How to use

multimapView

method

in

org.apache.beam.sdk.values.PCollectionViews

 @Override
 public PCollectionView<Map<K, Iterable<V>>> expand(PCollection<KV<K, V>> input) {
  try {
   GroupByKey.applicableTo(input);
  } catch (IllegalStateException e) {
   throw new IllegalStateException("Unable to create a side-input view from input", e);
  }
  PCollection<KV<Void, KV<K, V>>> materializationInput =
    input.apply(new VoidKeyToMultimapMaterialization<>());
  PCollectionView<Map<K, Iterable<V>>> view =
    PCollectionViews.multimapView(
      materializationInput, materializationInput.getWindowingStrategy());
  materializationInput.apply(CreatePCollectionView.of(view));
  return view;
 }
}