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