paho mqtt java client demo

==pom依赖==

<dependency>
    <groupId>org.eclipse.paho</groupId>
    <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
    <version>1.2.1</version>
</dependency>

==Java样例代码==

【工具类】

package examples;

import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

import java.util.HashMap;
import java.util.Map;

/**
 * MQTT Client
 *
 * @author chunui.qu
 */
public class MqttUtils {
    private final Map<String, MqttClient> clientMap = new HashMap<>();

    /**
     * 构造函数
     */
    private MqttUtils() {
    }

    /**
     * 单例模式
     */
    private static class SingletonInstance {
        private static final MqttUtils INSTANCE = new MqttUtils();
    }

    /**
     * 获取对象句柄
     */
    public static MqttUtils getInstance() {
        return SingletonInstance.INSTANCE;
    }

    /**
     * 创建客户端连接
     *
     * @param clientId clientId
     * @return 结果
     */
    public MqttClient getMqttClient(String clientId) {
        if (clientMap.containsKey(clientId)) {
            return clientMap.get(clientId);
        }

        String serverUrl = "tcp://36.137.154.92:1883";
        String username = "root";
        String password = "test123";

        try {
            MqttConnectOptions options = new MqttConnectOptions();
            // 设置连接的用户名
            options.setUserName(username);
            // 设置连接的密码
            options.setPassword(password.toCharArray());
            // 设置是否清空session
            // 设置为false表示服务器会保留客户端的连接记录
            // 设置为true表示每次连接到服务器都以新的身份连接
            options.setCleanSession(false);
            // 设置会话心跳时间
            options.setAutomaticReconnect(true);
            // 设置超时时间,单位为秒
            options.setConnectionTimeout(10);
            // 设置会话心跳时间,单位为秒
            // 服务器会每隔1.5*20秒的时间向客户端发送个消息判断客户端是否在线，但这个方法并没有重连的机制
            options.setKeepAliveInterval(20);

            // host:服务连接地址
            // clientIId:连接MQTT的客户端ID，一般以唯一标识符表示
            // MemoryPersistence:clientId的保存形式，默认为以内存保存
            MqttClient client = new MqttClient(serverUrl, clientId, new MemoryPersistence());
            // 设置回调
            MyMqttCallback callback = new MyMqttCallback();
            client.setCallback(callback);
            // 建立连接
            client.connect(options);
            // 按clientId保存
            clientMap.put(clientId, client);
            return  client;
        } catch (MqttException e) {
            e.printStackTrace();
            return null;
        }
    }

    static class MyMqttCallback implements MqttCallbackExtended {
        @Override
        public void connectComplete(boolean b, String s) {
            System.out.println("连接成功");
        }

        @Override
        public void connectionLost(Throwable throwable) {
            System.out.println("连接断开:" + throwable.getMessage());
        }

        @Override
        public void messageArrived(String topic, MqttMessage message) {
            System.out.println("接收消息主题:" + topic);
            System.out.println("接收消息Qos:" + message.getQos());
            System.out.println("接收消息内容:" + new String(message.getPayload()));
        }

        @Override
        public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
            System.out.println("发送成功:" + iMqttDeliveryToken.isComplete());
        }
    }
}

【生产者】

package examples;

import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.MqttTopic;

/**
 * PublishDemo
 *
 * @author Chunhui.Qu
 */
public class PublishDemo {
    public static void main(String[] args) {
        MqttUtils mqttUtils = MqttUtils.getInstance();
        MqttClient mqttClient = mqttUtils.getMqttClient("publish_client");

        MqttTopic topic1 = mqttClient.getTopic("qch_test1");
        MqttMessage msg1 = new MqttMessage();
        msg1.setPayload("第1个消息".getBytes());
        msg1.setQos(2);
        msg1.setRetained(true);
        try {
            topic1.publish(msg1);
        } catch (MqttException e) {
            e.printStackTrace();
        }

        MqttTopic topic2 = mqttClient.getTopic("qch_test2");
        MqttMessage msg2 = new MqttMessage();
        msg2.setPayload("第2个消息".getBytes());
        msg2.setQos(2);
        msg2.setRetained(true);
        try {
            topic2.publish(msg2);
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }
}

【消费者】

package examples;

import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttException;

/**
 * SubscribeDemo
 *
 * @author Chunhui.Qu
 */
public class SubscribeDemo {
    public static void main(String[] args) {
        MqttUtils mqttUtils = MqttUtils.getInstance();
        MqttClient mqttClient = mqttUtils.getMqttClient("subscribe_client");

        int[] qos  = {2, 2};
        String[] topics = {"qch_test1", "qch_test2"};
        try {
            mqttClient.subscribe(topics, qos);
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }
}

==执行结果==

连接成功
接收消息主题:qch_test1
接收消息Qos:2
接收消息内容:第1个消息
接收消息主题:qch_test2
接收消息Qos:2
接收消息内容:第2个消息