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.collect.ImmutableMap;
19 import com.google.common.collect.Maps;
20 import com.google.common.util.concurrent.UncheckedExecutionException;
21 import java.util.Map;
22 import java.util.concurrent.Callable;
23 import java.util.concurrent.ExecutionException;
24
25 /**
26 * This class provides a skeletal implementation of the {@code Cache} interface to minimize the
27 * effort required to implement this interface.
28 *
29 * <p>To implement a cache, the programmer needs only to extend this class and provide an
30 * implementation for the {@link #get(Object)} and {@link #getIfPresent} methods. {@link
31 * #getUnchecked}, {@link #get(Object, Callable)}, and {@link #getAll} are implemented in terms of
32 * {@code get}; {@link #getAllPresent} is implemented in terms of {@code getIfPresent}; {@link
33 * #putAll} is implemented in terms of {@link #put}, {@link #invalidateAll(Iterable)} is implemented
34 * in terms of {@link #invalidate}. The method {@link #cleanUp} is a no-op. All other methods throw
35 * an {@link UnsupportedOperationException}.
36 *
37 * @author Charles Fry
38 * @since 11.0
39 */
40 @GwtIncompatible
41 public abstract class AbstractLoadingCache<K, V> extends AbstractCache<K, V>
42 implements LoadingCache<K, V> {
43
44 /** Constructor for use by subclasses. */
45 protected AbstractLoadingCache() {}
46
47 @Override
48 public V getUnchecked(K key) {
49 try {
50 return get(key);
51 } catch (ExecutionException e) {
52 throw new UncheckedExecutionException(e.getCause());
53 }
54 }
55
56 @Override
57 public ImmutableMap<K, V> getAll(Iterable<? extends K> keys) throws ExecutionException {
58 Map<K, V> result = Maps.newLinkedHashMap();
59 for (K key : keys) {
60 if (!result.containsKey(key)) {
61 result.put(key, get(key));
62 }
63 }
64 return ImmutableMap.copyOf(result);
65 }
66
67 @Override
68 public final V apply(K key) {
69 return getUnchecked(key);
70 }
71
72 @Override
73 public void refresh(K key) {
74 throw new UnsupportedOperationException();
75 }
76 }