org.apache.beam.sdk.transforms

Class FlatMapElements<InputT,OutputT>

java.lang.Object

org.apache.beam.sdk.transforms.PTransform<PCollection<? extends InputT>,PCollection<OutputT>>

org.apache.beam.sdk.transforms.FlatMapElements<InputT,OutputT>

All Implemented Interfaces:

java.io.Serializable, HasDisplayData

public class FlatMapElements<InputT,OutputT>
extends PTransform<PCollection<? extends InputT>,PCollection<OutputT>>

PTransforms for mapping a simple function that returns iterables over the elements of a PCollection and merging the results.

See Also:

Serialized Form

Field Summary

Fields inherited from class org.apache.beam.sdk.transforms.PTransform

name

Method Summary

Modifier and Type	Method and Description
PCollection<OutputT>	expand(PCollection<? extends InputT> input) Override this method to specify how this PTransform should be expanded on the given InputT.
static <OutputT> FlatMapElements<?,OutputT>	into(TypeDescriptor<OutputT> outputType) Returns a new FlatMapElements transform with the given type descriptor for the output type, but the mapping function yet to be specified using via(SerializableFunction).
void	populateDisplayData(DisplayData.Builder builder) Register display data for the given transform or component.
<NewInputT> FlatMapElements<NewInputT,OutputT>	via(Contextful<Contextful.Fn<NewInputT,java.lang.Iterable<OutputT>>> fn) Like via(SerializableFunction), but allows access to additional context.
<NewInputT> FlatMapElements<NewInputT,OutputT>	via(SerializableFunction<NewInputT,? extends java.lang.Iterable<OutputT>> fn) For a SerializableFunction<InputT, ? extends Iterable<OutputT>> fn, returns a PTransform that applies fn to every element of the input PCollection<InputT> and outputs all of the elements to the output PCollection<OutputT>.
static <InputT,OutputT> FlatMapElements<InputT,OutputT>	via(SimpleFunction<? super InputT,? extends java.lang.Iterable<OutputT>> fn) For a SimpleFunction<InputT, ? extends Iterable<OutputT>> fn, return a PTransform that applies fn to every element of the input PCollection<InputT> and outputs all of the elements to the output PCollection<OutputT>.

Methods inherited from class org.apache.beam.sdk.transforms.PTransform

compose, getAdditionalInputs, getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, toString, validate

Methods inherited from class java.lang.Object

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

Method Detail

via

public static <InputT,OutputT> FlatMapElements<InputT,OutputT> via(SimpleFunction<? super InputT,? extends java.lang.Iterable<OutputT>> fn)

For a SimpleFunction<InputT, ? extends Iterable<OutputT>> fn, return a PTransform that applies fn to every element of the input PCollection<InputT> and outputs all of the elements to the output PCollection<OutputT>.

This overload is intended primarily for use in Java 7. In Java 8, the overload via(SerializableFunction) supports use of lambda for greater concision.

Example of use in Java 7:

 PCollection<String> lines = ...;
 PCollection<String> words = lines.apply(FlatMapElements.via(
     new SimpleFunction<String, List<String>>() {
       public Integer apply(String line) {
         return Arrays.asList(line.split(" "));
       }
     });
 

To use a Java 8 lambda, see via(SerializableFunction).

into

public static <OutputT> FlatMapElements<?,OutputT> into(TypeDescriptor<OutputT> outputType)

Returns a new FlatMapElements transform with the given type descriptor for the output type, but the mapping function yet to be specified using via(SerializableFunction).

via

public <NewInputT> FlatMapElements<NewInputT,OutputT> via(SerializableFunction<NewInputT,? extends java.lang.Iterable<OutputT>> fn)

For a SerializableFunction<InputT, ? extends Iterable<OutputT>> fn, returns a PTransform that applies fn to every element of the input PCollection<InputT> and outputs all of the elements to the output PCollection<OutputT>.

Example of use in Java 8:

 PCollection<String> words = lines.apply(
     FlatMapElements.into(TypeDescriptors.strings())
                    .via((String line) -> Arrays.asList(line.split(" ")))
 

In Java 7, the overload via(SimpleFunction) is more concise as the output type descriptor need not be provided.

via

@Experimental(value=CONTEXTFUL)
public <NewInputT> FlatMapElements<NewInputT,OutputT> via(Contextful<Contextful.Fn<NewInputT,java.lang.Iterable<OutputT>>> fn)

Like via(SerializableFunction), but allows access to additional context.

expand

public PCollection<OutputT> expand(PCollection<? extends InputT> input)

Description copied from class: PTransform

Override this method to specify how this PTransform should be expanded on the given InputT.

NOTE: This method should not be called directly. Instead apply the PTransform should be applied to the InputT using the apply method.

Composite transforms, which are defined in terms of other transforms, should return the output of one of the composed transforms. Non-composite transforms, which do not apply any transforms internally, should return a new unbound output and register evaluators (via backend-specific registration methods).

Specified by:

expand in class PTransform<PCollection<? extends InputT>,PCollection<OutputT>>

populateDisplayData

public void populateDisplayData(DisplayData.Builder builder)

Description copied from class: PTransform

Register display data for the given transform or component.

populateDisplayData(DisplayData.Builder) is invoked by Pipeline runners to collect display data via DisplayData.from(HasDisplayData). Implementations may call super.populateDisplayData(builder) in order to register display data in the current namespace, but should otherwise use subcomponent.populateDisplayData(builder) to use the namespace of the subcomponent.

By default, does not register any display data. Implementors may override this method to provide their own display data.

Specified by:

populateDisplayData in interface HasDisplayData

Overrides:

populateDisplayData in class PTransform<PCollection<? extends InputT>,PCollection<OutputT>>

Parameters:

builder - The builder to populate with display data.

See Also:

HasDisplayData