org.apache.flink.streaming.tests

Class SemanticsCheckMapper

java.lang.Object

org.apache.flink.api.common.functions.AbstractRichFunction

org.apache.flink.api.common.functions.RichFlatMapFunction<Event,String>

org.apache.flink.streaming.tests.SemanticsCheckMapper

All Implemented Interfaces:

Serializable, FlatMapFunction<Event,String>, Function, RichFunction

public class SemanticsCheckMapper
extends RichFlatMapFunction<Event,String>

This mapper validates exactly-once and at-least-once semantics in connection with SequenceGeneratorSource.

See Also:

Serialized Form

Method Summary

Modifier and Type	Method and Description
void	flatMap(Event event, Collector<String> out) The core method of the FlatMapFunction.
void	open(OpenContext openContext) Initialization method for the function.

Methods inherited from class org.apache.flink.api.common.functions.AbstractRichFunction

close, getIterationRuntimeContext, getRuntimeContext, open, setRuntimeContext

Methods inherited from class java.lang.Object

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

Method Detail

flatMap

public void flatMap(Event event,
                    Collector<String> out)
             throws Exception

Description copied from interface: FlatMapFunction

The core method of the FlatMapFunction. Takes an element from the input data set and transforms it into zero, one, or more elements.

Specified by:

flatMap in interface FlatMapFunction<Event,String>

Specified by:

flatMap in class RichFlatMapFunction<Event,String>

Parameters:

event - The input value.

out - The collector for returning result values.

Throws:

Exception - This method may throw exceptions. Throwing an exception will cause the operation to fail and may trigger recovery.

open

public void open(OpenContext openContext)

Description copied from interface: RichFunction

Initialization method for the function. It is called before the actual working methods (like map or join) and thus suitable for one time setup work. For functions that are part of an iteration, this method will be invoked at the beginning of each iteration superstep.

The openContext object passed to the function can be used for configuration and initialization. The openContext contains some necessary information that were configured on the function in the program composition.

 public class MyFilter extends RichFilterFunction<String> {

     private String searchString;

     public void open(OpenContext openContext) {
         // initialize the value of searchString
     }

     public boolean filter(String value) {
         return value.equals(searchString);
     }
 }
 

By default, this method does nothing.

1. If you implement open(OpenContext openContext), the open(OpenContext openContext) will be invoked and the open(Configuration parameters) won't be invoked. 2. If you don't implement open(OpenContext openContext), the open(Configuration parameters) will be invoked in the default implementation of the open(OpenContext openContext).

Parameters:

openContext - The context containing information about the context in which the function is opened.