/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.flink.api.java.functions;
import java.util.Iterator;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.api.common.functions.RichFlatMapFunction;
import org.apache.flink.util.Collector;
/**
* A convenience variant of the {@link org.apache.flink.api.common.functions.RichFlatMapFunction} that returns elements through an iterator, rather then
* through a collector. In all other respects, it behaves exactly like the FlatMapFunction.
* <p>
* The function 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.
*/
@PublicEvolving
public abstract class FlatMapIterator<IN, OUT> extends RichFlatMapFunction<IN, OUT> {
private static final long serialVersionUID = 1L;
/**
* The core method of the function. Takes an element from the input data set and transforms
* it into zero, one, or more elements.
*
* @param value The input value.
* @return An iterator over the returned elements.
*
* @throws Exception This method may throw exceptions. Throwing an exception will cause the operation
* to fail and may trigger recovery.
*/
public abstract Iterator<OUT> flatMap(IN value) throws Exception;
// --------------------------------------------------------------------------------------------
/**
* Delegates calls to the {@link #flatMap(Object)} method.
*/
@Override
public final void flatMap(IN value, Collector<OUT> out) throws Exception {
for (Iterator<OUT> iter = flatMap(value); iter.hasNext(); ) {
out.collect(iter.next());
}
}
}