SpecificMain.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * 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
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package example;

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

import org.apache.avro.file.DataFileReader;
import org.apache.avro.file.DataFileWriter;
import org.apache.avro.io.DatumReader;
import org.apache.avro.io.DatumWriter;
import org.apache.avro.specific.SpecificDatumReader;
import org.apache.avro.specific.SpecificDatumWriter;

import example.avro.User;

public class SpecificMain {
  public static void main(String[] args) throws IOException {
    User user1 = new User();
    user1.setName("Alyssa");
    user1.setFavoriteNumber(256);
    // Leave favorite color null

    // Alternate constructor
    User user2 = new User("Ben", 7, "red");

    // Construct via builder
    User user3 = User.newBuilder()
             .setName("Charlie")
             .setFavoriteColor("blue")
             .setFavoriteNumber(null)
             .build();

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

    // Deserialize Users from disk
    DatumReader<User> userDatumReader = new SpecificDatumReader<User>(User.class);
    DataFileReader<User> dataFileReader = new DataFileReader<User>(file, userDatumReader);
    User user = null;
    while (dataFileReader.hasNext()) {
      // Reuse user object by passing it to next(). This saves us from
      // allocating and garbage collecting many objects for files with
      // many items.
      user = dataFileReader.next(user);
      System.out.println(user);
    }

  }
}