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.base.Preconditions; 019import com.google.common.collect.ImmutableMap; 020import com.google.errorprone.annotations.CanIgnoreReturnValue; 021import java.util.concurrent.ExecutionException; 022 023/** 024 * A cache which forwards all its method calls to another cache. Subclasses should override one or 025 * more methods to modify the behavior of the backing cache as desired per the <a 026 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 027 * 028 * <p>Note that {@link #get}, {@link #getUnchecked}, and {@link #apply} all expose the same 029 * underlying functionality, so should probably be overridden as a group. 030 * 031 * @author Charles Fry 032 * @since 11.0 033 */ 034@GwtIncompatible 035@ElementTypesAreNonnullByDefault 036public abstract class ForwardingLoadingCache<K, V> extends ForwardingCache<K, V> 037 implements LoadingCache<K, V> { 038 039 /** Constructor for use by subclasses. */ 040 protected ForwardingLoadingCache() {} 041 042 @Override 043 protected abstract LoadingCache<K, V> delegate(); 044 045 @CanIgnoreReturnValue // TODO(b/27479612): consider removing this 046 @Override 047 public V get(K key) throws ExecutionException { 048 return delegate().get(key); 049 } 050 051 @CanIgnoreReturnValue // TODO(b/27479612): consider removing this 052 @Override 053 public V getUnchecked(K key) { 054 return delegate().getUnchecked(key); 055 } 056 057 @CanIgnoreReturnValue // TODO(b/27479612): consider removing this 058 @Override 059 public ImmutableMap<K, V> getAll(Iterable<? extends K> keys) throws ExecutionException { 060 return delegate().getAll(keys); 061 } 062 063 @Override 064 public V apply(K key) { 065 return delegate().apply(key); 066 } 067 068 @Override 069 public void refresh(K key) { 070 delegate().refresh(key); 071 } 072 073 /** 074 * A simplified version of {@link ForwardingLoadingCache} where subclasses can pass in an already 075 * constructed {@link LoadingCache} as the delegate. 076 * 077 * @since 10.0 078 */ 079 public abstract static class SimpleForwardingLoadingCache<K, V> 080 extends ForwardingLoadingCache<K, V> { 081 private final LoadingCache<K, V> delegate; 082 083 protected SimpleForwardingLoadingCache(LoadingCache<K, V> delegate) { 084 this.delegate = Preconditions.checkNotNull(delegate); 085 } 086 087 @Override 088 protected final LoadingCache<K, V> delegate() { 089 return delegate; 090 } 091 } 092}