Trigger.OnceTrigger (core 2.44.0 API)

java.lang.Object
- org.apache.beam.sdk.transforms.windowing.Trigger
- - org.apache.beam.sdk.transforms.windowing.Trigger.OnceTrigger

All Implemented Interfaces:

java.io.Serializable

Direct Known Subclasses:

AfterAll, AfterFirst, AfterPane, AfterProcessingTime, AfterSynchronizedProcessingTime, AfterWatermark.FromEndOfWindow, Never.NeverTrigger

Enclosing class:

Trigger
```
@Internal
public abstract static class Trigger.OnceTrigger
extends Trigger
```
For internal use only; no backwards-compatibility guarantees.
Triggers that are guaranteed to fire at most once should extend Trigger.OnceTrigger rather than the general Trigger class to indicate that behavior.

See Also:

Serialized Form

Nested Class Summary
- Nested classes/interfaces inherited from class org.apache.beam.sdk.transforms.windowing.Trigger
  Trigger.OnceTrigger

Field Summary
- Fields inherited from class org.apache.beam.sdk.transforms.windowing.Trigger
  subTriggers

Constructor Summary

Constructors
Modifier Constructor Description

protected OnceTrigger(java.util.List<Trigger> subTriggers)

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`Trigger.OnceTrigger`	`getContinuationTrigger()`	Return a trigger to use after a `GroupByKey` to preserve the intention of this trigger.
`boolean`	`mayFinish()`	*For internal use only; no backwards-compatibility guarantees.*

Methods inherited from class org.apache.beam.sdk.transforms.windowing.Trigger
equals, getContinuationTrigger, getWatermarkThatGuaranteesFiring, hashCode, isCompatible, orFinally, subTriggers, toString

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - OnceTrigger
```
protected OnceTrigger(java.util.List<Trigger> subTriggers)
```
- Method Detail
  - mayFinish
```
public final boolean mayFinish()
```
    Description copied from class: Trigger
    
    For internal use only; no backwards-compatibility guarantees.
    Indicates whether this trigger may "finish". A top level trigger that finishes can cause data loss, so is rejected by GroupByKey validation.
    
    Specified by:
    
    mayFinish in class Trigger
  - getContinuationTrigger
```
public final Trigger.OnceTrigger getContinuationTrigger()
```
    Description copied from class: Trigger
    
    Return a trigger to use after a GroupByKey to preserve the intention of this trigger. Specifically, triggers that are time based and intended to provide speculative results should continue providing speculative results. Triggers that fire once (or multiple times) should continue firing once (or multiple times).
    If this method is not overridden, its default implementation delegates its behavior to Trigger.getContinuationTrigger(List) which is expected to be implemented by subclasses.
    
    Overrides:
    
    getContinuationTrigger in class Trigger