org.apache.flink.streaming.api.functions.windowing

Interface WindowFunction<IN,OUT,KEY,W extends Window>

Type Parameters:

IN - The type of the input value.

OUT - The type of the output value.

KEY - The type of the key.

W - The type of Window that this window function can be applied on.

All Superinterfaces:

Function, Serializable

All Known Implementing Classes:

AggregateApplyWindowFunction, FoldApplyWindowFunction, PassThroughWindowFunction, PythonApplyFunction, ReduceApplyWindowFunction, RichWindowFunction

@Public
public interface WindowFunction<IN,OUT,KEY,W extends Window>
extends Function, Serializable

Base interface for functions that are evaluated over keyed (grouped) windows.

Method Summary

Modifier and Type	Method and Description
void	apply(KEY key, W window, Iterable<IN> input, Collector<OUT> out) Evaluates the window and outputs none or several elements.

Method Detail

apply

void apply(KEY key,
           W window,
           Iterable<IN> input,
           Collector<OUT> out)
    throws Exception

Evaluates the window and outputs none or several elements.

Parameters:

key - The key for which this window is evaluated.

window - The window that is being evaluated.

input - The elements in the window being evaluated.

out - A collector for emitting elements.

Throws:

Exception - The function may throw exceptions to fail the program and trigger recovery.