Detailed Guide to Accessing MQTT in SpringBoot Project

1. Introduction

MQTT (Message Queuing Telemetry Transport) is a lightweight message transmission protocol, especially suitable for Internet of Things (IoT) scenarios, with the advantages of low bandwidth and high latency network environments. As a popular Java development framework, Spring Boot can easily integrate with MQTT to achieve efficient message communication. This article will explain in detail how to access MQTT in Spring Boot projects.

2. Environmental preparation

• Development Environment

  • JDK 1.8 and above
  • Maven or Gradle
  • Spring Boot and above

• MQTT ServerYou can choose to use a public MQTT server, such as HiveMQ public server (tcp://:1883), or you can also build MQTT servers such as Mosquitto.

3. Create Spring Boot Project

Spring Initializr can be used (/) Quickly create a Spring Boot project and add the following dependencies:

• Spring Web
• Spring for Apache Pulsar (because Pulsar also supports the MQTT protocol, and here we will use its related MQTT dependencies)

If using Maven,Add the following dependencies:

<dependencies>
    <dependency>
        <groupId></groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId></groupId>
        <artifactId>spring-integration-mqtt</artifactId>
    </dependency>
</dependencies>

explain

• url: The address and port of the MQTT server.
• client-id: The unique identity of the client.
• default-topic: The theme to subscribe to by default.
• usernameandpassword: If the MQTT server requires authentication, fill in the corresponding username and password.

5. Create an MQTT configuration class

Create a configuration class to configure MQTT connections and message processing.

import .;
import ;
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@Configuration
public class MqttConfig {

    @Bean
    public MqttPahoClientFactory mqttClientFactory() {
        DefaultMqttPahoClientFactory factory = new DefaultMqttPahoClientFactory();
        MqttConnectOptions options = new MqttConnectOptions();
        (new String[]{"${}"});
        ("${}");
        ("${}".toCharArray());
        (options);
        return factory;
    }

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

    @Bean
    public MqttPahoMessageDrivenChannelAdapter inbound() {
        MqttPahoMessageDrivenChannelAdapter adapter =
                new MqttPahoMessageDrivenChannelAdapter("${-id}", mqttClientFactory(),
                        "${-topic}");
        (5000);
        (new DefaultPahoMessageConverter());
        (1);
        (mqttInputChannel());
        return adapter;
    }

    @Bean
    @ServiceActivator(inputChannel = "mqttInputChannel")
    public MessageHandler handler() {
        return message -> {
            ("Received message: " + ());
        };
    }

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

    @Bean
    @ServiceActivator(inputChannel = "mqttOutputChannel")
    public MessageHandler mqttOutbound() {
        MqttPahoMessageHandler messageHandler =
                new MqttPahoMessageHandler("${-id}-publisher", mqttClientFactory());
        (true);
        ("${-topic}");
        return messageHandler;
    }
}

explain

• mqttClientFactory: Create an MQTT client factory and configure connection options.
• mqttInputChannelandmqttOutputChannel: Define message channels for receiving and sending messages.
• inbound: Create an MQTT message-driven channel adapter to subscribe to topics and receive messages.
• handler: Process the received MQTT message.
• mqttOutbound: Create an MQTT message handler to publish messages.

6. Send and receive MQTT messages

Send a message

Create a service class to send an MQTT message.

import ;
import ;
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@Service
public class MqttMessageSender {

    @Autowired
    private MessageChannel mqttOutputChannel;

    public void sendMessage(String message) {
        (new GenericMessage<>(message));
    }
}

Receive message

Message processing logic has been defined in the configuration class. When a message is received, it will behandlerProcessing in the method.

7. Test MQTT connection

Create a controller to test the sending of MQTT messages.

import ;
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import ;
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@RestController
public class MqttController {

    @Autowired
    private MqttMessageSender mqttMessageSender;

    @GetMapping("/send")
    public String sendMessage(@RequestParam String message) {
        (message);
        return "Message sent: " + message;
    }
}

Start the Spring Boot application and accesshttp://localhost:8080/send?message=Hello, MQTT!You can send an MQTT message.

8. Summary

Through the above steps, we successfully connected MQTT to the Spring Boot project, realizing the sending and receiving of messages. As a lightweight message transmission protocol, MQTT integration with Spring Boot can help us quickly build an efficient and stable IoT messaging system. In actual applications, it can be further expanded and optimized according to needs, such as adding functions such as message persistence, multi-theme subscription, etc.

The above is the detailed guide for accessing MQTT in SpringBoot project. For more information about accessing MQTT in SpringBoot, please follow my other related articles!