MapElements (Google Cloud Dataflow SDK 1.9.1 API)

Google Cloud Dataflow SDK for Java, version 1.9.1

Warning: Dataflow SDK 1.x for Java is unsupported as of October 16, 2018. After August 12, 2020, you can use unsupported SDKs temporarily while you upgrade your pipelines. For more information, see Using an unsupported SDK.

For information on migrating from the 1.x SDK, see Migrating from Dataflow SDK 1.x for Java.

Note: If you are using Cloud Dataflow SDK version 2.x, see the Apache Beam API reference documentation.

com.google.cloud.dataflow.sdk.transforms

Class MapElements<InputT,OutputT>

• java.lang.Object
• • com.google.cloud.dataflow.sdk.transforms.PTransform<PCollection<InputT>,PCollection<OutputT>>
  • • com.google.cloud.dataflow.sdk.transforms.MapElements<InputT,OutputT>

• All Implemented Interfaces:

  HasDisplayData, Serializable

  ---

  
  

  public class MapElements<InputT,OutputT>
  extends PTransform<PCollection<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.MissingOutputTypeDescriptor<InputT,OutputT> An intermediate builder for a MapElements transform.

  • Field Summary

    • Fields inherited from class com.google.cloud.dataflow.sdk.transforms.PTransform

      name

  • Method Summary

    All Methods Static Methods Instance Methods Concrete Methods 

    Modifier and Type	Method and Description
    PCollection<OutputT>	apply(PCollection<InputT> input) Applies this PTransform on the given InputT, and returns its Output.
    void	populateDisplayData(DisplayData.Builder builder) Register display data for the given transform or component.
    static <InputT,OutputT> MapElements.MissingOutputTypeDescriptor<InputT,OutputT>	via(SerializableFunction<InputT,OutputT> fn) For a SerializableFunction<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.
    static <InputT,OutputT> MapElements<InputT,OutputT>	via(SimpleFunction<InputT,OutputT> fn) For a SimpleFunction<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.

    • Methods inherited from class com.google.cloud.dataflow.sdk.transforms.PTransform

      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> MapElements.MissingOutputTypeDescriptor<InputT,OutputT> via(SerializableFunction<InputT,OutputT> fn)

      For a SerializableFunction<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 of use in Java 8:

      
       PCollection<Integer> wordLengths = words.apply(
           MapElements.via((String word) -> word.length())
               .withOutputType(new TypeDescriptor<Integer>() {});
       

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

    • via

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

      For a SimpleFunction<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.

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

    • apply

      public PCollection<OutputT> apply(PCollection<InputT> input)

      Description copied from class: PTransform
      Applies this PTransform on the given InputT, and returns its Output.

      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).

      The default implementation throws an exception. A derived class must either implement apply, or else each runner must supply a custom implementation via PipelineRunner.apply(com.google.cloud.dataflow.sdk.transforms.PTransform<InputT, OutputT>, InputT).

      Overrides:

      apply in class PTransform<PCollection<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<InputT>,PCollection<OutputT>>

      Parameters:

      builder - The builder to populate with display data.

      See Also:

      HasDisplayData