org.apache.beam.sdk.transforms

Class MapElements<InputT,OutputT>

java.lang.Object

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

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

All Implemented Interfaces:

java.io.Serializable, HasDisplayData

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

PTransforms for mapping a simple function over the elements of a PCollection.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	MapElements.MapWithFailures<InputT,OutputT,FailureT> A PTransform that adds exception handling to MapElements.

Field Summary

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

annotations, name, resourceHints

Method Summary

Modifier and Type	Method and Description
<NewFailureT> MapElements.MapWithFailures<InputT,OutputT,NewFailureT>	exceptionsInto(TypeDescriptor<NewFailureT> failureTypeDescriptor) Returns a new MapElements.MapWithFailures transform that catches exceptions raised while mapping elements, with the given type descriptor used for the failure collection but the exception handler yet to be specified using MapElements.MapWithFailures.exceptionsVia(ProcessFunction).
<FailureT> MapElements.MapWithFailures<InputT,OutputT,FailureT>	exceptionsVia(InferableFunction<WithFailures.ExceptionElement<InputT>,FailureT> exceptionHandler) Returns a new MapElements.MapWithFailures transform that catches exceptions raised while mapping elements, passing the raised exception instance and the input element being processed through the given exceptionHandler and emitting the result to a failure collection.
PCollection<OutputT>	expand(PCollection<? extends InputT> input) Override this method to specify how this PTransform should be expanded on the given InputT.
static <OutputT> MapElements<?,OutputT>	into(TypeDescriptor<OutputT> outputType) Returns a new MapElements transform with the given type descriptor for the output type, but the mapping function yet to be specified using via(ProcessFunction).
void	populateDisplayData(DisplayData.Builder builder) Register display data for the given transform or component.
<NewInputT> MapElements<NewInputT,OutputT>	via(Contextful<Contextful.Fn<NewInputT,OutputT>> fn) Like via(ProcessFunction), but supports access to context, such as side inputs.
static <InputT,OutputT> MapElements<InputT,OutputT>	via(InferableFunction<InputT,OutputT> fn) For InferableFunction<InputT, OutputT> fn, returns a PTransform that takes an input PCollection<InputT> and returns a PCollection<OutputT> containing fn.apply(v) for every element v in the input.
<NewInputT> MapElements<NewInputT,OutputT>	via(ProcessFunction<NewInputT,OutputT> fn) For a ProcessFunction<InputT, OutputT> fn and output type descriptor, returns a PTransform that takes an input PCollection<InputT> and returns a PCollection<OutputT> containing fn.apply(v) for every element v in the input.
<NewInputT> MapElements<NewInputT,OutputT>	via(SerializableFunction<NewInputT,OutputT> fn) Binary compatibility adapter for via(ProcessFunction).
static <InputT,OutputT> MapElements<InputT,OutputT>	via(SimpleFunction<InputT,OutputT> fn) Binary compatibility adapter for via(InferableFunction).

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

addAnnotation, compose, compose, getAdditionalInputs, getAnnotations, getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, getResourceHints, setResourceHints, toString, validate, 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> MapElements<InputT,OutputT> via(InferableFunction<InputT,OutputT> fn)

For InferableFunction<InputT, OutputT> fn, returns a PTransform that takes an input PCollection<InputT> and returns a PCollection<OutputT> containing fn.apply(v) for every element v in the input.

InferableFunction has the advantage of providing type descriptor information, but it is generally more convenient to specify output type via into(TypeDescriptor), and provide the mapping as a lambda expression to via(ProcessFunction).

Example usage:

 PCollection<String> words = ...;
 PCollection<Integer> wordsPerLine = words.apply(MapElements.via(
     new InferableFunction<String, Integer>() {
       public Integer apply(String word) throws Exception {
         return word.length();
       }
     }));
 

via

public static <InputT,OutputT> MapElements<InputT,OutputT> via(SimpleFunction<InputT,OutputT> fn)

Binary compatibility adapter for via(InferableFunction).

into

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

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

via

public <NewInputT> MapElements<NewInputT,OutputT> via(ProcessFunction<NewInputT,OutputT> fn)

For a ProcessFunction<InputT, OutputT> fn and output type descriptor, returns a PTransform that takes an input PCollection<InputT> and returns a PCollection<OutputT> containing fn.apply(v) for every element v in the input.

Example usage:

 PCollection<Integer> wordLengths = words.apply(
     MapElements.into(TypeDescriptors.integers())
                .via((String word) -> word.length()));
 

via

public <NewInputT> MapElements<NewInputT,OutputT> via(SerializableFunction<NewInputT,OutputT> fn)

Binary compatibility adapter for via(ProcessFunction).

via

public <NewInputT> MapElements<NewInputT,OutputT> via(Contextful<Contextful.Fn<NewInputT,OutputT>> fn)

Like via(ProcessFunction), but supports access to context, such as side inputs.

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

exceptionsInto

public <NewFailureT> MapElements.MapWithFailures<InputT,OutputT,NewFailureT> exceptionsInto(TypeDescriptor<NewFailureT> failureTypeDescriptor)

Returns a new MapElements.MapWithFailures transform that catches exceptions raised while mapping elements, with the given type descriptor used for the failure collection but the exception handler yet to be specified using MapElements.MapWithFailures.exceptionsVia(ProcessFunction).

See WithFailures documentation for usage patterns of the returned WithFailures.Result.

exceptionsVia

public <FailureT> MapElements.MapWithFailures<InputT,OutputT,FailureT> exceptionsVia(InferableFunction<WithFailures.ExceptionElement<InputT>,FailureT> exceptionHandler)

Returns a new MapElements.MapWithFailures transform that catches exceptions raised while mapping elements, passing the raised exception instance and the input element being processed through the given exceptionHandler and emitting the result to a failure collection.

This method takes advantage of the type information provided by InferableFunction, meaning that a call to exceptionsInto(TypeDescriptor) may not be necessary.

See WithFailures documentation for usage patterns of the returned WithFailures.Result.

Example usage:

 Result<PCollection<String>, String>> result = words.apply(
     MapElements
         .into(TypeDescriptors.integers())
         .via((String word) -> 1 / word.length)  // Could throw ArithmeticException
         .exceptionsVia(new WithFailures.ExceptionAsMapHandler<String>() {}));
 PCollection<Integer> output = result.output();
 PCollection<String> failures = result.failures();