com.hazelcast.mapreduce.aggregation.impl.SupplierConsumingMapper 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.mapreduce.aggregation.impl;
import com.hazelcast.mapreduce.Context;
import com.hazelcast.mapreduce.Mapper;
import com.hazelcast.mapreduce.aggregation.Supplier;
import com.hazelcast.nio.ObjectDataInput;
import com.hazelcast.nio.ObjectDataOutput;
import com.hazelcast.nio.serialization.IdentifiedDataSerializable;
import java.io.IOException;
import java.util.Map;
/**
* The default mapper implementation for most (but not DistinctValues) aggregations.
*
* @param the input key type
* @param the input value type
* @param the output value type
*/
@edu.umd.cs.findbugs.annotations.SuppressWarnings("SE_NO_SERIALVERSIONID")
class SupplierConsumingMapper
implements Mapper, IdentifiedDataSerializable {
private transient SimpleEntry entry = new SimpleEntry();
private Supplier supplier;
SupplierConsumingMapper() {
}
SupplierConsumingMapper(Supplier supplier) {
this.supplier = supplier;
}
@Override
public void map(Key key, ValueIn value, Context context) {
entry.key = key;
entry.value = value;
ValueOut valueOut = supplier.apply(entry);
if (valueOut != null) {
context.emit(key, valueOut);
}
}
@Override
public int getFactoryId() {
return AggregationsDataSerializerHook.F_ID;
}
@Override
public int getId() {
return AggregationsDataSerializerHook.SUPPLIER_CONSUMING_MAPPER;
}
@Override
public void writeData(ObjectDataOutput out)
throws IOException {
out.writeObject(supplier);
}
@Override
public void readData(ObjectDataInput in)
throws IOException {
supplier = in.readObject();
}
/**
* Internal implementation of an map entry with changeable value to prevent
* to much object allocation while supplying
*
* @param key type
* @param value type
*/
private static final class SimpleEntry
implements Map.Entry {
private K key;
private V value;
@Override
public K getKey() {
return key;
}
@Override
public V getValue() {
return value;
}
@Override
public V setValue(V value) {
throw new UnsupportedOperationException();
}
}
}