001/*
002 * Copyright (C) 2011 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.cache;
016
017import com.google.common.annotations.GwtIncompatible;
018import com.google.common.annotations.J2ktIncompatible;
019import com.google.common.base.Preconditions;
020import com.google.common.collect.ImmutableMap;
021import com.google.errorprone.annotations.CanIgnoreReturnValue;
022import java.util.concurrent.ExecutionException;
023
024/**
025 * A cache which forwards all its method calls to another cache. Subclasses should override one or
026 * more methods to modify the behavior of the backing cache as desired per the <a
027 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
028 *
029 * <p>Note that {@link #get}, {@link #getUnchecked}, and {@link #apply} all expose the same
030 * underlying functionality, so should probably be overridden as a group.
031 *
032 * @author Charles Fry
033 * @since 11.0
034 */
035@GwtIncompatible
036@J2ktIncompatible // Compiles fine, but hidden for safety because the tests have not been ported
037public abstract class ForwardingLoadingCache<K, V> extends ForwardingCache<K, V>
038    implements LoadingCache<K, V> {
039
040  /** Constructor for use by subclasses. */
041  protected ForwardingLoadingCache() {}
042
043  @Override
044  protected abstract LoadingCache<K, V> delegate();
045
046  @CanIgnoreReturnValue // TODO(b/27479612): consider removing this
047  @Override
048  public V get(K key) throws ExecutionException {
049    return delegate().get(key);
050  }
051
052  @CanIgnoreReturnValue // TODO(b/27479612): consider removing this
053  @Override
054  public V getUnchecked(K key) {
055    return delegate().getUnchecked(key);
056  }
057
058  @CanIgnoreReturnValue // TODO(b/27479612): consider removing this
059  @Override
060  public ImmutableMap<K, V> getAll(Iterable<? extends K> keys) throws ExecutionException {
061    return delegate().getAll(keys);
062  }
063
064  @Override
065  public V apply(K key) {
066    return delegate().apply(key);
067  }
068
069  @Override
070  public void refresh(K key) {
071    delegate().refresh(key);
072  }
073
074  /**
075   * A simplified version of {@link ForwardingLoadingCache} where subclasses can pass in an already
076   * constructed {@link LoadingCache} as the delegate.
077   *
078   * @since 10.0
079   */
080  public abstract static class SimpleForwardingLoadingCache<K, V>
081      extends ForwardingLoadingCache<K, V> {
082    private final LoadingCache<K, V> delegate;
083
084    /** Constructor for use by subclasses. */
085    protected SimpleForwardingLoadingCache(LoadingCache<K, V> delegate) {
086      this.delegate = Preconditions.checkNotNull(delegate);
087    }
088
089    @Override
090    protected final LoadingCache<K, V> delegate() {
091      return delegate;
092    }
093  }
094}