sdks/java/io/snowflake/src/main/java/org/apache/beam/sdk/io/snowflake/crosslanguage/SnowflakeReadRegistrar.java

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 * 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
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 * distributed under the License is distributed on an "AS IS" BASIS,
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 * See the License for the specific language governing permissions and
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package org.apache.beam.sdk.io.snowflake.crosslanguage;

import com.google.auto.service.AutoService;
import java.io.Serializable;
import java.nio.charset.Charset;
import java.util.Map;
import javax.sql.DataSource;
import org.apache.beam.sdk.annotations.Experimental;
import org.apache.beam.sdk.coders.ByteArrayCoder;
import org.apache.beam.sdk.expansion.ExternalTransformRegistrar;
import org.apache.beam.sdk.io.snowflake.SnowflakeIO;
import org.apache.beam.sdk.io.snowflake.credentials.SnowflakeCredentials;
import org.apache.beam.sdk.io.snowflake.credentials.SnowflakeCredentialsFactory;
import org.apache.beam.sdk.transforms.ExternalTransformBuilder;
import org.apache.beam.sdk.transforms.PTransform;
import org.apache.beam.sdk.transforms.SerializableFunction;
import org.apache.beam.sdk.values.PBegin;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.ImmutableMap;

/** Exposes {@link SnowflakeIO.Read} as an external transform for cross-language usage. */
@Experimental
@AutoService(ExternalTransformRegistrar.class)
public final class SnowflakeReadRegistrar implements ExternalTransformRegistrar {

  public static final String URN = "beam:external:java:snowflake:read:v1";

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

  /** Parameters class to expose the transform to an external SDK. */
  public static class ReadConfiguration extends Configuration {}

  public static class ReadBuilder
      implements ExternalTransformBuilder<ReadConfiguration, PBegin, PCollection<byte[]>> {
    public ReadBuilder() {}

    @Override
    public PTransform<PBegin, PCollection<byte[]>> buildExternal(ReadConfiguration c) {
      SnowflakeCredentials credentials = SnowflakeCredentialsFactory.of(c);

      SerializableFunction<Void, DataSource> dataSourceSerializableFunction =
          SnowflakeIO.DataSourceProviderFromDataSourceConfiguration.of(
              SnowflakeIO.DataSourceConfiguration.create(credentials)
                  .withServerName(c.getServerName())
                  .withDatabase(c.getDatabase())
                  .withSchema(c.getSchema()));

      return SnowflakeIO.<byte[]>read()
          .withStorageIntegrationName(c.getStorageIntegrationName())
          .withStagingBucketName(c.getStagingBucketName())
          .withDataSourceProviderFn(dataSourceSerializableFunction)
          .withCsvMapper(CsvMapper.getCsvMapper())
          .withCoder(ByteArrayCoder.of())
          .fromTable(c.getTable())
          .fromQuery(c.getQuery());
    }
  }

  private static class CsvMapper implements Serializable {

    public static SnowflakeIO.CsvMapper getCsvMapper() {
      return (SnowflakeIO.CsvMapper<byte[]>)
          parts -> {
            String partsCSV = String.join(",", parts);

            return partsCSV.getBytes(Charset.defaultCharset());
          };
    }
  }
}