1 /* 2 * Copyright (C) 2011 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.cache; 18 19 import com.google.common.annotations.Beta; 20 import com.google.common.collect.ImmutableMap; 21 import com.google.common.collect.Maps; 22 import com.google.common.util.concurrent.UncheckedExecutionException; 23 24 import java.util.Map; 25 import java.util.concurrent.Callable; 26 import java.util.concurrent.ExecutionException; 27 28 /** 29 * This class provides a skeletal implementation of the {@code Cache} interface to minimize the 30 * effort required to implement this interface. 31 * 32 * <p>To implement a cache, the programmer needs only to extend this class and provide an 33 * implementation for the {@link #get(Object)} and {@link #getIfPresent} methods. 34 * {@link #getUnchecked}, {@link #get(Object, Callable)}, and {@link #getAll} are implemented in 35 * terms of {@code get}; {@link #getAllPresent} is implemented in terms of {@code getIfPresent}; 36 * {@link #putAll} is implemented in terms of {@link #put}, {@link #invalidateAll(Iterable)} is 37 * implemented in terms of {@link #invalidate}. The method {@link #cleanUp} is a no-op. All other 38 * methods throw an {@link UnsupportedOperationException}. 39 * 40 * @author Charles Fry 41 * @since 11.0 42 */ 43 @Beta 44 public abstract class AbstractLoadingCache<K, V> 45 extends AbstractCache<K, V> implements LoadingCache<K, V> { 46 47 /** Constructor for use by subclasses. */ AbstractLoadingCache()48 protected AbstractLoadingCache() {} 49 50 @Override getUnchecked(K key)51 public V getUnchecked(K key) { 52 try { 53 return get(key); 54 } catch (ExecutionException e) { 55 throw new UncheckedExecutionException(e.getCause()); 56 } 57 } 58 59 @Override getAll(Iterable<? extends K> keys)60 public ImmutableMap<K, V> getAll(Iterable<? extends K> keys) throws ExecutionException { 61 Map<K, V> result = Maps.newLinkedHashMap(); 62 for (K key : keys) { 63 if (!result.containsKey(key)) { 64 result.put(key, get(key)); 65 } 66 } 67 return ImmutableMap.copyOf(result); 68 } 69 70 @Override apply(K key)71 public final V apply(K key) { 72 return getUnchecked(key); 73 } 74 75 @Override refresh(K key)76 public void refresh(K key) { 77 throw new UnsupportedOperationException(); 78 } 79 } 80