Java tutorial
/** * 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.bookkeeper.common.util; import com.google.common.util.concurrent.ForwardingExecutorService; import java.util.Collection; import java.util.List; import java.util.concurrent.BlockingQueue; import java.util.concurrent.Callable; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Future; import java.util.concurrent.RejectedExecutionException; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; import java.util.concurrent.TimeoutException; /** * Implements {@link ExecutorService} and allows limiting the number of tasks to * be scheduled in the thread's queue. */ public class BoundedExecutorService extends ForwardingExecutorService { private final BlockingQueue<Runnable> queue; private final ThreadPoolExecutor thread; private final int maxTasksInQueue; public BoundedExecutorService(ThreadPoolExecutor thread, int maxTasksInQueue) { this.queue = thread.getQueue(); this.thread = thread; this.maxTasksInQueue = maxTasksInQueue; } @Override protected ExecutorService delegate() { return this.thread; } private void checkQueue(int numberOfTasks) { if (maxTasksInQueue > 0 && (queue.size() + numberOfTasks) > maxTasksInQueue) { throw new RejectedExecutionException("Queue at limit of " + maxTasksInQueue + " items"); } } @Override public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) throws InterruptedException { checkQueue(tasks.size()); return super.invokeAll(tasks); } @Override public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit) throws InterruptedException { checkQueue(tasks.size()); return super.invokeAll(tasks, timeout, unit); } @Override public <T> T invokeAny(Collection<? extends Callable<T>> tasks) throws InterruptedException, ExecutionException { checkQueue(tasks.size()); return super.invokeAny(tasks); } @Override public <T> T invokeAny(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException { checkQueue(tasks.size()); return super.invokeAny(tasks, timeout, unit); } @Override public void execute(Runnable command) { checkQueue(1); super.execute(command); } @Override public <T> Future<T> submit(Callable<T> task) { checkQueue(1); return super.submit(task); } @Override public Future<?> submit(Runnable task) { checkQueue(1); return super.submit(task); } @Override public <T> Future<T> submit(Runnable task, T result) { checkQueue(1); return super.submit(task, result); } }