Java tutorial
/* * Copyright 2015 the original author or authors. * * Licensed 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.gradle.internal.operations; import com.google.common.collect.Lists; import com.google.common.collect.Queues; import com.google.common.util.concurrent.*; import org.gradle.internal.UncheckedException; import java.util.Collection; import java.util.List; import java.util.Queue; import java.util.concurrent.CountDownLatch; import java.util.concurrent.ExecutorService; class DefaultBuildOperationQueue<T extends BuildOperation> implements BuildOperationQueue<T> { private final ListeningExecutorService executor; private final BuildOperationWorker<T> worker; private final List<ListenableFuture> operations; private final String logLocation; private boolean waitingForCompletion; DefaultBuildOperationQueue(ExecutorService executor, BuildOperationWorker<T> worker, String logLocation) { this.logLocation = logLocation; this.executor = MoreExecutors.listeningDecorator(executor); this.worker = worker; this.operations = Lists.newLinkedList(); } public void add(final T operation) { if (waitingForCompletion) { throw new IllegalStateException("BuildOperationQueue cannot be reused once it has started completion."); } ListenableFuture<?> future = executor.submit(new OperationHolder(operation)); operations.add(future); } public void waitForCompletion() throws MultipleBuildOperationFailures { waitingForCompletion = true; CountDownLatch finished = new CountDownLatch(operations.size()); Queue<Throwable> failures = Queues.newConcurrentLinkedQueue(); for (ListenableFuture operation : operations) { Futures.addCallback(operation, new CompletionCallback(finished, failures)); } try { finished.await(); } catch (InterruptedException e) { throw UncheckedException.throwAsUncheckedException(e); } // all operations are complete, check for errors if (!failures.isEmpty()) { throw new MultipleBuildOperationFailures(getFailureMessage(failures), failures, logLocation); } } private String getFailureMessage(Collection<Throwable> failures) { if (failures.size() == 1) { return "A build operation failed."; } return "Multiple build operations failed."; } private static class CompletionCallback implements FutureCallback { private final CountDownLatch finished; private final Collection<Throwable> failures; private CompletionCallback(CountDownLatch finished, Collection<Throwable> failures) { this.finished = finished; this.failures = failures; } public void onSuccess(Object result) { finished.countDown(); } public void onFailure(Throwable t) { failures.add(t); finished.countDown(); } } private class OperationHolder implements Runnable { private final T operation; OperationHolder(T operation) { this.operation = operation; } public void run() { worker.execute(operation); } public String toString() { return "Worker ".concat(worker.getDisplayName()).concat(" for operation ") .concat(operation.getDescription()); } } }