项目用到了HIVEMQ连接IOT设备，一开始使用了 spring-integration-mqtt，后来逛了逛HiveMq的官网发现他们有自己的SDK，所以记录一下。
Maven坐标：
<dependency><groupId>com.hivemq</groupId><artifactId>hivemq-mqtt-client</artifactId><version>1.2.1</version></dependency>异步代码示例：
package com.hive.mqtt.example;import com.hivemq.client.mqtt.datatypes.MqttQos;
import com.hivemq.client.mqtt.mqtt3.Mqtt3AsyncClient;
import com.hivemq.client.mqtt.mqtt3.Mqtt3Client;
import com.hivemq.client.mqtt.mqtt3.message.publish.Mqtt3Publish;import java.util.UUID;
import java.util.function.Consumer;import static javax.xml.bind.DatatypeConverter.printHexBinary;/*** @author qingtaiJiang* @date 2020/10/10 15:06*/
public class MqttExample {public static void main(final String[] args) {//回调函数Consumer<Mqtt3Publish> consumer = new Consumer<Mqtt3Publish>() {@Overridepublic void accept(Mqtt3Publish mqtt3Publish) {System.out.println("getPayload:" + mqtt3Publish.getPayload());System.out.println("qos:" + mqtt3Publish.getQos());System.out.println("extend:" + mqtt3Publish.extend());System.out.println("AsBytes:" + printHexBinary(mqtt3Publish.getPayloadAsBytes()));System.out.println("getTopic:" + mqtt3Publish.getTopic());System.out.println("getType:" + mqtt3Publish.getType());System.out.println("isRetain:" + mqtt3Publish.isRetain());}};//和Mqtt服务建立连接final Mqtt3AsyncClient client = Mqtt3Client.builder().identifier(UUID.randomUUID().toString()).serverHost("zrcentos03").buildAsync();client.connect().thenAccept(connAck -> System.out.println("connected:" + connAck));//订阅主题client.toAsync().subscribeWith().topicFilter("/test/aa") //指定订阅主题.qos(MqttQos.AT_LEAST_ONCE) //指定订阅质量.callback(consumer) //接收到订阅消息后的处理函数.send();//订阅主题client.toAsync().subscribeWith().topicFilter("/test/bb").qos(MqttQos.AT_LEAST_ONCE).callback(consumer).send();//取消订阅client.toAsync().unsubscribeWith().topicFilter("/test/bb").send();while (true) {System.out.println("");//发布消息client.toAsync().publishWith().topic("/message/certification").payload("1".getBytes()).qos(MqttQos.EXACTLY_ONCE).send();try {Thread.sleep(10000);} catch (InterruptedException e) {e.printStackTrace();}}}
}