| /* |
| * 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.Experimental; |
| import org.apache.beam.sdk.annotations.Experimental.Kind; |
| import org.apache.beam.sdk.values.PCollectionView; |
| import org.apache.beam.vendor.guava.v20_0.com.google.common.base.MoreObjects; |
| |
| /** Pair of a bit of user code (a "closure") and the {@link Requirements} needed to run it. */ |
| @Experimental(Kind.CONTEXTFUL) |
| public final class Contextful<ClosureT> implements Serializable { |
| private final ClosureT closure; |
| private final Requirements requirements; |
| |
| private Contextful(ClosureT closure, Requirements requirements) { |
| this.closure = closure; |
| this.requirements = requirements; |
| } |
| |
| /** Returns the closure. */ |
| public ClosureT getClosure() { |
| return closure; |
| } |
| |
| /** Returns the requirements needed to run the closure. */ |
| public Requirements getRequirements() { |
| return requirements; |
| } |
| |
| /** Constructs a pair of the given closure and its requirements. */ |
| public static <ClosureT> Contextful<ClosureT> of(ClosureT closure, Requirements requirements) { |
| return new Contextful<>(closure, requirements); |
| } |
| |
| @Override |
| public String toString() { |
| return MoreObjects.toStringHelper(this) |
| .add("closure", closure) |
| .add("requirements", requirements) |
| .toString(); |
| } |
| |
| /** |
| * A function from an input to an output that may additionally access {@link Context} when |
| * computing the result. |
| */ |
| public interface Fn<InputT, OutputT> extends Serializable { |
| /** |
| * Invokes the function on the given input with the given context. The function may use the |
| * context only for the capabilities declared in the {@link Contextful#getRequirements} of the |
| * enclosing {@link Contextful}. |
| */ |
| OutputT apply(InputT element, Context c) throws Exception; |
| |
| /** An accessor for additional capabilities available in {@link #apply}. */ |
| abstract class Context { |
| /** |
| * Accesses the given side input. The window in which it is accessed is unspecified, depends |
| * on usage by the enclosing {@link PTransform}, and must be documented by that transform. |
| */ |
| public <T> T sideInput(PCollectionView<T> view) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * Convenience wrapper for creating a {@link Context} from a {@link DoFn.ProcessContext}, to |
| * support the common case when a {@link PTransform} is invoking the {@link |
| * Contextful#getClosure() closure} from inside a {@link DoFn}. |
| */ |
| public static <InputT> Context wrapProcessContext(final DoFn<InputT, ?>.ProcessContext c) { |
| return new ContextFromProcessContext<>(c); |
| } |
| |
| private static class ContextFromProcessContext<InputT> extends Context { |
| private final DoFn<InputT, ?>.ProcessContext c; |
| |
| ContextFromProcessContext(DoFn<InputT, ?>.ProcessContext c) { |
| this.c = c; |
| } |
| |
| @Override |
| public <T> T sideInput(PCollectionView<T> view) { |
| return c.sideInput(view); |
| } |
| } |
| } |
| } |
| |
| /** |
| * Wraps a {@link ProcessFunction} as a {@link Contextful} of {@link Fn} with empty {@link |
| * Requirements}. |
| */ |
| public static <InputT, OutputT> Contextful<Fn<InputT, OutputT>> fn( |
| final ProcessFunction<InputT, OutputT> fn) { |
| return new Contextful<>((element, c) -> fn.apply(element), Requirements.empty()); |
| } |
| |
| /** Binary compatibility adapter for {@link #fn(ProcessFunction)}. */ |
| public static <InputT, OutputT> Contextful<Fn<InputT, OutputT>> fn( |
| final SerializableFunction<InputT, OutputT> fn) { |
| return fn((ProcessFunction<InputT, OutputT>) fn); |
| } |
| |
| /** Same with {@link #of} but with better type inference behavior for the case of {@link Fn}. */ |
| public static <InputT, OutputT> Contextful<Fn<InputT, OutputT>> fn( |
| final Fn<InputT, OutputT> fn, Requirements requirements) { |
| return of(fn, requirements); |
| } |
| } |