✨ mica-mqtt client 重复订阅优化。

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

@@ -64,7 +64,24 @@ public final class DefaultMqttClientSession implements IMqttClientSession {
 		if (subscriptionSet == null || subscriptionSet.isEmpty()) {
 			return false;
 		}
-		return subscriptionSet.contains(new MqttClientSubscription(mqttQoS, topicFilter, listener));
+		MqttClientSubscription clientSubscription = new MqttClientSubscription(mqttQoS, topicFilter, listener);
+		for (MqttClientSubscription subscription : subscriptionSet) {
+			// 1. 已经存在订阅
+			if (clientSubscription.equals(subscription)) {
+				return true;
+			}
+			MqttQoS subQos = subscription.getMqttQoS();
+			IMqttClientMessageListener subListener = subscription.getListener();
+			// 2. 如果已经存在更高或同级别 qos
+			if (subQos.value() >= mqttQoS.value()) {
+				// 3. 监听器不相同则直接添加
+				if (subListener != listener) {
+					subscriptions.add(topicFilter, clientSubscription);
+				}
+				return true;
+			}
+		}
+		return false;
 	}
 
 	@Override