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package org.cache2k.integration;
/*
* #%L
* cache2k API
* %%
* Copyright (C) 2000 - 2016 headissue GmbH, Munich
* %%
* 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.
* #L%
*/
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.Executor;
/**
* Retrieves or generates a value to load into the cache.
*
* The alternative loader interface {@link AdvancedCacheLoader} provides the loader
* with the current cache value.
*
* @author Jens Wilke
* @see AdvancedCacheLoader
*/
public abstract class CacheLoader {
/**
* Retrieves or generates data based on the key.
*
* Concurrent load requests on the same key will be blocked.
*
*
This method may not mutate the cache contents directly.
*
*
API rationale: This method declares an exception to allow any unhandled
* exceptions of the loader implementation to just pass through. Since the cache
* needs to catch an deal with loader exceptions in any way, this saves otherwise
* necessary try/catch clauses in the loader.
*
* @param key the non-null key to provide the value for.
* @return value to be associated with the key. If the cache permits null values
* a null is associated with the key.
* @throws Exception Unhandled exception from the loader. The exception will be
* handled by the cache based on its configuration.
*/
public abstract V load(K key) throws Exception;
/**
* Loads multiple values to the cache.
*
*
This method may not mutate the cache contents directly.
*
*
The method is provided to complete the API. At the moment cache2k is not
* using it. Please see the road map.
*
* @param keys set of keys for the values to be loaded
* @param executor an executor for concurrent loading
* @return The loaded values. A key may map to null if the cache permits null values.
* @throws Exception Unhandled exception from the loader. The exception will be
* handled by the cache based on its configuration. If an exception happens
* the cache will retry the load with the single value load method.
*/
public Map loadAll(Iterable keys, Executor executor) throws Exception {
throw new UnsupportedOperationException();
}
}