What is the purpose of DatumWriter in Avro

Question

Avro website has an example:

DatumWriter<User> userDatumWriter = new SpecificDatumWriter<User>(User.class);
DataFileWriter<User> dataFileWriter = new DataFileWriter<User>(userDatumWriter);
dataFileWriter.create(user1.getSchema(), new File("users.avro"));
dataFileWriter.append(user1);
dataFileWriter.append(user2);
dataFileWriter.append(user3);
dataFileWriter.close();

What is the purpose of DatumWriter<User>? I mean what it does provide? It provides write method, but instead of using it we use DataFileWriter. Can someone explain the design purpose of it?

Answer 1

The DatumWriter class responsible for translating the given data object into an avro record with a given schema (which is extracted in your case from the User class).

Given this record the DataFileWriter is responsible to write it to a file.