/*
* 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.streaming.api.functions.windowing;
import java.util.Collections;
import org.apache.flink.annotation.Internal;
import org.apache.flink.api.common.functions.ReduceFunction;
import org.apache.flink.api.java.operators.translation.WrappingFunction;
import org.apache.flink.streaming.api.windowing.windows.Window;
import org.apache.flink.util.Collector;
/**
* Internal {@link AllWindowFunction} that is used for implementing a fold on a window configuration
* that only allows {@link AllWindowFunction} and cannot directly execute a {@link ReduceFunction}.
*/
@Internal
public class ReduceApplyAllWindowFunction<W extends Window, T, R>
extends WrappingFunction<AllWindowFunction<T, R, W>>
implements AllWindowFunction<T, R, W> {
private static final long serialVersionUID = 1L;
private final ReduceFunction<T> reduceFunction;
public ReduceApplyAllWindowFunction(ReduceFunction<T> reduceFunction,
AllWindowFunction<T, R, W> windowFunction) {
super(windowFunction);
this.reduceFunction = reduceFunction;
}
@Override
public void apply(W window, Iterable<T> input, Collector<R> out) throws Exception {
T curr = null;
for (T val: input) {
if (curr == null) {
curr = val;
} else {
curr = reduceFunction.reduce(curr, val);
}
}
wrappedFunction.apply(window, Collections.singletonList(curr), out);
}
}