JAVA实现MQTT客户端订阅消息并消费

MQTT客户端订阅消息

mqtt发送消息首先要建立与服务器连接，接下来订阅主题topic就可以接收到这个消息

客户端：

    package com.gw.device.mqtt;
    import lombok.extern.slf4j.Slf4j;
    import org.eclipse.paho.client.mqttv3.MqttClient;
    import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
    import org.eclipse.paho.client.mqttv3.MqttException;
    import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
    
    /**
     * MQTT客户端
     */
    @Slf4j
    public class MyMqttClient {
        private static String HOST = "ws://xx.xxx.com:8083";
        private static String CLIENTID = "03232983-20ea-42b8-84c5-1c6c80bdabef";
        private static String userName = "username";
        private static String passWord = "password";
        private MqttClient client;
        private static volatile MyMqttClient mqttClient = null;
    
        public static MyMqttClient getInstance() {
            if (mqttClient == null) {
                synchronized (MyMqttClient.class) {
                    if (mqttClient == null) {
                        mqttClient = new MyMqttClient();
                    }
                }
            }
            return mqttClient;
        }
    
        private MyMqttClient() {
            log.info("Connect MQTT: " + this);
            connect();
        }
    
        /**
         * 创建连接
         */
        private void connect() {
            try {
                //初始化连接设置对象
                MqttConnectOptions mqttConnectOptions = new MqttConnectOptions();
                //true可以安全地使用内存持久性作为客户端断开连接时清除的所有状态
                mqttConnectOptions.setCleanSession(true);
                mqttConnectOptions.setConnectionTimeout(30);//设置连接超时
                mqttConnectOptions.setUserName(userName); // 设置连接的用户名
                mqttConnectOptions.setPassword(passWord.toCharArray());// 设置连接的密码
                client = new MqttClient(HOST,CLIENTID, new MemoryPersistence());
                client.setCallback(new MqttRecieveCallback());//执行回调
                client.connect(mqttConnectOptions);//创建连接
            } catch (MqttException e) {
                log.info(e.getMessage());
                e.printStackTrace();
            }
    
        }
    
        /**
         * 订阅主题
         *
         * @param topic qos默认为1
         */
        public void subTopic(String topic) {
            try {
                client.subscribe(topic, 1);
            } catch (MqttException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        
        /**
         * 订阅某个主题
         *
         * @param topic
         * @param gos
         */
        public void subTopic(String topic, int gos) {
            try {
                client.subscribe(topic, gos);
            } catch (MqttException e) {
                log.error(e.getMessage());
                e.printStackTrace();
            }
        }
    
        /**
         * 清空主题
         * @param topic
         */
        public void cleanTopic(String topic) {
            try {
                client.unsubscribe(topic);
            } catch (MqttException e) {
                log.error(e.getMessage());
                e.printStackTrace();
            }
        }
    
    }

回调函数类：

    package com.gw.device.mqtt;
    import com.alibaba.fastjson.JSONObject;
    import com.gw.common.HttpClientUtil;
    import com.gw.device.pushData.AlarmBJZJInData;
    import com.gw.device.pushData.LoraDeviceStatusData;
    import com.gw.device.receiveData.AlarmData;
    import com.gw.device.receiveData.DeviceStatusData;
    import lombok.extern.slf4j.Slf4j;
    import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
    import org.eclipse.paho.client.mqttv3.MqttCallback;
    import org.eclipse.paho.client.mqttv3.MqttMessage;
    
    /**
     * 接收消息回调函数
     */
    @Slf4j
    public class MqttRecieveCallback implements MqttCallback {
    
        /**
         * 断连后重新连接并订阅相关主题
         * @param cause
         */
        @Override
        public void connectionLost(Throwable cause) {
            log.error(cause.getMessage());
            MyMqttClient client = MyMqttClient.getInstance();
            client.subTopic("topic主题");
        }
    
        /**
         * 消费消息
         * @param topic
         * @param message
         * @throws Exception
         */
        @Override
        public void messageArrived(String topic, MqttMessage message) throws Exception {
            String msg = new String(message.getPayload());
            log.info("主题名：" + topic);
            log.info("订阅消息：" + msg);
            if (topic.indexOf("topic主题") > -1 ) {
    
            }
            if (topic.indexOf("topic主题")>-1) {
              
            }
        }
    
        /**
         *  接收到已经发布的 QoS 1 或 QoS 2 消息的传递令牌时调用
         * @param token
         */
        @Override
        public void deliveryComplete(IMqttDeliveryToken token) {
    
        }
    
    }

总结

个人整理并已实践，有问题欢迎大家交流指正！

本文地址：https://blog.csdn.net/Zeng_1997/article/details/108990100