com.hazelcast.core.MapLoader Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2013, 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.core;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
/**
* Hazelcast distributed map implementation is an in-memory data store but
* it can be backed by any type of data store such as RDBMS, OODBMS, or simply
* a file based data store.
*
* IMap.get(key) normally returns the value that is available in-memory. If the entry
* doesn't exist in-memory, Hazelcast returns null. If a Loader implementation
* is provided then, instead of returning null, Hazelcast will load the unknown entry by
* calling the implementation's load (key) or loadAll(keys) methods. Loaded entries
* will be placed into the distributed map and they will stay in-memory until they are
* explicitly removed or implicitly evicted (if eviction is configured).
*/
public interface MapLoader {
/**
* Loads the value of a given key. If distributed map doesn't contain the value
* for the given key then Hazelcast will call implementation's load (key) method
* to obtain the value. Implementation can use any means of loading the given key;
* such as an O/R mapping tool, simple SQL or reading a file etc.
*
* @param key
* @return value of the key
*/
V load(K key);
/**
* Loads given keys. This is batch load operation so that implementation can
* optimize the multiple loads.
*
* @param keys keys of the values entries to load
* @return map of loaded key-value pairs.
*/
Map loadAll(Collection keys);
/**
* Loads all of the keys from the store.
*
* @return all the keys
*/
Set loadAllKeys();
}