sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/pubsub/ExternalWrite.java

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 * distributed with this work for additional information
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 * 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
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package org.apache.beam.sdk.io.gcp.pubsub;

import com.google.auto.service.AutoService;
import java.util.Map;
import org.apache.beam.sdk.annotations.Experimental;
import org.apache.beam.sdk.expansion.ExternalTransformRegistrar;
import org.apache.beam.sdk.io.gcp.pubsub.PubsubIO.PubsubTopic;
import org.apache.beam.sdk.io.gcp.pubsub.PubsubMessages.ParsePubsubMessageProtoAsPayload;
import org.apache.beam.sdk.options.ValueProvider.NestedValueProvider;
import org.apache.beam.sdk.options.ValueProvider.StaticValueProvider;
import org.apache.beam.sdk.transforms.ExternalTransformBuilder;
import org.apache.beam.sdk.transforms.PTransform;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.PDone;
import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.ImmutableMap;
import org.checkerframework.checker.nullness.qual.Nullable;

/** Exposes {@link PubsubIO.Write} as an external transform for cross-language usage. */
@Experimental
@AutoService(ExternalTransformRegistrar.class)
@SuppressWarnings({
  "nullness" // TODO(https://issues.apache.org/jira/browse/BEAM-10402)
})
public final class ExternalWrite implements ExternalTransformRegistrar {
  public ExternalWrite() {}

  public static final String URN = "beam:external:java:pubsub:write:v1";

  @Override
  public Map<String, Class<? extends ExternalTransformBuilder<?, ?, ?>>> knownBuilders() {
    return ImmutableMap.of(URN, WriteBuilder.class);
  }

  /** Parameters class to expose the transform to an external SDK. */
  public static class Configuration {
    private String topic;
    private @Nullable String idAttribute;
    private @Nullable String timestampAttribute;

    public void setTopic(String topic) {
      this.topic = topic;
    }

    public void setIdLabel(@Nullable String idAttribute) {
      this.idAttribute = idAttribute;
    }

    public void setTimestampAttribute(@Nullable String timestampAttribute) {
      this.timestampAttribute = timestampAttribute;
    }
  }

  public static class WriteBuilder
      implements ExternalTransformBuilder<Configuration, PCollection<byte[]>, PDone> {
    public WriteBuilder() {}

    @Override
    public PTransform<PCollection<byte[]>, PDone> buildExternal(Configuration config) {
      PubsubIO.Write.Builder<byte[]> writeBuilder =
          PubsubIO.Write.newBuilder(new ParsePubsubMessageProtoAsPayload());
      if (config.topic != null) {
        StaticValueProvider<String> topic = StaticValueProvider.of(config.topic);
        writeBuilder.setTopicProvider(NestedValueProvider.of(topic, PubsubTopic::fromPath));
      }
      if (config.idAttribute != null) {
        writeBuilder.setIdAttribute(config.idAttribute);
      }
      if (config.timestampAttribute != null) {
        writeBuilder.setTimestampAttribute(config.timestampAttribute);
      }
      return writeBuilder.build();
    }
  }
}