| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.beam.sdk.transforms; |
| |
| import java.io.Serializable; |
| import org.apache.beam.sdk.annotations.Internal; |
| import org.apache.beam.sdk.values.PCollection; |
| import org.apache.beam.sdk.values.PCollectionView; |
| import org.apache.beam.sdk.values.TypeDescriptor; |
| |
| /** |
| * <b><i>For internal use only; no backwards-compatibility guarantees.</i></b> |
| * |
| * <p>A function to adapt a primitive "view" of a {@link PCollection} - some materialization |
| * specified in the Beam model and implemented by the runner - to a user-facing view type for side |
| * input. |
| * |
| * <p>Both the underlying primitive view and the user-facing view are immutable. |
| * |
| * <p>The most common case is using the {@link View} transforms to prepare a {@link PCollection} for |
| * use as a side input to {@link ParDo}. See {@link View#asSingleton()}, {@link View#asIterable()}, |
| * and {@link View#asMap()} for more detail on specific views available in the SDK. |
| * |
| * @param <PrimitiveViewT> the type of the underlying primitive view required |
| * @param <ViewT> the type of the value(s) accessible via this {@link PCollectionView} |
| */ |
| @Internal |
| public abstract class ViewFn<PrimitiveViewT, ViewT> implements Serializable { |
| /** Gets the materialization of this {@link ViewFn}. */ |
| public abstract Materialization<PrimitiveViewT> getMaterialization(); |
| |
| /** A function to adapt a primitive view type to a desired view type. */ |
| public abstract ViewT apply(PrimitiveViewT primitiveViewT); |
| |
| /** Return the {@link TypeDescriptor} describing the output of this fn. */ |
| public abstract TypeDescriptor<ViewT> getTypeDescriptor(); |
| } |