/*
* 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 org.elasticsearch.common.inject.internal;
import java.util.concurrent.ConcurrentHashMap;
/**
* 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 ConcurrentHashMap<K, Object> cache = new ConcurrentHashMap<>();
protected abstract V create(K key, Errors errors) throws ErrorsException;
public V get(K key, Errors errors) throws ErrorsException {
Object resultOrError = cache.get(key);
if (resultOrError == null) {
synchronized (this) {
resultOrError = load(key);
// we can't use cache.computeIfAbsent since this might be recursively call this API
cache.putIfAbsent(key, resultOrError);
}
}
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;
}
}
private Object load(K key) {
Errors errors = new Errors();
V result = null;
try {
result = create(key, errors);
} catch (ErrorsException e) {
errors.merge(e.getErrors());
}
return errors.hasErrors() ? errors : result;
}
}