1 /* 2 * Copyright (C) 2015 Google, Inc. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 package dagger.producers.internal; 17 18 import com.google.common.base.Function; 19 import com.google.common.collect.ImmutableSet; 20 import com.google.common.util.concurrent.Futures; 21 import com.google.common.util.concurrent.ListenableFuture; 22 import dagger.producers.Producer; 23 import dagger.producers.monitoring.ProducerMonitor; 24 import java.util.ArrayList; 25 import java.util.List; 26 import java.util.Set; 27 28 /** 29 * A {@link Producer} implementation used to implement {@link Set} bindings. This producer returns 30 * a future {@link Set} whose elements are populated by subsequent calls to the delegate 31 * {@link Producer#get} methods. 32 * 33 * @author Jesse Beder 34 * @since 2.0 35 */ 36 public final class SetProducer<T> extends AbstractProducer<Set<T>> { 37 /** 38 * Returns a new producer that creates {@link Set} futures from the union of the given 39 * {@link Producer} instances. 40 */ 41 @SafeVarargs create(Producer<Set<T>>.... producers)42 public static <T> Producer<Set<T>> create(Producer<Set<T>>... producers) { 43 return new SetProducer<T>(ImmutableSet.copyOf(producers)); 44 } 45 46 private final Set<Producer<Set<T>>> contributingProducers; 47 SetProducer(Set<Producer<Set<T>>> contributingProducers)48 private SetProducer(Set<Producer<Set<T>>> contributingProducers) { 49 super(); 50 this.contributingProducers = contributingProducers; 51 } 52 53 /** 54 * Returns a future {@link Set} whose iteration order is that of the elements given by each of the 55 * producers, which are invoked in the order given at creation. 56 * 57 * <p>If any of the delegate sets, or any elements therein, are null, then this future will fail 58 * with a NullPointerException. 59 * 60 * <p>Canceling this future will attempt to cancel all of the component futures, and if any of the 61 * delegate futures fails or is canceled, this one is, too. 62 * 63 * @throws NullPointerException if any of the delegate producers return null 64 */ 65 @Override compute(ProducerMonitor unusedMonitor)66 public ListenableFuture<Set<T>> compute(ProducerMonitor unusedMonitor) { 67 List<ListenableFuture<Set<T>>> futureSets = 68 new ArrayList<ListenableFuture<Set<T>>>(contributingProducers.size()); 69 for (Producer<Set<T>> producer : contributingProducers) { 70 ListenableFuture<Set<T>> futureSet = producer.get(); 71 if (futureSet == null) { 72 throw new NullPointerException(producer + " returned null"); 73 } 74 futureSets.add(futureSet); 75 } 76 return Futures.transform(Futures.allAsList(futureSets), new Function<List<Set<T>>, Set<T>>() { 77 @Override public Set<T> apply(List<Set<T>> sets) { 78 ImmutableSet.Builder<T> builder = ImmutableSet.builder(); 79 for (Set<T> set : sets) { 80 builder.addAll(set); 81 } 82 return builder.build(); 83 } 84 }); 85 } 86 } 87