Java使用Json+mqtt进行通讯

一、简介

记录学习java语言中进行mqtt通讯的一些代码,通讯解析采用fastjson

二、工程代码

gradle依赖

repositories {
    mavenCentral()
    maven {
        url "https://repository.mulesoft.org/nexus/content/repositories/public"
        }
}
dependencies {
    implementation group: 'org.eclipse.paho', name: 'org.eclipse.paho.client.mqttv3', version: '1.2.2'
    implementation group: 'com.alibaba', name: 'fastjson', version: '1.2.75'
}

MqttCommunication

package app;

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.MqttPersistenceException;
import org.eclipse.paho.client.mqttv3.MqttTopic;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;

/*
mqtt 通讯类
*/
public class MqttCommunication {

    private MqttClient client;
    private String userName = "admin";
    private String passWord = "password";
    private MqttMessage message;
    private MqttTopic mqttTopic;

    public MqttCommunication(String id) {
        this(id, null, "tcp://127.0.0.1:1883");
    }
    /*
     * 初始化化时每个应用应该具有唯一性 host = "tcp://127.0.0.1:1883";
     */
    public MqttCommunication(String id, MqttCallback callback, String host) {
        try {

            client = new MqttClient(host, id, new MemoryPersistence());
            MqttConnectOptions options = new MqttConnectOptions();
            options.setCleanSession(false);
            options.setUserName(userName);
            options.setPassword(passWord.toCharArray());
            options.setConnectionTimeout(10);
            options.setKeepAliveInterval(20);

            message = new MqttMessage();

            if (callback == null) {
                client.setCallback(new MqttCallback() {

                    @Override
                    public void connectionLost(Throwable arg0) {

                        System.out.println(" connectionLost " + arg0);
                    }

                    @Override
                    public void deliveryComplete(IMqttDeliveryToken arg0) {

                        System.out.println(" deliveryComplete " + arg0);
                    }

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

                        System.out.println(topic + " messageArrived: " + msg.toString());
                    }
                });
            } else {
                client.setCallback(callback);
            }
            client.connect(options);
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }

    public void sendMessage(String topic, String msg) {
        try {
            message.setQos(0);
            message.setRetained(true);
            message.setPayload(msg.getBytes());
            mqttTopic = client.getTopic(topic);

            MqttDeliveryToken token = mqttTopic.publish(message);// 发布主题
            token.waitForCompletion();
        } catch (MqttPersistenceException e) {

            e.printStackTrace();
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }

    /*
     * String[] topics = new String[] { "Tcs/test1" }; int[] qoss = new int[] { 0 };
     */
    public void subscribe(String[] topicFilters, int[] qos) {
        try {
            client.subscribe(topicFilters, qos);
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }

}

进行json通讯，网上好像没有像cjson一样简单快捷的方式来操作json，目前使用了阿里的fastjson，但json对象生成json必须符合一定规则，即Java Bean对象

// 这个是符合规则的Java Bean 对象
public class TestObject {

    private int key1;
    private String key2;
    private double key3=3.14;

    public void setKey1(int key1) {
        this.key1 = key1;
    }

    public int getKey1() {
        return key1;
    }

    public void setKey2(String key2) {
        this.key2 = key2;
    }

    public String getKey2() {
        return key2;
    }

    public void setKey3(double key1) {
        this.key3 = key1;
    }

    public double getKey3() {
        return key3;
    }

}

使用fastjson进行序列化后结果如下

{
  "key1" : 780,
  "key2" : "key2",
  "key3" : 3.14
}

App

package app;

import com.alibaba.fastjson.JSON;

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

public class App extends Thread {

    private TestObject obj;

    public App() {
        obj = new TestObject();
    }
    
    //实现Javabaice类转换成json字符串
    public String JsonDataCnt(int cnt) {
        obj.setKey1(cnt);
        obj.setKey2("key2");
        // 这里将javabean转化成json字符串
        String jsonString = JSON.toJSONString(obj);
        return jsonString;
    }

    public void TopicTest() {

        MqttCallback callback = new MqttCallback() {
            @Override
            /* 断开连接回调 */
            public void connectionLost(Throwable arg0) {
                System.out.println(" connectionLost " + arg0);
            }

            @Override
            /* 发送完成回调函数 */
            public void deliveryComplete(IMqttDeliveryToken arg0) {
                // System.out.println(" deliveryComplete " + arg0);
            }

            @Override
            /* 接收回调 */
            public void messageArrived(String Topic, MqttMessage msg) throws Exception {
                System.out.println(Topic + " messageArrived: " + msg.toString());
            }
        };

        MqttCommunication myMqtt = new MqttCommunication("Server", callback, "tcp://192.168.2.18:1883");
        String[] topics = new String[] { "Tcs/test1" };
        int[] qoss = new int[] { 0 };
        myMqtt.subscribe(topics, qoss);
        int cnt = 0;

        while (true) {
            myMqtt.sendMessage("Topic", JsonDataCnt(cnt++));
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        System.out.println("hello");
        App a = new App();
        a.TopicTest();
        System.out.println("end");

    }
}

三、其他