core/src/com/google/inject/internal/ProvisionListenerCallbackStore.java

/**
 * Copyright (C) 2011 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.Function;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import com.google.common.collect.MapMaker;
import com.google.inject.Key;
import com.google.inject.spi.ProvisionListener;
import com.google.inject.spi.ProvisionListenerBinding;

import java.util.List;
import java.util.Map;

/**
 * {@link ProvisionListenerStackCallback} for each key.
 *
 * @author sameb@google.com (Sam Berlin)
 */
final class ProvisionListenerCallbackStore {
  private final ImmutableList<ProvisionListenerBinding> listenerBindings;

  private final Map<Key<?>, ProvisionListenerStackCallback<?>> cache
      = new MapMaker().makeComputingMap(
          new Function<Key<?>, ProvisionListenerStackCallback<?>>() {
            public ProvisionListenerStackCallback<?> apply(Key<?> key) {
              return create(key);
            }
          });

  ProvisionListenerCallbackStore(List<ProvisionListenerBinding> listenerBindings) {
    this.listenerBindings = ImmutableList.copyOf(listenerBindings);
  }

  /** Returns a new {@link ProvisionListenerStackCallback} for the key.
   */
  @SuppressWarnings("unchecked") // the ProvisionListenerStackCallback type always agrees with the passed type
  public <T> ProvisionListenerStackCallback<T> get(Key<T> key) {
    return (ProvisionListenerStackCallback<T>) cache.get(key);
  }

  /**
   * Purges a key from the cache. Use this only if the type is not actually valid for
   * binding and needs to be purged. (See issue 319 and
   * ImplicitBindingTest#testCircularJitBindingsLeaveNoResidue and
   * #testInstancesRequestingProvidersForThemselvesWithChildInjectors for examples of when this is
   * necessary.)
   * 
   * Returns true if the type was stored in the cache, false otherwise.
   */
  boolean remove(Key<?> type) {
    return cache.remove(type) != null;
  }

  /**
   * Creates a new {@link ProvisionListenerStackCallback} with the correct listeners
   * for the key.
   */
  private <T> ProvisionListenerStackCallback<T> create(Key<T> key) {
    List<ProvisionListener> listeners = null;
    for (ProvisionListenerBinding binding : listenerBindings) {
      if (binding.getKeyMatcher().matches(key)) {
        if (listeners == null) {
          listeners = Lists.newArrayList();
        }
        listeners.addAll(binding.getListeners());
      }
    }
    if (listeners == null) {
      listeners = ImmutableList.of();
    }
    return new ProvisionListenerStackCallback<T>(key, listeners);
  }
}