| /* |
| * 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.runners.core; |
| |
| import javax.annotation.Nullable; |
| import org.apache.beam.sdk.transforms.windowing.BoundedWindow; |
| import org.apache.beam.sdk.values.PCollectionView; |
| |
| /** |
| * The interface to objects that provide side inputs. Particular implementations may read a side |
| * input directly or use appropriate sorts of caching, etc. |
| */ |
| public interface SideInputReader { |
| /** |
| * Returns the value of the given {@link PCollectionView} for the given {@link BoundedWindow}. |
| * |
| * <p>It is valid for a side input to be {@code null}. It is <i>not</i> valid for this to return |
| * {@code null} for any other reason. |
| */ |
| @Nullable |
| <T> T get(PCollectionView<T> view, BoundedWindow window); |
| |
| /** Returns true if the given {@link PCollectionView} is valid for this reader. */ |
| <T> boolean contains(PCollectionView<T> view); |
| |
| /** Returns true if there are no side inputs in this reader. */ |
| boolean isEmpty(); |
| } |