src/main/java/org/apache/hadoop/mrunit/internal/io/Serialization.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.hadoop.mrunit.internal.io;

import com.google.common.base.Preconditions;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.DataInputBuffer;
import org.apache.hadoop.io.DataOutputBuffer;
import org.apache.hadoop.io.serializer.Deserializer;
import org.apache.hadoop.io.serializer.SerializationFactory;
import org.apache.hadoop.io.serializer.Serializer;

public class Serialization {

  private SerializationFactory serializationFactory;

  /**
   * @param conf
   */
  public Serialization(Configuration conf) {
    serializationFactory = new SerializationFactory(conf);
  }

  /**
   * Creates a new copy of the orig object. Depending on the serialization used,
   * the serialization class may or may not copy the orig object into the copy
   * object based on the contract on
   * org.apache.hadoop.io.serializer.Deserializer.deserialize
   *
   * @param orig
   * @param copy
   *          if null always returns a new object, if not null may or may not
   *          copy orig into copy depending on what serialization class is used
   * @return a copy of the orig object
   */
  @SuppressWarnings("unchecked")
  public <T> T copy(final T orig, final T copy) {
    if (copy != null && orig.getClass() != copy.getClass()) {
      throw new IllegalArgumentException(orig.getClass() + " != "
          + copy.getClass());
    }
    final Class<?> clazz = orig.getClass();
    final Serializer<Object> serializer;
    final Deserializer<Object> deserializer;
    String errorMsg = "No applicable class implementing Serialization in conf "
                      + "at io.serializations: " + clazz;
    try {
      serializer = (Serializer<Object>) serializationFactory
          .getSerializer(clazz);
      deserializer = (Deserializer<Object>) serializationFactory
          .getDeserializer(clazz);
    // hadoop 1.x will throw
    } catch (NullPointerException e) {
      throw new IllegalStateException(errorMsg, e);
    }
    // hadoop 2.x will return a null
    Preconditions.checkState(serializer != null, errorMsg);
    Preconditions.checkState(deserializer != null, errorMsg);
    try {
      final DataOutputBuffer outputBuffer = new DataOutputBuffer();
      serializer.open(outputBuffer);
      serializer.serialize(orig);
      final DataInputBuffer inputBuffer = new DataInputBuffer();
      inputBuffer.reset(outputBuffer.getData(), outputBuffer.getLength());
      deserializer.open(inputBuffer);
      return (T) deserializer.deserialize(copy);
    } catch (final IOException e) {
      throw new RuntimeException(e);
    }
  }

  /**
   * Creates a new copy of the orig object
   *
   * @param orig
   * @return a new copy of the orig object
   */
  public <T> T copy(final T orig) {
    return copy(orig, null);
  }

  /**
   * Creates a new copy of the orig object
   *
   * @param orig
   * @param conf
   *          new Configuration object to use
   * @return a new copy of the orig object
   */
  public <T> T copyWithConf(final T orig, final Configuration conf) {
    serializationFactory = new SerializationFactory(conf);
    return copy(orig);
  }

}