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 = () -> false; 45 46 /** 47 * This class represents a {@link Future} in the completed state with a fixed result. 48 * The outcome of the future cannot be altered and it cannot be cancelled. 49 * 50 * @param <T> operation result representation. 51 */ 52 public static class CompletedFuture<T> implements Future<T> { 53 54 private final T result; 55 56 public CompletedFuture(final T result) { 57 this.result = result; 58 } 59 60 @Override 61 public T get() throws InterruptedException, ExecutionException { 62 return result; 63 } 64 65 @Override 66 public T get(final long timeout, final TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException { 67 return result; 68 } 69 @Override 70 public boolean cancel(final boolean mayInterruptIfRunning) { 71 return false; 72 } 73 74 @Override 75 public boolean isCancelled() { 76 return false; 77 } 78 79 @Override 80 public boolean isDone() { 81 return true; 82 } 83 84 } 85 86 /** 87 * Creates a {@link Cancellable} operation handle for an ongoing process 88 * or operation that cannot be cancelled. Attempts to cancel the operation 89 * with this handle will have no effect. 90 * 91 * @return the no-op cancellable operation handle. 92 */ 93 public static Cancellable nonCancellable() { 94 return NOOP_CANCELLABLE; 95 } 96 97 /** 98 * Creates a {@link Cancellable} operation handle for an ongoing process 99 * or operation represented by a {@link Future}. 100 * 101 * @param future the result future 102 * @return the cancellable operation handle. 103 */ 104 public static Cancellable cancellable(final Future<?> future) { 105 if (future == null) { 106 return NOOP_CANCELLABLE; 107 } 108 if (future instanceof Cancellable) { 109 return (Cancellable) future; 110 } 111 return () -> future.cancel(true); 112 } 113 114 }