使用Java操作Zookeeper

一、介紹

　　這里主要記錄通過Java調用API來操作Zookeeper集群的數據，對于zookeeper集群的搭建或者命令，可以參考：

　　目前接觸到的Java操作Zookeeper，有兩套API，一套是zookeeper官方提供的（zookeeper），另外一套是封裝了官方API的API（zkClient），從描述上來看，就知道，官方的API可能不是那么好用，不然也不會在封裝。　　

二、zookeeper API

2.1、導入依賴

　　使用zookeeper官方api的時候，請保證jar包的版本，和zk集群中zk的版本相同

<!-- https://mvnrepository.com/artifact/org.apache.zookeeper/zookeeper -->
<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.4.7</version>
</dependency>

2.2、連接zk集群

　　下面是代碼示例，兩種形式（分別使用匿名類和Lambda表達式）：

package cn.ganlixin.zk;

import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.junit.Test;

import java.io.IOException;

public class ZookeeperDemo {

    @Test
    public void connectZkCluster() throws IOException, KeeperException, InterruptedException {

        // 構造方法
        // ZooKeeper(String connectString, int sessionTimeout, Watcher watcher)
        
        // 匿名對象形式
        ZooKeeper zooKeeper = new ZooKeeper(
                "192.168.1.3:2181,192.168.1.4:2181,192.168.1.5:2181",
                20000,
                new Watcher() {
                    @Override
                    public void process(WatchedEvent watchedEvent) {
                        // 發生變更的節點路徑
                        String path = watchedEvent.getPath();
                        System.out.println("path:" + path);

                        // 通知狀態
                        Watcher.Event.KeeperState state = watchedEvent.getState();
                        System.out.println("KeeperState:" + state);

                        // 事件類型
                        Watcher.Event.EventType type = watchedEvent.getType();
                        System.out.println("EventType:" + type);
                    }
                }
        );

        // 關閉連接
        zooKeeper.close();

        // Lamdba形式
        ZooKeeper zk = new ZooKeeper(
                "192.168.1.3:2181,192.168.1.4:2181,192.168.1.5:2181",
                20000,
                watchedEvent -> {
                    // 發生變更的節點路徑
                    String path = watchedEvent.getPath();
                    System.out.println("path:" + path);

                    // 通知狀態
                    Watcher.Event.KeeperState state = watchedEvent.getState();
                    System.out.println("KeeperState:" + state);

                    // 事件類型
                    Watcher.Event.EventType type = watchedEvent.getType();
                    System.out.println("EventType:" + type);
                }
        );

        zk.close();
    }
}

　　運行上面的代碼，控制臺輸出如下（輸出了兩遍，是因為創建了兩次連接）

path:null
KeeperState:SyncConnected
EventType:None
path:null
KeeperState:SyncConnected
EventType:None

2.3、操作數據操作

　　操作Zk中的數據，方式也很簡單，只需要使用創建的zk連接，調用對應的方法即可（方法名與zk命令行中命令相同）

package cn.ganlixin.zk;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.ZooDefs;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
import org.junit.Test;

import java.io.IOException;

public class ZookeeperDemo {

    @Test
    public void manageData() throws KeeperException, InterruptedException, IOException {

        // 創建zk連接
        ZooKeeper zk = new ZooKeeper(
                "192.168.1.3:2181,192.168.1.4:2181,192.168.1.5:2181",
                20000,
                null
        );

        // 創建節點
        zk.create("/abc", "123".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);

        // 獲取節點數據
        // getData(String path, boolean watch, Stat stat);
        Stat stat = new Stat();
        byte[] data = zk.getData("/abc", false, stat);
        System.out.println(new String(data));       // 數據內容 123
        System.out.println(stat.getDataLength());   // 節點狀態（數據長度） 3

        // 對/abc進行watch
        zk.getData("/abc",
                watchedEvent -> {
                    System.out.println("path:" + watchedEvent.getPath());
                    System.out.println("KeeperState:" + watchedEvent.getState());
                    System.out.println("EventType:" + watchedEvent.getType());
                },
                null);

        // 設置節點數據
        // setData(String path, byte[] data, int version)
        // 指定version為-1，表示不關心版本
        zk.setData("/abc", "456".getBytes(), -1);

        // 設置兩次，第二次不會觸發通知
        zk.setData("/abc", "789".getBytes(), -1);

        // 阻塞，以等待通知
        Thread.sleep(1000);
        zk.close();
    }
}

　　上面的程序，運行輸出結果如下：

123
3
path:/abc
KeeperState:SyncConnected
EventType:NodeDataChanged

　　可以看到，只顯示了一次通知，和與預期相符。

三、zkClient API

　　因為Zookeeper API比較復雜，使用并不方便，所以出現了ZkClient，ZkClient對Zookeeper API進行了封裝，利用ZkClient可以更加方便地對Zookeeper進行操作。

3.1、導入依賴

　　因為zkClient是對zookeeper的再封裝，所以需要注意zkClient中zookeeper的版本與zk集群的版本相同，可以在maven倉庫中查看對應關系

<!-- https://mvnrepository.com/artifact/com.101tec/zkclient -->
<dependency>
    <groupId>com.101tec</groupId>
    <artifactId>zkclient</artifactId>
    <version>0.10</version>
</dependency>

3.2、使用示例

　　下面是個簡單的示例：

package cn.ganlixin.zk;

import org.I0Itec.zkclient.IZkChildListener;
import org.I0Itec.zkclient.IZkStateListener;
import org.I0Itec.zkclient.ZkClient;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.Watcher;
import org.junit.Test;

import java.util.List;

public class ZkClientDemo {

    @Test
    public void testConn() throws InterruptedException {
        ZkClient zkClient = new ZkClient(
                "192.168.1.3:2181,192.168.1.4:2181,192.168.1.5:2181",
                20000
        );

        // 創建節點
        zkClient.createPersistent("/abc", "hello");
        zkClient.createEphemeral("/xyz", "world");
        zkClient.create("/opq", "world", CreateMode.EPHEMERAL_SEQUENTIAL);

        String data = zkClient.readData("/abc");
        System.out.println(data);

        // 監聽狀態變化
        zkClient.subscribeStateChanges(new IZkStateListener() {
            @Override
            public void handleStateChanged(Watcher.Event.KeeperState keeperState) throws Exception {
                System.out.println("state:" + keeperState);
            }

            @Override
            public void handleNewSession() throws Exception {
                System.out.println("new session");
            }

            @Override
            public void handleSessionEstablishmentError(Throwable throwable) throws Exception {
                throwable.printStackTrace();
            }
        });

        // 監聽子節點發生變化
        zkClient.subscribeChildChanges("/", new IZkChildListener() {
            @Override
            public void handleChildChange(String path, List<String> list) throws Exception {
                System.out.println("watch path:" + path);
                // 輸出所有子節點
                list.forEach(str -> {
                    System.out.println(str);
                });
            }
        });

        Thread.sleep(100000);
    }
}

posted @ 2019-06-09 16:33 尋覓beyond 閱讀(8165) 評論(0) 收藏舉報

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