Prompt: What does this code do?

package jdbc;

import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.io.jdbc.JdbcIO;
import org.apache.beam.sdk.options.Default;
import org.apache.beam.sdk.options.Description;
import org.apache.beam.sdk.options.PipelineOptions;
import org.apache.beam.sdk.options.PipelineOptionsFactory;
import org.apache.beam.sdk.options.Validation;
import org.apache.beam.sdk.transforms.DoFn;
import org.apache.beam.sdk.transforms.ParDo;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.Serializable;
import java.sql.ResultSet;
import java.util.Objects;

public class ReadFormJdbcPartition {

  private static final Logger LOG = LoggerFactory.getLogger(ReadFormJdbcPartition.class);

  public static class SampleRow implements Serializable {
    public static final String ID_COLUMN = "id";
    public static final String MONTH_COLUMN = "month";
    public static final String AMOUNT_COLUMN = "amount";

    private int id;
    private String month;
    private String amount;

    public SampleRow() {}

    public SampleRow(int id, String month, String amount) {
      this.id = id;
      this.month = month;
      this.amount = amount;
    }

    @Override
    public String toString() {
      return "SampleRow{" + "id=" + id + ", month='" + month + "', amount='" + amount + '\'' + '}';
    }
  }

  public static class CreateExampleRow implements JdbcIO.RowMapper<ExampleRow> {
    @Override
    public ExampleRow mapRow(ResultSet resultSet) throws Exception {
      return new ExampleRow(
          Long.valueOf(resultSet.getLong(ExampleRow.ID_COLUMN)).intValue(),
          resultSet.getString(ExampleRow.MONTH_COLUMN),
          resultSet.getString(ExampleRow.AMOUNT_COLUMN));
    }
  }

  public interface ReadFromJdbcPartitionOptions extends PipelineOptions {
    @Description("Table name to read from")
    @Validation.Required
    String getTableName();

    void setTableName(String tableName);

    @Description("JDBC Source URL")
    @Validation.Required
    String getJdbcSourceUrl();

    void setJdbcSourceUrl(String jdbcUrl);

    @Description("JDBC driver class name")
    @Default.String("org.postgresql.Driver")
    String getDriverClassName();

    void setDriverClassName(String driverClassName);

    @Description("Jdbc DB Username")
    @Validation.Required
    String getSourceUsername();

    void setSourceUsername(String username);

    @Description("Jdbc DB password")
    @Validation.Required
    String getSourcePassword();

    void setSourcePassword(String password);
  }

  public static void main(String[] args) {
    ReadFromJdbcPartitionOptions options =
        PipelineOptionsFactory.fromArgs(args).withValidation().as(ReadFromJdbcPartitionOptions.class);

    JdbcIO.DataSourceConfiguration config =
        JdbcIO.DataSourceConfiguration.create(options.getDriverClassName(), options.getJdbcSourceUrl())
            .withUsername(options.getSourceUsername())
            .withPassword(options.getSourcePassword());

    Pipeline p = Pipeline.create(options);

    p.apply(
            "Read from Jdbc source",
            JdbcIO.<ExampleRow>readWithPartitions()
                .withDataSourceConfiguration(config)
                .withRowMapper(new CreateExampleRow())
                .withTable(options.getTableName())
                .withNumPartitions(1)
                .withPartitionColumn(ExampleRow.ID_COLUMN)
                .withLowerBound(0L)
                .withUpperBound(1000L))
        .apply(
            "Log Source Data",
            ParDo.of(
                new DoFn<ExampleRow, ExampleRow>() {
                  @ProcessElement
                  public void processElement(ProcessContext c) {
                    LOG.info(Objects.requireNonNull(c.element()).toString());
                    c.output(c.element());
                  }
                }));

    p.run();
  }
}

Response: This code reads data from an Oracle Java Database Connectivity (JDBC) enabled database using the Apache Beam JdbcIO connector.

The SampleRow class models the rows fetched from the JDBC source. It includes the fields id, month, and amount that correspond to the constants representing column names in the database table. Additionally, it overrides the toString method to provide a string representation of the SampleRow object.

public static class SampleRow implements Serializable {
    public static final String ID_COLUMN = "id";
    public static final String MONTH_COLUMN = "month";
    public static final String AMOUNT_COLUMN = "amount";

    private int id;
    private String month;
    private String amount;

    public SampleRow() {}

    public SampleRow(int id, String month, String amount) {
      this.id = id;
      this.month = month;
      this.amount = amount;
    }

    @Override
    public String toString() {
      return "SampleRow{" + "id=" + id + ", month='" + month + "', amount='" + amount + '\'' + '}';
    }
  }

The CreateExampleRow class implements the JdbcIO.RowMapper interface to map rows from the JDBC source to ExampleRow objects. The mapRow method extracts column values from the ResultSet interface and creates an ExampleRow object.

  public static class CreateExampleRow implements JdbcIO.RowMapper<ExampleRow> {
    @Override
    public ExampleRow mapRow(ResultSet resultSet) throws Exception {
      return new ExampleRow(
          Long.valueOf(resultSet.getLong(ExampleRow.ID_COLUMN)).intValue(),
          resultSet.getString(ExampleRow.MONTH_COLUMN),
          resultSet.getString(ExampleRow.AMOUNT_COLUMN));
    }
  }

The ReadFromJdbcPartitionOptions interface specifies the table name, JDBC source URL, driver class name, username, and password. The @Description annotation provides a description of the option. Use the command-line arguments --tableName, --jdbcSourceUrl, --driverClassName, --sourceUsername, and --sourcePassword to set these options when executing the pipeline.

public interface ReadFromJdbcPartitionOptions extends PipelineOptions {
    @Description("Table name to read from")
    @Validation.Required
    String getTableName();

    void setTableName(String tableName);

    @Description("JDBC Source URL")
    @Validation.Required
    String getJdbcSourceUrl();

    void setJdbcSourceUrl(String jdbcUrl);

    @Description("JDBC driver class name")
    @Default.String("org.postgresql.Driver")
    String getDriverClassName();

    void setDriverClassName(String driverClassName);

    @Description("Jdbc DB Username")
    @Validation.Required
    String getSourceUsername();

    void setSourceUsername(String username);

    @Description("Jdbc DB password")
    @Validation.Required
    String getSourcePassword();

    void setSourcePassword(String password);
  }

In the main method, the PipelineOptionsFactory class creates a ReadFromJdbcPartitionOptions object from the command-line arguments. The Pipeline.create method creates a new pipeline with the specified options. The DataSourceConfiguration class represents a configuration object that encapsulates the necessary information for establishing the connection to the JDBC source.

 ReadFromJdbcPartitionOptions options =
        PipelineOptionsFactory.fromArgs(args).withValidation().as(ReadFromJdbcPartitionOptions.class);

    JdbcIO.DataSourceConfiguration config =
        JdbcIO.DataSourceConfiguration.create(options.getDriverClassName(), options.getJdbcSourceUrl())
            .withUsername(options.getSourceUsername())
            .withPassword(options.getSourcePassword());

    Pipeline p = Pipeline.create(options);

To read data from the JDBC source in parallel, the code snippet uses the JdbcIO.readWithPartitions method. The .withNumPartitions() method determines how many partitions the data will be split into for parallel processing. The withPartitionColumn method specifies the column to use for partitioning the data. The withLowerBound and withUpperBound methods specify the lower and upper bounds of the data to read.

    p.apply(
            "Read from Jdbc source",
            JdbcIO.<ExampleRow>readWithPartitions()
                .withDataSourceConfiguration(config)
                .withRowMapper(new CreateExampleRow())
                .withTable(options.getTableName())
                .withNumPartitions(1)
                .withPartitionColumn(ExampleRow.ID_COLUMN)
                .withLowerBound(0L)
                .withUpperBound(1000L))
        .apply(
            "Log Source Data",
            ParDo.of(
                new DoFn<ExampleRow, ExampleRow>() {
                  @ProcessElement
                  public void processElement(ProcessContext c) {
                    LOG.info(Objects.requireNonNull(c.element()).toString());
                    c.output(c.element());
                  }
                }));

Finally, the run method executes the pipeline.

    p.run();