1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27
28 package org.apache.hc.client5.http.impl;
29
30 import java.util.concurrent.ExecutionException;
31 import java.util.concurrent.Future;
32 import java.util.concurrent.TimeUnit;
33 import java.util.concurrent.TimeoutException;
34
35 import org.apache.hc.core5.concurrent.Cancellable;
36
37 /**
38 * Common cancellable operations.
39 *
40 * @since 5.0
41 */
42 public final class Operations {
43
44 private final static Cancellable NOOP_CANCELLABLE = new Cancellable() {
45
46 @Override
47 public boolean cancel() {
48 return false;
49 }
50
51 };
52
53 /**
54 * This class represents a {@link Future} in the completed state with a fixed result.
55 * The outcome of the future cannot be altered and it cannot be cancelled.
56 *
57 * @param <T> operation result representation.
58 */
59 public static class CompletedFuture<T> implements Future<T> {
60
61 private final T result;
62
63 public CompletedFuture(final T result) {
64 this.result = result;
65 }
66
67 @Override
68 public T get() throws InterruptedException, ExecutionException {
69 return result;
70 }
71
72 @Override
73 public T get(final long timeout, final TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
74 return result;
75 }
76 @Override
77 public boolean cancel(final boolean mayInterruptIfRunning) {
78 return false;
79 }
80
81 @Override
82 public boolean isCancelled() {
83 return false;
84 }
85
86 @Override
87 public boolean isDone() {
88 return true;
89 }
90
91 }
92
93 /**
94 * Creates a {@link Cancellable} operation handle for an ongoing process
95 * or operation that cannot be cancelled. Attempts to cancel the operation
96 * with this handle will have no effect.
97 *
98 * @return the no-op cancellable operation handle.
99 */
100 public static Cancellable nonCancellable() {
101 return NOOP_CANCELLABLE;
102 }
103
104 /**
105 * Creates a {@link Cancellable} operation handle for an ongoing process
106 * or operation represented by a {@link Future}.
107 *
108 * @param future the result future
109 * @return the cancellable operation handle.
110 */
111 public static Cancellable cancellable(final Future<?> future) {
112 if (future == null) {
113 return NOOP_CANCELLABLE;
114 }
115 if (future instanceof Cancellable) {
116 return (Cancellable) future;
117 }
118 return new Cancellable() {
119
120 @Override
121 public boolean cancel() {
122 return future.cancel(true);
123 }
124
125 };
126 }
127
128 }