ProcessFunction (Flink : DataStream : API 1.20.0-cp1 API)

All Superinterfaces:

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

All Known Subinterfaces:

OneInputStreamProcessFunction<IN,OUT>, TwoInputBroadcastStreamProcessFunction<IN1,IN2,OUT>, TwoInputNonBroadcastStreamProcessFunction<IN1,IN2,OUT>, TwoOutputStreamProcessFunction<IN,OUT1,OUT2>
```
@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 void`	`open()`	Initialization method for the function.
`default Set<org.apache.flink.api.common.state.StateDeclaration>`	`usesStates()`	Explicitly declares states upfront.

- Method Detail
  - open
```
default void open()
           throws Exception
```
    Initialization method for the function. It is called before the actual working methods (like processRecord) and thus suitable for one time setup work.
    By default, this method does nothing.
    
    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.
  - 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.
  - 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.