/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.inject.internal;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;

Lazily creates (and caches) values for keys. If creating the value fails (with errors), an exception is thrown on retrieval.
Author:jessewilson@google.com (Jesse Wilson)
/** * Lazily creates (and caches) values for keys. If creating the value fails (with errors), an * exception is thrown on retrieval. * * @author jessewilson@google.com (Jesse Wilson) */
public abstract class FailableCache<K, V> { private final LoadingCache<K, Object> delegate = CacheBuilder.newBuilder() .build( new CacheLoader<K, Object>() { @Override public Object load(K key) { Errors errors = new Errors(); V result = null; try { result = FailableCache.this.create(key, errors); } catch (ErrorsException e) { errors.merge(e.getErrors()); } return errors.hasErrors() ? errors : result; } }); protected abstract V create(K key, Errors errors) throws ErrorsException; public V get(K key, Errors errors) throws ErrorsException { Object resultOrError = delegate.getUnchecked(key); if (resultOrError instanceof Errors) { errors.merge((Errors) resultOrError); throw errors.toException(); } else { @SuppressWarnings("unchecked") // create returned a non-error result, so this is safe V result = (V) resultOrError; return result; } } boolean remove(K key) { return delegate.asMap().remove(key) != null; } }