由于篇幅所限,以下仅展示核心函数和部分核心代码。
// MQTT消息订阅服务
@Service
public class MqttSubscriptionService {
private static final Logger LOGGER = LoggerFactory.com.example.demo.controller.getLogger(MqttSubscriptionService.class);
@Autowired
private MqttPushClient mqttPushClient;
public void subscribeTopic(String topicName, MqttMessageListener listener) {
try {
mqttPushClient.subscribeTopic(topicName, listener);
LOGGER.info("Subscribed to topic: " + topicName);
} catch (MqttException e) {
LOGGER.error("Subscription to topic " + topicName + " failed", e);
}
}
}
// MQTT推送客户端
@Component
public class MqttPushClient {
private static final Logger LOGGER = LoggerFactory.getLogger(MqttPushClient.class);
private MqttClient mqttClient;
public void subscribeTopic(String topicName, MqttMessageListener listener) throws MqttException {
IMqttMessageListener topicListener = new MqttMessageListener() {
@Override
public void messageArrived(String topic, MqttMessage message) throws Exception {
listener.messageArrived(topic, message);
}
};
mqttClient.subscribe(topicName, topicListener);
}
// 省略其他方法,如建立连接、发布消息等
}
// 前端React Native代码片段
export default class HomeScreen extends Component {
componentDidMount() {
// 订阅MQTT主题
this.props.mqttSubscriptionService.subscribeTopic('smart_parking/telemetry', this.handleIncomingMessage);
}
handleIncomingMessage = (topic, message) => {
// 处理接收到的消息
console.log('Received message on topic: ', topic, ' - Message: ', message.toString());
};
render() {
return (
<View style={styles.container}>
{/* 渲染UI组件 */}
</View>
);
}
}
const styles = StyleSheet.create({
container: {
flex: 1,
justifyContent: 'center',
alignItems: 'center',
backgroundColor: '#F5FCFF',
},
// 其他样式定义
});
以上代码展示了如何在智能停车管理系统中使用MQTT协议进行消息订阅和处理。代码中包含了服务层、推送客户端和前端React Native组件的简化示例,展示了如何在实际应用中集成MQTT通信。