Revive Channel.closeFuture

- ChannelPipeline now rejects an unsafe ChannelFuture, so there's no
  need to hide/remove closeFuture.

transport/src/main/java/io/netty/channel/AbstractChannel.java

@@ -24,8 +24,6 @@ import java.io.IOException;
 import java.net.ConnectException;
 import java.net.SocketAddress;
 import java.nio.channels.ClosedChannelException;
-import java.util.ArrayList;
-import java.util.List;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
@@ -74,13 +72,12 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
     private final Integer id;
     private final Unsafe unsafe;
     private final ChannelPipeline pipeline = new DefaultChannelPipeline(this);
-    private final List<ChannelFutureListener> closureListeners = new ArrayList<ChannelFutureListener>(4);
     private final ChannelFuture succeededFuture = new SucceededChannelFuture(this);
-    private final ChannelFuture voidFuture = new VoidChannelFuture(AbstractChannel.this);
+    private final ChannelFuture voidFuture = new VoidChannelFuture(this);
+    private final CloseFuture closeFuture = new CloseFuture(this);
 
     private volatile EventLoop eventLoop;
     private volatile boolean registered;
-    private volatile boolean notifiedClosureListeners;
 
     /**
      * The future of the current connection attempt.  If not null, subsequent
@@ -125,7 +122,7 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
         this.id = id;
         unsafe = new DefaultUnsafe();
 
-        closureListeners.add(new ChannelFutureListener() {
+        closeFuture().addListener(new ChannelFutureListener() {
             @Override
             public void operationComplete(ChannelFuture future) {
                 allChannels.remove(id());
@@ -267,63 +264,8 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
     }
 
     @Override
-    public void addClosureListener(final ChannelFutureListener listener) {
-        if (listener == null) {
-            throw new NullPointerException("listener");
-        }
-        synchronized (closureListeners) {
-            if (notifiedClosureListeners) {
-                eventLoop().execute(new Runnable() {
-                    @Override
-                    public void run() {
-                        notifyClosureListener(listener);
-                    }
-                });
-            } else {
-                closureListeners.add(listener);
-            }
-        }
-    }
-
-    @Override
-    public void removeClosureListener(ChannelFutureListener listener) {
-        if (listener == null) {
-            throw new NullPointerException("listener");
-        }
-        synchronized (closureListeners) {
-            if (!notifiedClosureListeners) {
-                closureListeners.remove(listener);
-            }
-        }
-    }
-
-    private void notifyClosureListeners() {
-        final ChannelFutureListener[] array;
-        synchronized (closureListeners) {
-            if (notifiedClosureListeners) {
-                return;
-            }
-            notifiedClosureListeners = true;
-            array = closureListeners.toArray(new ChannelFutureListener[closureListeners.size()]);
-            closureListeners.clear();
-        }
-
-        eventLoop().execute(new Runnable() {
-            @Override
-            public void run() {
-                for (ChannelFutureListener l: array) {
-                    notifyClosureListener(l);
-                }
-            }
-        });
-    }
-
-    private void notifyClosureListener(final ChannelFutureListener listener) {
-        try {
-            listener.operationComplete(newSucceededFuture());
-        } catch (Exception e) {
-            logger.warn("Failed to notify a closure listener.", e);
-        }
+    public ChannelFuture closeFuture() {
+        return closeFuture;
     }
 
     @Override
@@ -610,12 +552,12 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
                     }
 
                     notifyFlushFutures(closedChannelException);
-                    notifyClosureListeners();
 
                     if (wasActive && !isActive()) {
                         pipeline().fireChannelInactive();
                     }
 
+                    closeFuture.setClosed();
                     deregister(voidFuture());
                 } else {
                     // Closed already.
@@ -807,6 +749,28 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
         }
     }
 
+    private static final class CloseFuture extends DefaultChannelFuture implements ChannelFuture.Unsafe {
+
+        CloseFuture(AbstractChannel ch) {
+            super(ch, false);
+        }
+
+        @Override
+        public boolean setSuccess() {
+            throw new IllegalStateException();
+        }
+
+        @Override
+        public boolean setFailure(Throwable cause) {
+            throw new IllegalStateException();
+        }
+
+        void setClosed() {
+            boolean set = super.setSuccess();
+            assert set;
+        }
+    }
+
     protected abstract boolean isCompatible(EventLoop loop);
 
     protected abstract java.nio.channels.Channel javaChannel();

transport/src/main/java/io/netty/channel/Channel.java

@@ -163,10 +163,11 @@ public interface Channel extends AttributeMap, ChannelOutboundInvoker, ChannelFu
      */
     SocketAddress remoteAddress();
 
-    // FIXME: Introduce more flexible channel state notification mechanism
-    //        - notify me when channel becomes (un)registered, (in)active
-    void addClosureListener(ChannelFutureListener listener);
-    void removeClosureListener(ChannelFutureListener remover);
+    /**
+     * Returns the {@link ChannelFuture} which will be notified when this
+     * channel is closed.  This method always returns the same future instance.
+     */
+    ChannelFuture closeFuture();
 
     Unsafe unsafe();