com.hazelcast.mapreduce.aggregation.PropertyExtractor 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;
import com.hazelcast.spi.annotation.Beta;
import java.io.Serializable;
/**
* The PropertyExtractor interface is used in suppliers to retrieve values from
* input value types and extract or transform them to some other type to be used
* in aggregations.
*
* For Java 6 and 7:
*
* public class EmployeeIntTransformer implements PropertyExtractor<Employee, Integer> {
* public Integer extract(Employee value) {
* return value.getSalaryPerMonth();
* }
* }
*
* Supplier supplier = Supplier.all(new EmployeeIntTransformer());
*
*
* Or in Java 8:
*
* Supplier supplier = Supplier.all((value) -> value.getSalaryPerMonth());
*
*
* @param the input value type
* @param the extracted / transformed value type
* @since 3.3
*/
@Beta
public interface PropertyExtractor
extends Serializable {
/**
* This method is called for every value that is about to be supplied to
* an aggregation (maybe filtered through an {@link com.hazelcast.query.Predicate}
* or {@link com.hazelcast.mapreduce.KeyPredicate}). It is responsible to either
* transform the input value to an type of {@link ValueOut} or to extract an
* attribute of this type.
*
* @param value the input value
* @return the extracted / transformed value
*/
ValueOut extract(ValueIn value);
}