Switched from plain synchronized to ReadWrite locking

parser/src/main/java/org/dna/mqtt/moquette/messaging/spi/impl/SimpleMessaging.java

@@ -2,6 +2,8 @@ package org.dna.mqtt.moquette.messaging.spi.impl;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
 import org.dna.mqtt.moquette.messaging.spi.IMessaging;
 import org.dna.mqtt.moquette.messaging.spi.INotifier;
 import org.dna.mqtt.moquette.proto.messages.AbstractMessage.QOSType;
@@ -12,6 +14,8 @@ import org.dna.mqtt.moquette.proto.messages.AbstractMessage.QOSType;
  */
 public class SimpleMessaging implements IMessaging {
     //TODO is poorly performace on concurrent load, use at least ReadWriteLock
+    
+    private ReadWriteLock rwLock = new ReentrantReadWriteLock();
     private List<Subscription> subscriptions = new ArrayList<Subscription>();
     
     private INotifier m_notifier;
@@ -24,23 +28,27 @@ public class SimpleMessaging implements IMessaging {
         //TODO for this moment no retain management and no qos > 0
         //trivial implementation
         QOSType defQos = QOSType.MOST_ONE;
-        synchronized(subscriptions) {
+        
+        rwLock.readLock().lock();
+        try {
             for (Subscription sub : subscriptions) {
                 if (sub.match(topic)) {
                     m_notifier.notify(sub.clientId, topic, defQos, message);
                 }
             }
+        } finally {
+            rwLock.readLock().unlock();
         }
     }
 
     public void subscribe(String clientId, String topic, QOSType qos) {
         Subscription newSubscription = new Subscription(clientId, topic, qos);
-        synchronized(subscriptions) {
-            if (subscriptions.contains(newSubscription)) {
-                return;
-            }
-            subscriptions.add(newSubscription);
+        rwLock.writeLock().lock();
+        if (subscriptions.contains(newSubscription)) {
+            return;
         }
+        subscriptions.add(newSubscription);
+        rwLock.writeLock().unlock();
     }
     
     protected List<Subscription> getSubscriptions() {