從資料庫讀取資料到 Dataflow

如要從關聯式資料庫讀取資料至 Dataflow，請使用受管理 I/O 連接器。

依附元件

將下列依附元件新增至專案：

Java

<dependency>
  <groupId>org.apache.beam</groupId>
  <artifactId>beam-sdks-java-managed</artifactId>
  <version>${beam.version}</version>
</dependency>

<dependency>
  <groupId>org.apache.beam</groupId>
  <artifactId>beam-sdks-java-io-jdbc</artifactId>
  <version>${beam.version}</version>
</dependency>

範例

以下範例會從 PostgreSQL 資料庫讀取資料，並將資料寫入文字檔。雖然這個範例使用 PostgreSQL，但設定其他支援的資料庫也類似。

Java

如要向 Dataflow 進行驗證，請設定應用程式預設憑證。詳情請參閱「為本機開發環境設定驗證機制」。

import com.google.common.collect.ImmutableMap;
import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.PipelineResult;
import org.apache.beam.sdk.io.TextIO;
import org.apache.beam.sdk.managed.Managed;
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.transforms.MapElements;
import org.apache.beam.sdk.values.TypeDescriptors;

public class PostgresRead {

  public interface Options extends PipelineOptions {
    @Description("The JDBC URL of the PostgreSQL database to read from.")
    String getJdbcUrl();

    void setJdbcUrl(String value);

    @Description("The PostgresSQL table to read from.")
    String getTable();

    void setTable(String value);

    @Description("The username for the PostgreSQL database.")
    String getUsername();

    void setUsername(String value);

    @Description("The password for the PostgreSQL database.")
    String getPassword();

    void setPassword(String value);

    @Description(
        "The path to write the output file. Can be a local file path, "
            + "a GCS path, or a path to any other supported file systems.")
    String getOutputPath();

    void setOutputPath(String value);
  }

  public static PipelineResult.State main(String[] args) {
    // Parse the pipeline options passed into the application. Example:
    //   --runner=DirectRunner --jdbcUrl=$JDBC_URL --table=$TABLE
    //   --username=$USERNAME --password=$PASSWORD --outputPath=$OUTPUT_FILE
    // For more information, see
    // https://beam.apache.org/documentation/programming-guide/#configuring-pipeline-options
    var options = PipelineOptionsFactory.fromArgs(args).withValidation().as(Options.class);
    Pipeline pipeline = createPipeline(options);
    return pipeline.run().waitUntilFinish();
  }

  public static Pipeline createPipeline(Options options) {

    // Create configuration parameters for the Managed I/O transform.
    ImmutableMap<String, Object> config =
        ImmutableMap.<String, Object>builder()
            .put("jdbc_url", options.getJdbcUrl())
            .put("location", options.getTable())
            .put("username", options.getUsername())
            .put("password", options.getPassword())
            .build();

    // Build the pipeline.
    var pipeline = Pipeline.create(options);
    pipeline
        // Read data from a Postgres database using Managed I/O.
        .apply(Managed.read(Managed.POSTGRES).withConfig(config))
        .getSinglePCollection()
        // Convert each row to a string.
        .apply(
            MapElements.into(TypeDescriptors.strings())
                .via((row -> String.format("%d,%s", row.getInt32("id"), row.getString("name")))))
        // Write strings to a text file.
        .apply(TextIO.write().to(options.getOutputPath()).withSuffix(".txt").withNumShards(1));
    return pipeline;
  }
}

後續步驟

• 寫入資料庫。
• 進一步瞭解受管理 I/O。