1 /** 2 * Copyright (C) 2008 Google Inc. 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.inject.internal; 18 19 import com.google.common.cache.CacheBuilder; 20 import com.google.common.cache.CacheLoader; 21 import com.google.common.cache.LoadingCache; 22 23 /** 24 * Lazily creates (and caches) values for keys. If creating the value fails (with errors), an 25 * exception is thrown on retrieval. 26 * 27 * @author jessewilson (at) google.com (Jesse Wilson) 28 */ 29 public abstract class FailableCache<K, V> { 30 31 private final LoadingCache<K, Object> delegate = CacheBuilder.newBuilder().build( 32 new CacheLoader<K, Object>() { 33 public Object load(K key) { 34 Errors errors = new Errors(); 35 V result = null; 36 try { 37 result = FailableCache.this.create(key, errors); 38 } catch (ErrorsException e) { 39 errors.merge(e.getErrors()); 40 } 41 return errors.hasErrors() ? errors : result; 42 } 43 }); 44 45 protected abstract V create(K key, Errors errors) throws ErrorsException; 46 47 public V get(K key, Errors errors) throws ErrorsException { 48 Object resultOrError = delegate.getUnchecked(key); 49 if (resultOrError instanceof Errors) { 50 errors.merge((Errors) resultOrError); 51 throw errors.toException(); 52 } else { 53 @SuppressWarnings("unchecked") // create returned a non-error result, so this is safe 54 V result = (V) resultOrError; 55 return result; 56 } 57 } 58 59 boolean remove(K key) { 60 return delegate.asMap().remove(key) != null; 61 } 62 } 63
