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 }