Package org.apache.beam.sdk.transforms

Class MapValues<K,​V1,​V2>

  • Type Parameters:
    V1 - the type of the values in the input PCollection
    V2 - the type of the elements in the output PCollection
    All Implemented Interfaces:
    java.io.Serializable, HasDisplayData
    public class MapValues<K,​V1,​V2>
extends PTransform<PCollection<KV<K,​V1>>,​PCollection<KV<K,​V2>>>
    MapValues maps a SerializableFunction<V1,V2> over values of a PCollection<KV<K,V1>> and returns a PCollection<KV<K, V2>>.

    Example of use: 

    
 PCollection<KV<String, Integer>> input = ...;
 PCollection<KV<String, Double> output =
      input.apply(MapValues.into(TypeDescriptors.doubles()).via(Integer::doubleValue));

    See also MapKeys.

    See Also:
    Serialized Form

    • Method Detail

      • via

        public <NewKeyT,​NewValueT> MapValues<NewKeyT,​NewValueT,​V2> via​(SerializableFunction<NewValueT,​V2> fn)
        Returns a MapValues transform for a ProcessFunction<NewV1, V2> with predefined outputType.
        Type Parameters:
        NewKeyT - the type of the keys in the input and output PCollections
        NewValueT - the type of the values in the input PCollection

      • exceptionsInto

        @RequiresNonNull("fn")
public <FailureT> org.apache.beam.sdk.transforms.SimpleMapWithFailures<KV<K,​V1>,​KV<K,​V2>,​FailureT> exceptionsInto​(TypeDescriptor<FailureT> failureTypeDescriptor)
        Returns a new SimpleMapWithFailures 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 SimpleMapWithFailures.exceptionsVia(ProcessFunction).

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

        Example usage: 

        
 Result<PCollection<KV<String, Integer>>, String> result =
         input.apply(
             MapValues.into(TypeDescriptors.integers())
                 .<String, String>via(word -> 1 / word.length)  // Could throw ArithmeticException
                 .exceptionsInto(TypeDescriptors.strings())
                 .exceptionsVia(ee -> ee.exception().getMessage()));
 PCollection<KV<String, Integer>> output = result.output();
 PCollection<String> failures = result.failures();

      • exceptionsVia

        @RequiresNonNull("fn")
public <FailureT> org.apache.beam.sdk.transforms.SimpleMapWithFailures<KV<K,​V1>,​KV<K,​V2>,​FailureT> exceptionsVia​(InferableFunction<WithFailures.ExceptionElement<KV<K,​V1>>,​FailureT> exceptionHandler)
        Returns a new SimpleMapWithFailures 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<KV<String, Integer>>, String> result =
         input.apply(
             MapValues.into(TypeDescriptors.integers())
                 .<String, String>via(word -> 1 / word.length)  // Could throw ArithmeticException
                 .exceptionsVia(
                     new InferableFunction<ExceptionElement<KV<String, String>>, String>() {
                       @Override
                       public String apply(ExceptionElement<KV<String, String>> input) {
                         return input.exception().getMessage();
                       }
                     }));
 PCollection<KV<String, Integer>> output = result.output();
 PCollection<String> failures = result.failures();

      • expand

        public PCollection<KV<K,​V2>> expand​(PCollection<KV<K,​V1>> 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<KV<K,​V1>>,​PCollection<KV<K,​V2>>>