zookeeper curator 基本使用

下面，我們將通過一個簡單的示例演示curator最基本的crud功能：

maven依賴：

<dependencies>
    <dependency>
      <groupId>org.apache.zookeeper</groupId>
      <artifactId>zookeeper</artifactId>
      <version>3.4.12</version>
    </dependency>

    <dependency>
      <groupId>org.apache.curator</groupId>
      <artifactId>curator-recipes</artifactId>
      <version>2.12.0</version>
    </dependency>

      <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>4.12</version>
          <scope>test</scope>
      </dependency>
  </dependencies>

測試類：

package per.ym.zookeeper;

import java.util.List;

import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.retry.BoundedExponentialBackoffRetry;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.curator.retry.RetryForever;
import org.apache.curator.retry.RetryNTimes;
import org.apache.curator.retry.RetryOneTime;
import org.apache.curator.retry.RetryUntilElapsed;
import org.apache.zookeeper.data.Stat;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class CuratorBasicAPI {

    private CuratorFramework client;

    private String connectString = "192.168.61.131:2184";

    private int sessionTimeoutMs = 60000;

    private int connectionTimeoutMs = 60000;

    private String path = "/test";

    private String rootPath = "/";

    private byte[] data = "data".getBytes();

    private byte[] newData = "newData".getBytes();

    private int baseSleepTimeMs = 1000;

    private int maxRetries = 3;

    @Before
    public void connect() {
        //baseSleepTimeMs：基礎睡眠時間；maxRetries：最大重試次數；maxSleepMs：兩次重試之間最大睡眠時間
        //其睡眠時間計算公式為：sleepMs = baseSleepTimeMs * Math.max(1, random.nextInt(1 << (retryCount + 1)));
        RetryPolicy retryPolicy1 = new ExponentialBackoffRetry(baseSleepTimeMs, maxRetries);

        //ExponentialBackoffRetry的子類，重寫了父類的getSleepTimeMs方法
        //其睡眠時間計算公式為：Math.min(maxSleepTimeMs, super.getSleepTimeMs(retryCount, elapsedTimeMs));
        RetryPolicy retryPolicy2 = new BoundedExponentialBackoffRetry(baseSleepTimeMs, 50000, maxRetries);

        //最大重試3次，每次相隔時間為5000毫秒
        RetryPolicy retryPolicy3 = new RetryNTimes(3, 5000);

        //只重試一次，RetryNTimes的子類，就是將次數指定為1
        RetryPolicy retryPolicy4 = new RetryOneTime(3000);

        //一直重試，重試間隔為3000毫秒
        RetryPolicy retryPolicy5 = new RetryForever(3000);

        //最大重試時間為20000毫秒，若超過就不重試了，每次間隔3000毫秒
        RetryPolicy retryPolicy6 = new RetryUntilElapsed(20000, 3000);

        //client = CuratorFrameworkFactory.newClient(connectString, sessionTimeoutMs, connectionTimeoutMs, retryPolicy);

        //流式
        client = CuratorFrameworkFactory.builder()
                        .connectString(connectString) //服務器列表，格式host1:port1,host2:port2,…
                        .sessionTimeoutMs(sessionTimeoutMs) //會話超時時間，單位毫秒，默認60000ms
                        .connectionTimeoutMs(connectionTimeoutMs) //連接創建超時時間，單位毫秒，默認60000ms
                        .retryPolicy(retryPolicy1)
                        .build();

        //啟動
        client.start();
    }

    @Test
    public void showBasicAPI() throws Exception {
        exist();

        create();

        exist();

        getData();

        setData();

        getData();

        getChildren();

        delete();

        getChildren();

    }

    @After
    public void close() {
        //關閉連接
        client.close();
    }

    private void create() throws Exception {
        //創建一個節點
        //client.create().forPath(path);

        //創建一個節點附帶數據
        client.create().forPath(path, data);

        System.out.println("創建節點：" + path);

        //創建一個臨時節點，默認不指定是持久的，另外還有持久帶序列和臨時帶序列PERSISTENT_SEQUENTIAL、EPHEMERAL_SEQUENTIAL
        //client.create().withMode(CreateMode.EPHEMERAL).forPath(path);

        //如果沒有父目錄則一起創建
        //client.create().creatingParentsIfNeeded().forPath(path);

        //后天模式，還可以傳入自定義CallBack和線程池
        //client.create().inBackground().forPath(path);

        //帶權限的
        //List<ACL> aclList = new ArrayList<ACL>();
        //acls.add(new ACL(Perms.ALL, new Id("digest", "520:1314")));
        //client.create().withACL(aclList).forPath(path);

        //當然你也這可這樣
        //client.create().creatingParentsIfNeeded().withMode(CreateMode.EPHEMERAL).withACL(aclList).inBackground().forPath(path, data);
    }

    private void exist() throws Exception {
        Stat stat = client.checkExists().forPath(path);
        if (stat == null) {
            System.out.println("節點" + path + "不存在。");
        } else {
            System.out.println("節點" + path + "存在。");
        }
    }

    private void getData() throws Exception {
        byte[] byteData = client.getData().forPath(path);

        //client.getData().inBackground().forPath(path);

        //Stat stat = new Stat();
        //client.getData().storingStatIn(stat).forPath("path");

        System.out.println("節點" + path + "的數據為：" + new String(byteData));
    }

    private void setData() throws Exception {
        client.setData().forPath(path, newData);

        System.out.println("設置節點" + path + "數據為：" + new String(newData));

        //client.setData().inBackground().forPath(path, newData);

        //指定版本，若版本錯誤將拋出異常bad version
        //client.setData().withVersion(520).forPath(path,newData);
    }

    private void delete() throws Exception {
        client.delete().forPath(path);

        System.out.println("刪除節點：" + path);

        //client.delete().withVersion(1314).forPath(path);

        //只要會話有效將一直嘗試刪除，直到刪除成功
        //client.delete().guaranteed().forPath(path);

        //同
        //client.delete().deletingChildrenIfNeeded().forPath(path);

        //client.delete().inBackground().forPath(path);

        //client.delete().guaranteed().deletingChildrenIfNeeded().withVersion(1314).inBackground().forPath(path);
    }

    private void getChildren() throws Exception {
        List<String> names = client.getChildren().forPath(rootPath);

        System.out.println("根目錄下有節點：" + names);

        //client.getChildren().inBackground().forPath(rootPath);
    }
}

運行結果：
節點/test不存在。
創建節點：/test
節點/test存在。
節點/test的數據為：data
設置節點/test數據為：newData
節點/test的數據為：newData
根目錄下有節點：[zookeeper, test]
刪除節點：/test
根目錄下有節點：[zookeeper]