開，sessionTimeout,事件監聽器
        zk = new ZooKeeper("127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183", 5000, new GetData());
        // 2.等待連接完成
        connectedSemaphore.await();
        // 3.創建節點，節點類型爲ephemeral,數據爲123
        zk.create(path, "123".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        System.out.println("success create znode: " + path);

        // 4.獲取數據，且爲監聽模式，並把數據狀態存入 stat中
        System.out.println("the data of znode " + path + " is : " + new String(zk.getData(path, true, stat)));
        System.out.println("czxID: " + stat.getCzxid() + ", mzxID: " + stat.getMzxid() + ", version: " + stat.getVersion());

        // 5.根據版本號-1 修改數據1234
        zk.setData(path, "1234".getBytes(), -1);

        Thread.sleep(Integer.MAX_VALUE);
    }

    public void process(WatchedEvent event) {
        if (Event.KeeperState.SyncConnected == event.getState()) {
            // 連接監聽，連接狀態，空事件則爲連接session成功
            if (Event.EventType.None == event.getType() && null == event.getPath()) {
                connectedSemaphore.countDown();
            } else if (event.getType() == Event.EventType.NodeDataChanged) {
                // node data changed 監聽
                try {
                    System.out.println("the data of znode " + event.getPath() + " is : " + new String(zk.getData(event.getPath(), true, stat)));
                    System.out.println("czxID: " + stat.getCzxid() + ", mzxID: " + stat.getMzxid() + ", version: " + stat.getVersion());
                } catch (Exception e) {
                }
            }
        }
    }
}

3.設置數據

package com.szwn.zk;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;

import java.util.concurrent.CountDownLatch;

public class SetData implements Watcher {
    private static CountDownLatch connectedSemaphore = new CountDownLatch(1);
    private static ZooKeeper zk;

    public static void main(String[] args) throws Exception {
        String path = "/zk-book-set";
        // 1.連接zookeeper 客戶端，參數分別爲服務器連接地址，集羣用逗號隔開，sessionTimeout,事件監聽器
        zk = new ZooKeeper("127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183", 5000, new SetData());
        // 2.等待連接完成
        connectedSemaphore.await();

        // 3.創建節點，節點類型爲ephemeral,數據爲123
        zk.create(path, "123".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        System.out.println("success create znode: " + path);

        // 4.獲取數據，且爲監聽模式
        zk.getData(path, true, null);

        // 5.根據版本號-1 修改數據456
        Stat stat = zk.setData(path, "456".getBytes(), -1);
        System.out.println("czxID: " + stat.getCzxid() + ", mzxID: " + stat.getMzxid() + ", version: " + stat.getVersion());
        // 6.根據版本號，上一次修改後的版本號，設置數據456
        Stat stat2 = zk.setData(path, "456".getBytes(), stat.getVersion());
        System.out.println("czxID: " + stat2.getCzxid() + ", mzxID: " + stat2.getMzxid() + ", version: " + stat2.getVersion());
        try {
            // 7.錯誤版本號設置數據，報錯
            zk.setData(path, "456".getBytes(), stat.getVersion());
        } catch (KeeperException e) {
            System.out.println("Error: " + e.code() + "," + e.getMessage());
        }
        Thread.sleep(Integer.MAX_VALUE);
    }

    public void process(WatchedEvent event) {
        if (Event.KeeperState.SyncConnected == event.getState()) {
            // 連接監聽，連接狀態，空事件則爲連接session成功
            if (Event.EventType.None == event.getType() && null == event.getPath()) {
                connectedSemaphore.countDown();
            }
        }
    }
}

4.獲取子節點

package com.szwn.zk;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;

import java.util.List;
import java.util.concurrent.CountDownLatch;

public class GetChildren implements Watcher{
    private static CountDownLatch connectedSemaphore = new CountDownLatch(1);
    private static ZooKeeper zk = null;

    public static void main(String[] args) throws Exception {
        String path = "/zk-book-1";
        // 1.連接zookeeper 客戶端，參數分別爲服務器連接地址，集羣用逗號隔開，sessionTimeout,事件監聽器
        zk = new ZooKeeper("127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183", 5000, new GetChildren());
        // 2.等待連接完成
        connectedSemaphore.await();

        // 3.創建節點，節點類型爲persistent,數據爲空
        zk.create(path, "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        System.out.println("success create znode: " + path);
        // 4.創建子節點，路徑爲path/c1，節點類型爲ephemeral,數據爲空
        zk.create(path + "/c1", "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        System.out.println("success create znode: " + path + "/c1");
        // 5.獲取path的子節點，並監聽變化
        List<String> childrenList = zk.getChildren(path, true);
        System.out.println(childrenList);

        // 4.創建子節點，路徑爲path/c2，節點類型爲ephemeral,數據爲空
        zk.create(path + "/c2", "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        System.out.println("success create znode: " + path + "/c2");
        Thread.sleep(1000);
        // 4.創建子節點，路徑爲path/c3，節點類型爲ephemeral,數據爲空
        zk.create(path + "/c3", "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
        System.out.println("success create znode: " + path + "/c3");
        Thread.sleep(Integer.MAX_VALUE);
    }

    public void process(WatchedEvent event) {
        if (Event.KeeperState.SyncConnected == event.getState()) {
            // 連接監聽，連接狀態，空事件則爲連接session成功
            if (Event.EventType.None == event.getType() && null == event.getPath()) {
                connectedSemaphore.countDown();
                // 監聽node children changed event
            } else if (event.getType() == Event.EventType.NodeChildrenChanged) {
                try {
                    System.out.println("ReGet Child:" + zk.getChildren(event.getPath(), true));
                } catch (Exception e) {
                }
            }
        }
    }
}

5.節點權限控制

package com.szwn.zk;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;

public class Auth {
    final static String PATH = "/zk-book-auth_test";

    public static void main(String[] args) throws Exception {

        // 1.連接zookeeper 客戶端，參數分別爲服務器連接地址，集羣用逗號隔開，sessionTimeout,事件監聽器
        ZooKeeper zookeeper1 = new ZooKeeper("127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183", 5000, null);
        // 2.連接添加權限信息，scheme和data
        zookeeper1.addAuthInfo("digest", "foo:true".getBytes());
        // 3.創建節點，數據爲init
        // 權限爲 CREATOR_ALL_ACL（This ACL gives the creators authentication id's all permissions.）
        zookeeper1.create(PATH, "init".getBytes(), ZooDefs.Ids.CREATOR_ALL_ACL, CreateMode.EPHEMERAL);
        System.out.println("success create znode: " + PATH);
        // 4.創建第二個session
        ZooKeeper zookeeper2 = new ZooKeeper("127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183", 5000, null);
        // 5.獲取第一個數據
        byte[] data = zookeeper2.getData(PATH, false, null);
        System.out.println(new String(data));
    }
}

第二個客戶端沒有path的權限，運行結果爲

6.節點存在

package com.szwn.zk;

import java.util.concurrent.CountDownLatch;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;

public class Exist implements Watcher {
    private static CountDownLatch connectedSemaphore = new CountDownLatch(1);
    private static ZooKeeper zk;

    public static void main(String[] args) throws Exception {
        String path = "/zk-book";
        // 1.連接zookeeper 客戶端，參數分別爲服務器連接地址，集羣用逗號隔開，sessionTimeout,事件監聽器
        zk = new ZooKeeper("127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183", 5000, new Exist());
        // 2.等待連接完成
        connectedSemaphore.await();

        // 3.判斷path節點是否存在，並啓動監聽
        Stat exists = zk.exists(path, true);
        System.out.println(exists);

        // 4.創建path節點並設置數據爲123
        zk.create(path, "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        zk.setData(path, "123".getBytes(), -1);

        // 5.創建path/c1子節點
        zk.create(path + "/c1", "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        System.out.println("success create znode: " + path + "/c1");

        // 6.刪除path/c1子節點
        zk.delete(path + "/c1", -1);
        zk.delete(path, -1);

        Thread.sleep(Integer.MAX_VALUE);
    }

    public void process(WatchedEvent event) {
        try {
            if (Event.KeeperState.SyncConnected == event.getState()) {
                // 連接監聽，連接狀態，空事件則爲連接session成功
                if (Event.EventType.None == event.getType() && null == event.getPath()) {
                    connectedSemaphore.countDown();
                    // node created 監聽，因爲對節點的操作監聽爲下一次有效，所以設置監聽爲true,繼續監聽節點下次狀態變化
                } else if (Event.EventType.NodeCreated == event.getType()) {
                    System.out.println("success create znode: " + event.getPath());
                    zk.exists(event.getPath(), true);
                    // node deleted 監聽
                } else if (Event.EventType.NodeDeleted == event.getType()) {
                    System.out.println("success delete znode: " + event.getPath());
                    zk.exists(event.getPath(), true);
                    // node data changed 監聽
                } else if (Event.EventType.NodeDataChanged == event.getType()) {
                    System.out.println("data changed of znode: " + event.getPath());
                    zk.exists(event.getPath(), true);
                }
            }
        } catch (Exception e) {
        }
    }
}

7.刪除節點

package com.szwn.zk;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;

import java.util.concurrent.CountDownLatch;

public class DeleteNode implements Watcher {
    private static CountDownLatch connectedSemaphore = new CountDownLatch(1);
    private static ZooKeeper zk;

    public static void main(String[] args) throws Exception {
        String path = "/zk-book";
        // 1.連接zookeeper 客戶端，參數分別爲服務器連接地址，集羣用逗號隔開，sessionTimeout,事件監聽器
        zk = new ZooKeeper("127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183", 5000,
                new DeleteNode());
        // 2.等待連接完成
        connectedSemaphore.await();

        // 3.創建節點，節點類型爲persistent
        zk.create(path, "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        System.out.println("success create znode: " + path);
        // 4.創建子節點，節點類型爲persistent
        zk.create(path + "/c1", "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        System.out.println("success create znode: " + path + "/c1");
        try {
            // 5.刪除父節點，因爲有子節點，報錯
            zk.delete(path, -1);
        } catch (Exception e) {
            System.out.println("fail to delete znode: " + path);
        }

        // 6.刪除子節點
        zk.delete(path + "/c1", -1);
        System.out.println("success delete znode: " + path + "/c1");
        // 7.刪除父節點
        zk.delete(path, -1);
        System.out.println("success delete znode: " + path);

        Thread.sleep(Integer.MAX_VALUE);
    }

    public void process(WatchedEvent event) {
        if (Event.KeeperState.SyncConnected == event.getState()) {
            if (Event.EventType.None == event.getType() && null == event.getPath()) {
                connectedSemaphore.countDown();
            }
        }
    }
}

運行結果

zookeeper java api 操作（一） | 同步處理結果

目錄

一、zookeeper java api

二、pom 文件

三、同步操作

1.創建節點

2.獲取數據

3.設置數據

4.獲取子節點

5.節點權限控制

6.節點存在

7.刪除節點

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