ProcessFunction (Flink : DataStream : API 2.1.0 API)

All Superinterfaces:

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

All Known Subinterfaces:

EventTimeProcessFunction, OneInputEventTimeStreamProcessFunction<IN,OUT>, OneInputStreamProcessFunction<IN,OUT>, OneInputWindowStreamProcessFunction<IN,OUT>, TwoInputBroadcastEventTimeStreamProcessFunction<IN1,IN2,OUT>, TwoInputBroadcastStreamProcessFunction<IN1,IN2,OUT>, TwoInputNonBroadcastEventTimeStreamProcessFunction<IN1,IN2,OUT>, TwoInputNonBroadcastStreamProcessFunction<IN1,IN2,OUT>, TwoInputNonBroadcastWindowStreamProcessFunction<IN1,IN2,OUT>, TwoOutputEventTimeStreamProcessFunction<IN,OUT1,OUT2>, TwoOutputStreamProcessFunction<IN,OUT1,OUT2>, TwoOutputWindowStreamProcessFunction<IN,OUT1,OUT2>, WindowProcessFunction
```
@Experimental
public interface ProcessFunction
extends org.apache.flink.api.common.functions.Function
```
Base class for all user defined process functions.

Method Summary

All Methods Instance Methods Default Methods
Modifier and Type	Method	Description
`default void`	`close()`	Tear-down method for the user code.
`default Set<? extends org.apache.flink.api.common.watermark.WatermarkDeclaration>`	`declareWatermarks()`	Explicitly declare watermarks upfront.
`default Set<org.apache.flink.api.common.state.StateDeclaration>`	`usesStates()`	Explicitly declares states upfront.

- Method Detail
  - usesStates
```
default Set<org.apache.flink.api.common.state.StateDeclaration> usesStates()
```
    Explicitly declares states upfront. Each specific state must be declared in this method before it can be used.
    
    Returns:
    
    all declared states used by this process function.
  - declareWatermarks
```
default Set<? extends org.apache.flink.api.common.watermark.WatermarkDeclaration> declareWatermarks()
```
    Explicitly declare watermarks upfront. Each specific watermark must be declared in this method before it can be used.
    
    Returns:
    
    all watermark declarations used by this application.
  - close
```
default void close()
            throws Exception
```
    Tear-down method for the user code. It is called after the last call to the main working methods (e.g. processRecord).
    This method can be used for clean up work.
    
    Throws:
    
    Exception - Implementations may forward exceptions, which are caught by the runtime. When the runtime catches an exception, it aborts the task and lets the fail-over logic decide whether to retry the task execution.