java 通过mqtt对外发送数据

• pom配置

<!--mqtt相关依赖-->
    <dependency>
      <groupId>org.springframework.integration</groupId>
      <artifactId>spring-integration-stream</artifactId>
      <version>5.5.5</version>
    </dependency>
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-integration</artifactId>
      <version>2.5.1</version>
    </dependency>
    <dependency>
      <groupId>org.springframework.integration</groupId>
      <artifactId>spring-integration-mqtt</artifactId>
      <version>5.5.5</version>
    </dependency>

• yml配置

spring:
  application:
    name: provider
    #MQTT配置信息
  mqtt:
    #MQTT服务地址，端口号默认1883，如果有多个，用逗号隔开
    url: tcp://localhost:1883
    #用户名
    username: admin
    #密码
    password: 123456
    #客户端id(不能重复)
    client:
      id: my-client-id
    #MQTT默认的消息推送主题，实际可在调用接口是指定
    default:
      topic: my-topic
server:
  port: 8080

• MqttProviderCallBack类

package org.example.config;
import org.eclipse.paho.client.mqttv3.IMqttAsyncClient;
import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
@Configuration
public class MqttProviderCallBack implements MqttCallback{
    @Value("${spring.mqtt.client.id}")
    private String clientId;
    /**
     * 与服务器断开的回调
     */
    @Override
    public void connectionLost(Throwable cause) {
        System.out.println(clientId+"与服务器断开连接");
    }
    /**
     * 消息到达的回调
     */
    @Override
    public void messageArrived(String topic, MqttMessage message) throws Exception {
    }
    /**
     * 消息发布成功的回调
     */
    @Override
    public void deliveryComplete(IMqttDeliveryToken token) {
        IMqttAsyncClient client = token.getClient();
        System.out.println(client.getClientId()+"发布消息成功！");
    }
}

• MqttProviderConfig类

package org.example.config;
import lombok.extern.slf4j.Slf4j;
import javax.annotation.PostConstruct;
import org.eclipse.paho.client.mqttv3.*;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
@Configuration
@Slf4j
public class MqttProviderConfig {
    @Value("${spring.mqtt.username}")
    private String username;
    @Value("${spring.mqtt.password}")
    private String password;
    @Value("${spring.mqtt.url}")
    private String hostUrl;
    @Value("${spring.mqtt.client.id}")
    private String clientId;
    @Value("${spring.mqtt.default.topic}")
    private String defaultTopic;
    /**
     * 客户端对象
     */
    private MqttClient client;
    /**
     * 在bean初始化后连接到服务器
     */
    @PostConstruct
    public void init(){
        connect();
    }
    /**
     * 客户端连接服务端
     */
    public void connect(){
        try{
        //创建MQTT客户端对象
        client = new MqttClient(hostUrl,clientId,new MemoryPersistence());
        //连接设置
        MqttConnectOptions options = new MqttConnectOptions();
        //是否清空session，设置false表示服务器会保留客户端的连接记录（订阅主题，qos）,客户端重连之后能获取到服务器在客户端断开连接期间推送的消息
        //设置为true表示每次连接服务器都是以新的身份
        options.setCleanSession(true);
        //设置连接用户名
        options.setUserName(username);
        //设置连接密码
        options.setPassword(password.toCharArray());
        //设置超时时间，单位为秒
        options.setConnectionTimeout(100);
        //设置心跳时间 单位为秒，表示服务器每隔 1.5*20秒的时间向客户端发送心跳判断客户端是否在线
        options.setKeepAliveInterval(20);
        //设置遗嘱消息的话题，若客户端和服务器之间的连接意外断开，服务器将发布客户端的遗嘱信息
        options.setWill("willTopic",(clientId + "与服务器断开连接").getBytes(),0,false);
        //设置回调
        client.setCallback(new MqttProviderCallBack());
        client.connect(options);
        } catch(MqttException e){
            e.printStackTrace();
        }
    }
    public void publish(int qos,boolean retained,String topic,String message){
        MqttMessage mqttMessage = new MqttMessage();
        mqttMessage.setQos(qos);
        mqttMessage.setRetained(retained);
        mqttMessage.setPayload(message.getBytes());
        //主题的目的地，用于发布/订阅信息
        MqttTopic mqttTopic = client.getTopic(topic);
        //提供一种机制来跟踪消息的传递进度
        //用于在以非阻塞方式（在后台运行）执行发布是跟踪消息的传递进度
        MqttDeliveryToken token;
        try {
            //将指定消息发布到主题，但不等待消息传递完成，返回的token可用于跟踪消息的传递状态
            //一旦此方法干净地返回，消息就已被客户端接受发布，当连接可用，将在后台完成消息传递。
            token = mqttTopic.publish(mqttMessage);
            token.waitForCompletion();
        } catch (MqttException e) {
            e.printStackTrace();
        }
    }
}

• 测试类

package org.example.controller;
import com.alibaba.fastjson.JSONObject;
import org.example.config.MqttProviderConfig;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;
import java.util.Date;
@RestController
public class SendController {
    @Autowired
    private MqttProviderConfig providerClient;
    @RequestMapping("/sendMessage")
    public String sendMessage(int qos,boolean retained,String topic,String message){
        try {
            providerClient.publish(qos, retained, topic, message);
            return "发送成功";
        } catch (Exception e) {
            e.printStackTrace();
            return "发送失败";
        }
    }
}