1 /*
2 * Copyright (C) 2011 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
5 * in compliance with the License. You may obtain a copy of the License at
6 *
7 * http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software distributed under the License
10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
11 * or implied. See the License for the specific language governing permissions and limitations under
12 * the License.
13 */
14
15 package com.google.common.cache;
16
17 import com.google.common.annotations.GwtIncompatible;
18 import com.google.common.base.Preconditions;
19 import com.google.common.collect.ImmutableMap;
20 import java.util.concurrent.ExecutionException;
21
22 /**
23 * A cache which forwards all its method calls to another cache. Subclasses should override one or
24 * more methods to modify the behavior of the backing cache as desired per the <a
25 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
26 *
27 * <p>Note that {@link #get}, {@link #getUnchecked}, and {@link #apply} all expose the same
28 * underlying functionality, so should probably be overridden as a group.
29 *
30 * @author Charles Fry
31 * @since 11.0
32 */
33 @GwtIncompatible
34 public abstract class ForwardingLoadingCache<K, V> extends ForwardingCache<K, V>
35 implements LoadingCache<K, V> {
36
37 /** Constructor for use by subclasses. */
38 protected ForwardingLoadingCache() {}
39
40 @Override
41 protected abstract LoadingCache<K, V> delegate();
42
43 @Override
44 public V get(K key) throws ExecutionException {
45 return delegate().get(key);
46 }
47
48 @Override
49 public V getUnchecked(K key) {
50 return delegate().getUnchecked(key);
51 }
52
53 @Override
54 public ImmutableMap<K, V> getAll(Iterable<? extends K> keys) throws ExecutionException {
55 return delegate().getAll(keys);
56 }
57
58 @Override
59 public V apply(K key) {
60 return delegate().apply(key);
61 }
62
63 @Override
64 public void refresh(K key) {
65 delegate().refresh(key);
66 }
67
68 /**
69 * A simplified version of {@link ForwardingLoadingCache} where subclasses can pass in an already
70 * constructed {@link LoadingCache} as the delegate.
71 *
72 * @since 10.0
73 */
74 public abstract static class SimpleForwardingLoadingCache<K, V>
75 extends ForwardingLoadingCache<K, V> {
76 private final LoadingCache<K, V> delegate;
77
78 protected SimpleForwardingLoadingCache(LoadingCache<K, V> delegate) {
79 this.delegate = Preconditions.checkNotNull(delegate);
80 }
81
82 @Override
83 protected final LoadingCache<K, V> delegate() {
84 return delegate;
85 }
86 }
87 }