/***********************************************************************************************************************
*
* Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
*
* 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 eu.stratosphere.api.java.functions;
import eu.stratosphere.api.common.functions.AbstractFunction;
import eu.stratosphere.api.common.functions.GenericMap;
/**
* The abstract base class for Map functions. Map functions take elements and transform them,
* element wise. A Map function always produces a single result element for each input element.
* Typical applications are parsing elements, converting data types, or projecting out fields.
* Operations that produce multiple result elements from a single input element can be implemented
* using the {@link FlatMapFunction}.
* <p>
* The basic syntax for using a MapFunction is as follows:
* <pre><blockquote>
* DataSet<X> input = ...;
*
* DataSet<Y> result = input.map(new MyMapFunction());
* </blockquote></pre>
* <p>
* Like all functions, the MapFunction needs to be serializable, as defined in {@link java.io.Serializable}.
*
* @param <IN> Type of the input elements.
* @param <OUT> Type of the returned elements.
*/
public abstract class MapFunction<IN, OUT> extends AbstractFunction implements GenericMap<IN, OUT> {
private static final long serialVersionUID = 1L;
/**
* The core method of the MapFunction. Takes an element from the input data set and transforms
* it into another element.
*
* @param value The input value.
* @return The value produced by the map function from the input value.
*
* @throws Exception This method may throw exceptions. Throwing an exception will cause the operation
* to fail and may trigger recovery.
*/
@Override
public abstract OUT map(IN value) throws Exception;
}