1 /** 2 * Copyright (C) 2008 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 17 package com.google.inject.internal; 18 19 import com.google.common.base.Objects; 20 import com.google.common.base.Preconditions; 21 import com.google.common.cache.Cache; 22 import com.google.common.cache.CacheBuilder; 23 import com.google.common.cache.RemovalCause; 24 import com.google.common.cache.RemovalListener; 25 import com.google.common.cache.RemovalNotification; 26 import com.google.common.collect.LinkedHashMultiset; 27 import com.google.common.collect.Maps; 28 import com.google.common.collect.Multiset; 29 import com.google.common.collect.Sets; 30 import com.google.inject.Key; 31 import com.google.inject.internal.util.SourceProvider; 32 33 import java.util.Map; 34 import java.util.Set; 35 36 /** 37 * Minimal set that doesn't hold strong references to the contained keys. 38 * 39 * @author dweis (at) google.com (Daniel Weis) 40 */ 41 final class WeakKeySet { 42 43 private Map<Key<?>, Multiset<Object>> backingMap; 44 45 /** 46 * This is already locked externally on add and getSources but we need it to handle clean up in 47 * the evictionCache's RemovalListener. 48 */ 49 private final Object lock; 50 51 /** 52 * Tracks child injector lifetimes and evicts blacklisted keys/sources after the child injector is 53 * garbage collected. 54 */ 55 private final Cache<State, Set<KeyAndSource>> evictionCache = CacheBuilder.newBuilder() 56 .weakKeys() 57 .removalListener( 58 new RemovalListener<State, Set<KeyAndSource>>() { 59 @Override 60 public void onRemoval(RemovalNotification<State, Set<KeyAndSource>> notification) { 61 Preconditions.checkState(RemovalCause.COLLECTED.equals(notification.getCause())); 62 63 cleanUpForCollectedState(notification.getValue()); 64 } 65 }) 66 .build(); 67 68 /** 69 * There may be multiple child injectors blacklisting a certain key so only remove the source 70 * that's relevant. 71 */ 72 private void cleanUpForCollectedState(Set<KeyAndSource> keysAndSources) { 73 synchronized (lock) { 74 for (KeyAndSource keyAndSource : keysAndSources) { 75 Multiset<Object> set = backingMap.get(keyAndSource.key); 76 if (set != null) { 77 set.remove(keyAndSource.source); 78 if (set.isEmpty()) { 79 backingMap.remove(keyAndSource.key); 80 } 81 } 82 } 83 } 84 } 85 86 WeakKeySet(Object lock) { 87 this.lock = lock; 88 } 89 90 public void add(Key<?> key, State state, Object source) { 91 if (backingMap == null) { 92 backingMap = Maps.newHashMap(); 93 } 94 // if it's an instanceof Class, it was a JIT binding, which we don't 95 // want to retain. 96 if (source instanceof Class || source == SourceProvider.UNKNOWN_SOURCE) { 97 source = null; 98 } 99 Multiset<Object> sources = backingMap.get(key); 100 if (sources == null) { 101 sources = LinkedHashMultiset.create(); 102 backingMap.put(key, sources); 103 } 104 Object convertedSource = Errors.convert(source); 105 sources.add(convertedSource); 106 107 // Avoid all the extra work if we can. 108 if (state.parent() != State.NONE) { 109 Set<KeyAndSource> keyAndSources = evictionCache.getIfPresent(state); 110 if (keyAndSources == null) { 111 evictionCache.put(state, keyAndSources = Sets.newHashSet()); 112 } 113 keyAndSources.add(new KeyAndSource(key, convertedSource)); 114 } 115 } 116 117 public boolean contains(Key<?> key) { 118 evictionCache.cleanUp(); 119 return backingMap != null && backingMap.containsKey(key); 120 } 121 122 public Set<Object> getSources(Key<?> key) { 123 evictionCache.cleanUp(); 124 Multiset<Object> sources = (backingMap == null) ? null : backingMap.get(key); 125 return (sources == null) ? null : sources.elementSet(); 126 } 127 128 private static final class KeyAndSource { 129 final Key<?> key; 130 final Object source; 131 132 KeyAndSource(Key<?> key, Object source) { 133 this.key = key; 134 this.source = source; 135 } 136 137 @Override 138 public int hashCode() { 139 return Objects.hashCode(key, source); 140 } 141 142 @Override 143 public boolean equals(Object obj) { 144 if (this == obj) { 145 return true; 146 } 147 148 if (!(obj instanceof KeyAndSource)) { 149 return false; 150 } 151 152 KeyAndSource other = (KeyAndSource) obj; 153 return Objects.equal(key, other.key) 154 && Objects.equal(source, other.source); 155 } 156 } 157 } 158