在windows10环境下，springboot怎么用mqtt服务端发送json数据

在Windows10环境下，使用Spring Boot发送JSON数据可以按照以下步骤操作：

1. 添加依赖

在pom.xml文件中添加以下依赖：

<dependency>
    <groupId>org.springframework.integration</groupId>
    <artifactId>spring-integration-mqtt</artifactId>
    <version>5.3.2.RELEASE</version>
</dependency>

2. 配置MQTT服务端

在application.properties中添加以下配置信息：

spring.mqtt.username=<your_username>
spring.mqtt.password=<your_password>
spring.mqtt.url=<mqtt_server_url>
spring.mqtt.defaultTopic=<default_topic>

3. 编写发送JSON数据的代码

import org.springframework.integration.mqtt.support.MqttHeaders;
import org.springframework.messaging.Message;
import org.springframework.messaging.support.MessageBuilder;
import org.springframework.stereotype.Service;
import org.eclipse.paho.client.mqttv3.MqttConnectOptions;
import org.eclipse.paho.client.mqttv3.MqttMessage;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.persist.MemoryPersistence;
import com.fasterxml.jackson.databind.ObjectMapper;

@Service
public class MqttService {
    private static final String CHARSET = "UTF-8";
    private static final int QOS = 1;

    private final String mqttUrl;
    private final String username;
    private final String password;
    private final String defaultTopic;

    public MqttService(
            @Value("${spring.mqtt.url}") String mqttUrl,
            @Value("${spring.mqtt.username}") String username,
            @Value("${spring.mqtt.password}") String password,
            @Value("${spring.mqtt.defaultTopic}") String defaultTopic) {
        this.mqttUrl = mqttUrl;
        this.username = username;
        this.password = password;
        this.defaultTopic = defaultTopic;
    }

    public void sendMessage(Object payload, String topic) {
        String json = toJson(payload);
        Message<String> message = MessageBuilder
                .withPayload(json)
                .setHeader(MqttHeaders.TOPIC, topic)
                .setHeader(MqttHeaders.QOS, QOS)
                .build();
        send(message);
    }

    private void send(Message<String> message) {
        MqttConnectOptions options = new MqttConnectOptions();
        options.setUserName(username);
        options.setPassword(password.toCharArray());

        try {
            MqttClient client = new MqttClient(mqttUrl, MqttClient.generateClientId(), new MemoryPersistence());
            client.connect(options);
            client.publish(message.getHeaders().get(MqttHeaders.TOPIC).toString(),
                    new MqttMessage(message.getPayload().getBytes(CHARSET)));
            client.disconnect();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    private String toJson(Object value) {
        try {
            ObjectMapper objectMapper = new ObjectMapper();
            return objectMapper.writeValueAsString(value);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

4. 在需要发送JSON数据的地方调用MqttService.sendMessage()方法

例如，在Controller中调用MqttService的sendMessage()方法：

@RestController
public class MyController {
    @Autowired
    MqttService mqttService;

    @PostMapping("/send")
    public void send(@RequestBody MyData data) {
        mqttService.sendMessage(data, "my/topic");
    }
}

这样，就可以使用Spring Boot发送JSON数据到MQTT服务端了。