Package org.apache.flink.streaming.api.windowing.assigners

Class WindowAssigner<T,W extends Window>

java.lang.Object

org.apache.flink.streaming.api.windowing.assigners.WindowAssigner<T,W>

Type Parameters:

T - The type of elements that this WindowAssigner can assign windows to.

W - The type of Window that this assigner assigns.

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

GlobalWindows, MergingWindowAssigner, SlidingEventTimeWindows, SlidingProcessingTimeWindows, TumblingEventTimeWindows, TumblingProcessingTimeWindows

@PublicEvolving
public abstract class WindowAssigner<T,W extends Window>
extends Object
implements Serializable

A WindowAssigner assigns zero or more Windows to an element.

In a window operation, elements are grouped by their key (if available) and by the windows to which it was assigned. The set of elements with the same key and window is called a pane. When a Trigger decides that a certain pane should fire the WindowFunction is applied to produce output elements for that pane.

See Also:

• Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	WindowAssigner.WindowAssignerContext	A context provided to the WindowAssigner that allows it to query the current processing time.

Constructor Summary

Constructors

Constructor	Description
WindowAssigner()

Method Summary

Modifier and Type	Method	Description
abstract Collection<W>	assignWindows(T element, long timestamp, WindowAssigner.WindowAssignerContext context)	Returns a Collection of windows that should be assigned to the element.
abstract Trigger<T,W>	getDefaultTrigger()	Returns the default trigger associated with this WindowAssigner.
abstract org.apache.flink.api.common.typeutils.TypeSerializer<W>	getWindowSerializer(org.apache.flink.api.common.ExecutionConfig executionConfig)	Returns a TypeSerializer for serializing windows that are assigned by this WindowAssigner.
abstract boolean	isEventTime()	Returns true if elements are assigned to windows based on event time, false otherwise.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

WindowAssigner

public WindowAssigner()

Method Details

assignWindows

public abstract Collection<W> assignWindows(T element,
 long timestamp,
 WindowAssigner.WindowAssignerContext context)

Returns a Collection of windows that should be assigned to the element.

Parameters:

element - The element to which windows should be assigned.

timestamp - The timestamp of the element.

context - The WindowAssigner.WindowAssignerContext in which the assigner operates.

getDefaultTrigger

public abstract Trigger<T,W> getDefaultTrigger()

Returns the default trigger associated with this WindowAssigner.

1. If you override getDefaultTrigger(), the getDefaultTrigger() will be invoked and the getDefaultTrigger(StreamExecutionEnvironment env) won't be invoked. 2. If you don't override getDefaultTrigger(), the getDefaultTrigger(StreamExecutionEnvironment env) will be invoked in the default implementation of the getDefaultTrigger().

getWindowSerializer

public abstract org.apache.flink.api.common.typeutils.TypeSerializer<W> getWindowSerializer(org.apache.flink.api.common.ExecutionConfig executionConfig)

Returns a TypeSerializer for serializing windows that are assigned by this WindowAssigner.

isEventTime

public abstract boolean isEventTime()

Returns true if elements are assigned to windows based on event time, false otherwise.