✨ 代码优化

mica-mqtt-core/src/main/java/net/dreamlu/iot/mqtt/core/client/MqttClient.java

@@ -100,20 +100,19 @@ public final class MqttClient {
 	public MqttClient subscribe(MqttQoS mqttQoS, String topicFilter, IMqttClientMessageListener listener) {
 		// 先判断是否已经订阅过，重复订阅，直接跳出
 		boolean subscribed = clientSession.isSubscribed(topicFilter, mqttQoS, listener);
-		if (subscribed) {
-			return this;
+		if (!subscribed) {
+			// 没有订阅过
+			int messageId = MqttClientMessageId.getId();
+			MqttSubscribeMessage message = MqttMessageBuilders.subscribe()
+				.addSubscription(mqttQoS, topicFilter)
+				.messageId(messageId)
+				.build();
+			MqttPendingSubscription pendingSubscription = new MqttPendingSubscription(mqttQoS, topicFilter, listener, message);
+			Boolean result = Tio.send(context, message);
+			logger.info("MQTT Topic:{} mqttQoS:{} messageId:{} subscribing result:{}", topicFilter, mqttQoS, messageId, result);
+			pendingSubscription.startRetransmitTimer(executor, (msg) -> Tio.send(context, message));
+			clientSession.addPaddingSubscribe(messageId, pendingSubscription);
 		}
-		// 没有订阅过
-		int messageId = MqttClientMessageId.getId();
-		MqttSubscribeMessage message = MqttMessageBuilders.subscribe()
-			.addSubscription(mqttQoS, topicFilter)
-			.messageId(messageId)
-			.build();
-		MqttPendingSubscription pendingSubscription = new MqttPendingSubscription(mqttQoS, topicFilter, listener, message);
-		Boolean result = Tio.send(context, message);
-		logger.info("MQTT Topic:{} mqttQoS:{} messageId:{} subscribing result:{}", topicFilter, mqttQoS, messageId, result);
-		pendingSubscription.startRetransmitTimer(executor, (msg) -> Tio.send(context, message));
-		clientSession.addPaddingSubscribe(messageId, pendingSubscription);
 		return this;
 	}