com.hazelcast.replicatedmap.merge.PutIfAbsentMapMergePolicy Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2017, 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.replicatedmap.merge;
import com.hazelcast.nio.ObjectDataInput;
import com.hazelcast.nio.ObjectDataOutput;
import com.hazelcast.nio.serialization.IdentifiedDataSerializable;
import com.hazelcast.replicatedmap.impl.operation.ReplicatedMapDataSerializerHook;
import com.hazelcast.replicatedmap.impl.record.ReplicatedMapEntryView;
import java.io.IOException;
/**
* PutIfAbsentMapMergePolicy causes the merging entry to be merged from source to destination map
* if it does not exist in the destination map.
*/
public final class PutIfAbsentMapMergePolicy implements ReplicatedMapMergePolicy, IdentifiedDataSerializable {
/**
* Single instance of this class
*/
public static final PutIfAbsentMapMergePolicy INSTANCE = new PutIfAbsentMapMergePolicy();
private PutIfAbsentMapMergePolicy() {
}
@Override
public Object merge(String mapName, ReplicatedMapEntryView mergingEntry, ReplicatedMapEntryView existingEntry) {
if (existingEntry.getValue() == null) {
return mergingEntry.getValue();
}
return existingEntry.getValue();
}
@Override
public int getFactoryId() {
return ReplicatedMapDataSerializerHook.F_ID;
}
@Override
public int getId() {
return ReplicatedMapDataSerializerHook.PUT_IF_ABSENT_MERGE_POLICY;
}
@Override
public void writeData(ObjectDataOutput out) throws IOException {
}
@Override
public void readData(ObjectDataInput in) throws IOException {
}
private Object readResolve() {
return INSTANCE;
}
}