| /** |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.camel.util.concurrent; |
| |
| import java.util.ArrayList; |
| import java.util.List; |
| import java.util.concurrent.Callable; |
| import java.util.concurrent.CompletionService; |
| import java.util.concurrent.DelayQueue; |
| import java.util.concurrent.Delayed; |
| import java.util.concurrent.Executor; |
| import java.util.concurrent.Future; |
| import java.util.concurrent.FutureTask; |
| import java.util.concurrent.TimeUnit; |
| import java.util.concurrent.atomic.AtomicInteger; |
| |
| /** |
| * A {@link java.util.concurrent.CompletionService} that orders the completed tasks |
| * in the same order as they where submitted. |
| * |
| * @version |
| */ |
| public class SubmitOrderedCompletionService<V> implements CompletionService<V> { |
| |
| private final Executor executor; |
| |
| // the idea to order the completed task in the same order as they where submitted is to leverage |
| // the delay queue. With the delay queue we can control the order by the getDelay and compareTo methods |
| // where we can order the tasks in the same order as they where submitted. |
| private final DelayQueue<SubmitOrderFutureTask> completionQueue = new DelayQueue<SubmitOrderFutureTask>(); |
| |
| // id is the unique id that determines the order in which tasks was submitted (incrementing) |
| private final AtomicInteger id = new AtomicInteger(); |
| // index is the index of the next id that should expire and thus be ready to take from the delayed queue |
| private final AtomicInteger index = new AtomicInteger(); |
| |
| private class SubmitOrderFutureTask extends FutureTask<V> implements Delayed { |
| |
| // the id this task was assigned |
| private final long id; |
| |
| public SubmitOrderFutureTask(long id, Callable<V> voidCallable) { |
| super(voidCallable); |
| this.id = id; |
| } |
| |
| public SubmitOrderFutureTask(long id, Runnable runnable, V result) { |
| super(runnable, result); |
| this.id = id; |
| } |
| |
| public long getDelay(TimeUnit unit) { |
| // if the answer is 0 then this task is ready to be taken |
| return id - index.get(); |
| } |
| |
| @SuppressWarnings("unchecked") |
| public int compareTo(Delayed o) { |
| SubmitOrderFutureTask other = (SubmitOrderFutureTask) o; |
| return (int) (this.id - other.id); |
| } |
| |
| @Override |
| protected void done() { |
| // when we are done add to the completion queue |
| completionQueue.add(this); |
| } |
| |
| @Override |
| public String toString() { |
| // output using zero-based index |
| return "SubmitOrderedFutureTask[" + (id - 1) + "]"; |
| } |
| } |
| |
| public SubmitOrderedCompletionService(Executor executor) { |
| this.executor = executor; |
| } |
| |
| @SuppressWarnings("unchecked") |
| public Future<V> submit(Callable task) { |
| if (task == null) { |
| throw new IllegalArgumentException("Task must be provided"); |
| } |
| SubmitOrderFutureTask f = new SubmitOrderFutureTask(id.incrementAndGet(), task); |
| executor.execute(f); |
| return f; |
| } |
| |
| public Future<V> submit(Runnable task, Object result) { |
| if (task == null) { |
| throw new IllegalArgumentException("Task must be provided"); |
| } |
| SubmitOrderFutureTask f = new SubmitOrderFutureTask(id.incrementAndGet(), task, null); |
| executor.execute(f); |
| return f; |
| } |
| |
| public Future<V> take() throws InterruptedException { |
| index.incrementAndGet(); |
| return completionQueue.take(); |
| } |
| |
| @SuppressWarnings("unchecked") |
| public Future<V> poll() { |
| index.incrementAndGet(); |
| Future answer = completionQueue.poll(); |
| if (answer == null) { |
| // decrease counter if we didnt get any data |
| index.decrementAndGet(); |
| } |
| return answer; |
| } |
| |
| @SuppressWarnings("unchecked") |
| public Future<V> poll(long timeout, TimeUnit unit) throws InterruptedException { |
| index.incrementAndGet(); |
| Future answer = completionQueue.poll(timeout, unit); |
| if (answer == null) { |
| // decrease counter if we didnt get any data |
| index.decrementAndGet(); |
| } |
| return answer; |
| } |
| |
| /** |
| * Marks the current task as timeout, which allows you to poll the next |
| * tasks which may already have been completed. |
| */ |
| public void timeoutTask() { |
| index.incrementAndGet(); |
| } |
| |
| } |