| /* |
| * 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.extensions.jackson; |
| |
| import com.fasterxml.jackson.databind.ObjectMapper; |
| import java.io.IOException; |
| import org.apache.beam.sdk.transforms.MapElements; |
| import org.apache.beam.sdk.transforms.PTransform; |
| import org.apache.beam.sdk.transforms.SimpleFunction; |
| import org.apache.beam.sdk.values.PCollection; |
| import org.apache.beam.vendor.guava.v20_0.com.google.common.base.Optional; |
| |
| /** |
| * {@link PTransform} for serializing objects to JSON {@link String Strings}. Transforms a {@code |
| * PCollection<InputT>} into a {@link PCollection} of JSON {@link String Strings} representing |
| * objects in the original {@link PCollection} using Jackson. |
| */ |
| public class AsJsons<InputT> extends PTransform<PCollection<InputT>, PCollection<String>> { |
| private static final ObjectMapper DEFAULT_MAPPER = new ObjectMapper(); |
| |
| private final Class<? extends InputT> inputClass; |
| private ObjectMapper customMapper; |
| |
| /** |
| * Creates a {@link AsJsons} {@link PTransform} that will transform a {@code PCollection<InputT>} |
| * into a {@link PCollection} of JSON {@link String Strings} representing those objects using a |
| * Jackson {@link ObjectMapper}. |
| */ |
| public static <OutputT> AsJsons<OutputT> of(Class<? extends OutputT> outputClass) { |
| return new AsJsons<>(outputClass); |
| } |
| |
| private AsJsons(Class<? extends InputT> outputClass) { |
| this.inputClass = outputClass; |
| } |
| |
| /** Use custom Jackson {@link ObjectMapper} instead of the default one. */ |
| public AsJsons<InputT> withMapper(ObjectMapper mapper) { |
| AsJsons<InputT> newTransform = new AsJsons<>(inputClass); |
| newTransform.customMapper = mapper; |
| return newTransform; |
| } |
| |
| @Override |
| public PCollection<String> expand(PCollection<InputT> input) { |
| return input.apply( |
| MapElements.via( |
| new SimpleFunction<InputT, String>() { |
| @Override |
| public String apply(InputT input) { |
| try { |
| ObjectMapper mapper = Optional.fromNullable(customMapper).or(DEFAULT_MAPPER); |
| return mapper.writeValueAsString(input); |
| } catch (IOException e) { |
| throw new RuntimeException( |
| "Failed to serialize " + inputClass.getName() + " value: " + input, e); |
| } |
| } |
| })); |
| } |
| } |