compiler/frontend/spark/src/main/java/org/apache/nemo/compiler/frontend/spark/coder/SparkDecoderFactory.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 org.apache.nemo.compiler.frontend.spark.coder;

import org.apache.nemo.common.coder.DecoderFactory;
import org.apache.spark.serializer.DeserializationStream;
import org.apache.spark.serializer.Serializer;
import org.apache.spark.serializer.SerializerInstance;
import scala.reflect.ClassTag$;

import java.io.InputStream;

/**
 * Spark DecoderFactory for serialization.
 *
 * @param <T> type of the object to deserialize.
 */
public final class SparkDecoderFactory<T> implements DecoderFactory<T> {
  private final Serializer serializer;

  /**
   * Default constructor.
   *
   * @param serializer Spark serializer.
   */
  public SparkDecoderFactory(final Serializer serializer) {
    this.serializer = serializer;
  }

  @Override
  public Decoder<T> create(final InputStream inputStream) {
    return new SparkDecoder<>(inputStream, serializer.newInstance());
  }

  @Override
  public String toString() {
    return "SparkDecoderFactory{"
      + "serializer=" + serializer
      + '}';
  }

  /**
   * SparkDecoder.
   *
   * @param <T2> type of the object to deserialize.
   */
  private final class SparkDecoder<T2> implements Decoder<T2> {

    private final DeserializationStream in;

    /**
     * Constructor.
     *
     * @param inputStream             the input stream to decode.
     * @param sparkSerializerInstance the actual spark serializer instance to use.
     */
    private SparkDecoder(final InputStream inputStream,
                         final SerializerInstance sparkSerializerInstance) {
      this.in = sparkSerializerInstance.deserializeStream(inputStream);
    }

    @Override
    public T2 decode() {
      return (T2) in.readObject(ClassTag$.MODULE$.Any());
    }
  }
}