com.hazelcast.cache.CacheMergePolicy Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2016, Hazelcast, Inc. All Rights Reserved.
*
* 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.hazelcast.cache;
import java.io.Serializable;
/**
*
* Policy for merging cache entries.
*
*
*
* Passed {@link CacheEntryView} instances wraps the key and value as their original types
* with convertion to object from their storage types. If user doesn't need to original types of key and value,
* (s)he should use {@link StorageTypeAwareCacheMergePolicy} which is sub-type of this interface.
*
*/
public interface CacheMergePolicy extends Serializable {
/**
*
* Selects one of the merging and existing cache entries to be merged.
*
*
*
* Note that as mentioned also in arguments, the {@link CacheEntryView} instance that represents existing cache entry
* may be null if there is no existing entry for the specified key in the the {@link CacheEntryView} instance
* that represents merging cache entry.
*
*
* @param cacheName name of the cache
* @param mergingEntry {@link CacheEntryView} instance that has cache entry to be merged
* @param existingEntry {@link CacheEntryView} instance that has existing cache entry.
* This entry may be null if there is no existing cache entry.
* @return the selected value for merging
*/
Object merge(String cacheName, CacheEntryView mergingEntry, CacheEntryView existingEntry);
}