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.collect.ImmutableMap; 019import com.google.common.collect.Maps; 020import com.google.common.util.concurrent.UncheckedExecutionException; 021import java.util.Map; 022import java.util.concurrent.Callable; 023import java.util.concurrent.ExecutionException; 024 025/** 026 * This class provides a skeletal implementation of the {@code Cache} interface to minimize the 027 * effort required to implement this interface. 028 * 029 * <p>To implement a cache, the programmer needs only to extend this class and provide an 030 * implementation for the {@link #get(Object)} and {@link #getIfPresent} methods. 031 * {@link #getUnchecked}, {@link #get(Object, Callable)}, and {@link #getAll} are implemented in 032 * terms of {@code get}; {@link #getAllPresent} is implemented in terms of {@code getIfPresent}; 033 * {@link #putAll} is implemented in terms of {@link #put}, {@link #invalidateAll(Iterable)} is 034 * implemented in terms of {@link #invalidate}. The method {@link #cleanUp} is a no-op. All other 035 * methods throw an {@link UnsupportedOperationException}. 036 * 037 * @author Charles Fry 038 * @since 11.0 039 */ 040@GwtIncompatible 041public abstract class AbstractLoadingCache<K, V> extends AbstractCache<K, V> 042 implements LoadingCache<K, V> { 043 044 /** Constructor for use by subclasses. */ 045 protected AbstractLoadingCache() {} 046 047 @Override 048 public V getUnchecked(K key) { 049 try { 050 return get(key); 051 } catch (ExecutionException e) { 052 throw new UncheckedExecutionException(e.getCause()); 053 } 054 } 055 056 @Override 057 public ImmutableMap<K, V> getAll(Iterable<? extends K> keys) throws ExecutionException { 058 Map<K, V> result = Maps.newLinkedHashMap(); 059 for (K key : keys) { 060 if (!result.containsKey(key)) { 061 result.put(key, get(key)); 062 } 063 } 064 return ImmutableMap.copyOf(result); 065 } 066 067 @Override 068 public final V apply(K key) { 069 return getUnchecked(key); 070 } 071 072 @Override 073 public void refresh(K key) { 074 throw new UnsupportedOperationException(); 075 } 076}