關於MQTT

MQTT是一個基於客戶端-伺服器的訊息釋出/訂閱傳輸協議。MQTT協議是輕量、簡單、開放和易於實現的，這些特點使它適用範圍非常廣泛。在很多情況下，包括受限的環境中，如：機器與機器（M2M）通訊和物聯網（IoT）。

釋出訂閱

服務端

服務端使用 mosquitto

下載頁面：https://mosquitto.org/download/

客戶端

MQTTX

下載頁面：https://mqttx.app/#download

MQTT.fx

下載連結：http://www.jensd.de/apps/mqttfx/1.7.1/mqttfx-1.7.1-windows-x64.exe

paho

https://github.com/eclipse/paho.mqtt.java

paho是eclipse提供MQTT客戶端開源庫，Java程式碼整合這個客戶端用來收發訊息。

程式碼

依賴

pom.xml

<!-- MQTT -->
<dependency>
	<groupId>org.springframework.integration</groupId>
	<artifactId>spring-integration-mqtt</artifactId>
</dependency>

類MqttConfig

import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.integration.annotation.ServiceActivator;
import org.springframework.integration.channel.DirectChannel;
import org.springframework.integration.core.MessageProducer;
import org.springframework.integration.mqtt.core.DefaultMqttPahoClientFactory;
import org.springframework.integration.mqtt.core.MqttPahoClientFactory;
import org.springframework.integration.mqtt.inbound.MqttPahoMessageDrivenChannelAdapter;
import org.springframework.integration.mqtt.outbound.MqttPahoMessageHandler;
import org.springframework.integration.mqtt.support.DefaultPahoMessageConverter;
import org.springframework.messaging.MessageChannel;
import org.springframework.messaging.MessageHandler;

import java.util.Date;

@Configuration
public class MqttConfig {

    // 消費訊息
    /**
     * 建立MqttPahoClientFactory，設定MQTT Broker連線屬性，如果使用SSL驗證，也在這裡設定。
     * @return
     */
    @Bean
    public MqttPahoClientFactory mqttClientFactory() {
        DefaultMqttPahoClientFactory factory = new DefaultMqttPahoClientFactory();
        MqttConnectOptions options = new MqttConnectOptions();
        options.setServerURIs(new String[]{"tcp://127.0.0.1:1883"});
        factory.setConnectionOptions(options);
        return factory;
    }

    @Bean
    public MessageChannel mqttInputChannel() {
        return new DirectChannel();
    }

    @Bean
    public MessageProducer inbound() {
        MqttPahoMessageDrivenChannelAdapter adapter = new MqttPahoMessageDrivenChannelAdapter("consumerClient-SS",
                mqttClientFactory(), "boat", "collector", "battery", "+/sensor");
        adapter.setCompletionTimeout(5000);

        DefaultPahoMessageConverter defaultPahoMessageConverter = new DefaultPahoMessageConverter();
        defaultPahoMessageConverter.setPayloadAsBytes(true);
        adapter.setConverter(defaultPahoMessageConverter);
        adapter.setQos(1);
        adapter.setOutputChannel(mqttInputChannel());
        return adapter;
    }

    @Bean
    // ServiceActivator註解表明當前方法用於處理MQTT訊息，inputChannel引數指定了用於消費訊息的channel。
    @ServiceActivator(inputChannel = "mqttInputChannel")
    public MessageHandler handler() {
        return message -> {
            String payload = message.getPayload().toString();

            // byte[] bytes = (byte[]) message.getPayload(); // 收到的訊息是位元組格式
            String topic = message.getHeaders().get("mqtt_receivedTopic").toString();

            // 根據topic分別進行訊息處理。
            if (topic.matches(".+/sensor")) { // 匹配：1/sensor
                String sensorSn = topic.split("/")[0];
                System.out.println("感測器" + sensorSn + ": 的訊息： " + payload);

            } else if (topic.equals("collector")) {
                System.out.println("採集器的訊息：" + payload);
            } else {
                System.out.println("丟棄訊息：主題【" + topic  + "]，負載：" + payload);
            }
        };
    }


    // 傳送訊息
    @Bean
    public MessageChannel mqttOutboundChannel() {
        return new DirectChannel();
    }

    /**
     * 傳送訊息和消費訊息Channel可以使用相同MqttPahoClientFactory
     * @return
     */
    @Bean
    @ServiceActivator(inputChannel = "mqttOutboundChannel")
    public MessageHandler outbound() {
        // 在這裡進行mqttOutboundChannel的相關設定
        MqttPahoMessageHandler messageHandler = new MqttPahoMessageHandler("publishClient", mqttClientFactory());
        messageHandler.setAsync(true); //如果設定成true，即非同步，傳送訊息時將不會阻塞。
        messageHandler.setDefaultTopic("command");
        messageHandler.setDefaultQos(2);

        DefaultPahoMessageConverter defaultPahoMessageConverter = new DefaultPahoMessageConverter();

        // defaultPahoMessageConverter.setPayloadAsBytes(true); // 傳送預設按位元組型別傳送訊息
        messageHandler.setConverter(defaultPahoMessageConverter);
        return messageHandler;
    }

}
 

介面MqttGateway

import org.springframework.integration.annotation.MessagingGateway;
import org.springframework.integration.mqtt.support.MqttHeaders;
import org.springframework.messaging.handler.annotation.Header;

@MessagingGateway(defaultRequestChannel = "mqttOutboundChannel")
public interface MqttGateway {
    // 定義過載方法，用於訊息傳送
    void sendToMqtt(String payload);
    // 指定topic進行訊息傳送
    void sendToMqtt(@Header(MqttHeaders.TOPIC) String topic, String payload);
    void sendToMqtt(@Header(MqttHeaders.TOPIC) String topic, @Header(MqttHeaders.QOS) int qos, String payload);
    void sendToMqtt(@Header(MqttHeaders.TOPIC) String topic, @Header(MqttHeaders.QOS) int qos, byte[] payload);
}
 

測試

類MqttController

import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;


@RestController
public class MqttController {

    @Resource
    private MqttGateway mqttGateway;

    @RequestMapping("/send/{topic}/{message}")
    public String send(@PathVariable String topic, @PathVariable String message) {
        // 傳送訊息到指定topic
        mqttGateway.sendToMqtt(topic, 1, message);
        return "send message : " + message;
    }

}