Android移动设备连接接入到zookeeper分布式集群

在Android Studio中添加引用依赖：

compile group:'org.apache.zookeeper', name:'zookeeper', version:'3.5.5'

Android端代码：

package zhangphil.zookeeper;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

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.client.ZooKeeperSaslClient;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.TimeUnit;

public class MainActivity extends AppCompatActivity {

    private ZooKeeper zooKeeper;
    private String DEVICE_PATH = "/devices";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        //非常重要，如果没有，则Android手机客户端连接不到部署在PC上的ZooKeeper集群。
        System.setProperty(ZooKeeperSaslClient.ENABLE_CLIENT_SASL_KEY,"false");

        CompletableFuture.runAsync(new Runnable() {
            @Override
            public void run() {
                try {
                    zk();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    private void zk() throws Exception {
        zooKeeper = new ZooKeeper(getAddress(), 10 * 1000, new Watcher() {
            @Override
            public void process(WatchedEvent event) {
                System.out.println(event.toString());
            }
        });

        System.out.println("开始连接...");
        while (!zooKeeper.getState().isConnected()) {
            TimeUnit.SECONDS.sleep(3);
            System.out.println("尝试连接...");
        }
        System.out.println("连接建立");

        login();

        synchronized (this) {
            wait();
        }
    }

    private void login() throws Exception {
        //创建节点。
        String path = zooKeeper.create(DEVICE_PATH + "/client", "ip:127.0.0.1".getBytes("UTF-8"), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
        byte[] data = zooKeeper.getData(path, null, null);
        System.out.println(path + " => " + new String(data));
        System.out.println("注册设备成功");
    }

    private String getAddress() {
        String ip = "192.168.137.1";
        return ip + ":2181," + ip + ":2182," + ip + ":2183";
    }
}

需要保证Android手机与PC上部署的ZooKeeper集群连通，比如，可以让Android手机与PC同处于一个局域网（共同连接到一个WIFI）。

特别注意，在Android手机上跑的ZooKeeper程序，必须显示的关闭SASL认证，否则Android手机上的Zookeeper客户端连接不到处于PC网络的ZooKeeper集群。关闭SASL其实就一行代码：

System.setProperty(ZooKeeperSaslClient.ENABLE_CLIENT_SASL_KEY,"false");

接下来运行系统。首先要启动位于PC网络的ZooKeeper集群。

在Android手机上跑起上面的程序代码输出：

然后在PC上，通过命令行ls查询：

说明Android手机接入ZooKeeper成功。

这很有趣，一旦这条路走通，就意味着可以使用ZooKeeper做非常棒的Android设备在集群中的分布式系统应用，如，实时检测大规模集群中，某一Android设备是否在线，即心跳。