WindowProcessFunction (Flink : DataStream : API 2.1.0 API)

All Superinterfaces:

org.apache.flink.api.common.functions.Function, ProcessFunction, Serializable

All Known Subinterfaces:

OneInputWindowStreamProcessFunction<IN,OUT>, TwoInputNonBroadcastWindowStreamProcessFunction<IN1,IN2,OUT>, TwoOutputWindowStreamProcessFunction<IN,OUT1,OUT2>
```
@Experimental
public interface WindowProcessFunction
extends ProcessFunction
```
Base interface for functions evaluated over windows, providing callback functions for various stages of the window's lifecycle.

Method Summary

All Methods Instance Methods Default Methods
Modifier and Type	Method	Description
`default Set<org.apache.flink.api.common.state.StateDeclaration>`	`useWindowStates()`	Explicitly declares states that are bound to the window.

Methods inherited from interface org.apache.flink.datastream.api.function.ProcessFunction
close, declareWatermarks, usesStates

- Method Detail
  - useWindowStates
```
default Set<org.apache.flink.api.common.state.StateDeclaration> useWindowStates()
```
    Explicitly declares states that are bound to the window. Each specific window state must be declared in this method before it can be used.
    
    Returns:
    
    all declared window states used by this process function.