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.base.Preconditions;
019import com.google.common.collect.ForwardingObject;
020import com.google.common.collect.ImmutableMap;
021import java.util.Map;
022import java.util.concurrent.Callable;
023import java.util.concurrent.ConcurrentMap;
024import java.util.concurrent.ExecutionException;
025import org.jspecify.annotations.Nullable;
026
027/**
028 * A cache which forwards all its method calls to another cache. Subclasses should override one or
029 * more methods to modify the behavior of the backing cache as desired per the <a
030 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
031 *
032 * @author Charles Fry
033 * @since 10.0
034 */
035@GwtIncompatible
036public abstract class ForwardingCache<K, V> extends ForwardingObject implements Cache<K, V> {
037
038  /** Constructor for use by subclasses. */
039  protected ForwardingCache() {}
040
041  @Override
042  protected abstract Cache<K, V> delegate();
043
044  /**
045   * @since 11.0
046   */
047  @Override
048  public @Nullable V getIfPresent(Object key) {
049    return delegate().getIfPresent(key);
050  }
051
052  /**
053   * @since 11.0
054   */
055  @Override
056  public V get(K key, Callable<? extends V> valueLoader) throws ExecutionException {
057    return delegate().get(key, valueLoader);
058  }
059
060  /**
061   * @since 11.0
062   */
063  @Override
064  /*
065   * <? extends Object> is mostly the same as <?> to plain Java. But to nullness checkers, they
066   * differ: <? extends Object> means "non-null types," while <?> means "all types."
067   */
068  public ImmutableMap<K, V> getAllPresent(Iterable<? extends Object> keys) {
069    return delegate().getAllPresent(keys);
070  }
071
072  /**
073   * @since 11.0
074   */
075  @Override
076  public void put(K key, V value) {
077    delegate().put(key, value);
078  }
079
080  /**
081   * @since 12.0
082   */
083  @Override
084  public void putAll(Map<? extends K, ? extends V> m) {
085    delegate().putAll(m);
086  }
087
088  @Override
089  public void invalidate(Object key) {
090    delegate().invalidate(key);
091  }
092
093  /**
094   * @since 11.0
095   */
096  @Override
097  // For discussion of <? extends Object>, see getAllPresent.
098  public void invalidateAll(Iterable<? extends Object> keys) {
099    delegate().invalidateAll(keys);
100  }
101
102  @Override
103  public void invalidateAll() {
104    delegate().invalidateAll();
105  }
106
107  @Override
108  public long size() {
109    return delegate().size();
110  }
111
112  @Override
113  public CacheStats stats() {
114    return delegate().stats();
115  }
116
117  @Override
118  public ConcurrentMap<K, V> asMap() {
119    return delegate().asMap();
120  }
121
122  @Override
123  public void cleanUp() {
124    delegate().cleanUp();
125  }
126
127  /**
128   * A simplified version of {@link ForwardingCache} where subclasses can pass in an already
129   * constructed {@link Cache} as the delegate.
130   *
131   * @since 10.0
132   */
133  public abstract static class SimpleForwardingCache<K, V> extends ForwardingCache<K, V> {
134    private final Cache<K, V> delegate;
135
136    protected SimpleForwardingCache(Cache<K, V> delegate) {
137      this.delegate = Preconditions.checkNotNull(delegate);
138    }
139
140    @Override
141    protected final Cache<K, V> delegate() {
142      return delegate;
143    }
144  }
145}