java - GenericRecord 的 Avro 架构 : Be able to leave blank fields

Question

我正在使用 Java 将 JSON 转换为 Avro，并使用 Google DataFlow 将它们存储到 GCS。Avro 架构是在运行时使用 SchemaBuilder 创建的。

我在架构中定义的字段之一是可选的 LONG 字段，其定义如下:

SchemaBuilder.FieldAssembler<Schema> fields = SchemaBuilder.record(mainName).fields();
Schema concreteType = SchemaBuilder.nullable().longType();
fields.name("key1").type(concreteType).noDefault();

现在，当我使用上面的架构创建 GenericRecord 且未设置“key1”时，将生成的 GenericRecord 放入我的 DoFn 的上下文中时: context.output(res); 我得到出现以下错误:

Exception in thread "main" org.apache.beam.sdk.Pipeline$PipelineExecutionException: org.apache.avro.UnresolvedUnionException: Not in union ["long","null"]: 256

我也尝试使用 withDefault(0L) 做同样的事情，并得到了相同的结果。

我想念什么？谢谢

Answer 1

当尝试如下时，它对我来说效果很好，您可以尝试打印有助于比较的模式，您也可以删除长类型的 nullable() 来尝试。

fields.name("key1").type().nullable().longType().longDefault(0);

提供了我用来测试的完整代码:

import org.apache.avro.AvroRuntimeException;
import org.apache.avro.Schema;
import org.apache.avro.SchemaBuilder;
import org.apache.avro.SchemaBuilder.FieldAssembler;
import org.apache.avro.SchemaBuilder.RecordBuilder;
import org.apache.avro.file.DataFileReader;
import org.apache.avro.file.DataFileWriter;
import org.apache.avro.generic.GenericData.Record;
import org.apache.avro.generic.GenericDatumReader;
import org.apache.avro.generic.GenericDatumWriter;
import org.apache.avro.generic.GenericRecord;
import org.apache.avro.generic.GenericRecordBuilder;
import org.apache.avro.io.DatumReader;
import org.apache.avro.io.DatumWriter;

import java.io.File;
import java.io.IOException;

public class GenericRecordExample {

  public static void main(String[] args) {

    FieldAssembler<Schema> fields;
    RecordBuilder<Schema> record = SchemaBuilder.record("Customer");
    fields = record.namespace("com.example").fields();
    fields = fields.name("first_name").type().nullable().stringType().noDefault();
    fields = fields.name("last_name").type().nullable().stringType().noDefault();
    fields = fields.name("account_number").type().nullable().longType().longDefault(0);

    Schema schema = fields.endRecord();
    System.out.println(schema.toString());

    // we build our first customer
    GenericRecordBuilder customerBuilder = new GenericRecordBuilder(schema);
    customerBuilder.set("first_name", "John");
    customerBuilder.set("last_name", "Doe");
    customerBuilder.set("account_number", 999333444111L);
    Record myCustomer = customerBuilder.build();
    System.out.println(myCustomer);

    // writing to a file
    final DatumWriter<GenericRecord> datumWriter = new GenericDatumWriter<>(schema);
    try (DataFileWriter<GenericRecord> dataFileWriter = new DataFileWriter<>(datumWriter)) {
      dataFileWriter.create(myCustomer.getSchema(), new File("customer-generic.avro"));
      dataFileWriter.append(myCustomer);
      System.out.println("Written customer-generic.avro");
    } catch (IOException e) {
      System.out.println("Couldn't write file");
      e.printStackTrace();
    }

    // reading from a file
    final File file = new File("customer-generic.avro");
    final DatumReader<GenericRecord> datumReader = new GenericDatumReader<>();
    GenericRecord customerRead;
    try (DataFileReader<GenericRecord> dataFileReader = new DataFileReader<>(file, datumReader)){
      customerRead = dataFileReader.next();
      System.out.println("Successfully read avro file");
      System.out.println(customerRead.toString());

      // get the data from the generic record
      System.out.println("First name: " + customerRead.get("first_name"));

      // read a non existent field
      System.out.println("Non existent field: " + customerRead.get("not_here"));
    }
    catch(IOException e) {
      e.printStackTrace();
    }
  }
}