On retained republish message adapt the QoS to the one specified during subscription (fix issue #411)

broker/src/main/java/io/moquette/spi/IMessagesStore.java

@@ -31,7 +31,7 @@ public interface IMessagesStore {
     class StoredMessage implements Serializable {
 
         private static final long serialVersionUID = 1755296138639817304L;
-        final MqttQoS m_qos;
+        private MqttQoS m_qos;
         final byte[] m_payload;
         final String m_topic;
         private boolean m_retained;
@@ -44,6 +44,11 @@ public interface IMessagesStore {
             m_topic = topic;
         }
 
+
+        public void setQos(MqttQoS qos) {
+            this.m_qos = qos;
+        }
+
         public MqttQoS getQos() {
             return m_qos;
         }

broker/src/main/java/io/moquette/spi/impl/ProtocolProcessor.java

@@ -858,6 +858,14 @@ public class ProtocolProcessor {
                 newSubscription.getClientId(), newSubscription.getTopicFilter(), messages.size());
         }
         ClientSession targetSession = this.sessionsRepository.sessionForClient(newSubscription.getClientId());
+
+        // adapt the message QoS to subscriber's accepted accepted
+        for (IMessagesStore.StoredMessage msg : messages) {
+            int lowestQoS = Math.min(msg.getQos().value(), newSubscription.getRequestedQos().value());
+            MqttQoS qosToPublish = MqttQoS.valueOf(lowestQoS);
+            msg.setQos(qosToPublish);
+        }
+
         this.internalRepublisher.publishRetained(targetSession, messages);
 
         // notify the Observables