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.base.Preconditions; 21 import com.google.common.collect.ImmutableMap; 22 23 import java.util.concurrent.ExecutionException; 24 25 /** 26 * A cache which forwards all its method calls to another cache. Subclasses should override one or 27 * more methods to modify the behavior of the backing cache as desired per the 28 * <a href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 29 * 30 * <p>Note that {@link #get}, {@link #getUnchecked}, and {@link #apply} all expose the same 31 * underlying functionality, so should probably be overridden as a group. 32 * 33 * @author Charles Fry 34 * @since 11.0 35 */ 36 @Beta 37 public abstract class ForwardingLoadingCache<K, V> 38 extends ForwardingCache<K, V> implements LoadingCache<K, V> { 39 40 /** Constructor for use by subclasses. */ 41 protected ForwardingLoadingCache() {} 42 43 @Override 44 protected abstract LoadingCache<K, V> delegate(); 45 46 @Override 47 public V get(K key) throws ExecutionException { 48 return delegate().get(key); 49 } 50 51 @Override 52 public V getUnchecked(K key) { 53 return delegate().getUnchecked(key); 54 } 55 56 @Override 57 public ImmutableMap<K, V> getAll(Iterable<? extends K> keys) throws ExecutionException { 58 return delegate().getAll(keys); 59 } 60 61 @Override 62 public V apply(K key) { 63 return delegate().apply(key); 64 } 65 66 @Override 67 public void refresh(K key) { 68 delegate().refresh(key); 69 } 70 71 /** 72 * A simplified version of {@link ForwardingLoadingCache} where subclasses can pass in an already 73 * constructed {@link LoadingCache} as the delegete. 74 * 75 * @since 10.0 76 */ 77 @Beta 78 public abstract static class SimpleForwardingLoadingCache<K, V> 79 extends ForwardingLoadingCache<K, V> { 80 private final LoadingCache<K, V> delegate; 81 82 protected SimpleForwardingLoadingCache(LoadingCache<K, V> delegate) { 83 this.delegate = Preconditions.checkNotNull(delegate); 84 } 85 86 @Override 87 protected final LoadingCache<K, V> delegate() { 88 return delegate; 89 } 90 } 91 } 92
