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.ForwardingObject; 020import com.google.common.collect.ImmutableMap; 021import java.util.Map; 022import java.util.concurrent.Callable; 023import java.util.concurrent.ConcurrentMap; 024import java.util.concurrent.ExecutionException; 025import javax.annotation.CheckForNull; 026 027/** 028 * A cache which forwards all its method calls to another cache. Subclasses should override one or 029 * more methods to modify the behavior of the backing cache as desired per the <a 030 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>. 031 * 032 * @author Charles Fry 033 * @since 10.0 034 */ 035@GwtIncompatible 036@ElementTypesAreNonnullByDefault 037public abstract class ForwardingCache<K, V> extends ForwardingObject implements Cache<K, V> { 038 039 /** Constructor for use by subclasses. */ 040 protected ForwardingCache() {} 041 042 @Override 043 protected abstract Cache<K, V> delegate(); 044 045 /** @since 11.0 */ 046 @Override 047 @CheckForNull 048 public V getIfPresent(Object key) { 049 return delegate().getIfPresent(key); 050 } 051 052 /** @since 11.0 */ 053 @Override 054 public V get(K key, Callable<? extends V> valueLoader) throws ExecutionException { 055 return delegate().get(key, valueLoader); 056 } 057 058 /** @since 11.0 */ 059 @Override 060 /* 061 * <? extends Object> is mostly the same as <?> to plain Java. But to nullness checkers, they 062 * differ: <? extends Object> means "non-null types," while <?> means "all types." 063 */ 064 public ImmutableMap<K, V> getAllPresent(Iterable<? extends Object> keys) { 065 return delegate().getAllPresent(keys); 066 } 067 068 /** @since 11.0 */ 069 @Override 070 public void put(K key, V value) { 071 delegate().put(key, value); 072 } 073 074 /** @since 12.0 */ 075 @Override 076 public void putAll(Map<? extends K, ? extends V> m) { 077 delegate().putAll(m); 078 } 079 080 @Override 081 public void invalidate(Object key) { 082 delegate().invalidate(key); 083 } 084 085 /** @since 11.0 */ 086 @Override 087 // For discussion of <? extends Object>, see getAllPresent. 088 public void invalidateAll(Iterable<? extends Object> keys) { 089 delegate().invalidateAll(keys); 090 } 091 092 @Override 093 public void invalidateAll() { 094 delegate().invalidateAll(); 095 } 096 097 @Override 098 public long size() { 099 return delegate().size(); 100 } 101 102 @Override 103 public CacheStats stats() { 104 return delegate().stats(); 105 } 106 107 @Override 108 public ConcurrentMap<K, V> asMap() { 109 return delegate().asMap(); 110 } 111 112 @Override 113 public void cleanUp() { 114 delegate().cleanUp(); 115 } 116 117 /** 118 * A simplified version of {@link ForwardingCache} where subclasses can pass in an already 119 * constructed {@link Cache} as the delegate. 120 * 121 * @since 10.0 122 */ 123 public abstract static class SimpleForwardingCache<K, V> extends ForwardingCache<K, V> { 124 private final Cache<K, V> delegate; 125 126 protected SimpleForwardingCache(Cache<K, V> delegate) { 127 this.delegate = Preconditions.checkNotNull(delegate); 128 } 129 130 @Override 131 protected final Cache<K, V> delegate() { 132 return delegate; 133 } 134 } 135}