1 //
2 // ========================================================================
3 // Copyright (c) 1995-2013 Mort Bay Consulting Pty. Ltd.
4 // ------------------------------------------------------------------------
5 // All rights reserved. This program and the accompanying materials
6 // are made available under the terms of the Eclipse Public License v1.0
7 // and Apache License v2.0 which accompanies this distribution.
8 //
9 // The Eclipse Public License is available at
10 // http://www.eclipse.org/legal/epl-v10.html
11 //
12 // The Apache License v2.0 is available at
13 // http://www.opensource.org/licenses/apache2.0.php
14 //
15 // You may elect to redistribute this code under either of these licenses.
16 // ========================================================================
17 //
18
19 /*
20 * Copyright (c) 2012 the original author or authors.
21 *
22 * Licensed under the Apache License, Version 2.0 (the "License");
23 * you may not use this file except in compliance with the License.
24 * You may obtain a copy of the License at
25 *
26 * http://www.apache.org/licenses/LICENSE-2.0
27 *
28 * Unless required by applicable law or agreed to in writing, software
29 * distributed under the License is distributed on an "AS IS" BASIS,
30 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
31 * See the License for the specific language governing permissions and
32 * limitations under the License.
33 */
34
35 package org.eclipse.jetty.util;
36
37 import org.eclipse.jetty.util.log.Log;
38
39 /**
40 * <p>A callback abstraction that handles completed/failed events of asynchronous operations.</p>
41 *
42 * <p>Semantically this is equivalent to an optimise Promise<Void>, but callback is a more meaningful
43 * name than EmptyPromise</p>
44 */
45 public interface Callback
46 {
47 /**
48 * <p>Callback invoked when the operation completes.</p>
49 *
50 * @see #failed(Throwable)
51 */
52 public abstract void succeeded();
53
54 /**
55 * <p>Callback invoked when the operation fails.</p>
56 * @param x the reason for the operation failure
57 */
58 public void failed(Throwable x);
59
60 /**
61 * <p>Empty implementation of {@link Callback}</p>
62 */
63 public static class Adapter implements Callback
64 {
65 @Override
66 public void succeeded()
67 {
68 }
69
70 @Override
71 public void failed(Throwable x)
72 {
73 Log.getLogger(this.getClass()).warn(x);
74 }
75 }
76 }