[kernel][event bus] Fixing NPE due to loose of the reference to Inter…

…nalEventBusSKill.

The AgentEventListener internal class of InternalEventBusSkill looses
the weak reference to its enclosing object. The AgentEventListener class
is no more static to have this reference always set.

see #100.

Signed-off-by: Stéphane Galland <galland@arakhne.org>

io.janusproject.kernel/src/main/java/io/janusproject/kernel/bic/InternalEventBusSkill.java

@@ -31,7 +31,6 @@
 import io.sarl.lang.core.EventListener;
 import io.sarl.lang.core.Skill;
 
-import java.lang.ref.WeakReference;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Queue;
@@ -92,7 +91,7 @@ class InternalEventBusSkill extends Skill implements InternalEventBusCapacity {
 	 */
 	public InternalEventBusSkill(Agent agent, Address addressInInnerDefaultSpace) {
 		super(agent);
-		this.agentAsEventListener = new AgentEventListener(this);
+		this.agentAsEventListener = new AgentEventListener();
 		this.agentAddressInInnerDefaultSpace = addressInInnerDefaultSpace;
 	}
 
@@ -191,20 +190,17 @@ public final EventListener asEventListener() {
 	 * @mavengroupid $GroupId$
 	 * @mavenartifactid $ArtifactId$
 	 */
-	private static class AgentEventListener implements EventListener {
+	private class AgentEventListener implements EventListener {
 
 		private Queue<Event> buffer = Queues.newConcurrentLinkedQueue();
 
-		private final WeakReference<InternalEventBusSkill> skill;
-
 		private final UUID aid;
 
 		private boolean isKilled;
 
 		@SuppressWarnings("synthetic-access")
-		public AgentEventListener(InternalEventBusSkill skill) {
-			this.skill = new WeakReference<>(skill);
-			this.aid = skill.getOwner().getID();
+		public AgentEventListener() {
+			this.aid = InternalEventBusSkill.this.getOwner().getID();
 		}
 
 		@Override
@@ -219,31 +215,30 @@ public void receiveEvent(Event event) {
 					&& (!(event instanceof Destroy))
 					&& (!(event instanceof AsynchronousAgentKillingEvent)))
 					: "Unsupported type of event: " + event; //$NON-NLS-1$
-			InternalEventBusSkill s = this.skill.get();
-			synchronized (s) {
+			synchronized (InternalEventBusSkill.this) {
 				if (event instanceof AgentSpawned
-					&& this.aid.equals(((AgentSpawned) event).agentID)) {
+						&& this.aid.equals(((AgentSpawned) event).agentID)) {
 					// This permits to ensure that the killing event
 					// is correctly treated when fired from the initialization
 					// handler.
-					fireEnqueuedEvents(s);
+					fireEnqueuedEvents(InternalEventBusSkill.this);
 					if (this.isKilled) {
-						killOwner(s);
+						killOwner(InternalEventBusSkill.this);
 						return;
 					}
 				}
-				switch(s.state.get()) {
+				switch(InternalEventBusSkill.this.state.get()) {
 				case NEW:
 					this.buffer.add(event);
 					break;
 				case RUNNING:
-					fireEnqueuedEvents(s);
-					s.eventBus.post(event);
+					fireEnqueuedEvents(InternalEventBusSkill.this);
+					InternalEventBusSkill.this.eventBus.post(event);
 					break;
 				case DESTROYED:
 					// Dropping messages since agent is dying
-					s.logger.debug(InternalEventBusSkill.class,
-									"EVENT_DROP_WARNING", event); //$NON-NLS-1$
+					InternalEventBusSkill.this.logger.debug(InternalEventBusSkill.class,
+							"EVENT_DROP_WARNING", event); //$NON-NLS-1$
 					break;
 				default:
 					throw new IllegalStateException();
@@ -274,11 +269,10 @@ private void killOwner(InternalEventBusSkill s) {
 
 		@SuppressWarnings("synthetic-access")
 		void killOrMarkAsKilled() {
-			InternalEventBusSkill s = this.skill.get();
-			synchronized (s) {
+			synchronized (InternalEventBusSkill.this) {
 				this.isKilled = true;
-				if (s.state.get() != OwnerState.NEW) {
-					killOwner(s);
+				if (InternalEventBusSkill.this.state.get() != OwnerState.NEW) {
+					killOwner(InternalEventBusSkill.this);
 				}
 			}
 		}