物联网实际应用第七篇：利用MQTT模拟单向通信

文章目录

概要

两个springboot项目，一个作为发布方，一个作为订阅方，模拟设备向服务器发送mqtt请求上报消息，示例使用的是emqx官网的免费mqtt服务器，实际开发中可以使用搭建的mqtt服务器

发布方（模拟设备）

引入pom

 <dependency>
    <groupId>org.eclipse.paho</groupId>
     <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
     <version>1.2.5</version>
 </dependency>

回调MqttCallback

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttMessage;

public class OnMessageCallback implements MqttCallback {
    @Override
    public void connectionLost(Throwable cause) {
    }
    @Override
    public void messageArrived(String topic, MqttMessage message) throws Exception {
    }
    @Override
    public void deliveryComplete(IMqttDeliveryToken token) {
    }
}

发布的方法

import com.sci.web.system.controller.dev.OnMessageCallback;
import io.swagger.annotations.*;
import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/system/send")
public class TGlzzMenuController {


    @ApiOperation("发送mqtt消息")
    @GetMapping("/sendMqtt")
    public void sendMqtt() {
        String pubTopic = "publish111/topic";
        String content = "Hello World";
        int qos = 2;
//      emqx免费服务器
        String broker = "tcp://broker.emqx.io:1883";
        String clientId = "publishClient11";
        MemoryPersistence persistence = new MemoryPersistence();

        try {
            MqttClient client = new MqttClient(broker, clientId, persistence);

            // MQTT 连接选项
            MqttConnectOptions connOpts = new MqttConnectOptions();
//            connOpts.setUserName("test111");
//            connOpts.setPassword("test111".toCharArray());
            // 保留会话

            // 设置回调
            client.setCallback(new OnMessageCallback() {
                @Override
                public void connectionLost(Throwable cause) {
                }

                @Override
                public void messageArrived(String topic, MqttMessage message) throws Exception {
                }

                @Override
                public void deliveryComplete(IMqttDeliveryToken token) {
                    System.out.println("发送成功");
                }
            });

            // 建立连接
            client.connect(connOpts);
            // 消息发布所需参数
            MqttMessage message = new MqttMessage(content.getBytes());
            message.setQos(qos);
            client.publish(pubTopic, message);

        } catch (MqttException me) {
//          这里有失败原因
            me.printStackTrace();
        }
    }
}

订阅方（模拟服务器）

引入pom

  <dependency>
            <groupId>org.eclipse.paho</groupId>
            <artifactId>org.eclipse.paho.client.mqttv3</artifactId>
            <version>1.2.5</version>
        </dependency>

回调MqttCallback

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttMessage;

public class OnMessageCallback implements MqttCallback {
    @Override
    public void connectionLost(Throwable cause) {
    }

    @Override
    public void messageArrived(String topic, MqttMessage message) throws Exception {
    }

    @Override
    public void deliveryComplete(IMqttDeliveryToken token) {
    }
}

订阅的方法

import org.eclipse.paho.client.mqttv3.*;
import org.springframework.stereotype.Component;
import javax.annotation.PostConstruct;

@Component
public class MqttClientConfiguration{
    
    private MqttClient client;
//  emqx免费服务器
    private String broker = "tcp://broker.emqx.io:1883";
    private String clientId = "receiveClient11";
    //  订阅主题
    private String subscribeTopic = "publish111/topic";
    private MqttConnectOptions connOpts;

    @PostConstruct
    public void connect() {
        try {
            client = new MqttClient(broker, clientId);

//          MQTT 连接选项
            connOpts = new MqttConnectOptions();
//          connOpts.setUserName("test111");
//          connOpts.setPassword("test111".toCharArray());
//          保留会话
            connOpts.setCleanSession(true);

//          建立连接
            client.connect(connOpts);
//          设置回调
            client.setCallback(new OnMessageCallback() {
                @Override
                public void connectionLost(Throwable cause) {
                    // 连接丢失后，一般在这里面进行重连
                    System.out.println("连接断开，可以做重连");
                }
                @Override
                public void messageArrived(String topic, MqttMessage message) throws Exception {
                    // subscribe后得到的消息会执行到这里面
                    System.out.println("接收消息主题:" + topic);
                    System.out.println("接收消息内容:" + new String(message.getPayload()));
                }
                @Override
                public void deliveryComplete(IMqttDeliveryToken token) {
                }
            });
//          订阅
            client.subscribe(subscribeTopic);
        } catch (MqttException me) {
//          这里有失败原因
            me.printStackTrace();
        }
    }
}

测试结果

发布方

订阅方

实际应用

在订阅方的回调中把收到的数据解析存起来

作者：uutale