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1   /*
2    * Copyright 2012 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package org.jboss.netty.channel;
17  
18  import java.util.EventListener;
19  
20  /**
21   * Listens to the result of a {@link ChannelFuture}.  The result of the
22   * asynchronous {@link Channel} I/O operation is notified once this listener
23   * is added by calling {@link ChannelFuture#addListener(ChannelFutureListener)}.
24   *
25   * <h3>Return the control to the caller quickly</h3>
26   *
27   * {@link #operationComplete(ChannelFuture)} is directly called by an I/O
28   * thread.  Therefore, performing a time consuming task or a blocking operation
29   * in the handler method can cause an unexpected pause during I/O.  If you need
30   * to perform a blocking operation on I/O completion, try to execute the
31   * operation in a different thread using a thread pool.
32   */
33  public interface ChannelFutureListener extends EventListener {
34  
35      /**
36       * A {@link ChannelFutureListener} that closes the {@link Channel} which is
37       * associated with the specified {@link ChannelFuture}.
38       */
39      ChannelFutureListener CLOSE = new ChannelFutureListener() {
40          public void operationComplete(ChannelFuture future) {
41              future.getChannel().close();
42          }
43      };
44  
45      /**
46       * A {@link ChannelFutureListener} that closes the {@link Channel} when the
47       * operation ended up with a failure or cancellation rather than a success.
48       */
49      ChannelFutureListener CLOSE_ON_FAILURE = new ChannelFutureListener() {
50          public void operationComplete(ChannelFuture future) {
51              if (!future.isSuccess()) {
52                  future.getChannel().close();
53              }
54          }
55      };
56  
57      /**
58       * Invoked when the I/O operation associated with the {@link ChannelFuture}
59       * has been completed.
60       *
61       * @param future  the source {@link ChannelFuture} which called this
62       *                callback
63       */
64      void operationComplete(ChannelFuture future) throws Exception;
65  }