/hazelcast/src/main/java/com/hazelcast/merge/MergePolicy.java

 1/*
 2 * Copyright (c) 2008-2013, Hazelcast, Inc. All Rights Reserved.
 3 *
 4 * Licensed under the Apache License, Version 2.0 (the "License");
 5 * you may not use this file except in compliance with the License.
 6 * You may obtain a copy of the License at
 7 *
 8 * http://www.apache.org/licenses/LICENSE-2.0
 9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.hazelcast.merge;
18
19import com.hazelcast.core.MapEntry;
20
21public interface MergePolicy {
22
23    public static final Object REMOVE_EXISTING = new Object();
24
25    /**
26     * Returns the value of the entry after the merge
27     * of entries with the same key. Returning value can be
28     * You should consider the case where existingEntry is null.
29     *
30     * @param mapName       name of the map
31     * @param mergingEntry  entry merging into the destination cluster
32     * @param existingEntry existing entry in the destination cluster
33     * @return final value of the entry. If returns null then no change on the entry.
34     */
35    Object merge(String mapName, MapEntry mergingEntry, MapEntry existingEntry);
36}