MQTT是基于代理的轻量级的消息发布订阅传输协议。

1、下载安装代理

进入mosquitto下载地址：Download | Eclipse Mosquitto，进行下载，以win版本为例

下载完成后，在本地文件夹找到下载的代理安装文件

使用管理员身份打开安装

安装时选择自己的安装地址，其他不需要修改，直到安装结束

安装完成后需要做一下修改，进入安装路径

找到该配置文件，修改端口号，修改用户名密码

pwfile.example文件就在当前安装路径下，需要进行配置绝对路径

以管理员身份打开CMD，并切换到d:/mosquitto目录下，运行以下命令添加用户名和密码：

mosquitto_passwd.exe -c D:\softwork\mqtt\mosquitto\pwfile.example admin

提示连续两次输入密码、创建成功。命令解释： -c 创建一个用户、D:\softwork\mqtt\mosquitto\pwfile.example 是将用户创建到 pwfile.example 文件中、admin 是用户名。

修改用户名密码后mosquitto需要重启生效，可以在服务里面找到该服务重启

2、创建Spring Boot项目

2.1、pom.xml文件中引入依赖

<!-- MQTT 客户端依赖 -->
<dependency><groupId>org.eclipse.paho</groupId><artifactId>org.eclipse.paho.client.mqttv3</artifactId><version>1.2.5</version>
</dependency>

2.2、application.properties配置文件添加MQTT配置

# MQTT 配置
mqtt.broker=tcp://127.0.0.1:7788
mqtt.clientId=spring-boot-client
mqtt.username=admin
mqtt.password=admin
mqtt.topic=sensor
mqtt.qos=1
mqtt.cleanSession=true

2.3、创建消息发布类

package com.mqtt.mqttproject.service;import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;/*** @ Author : Gridsum* @ Description :*/
@Service
public class MqttPublisher {@Autowiredprivate MqttClient mqttClient;@Value("${mqtt.topic}")private String topic;@Value("${mqtt.qos}")private int qos;public void publish(String message) throws MqttException {MqttMessage mqttMessage = new MqttMessage(message.getBytes());mqttMessage.setQos(qos);mqttClient.publish(topic, mqttMessage);}
}

2.4、创建消息订阅类

package com.mqtt.mqttproject.service;import org.eclipse.paho.client.mqttv3.IMqttMessageListener;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttException;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;import javax.annotation.PostConstruct;/*** @ Author : Gridsum* @ Description :*/
@Service
public class MqttSubscriber {@Autowiredprivate MqttClient mqttClient;@Value("${mqtt.topic}")private String topic;@Value("${mqtt.qos}")private int qos;@PostConstructpublic void subscribe() throws MqttException {mqttClient.subscribe(topic, qos, new IMqttMessageListener() {@Overridepublic void messageArrived(String topic, MqttMessage message) throws Exception {System.out.println("Received message: " + new String(message.getPayload()));}});}
}

2.5、测试消息发布

@Controller
public class BasicController {@Autowiredprivate MqttPublisher mqttPublisher;// http://127.0.0.1:8080/hello?name=lisi@RequestMapping("/hello")@ResponseBodypublic String hello(@RequestParam(name = "name", defaultValue = "unknown user") String name) {try {mqttPublisher.publish("Hello " + name + ", MQTT from Spring Boot!");} catch (MqttException e) {e.printStackTrace();}return "Hello " + name;}
}

 2.6、启动服务调用接口，发送消息，会打印收到消息