springboot mqtt 发送json数据

在 Spring Boot 中使用 MQTT 发送 JSON 数据，你可以按照以下步骤进行操作：

1. 添加依赖：在 `pom.xml` 文件中添加以下依赖：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-integration</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.integration</groupId>
    <artifactId>spring-integration-mqtt</artifactId>
</dependency>

2. 创建配置文件：在 `application.properties` 文件中添加 MQTT 连接相关的配置信息，例如：

spring.mqtt.username=your_username
spring.mqtt.password=your_password
spring.mqtt.url=tcp://your_mqtt_broker_url:1883

3. 创建消息发送者：在需要发送 MQTT 消息的地方创建一个消息发送者的类，示例代码如下：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.integration.annotation.MessagingGateway;
import org.springframework.integration.mqtt.support.MqttHeaders;
import org.springframework.messaging.handler.annotation.Header;
import org.springframework.stereotype.Component;

@Component
@MessagingGateway(defaultRequestChannel = "mqttOutboundChannel")
public interface MqttMessageSender {

    void sendMessage(String payload, @Header(MqttHeaders.TOPIC) String topic);
}

4. 配置消息发送通道：在 `@Configuration` 类中配置消息发送通道，示例代码如下：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.integration.annotation.IntegrationComponentScan;
import org.springframework.integration.channel.DirectChannel;
import org.springframework.integration.config.EnableIntegration;
import org.springframework.messaging.MessageChannel;

@Configuration
@EnableIntegration
@IntegrationComponentScan
public class MqttConfig {

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

5. 发送 MQTT 消息：在需要发送 MQTT 消息的地方，通过调用 `MqttMessageSender` 接口的 `sendMessage` 方法发送消息，示例代码如下：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.integration.mqtt.support.MqttHeaders;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageHeaders;
import org.springframework.messaging.support.MessageBuilder;
import org.springframework.stereotype.Component;

@Component
public class MyMqttSender {

    private final MqttMessageSender mqttMessageSender;

    @Autowired
    public MyMqttSender(MqttMessageSender mqttMessageSender) {
        this.mqttMessageSender = mqttMessageSender;
    }

    public void sendJsonMessage(String topic, String payload) {
        Message<String> message = MessageBuilder.withPayload(payload)
                .setHeader(MqttHeaders.TOPIC, topic)
                .setHeader(MessageHeaders.CONTENT_TYPE, "application/json")
                .build();

        mqttMessageSender.sendMessage(message.getPayload(), topic);
    }
}

以上就是使用 Spring Boot 发送 JSON 数据到 MQTT 的基本步骤。你可以根据自己的实际需求进行相应的修改和扩展。