springboot mqtt自动重连

在使用Spring Boot创建MQTT客户端项目时，可以通过配置实现MQTT的自动重连。具体步骤如下：
1. 在application.properties文件中添加MQTT连接相关配置，例如：

spring.mqtt.username=your_username
spring.mqtt.password=your_password
spring.mqtt.url=tcp://your_mqtt_server_url:1883
spring.mqtt.clientId=your_client_id

2. 在MQTT配置类中添加MQTT连接工厂和消息监听器等相关配置，例如：

@Configuration
public class MqttConfig {

    @Autowired
    private MqttProperties mqttProperties;

    @Bean
    public MqttConnectOptions getMqttConnectOptions() {
        MqttConnectOptions mqttConnectOptions = new MqttConnectOptions();
        mqttConnectOptions.setUserName(mqttProperties.getUsername());
        mqttConnectOptions.setPassword(mqttProperties.getPassword().toCharArray());
        mqttConnectOptions.setServerURIs(new String[]{mqttProperties.getUrl()});
        mqttConnectOptions.setKeepAliveInterval(2);
        mqttConnectOptions.setAutomaticReconnect(true);
        return mqttConnectOptions;
    }

    @Bean
    public MqttClient getMqttClient() throws MqttException {
        MqttClient mqttClient = new MqttClient(mqttProperties.getUrl(), mqttProperties.getClientId());
        mqttClient.setCallback(new MqttCallback() {
            @Override
            public void connectionLost(Throwable throwable) {
                // 连接丢失后的处理逻辑
            }

            @Override
            public void messageArrived(String s, MqttMessage mqttMessage) throws Exception {
                // 消息到达后的处理逻辑
            }

            @Override
            public void deliveryComplete(IMqttDeliveryToken iMqttDeliveryToken) {
                // 消息发送完成后的处理逻辑
            }
        });
        mqttClient.connect(getMqttConnectOptions());        return mqttClient;
    }

    @Bean
    public MqttPahoMessageDrivenChannelAdapter mqttPahoMessageDrivenChannelAdapter() throws MqttException {
        MqttPahoMessageDrivenChannelAdapter adapter = new MqttPahoMessageDrivenChannelAdapter(
                mqttProperties.getUrl(), mqttProperties.getClientId(), getMqttClientFactory(),
                "your_topic");
        adapter.setCompletionTimeout(5000);
        adapter.setConverter(new DefaultPahoMessageConverter());
        adapter.setQos(1);
        return adapter;
    }

    @Bean
    public DefaultMqttPahoClientFactory getMqttClientFactory() {
        DefaultMqttPahoClientFactory factory = new DefaultMqttPahoClientFactory();
        factory.setConnectionOptions(getMqttConnectOptions());
        return factory;
    }
}

其中，setAutomaticReconnect(true)表示开启MQTT自动重连机制。

3. 在需要使用MQTT的地方注入MqttPahoMessageDrivenChannelAdapter，并调用start()方法启动消息监听器，例如：

@Autowired
private MqttPahoMessageDrivenChannelAdapter adapter;

public void start() {
    adapter.start();
}