/*
 * Copyright (C) 2008 Google Inc.
 *
 * 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 com.google.inject.internal;

import com.google.common.base.Objects;
import com.google.common.base.Preconditions;
import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.RemovalCause;
import com.google.common.cache.RemovalListener;
import com.google.common.cache.RemovalNotification;
import com.google.common.collect.LinkedHashMultiset;
import com.google.common.collect.Maps;
import com.google.common.collect.Multiset;
import com.google.common.collect.Sets;
import com.google.inject.Key;
import com.google.inject.internal.util.SourceProvider;
import java.util.Map;
import java.util.Set;

Minimal set that doesn't hold strong references to the contained keys.
Author:dweis@google.com (Daniel Weis)
/** * Minimal set that doesn't hold strong references to the contained keys. * * @author dweis@google.com (Daniel Weis) */
final class WeakKeySet { private Map<Key<?>, Multiset<Object>> backingMap;
This is already locked externally on add and getSources but we need it to handle clean up in the evictionCache's RemovalListener.
/** * This is already locked externally on add and getSources but we need it to handle clean up in * the evictionCache's RemovalListener. */
private final Object lock;
Tracks child injector lifetimes and evicts blacklisted keys/sources after the child injector is garbage collected.
/** * Tracks child injector lifetimes and evicts blacklisted keys/sources after the child injector is * garbage collected. */
private final Cache<State, Set<KeyAndSource>> evictionCache = CacheBuilder.newBuilder() .weakKeys() .removalListener( new RemovalListener<State, Set<KeyAndSource>>() { @Override public void onRemoval(RemovalNotification<State, Set<KeyAndSource>> notification) { Preconditions.checkState(RemovalCause.COLLECTED.equals(notification.getCause())); cleanUpForCollectedState(notification.getValue()); } }) .build();
There may be multiple child injectors blacklisting a certain key so only remove the source that's relevant.
/** * There may be multiple child injectors blacklisting a certain key so only remove the source * that's relevant. */
private void cleanUpForCollectedState(Set<KeyAndSource> keysAndSources) { synchronized (lock) { for (KeyAndSource keyAndSource : keysAndSources) { Multiset<Object> set = backingMap.get(keyAndSource.key); if (set != null) { set.remove(keyAndSource.source); if (set.isEmpty()) { backingMap.remove(keyAndSource.key); } } } } } WeakKeySet(Object lock) { this.lock = lock; } public void add(Key<?> key, State state, Object source) { if (backingMap == null) { backingMap = Maps.newHashMap(); } // if it's an instanceof Class, it was a JIT binding, which we don't // want to retain. if (source instanceof Class || source == SourceProvider.UNKNOWN_SOURCE) { source = null; } Multiset<Object> sources = backingMap.get(key); if (sources == null) { sources = LinkedHashMultiset.create(); backingMap.put(key, sources); } Object convertedSource = Errors.convert(source); sources.add(convertedSource); // Avoid all the extra work if we can. if (state.parent() != State.NONE) { Set<KeyAndSource> keyAndSources = evictionCache.getIfPresent(state); if (keyAndSources == null) { evictionCache.put(state, keyAndSources = Sets.newHashSet()); } keyAndSources.add(new KeyAndSource(key, convertedSource)); } } public boolean contains(Key<?> key) { evictionCache.cleanUp(); return backingMap != null && backingMap.containsKey(key); } public Set<Object> getSources(Key<?> key) { evictionCache.cleanUp(); Multiset<Object> sources = (backingMap == null) ? null : backingMap.get(key); return (sources == null) ? null : sources.elementSet(); } private static final class KeyAndSource { final Key<?> key; final Object source; KeyAndSource(Key<?> key, Object source) { this.key = key; this.source = source; } @Override public int hashCode() { return Objects.hashCode(key, source); } @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (!(obj instanceof KeyAndSource)) { return false; } KeyAndSource other = (KeyAndSource) obj; return Objects.equal(key, other.key) && Objects.equal(source, other.source); } } }