Package org.apache.beam.sdk.transforms

Class MapElements<InputT,​OutputT>

    • 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 <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()));

      • 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