content: /*
   * 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
   *
   *     https://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.avro.hadoop.io;
  
  import java.lang.reflect.Constructor;
  import java.util.Collection;
  
  import org.apache.avro.Schema;
  import org.apache.avro.generic.GenericData;
  import org.apache.avro.io.DatumReader;
  import org.apache.avro.io.DatumWriter;
  import org.apache.avro.mapred.AvroKey;
  import org.apache.avro.mapred.AvroValue;
  import org.apache.avro.mapred.AvroWrapper;
  import org.apache.avro.reflect.ReflectData;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.conf.Configured;
  import org.apache.hadoop.io.serializer.Deserializer;
  import org.apache.hadoop.io.serializer.Serialization;
  import org.apache.hadoop.io.serializer.Serializer;
  import org.apache.hadoop.util.ReflectionUtils;
  
  /**
   * The {@link org.apache.hadoop.io.serializer.Serialization} used by jobs
   * configured with {@link org.apache.avro.mapreduce.AvroJob}.
   *
   * @param <T> The Java type of the Avro data to serialize.
   */
  public class AvroSerialization<T> extends Configured implements Serialization<AvroWrapper<T>> {
    /**
     * Conf key for the writer schema of the AvroKey datum being
     * serialized/deserialized.
     */
    private static final String CONF_KEY_WRITER_SCHEMA = "avro.serialization.key.writer.schema";
  
    /**
     * Conf key for the reader schema of the AvroKey datum being
     * serialized/deserialized.
     */
    private static final String CONF_KEY_READER_SCHEMA = "avro.serialization.key.reader.schema";
  
    /**
     * Conf key for the writer schema of the AvroValue datum being
     * serialized/deserialized.
     */
    private static final String CONF_VALUE_WRITER_SCHEMA = "avro.serialization.value.writer.schema";
  
    /**
     * Conf key for the reader schema of the AvroValue datum being
     * serialized/deserialized.
     */
    private static final String CONF_VALUE_READER_SCHEMA = "avro.serialization.value.reader.schema";
  
    /** Conf key for the data model implementation class. */
    private static final String CONF_DATA_MODEL = "avro.serialization.data.model";
  
    /** {@inheritDoc} */
    @Override
    public boolean accept(Class<?> c) {
      return AvroKey.class.isAssignableFrom(c) || AvroValue.class.isAssignableFrom(c);
    }
  
    /**
     * Gets an object capable of deserializing the output from a Mapper.
     *
     * @param c The class to get a deserializer for.
     * @return A deserializer for objects of class <code>c</code>.
     */
    @Override
    public Deserializer<AvroWrapper<T>> getDeserializer(Class<AvroWrapper<T>> c) {
      Configuration conf = getConf();
      GenericData dataModel = createDataModel(conf);
      if (AvroKey.class.isAssignableFrom(c)) {
        Schema writerSchema = getKeyWriterSchema(conf);
        Schema readerSchema = getKeyReaderSchema(conf);
        DatumReader<T> datumReader = (readerSchema != null) ? dataModel.createDatumReader(writerSchema, readerSchema)
            : dataModel.createDatumReader(writerSchema);
        return new AvroKeyDeserializer<>(writerSchema, readerSchema, datumReader);
      } else if (AvroValue.class.isAssignableFrom(c)) {
        Schema writerSchema = getValueWriterSchema(conf);
        Schema readerSchema = getValueReaderSchema(conf);
        DatumReader<T> datumReader = (readerSchema != null) ? dataModel.createDatumReader(writerSchema, readerSchema)
            : dataModel.createDatumReader(writerSchema);
        return new AvroValueDeserializer<>(writerSchema, readerSchema, datumReader);
      } else {
        throw new IllegalStateException("Only AvroKey and AvroValue are supported.");
      }
    }
  
    /**
     * Gets an object capable of serializing output from a Mapper.
     *
     * @param c The class to get a serializer for.
     * @return A serializer for objects of class <code>c</code>.
     */
    @Override
    public Serializer<AvroWrapper<T>> getSerializer(Class<AvroWrapper<T>> c) {
      Configuration conf = getConf();
      Schema schema;
      if (AvroKey.class.isAssignableFrom(c)) {
        schema = getKeyWriterSchema(conf);
      } else if (AvroValue.class.isAssignableFrom(c)) {
        schema = getValueWriterSchema(conf);
      } else {
        throw new IllegalStateException("Only AvroKey and AvroValue are supported.");
      }
      GenericData dataModel = createDataModel(conf);
      DatumWriter<T> datumWriter = dataModel.createDatumWriter(schema);
      return new AvroSerializer<>(schema, datumWriter);
    }
  
    /**
     * Adds the AvroSerialization scheme to the configuration, so
     * SerializationFactory instances constructed from the given configuration will
     * be aware of it.
     *
     * @param conf The configuration to add AvroSerialization to.
     */
    public static void addToConfiguration(Configuration conf) {
      Collection<String> serializations = conf.getStringCollection("io.serializations");
      if (!serializations.contains(AvroSerialization.class.getName())) {
        serializations.add(AvroSerialization.class.getName());
        conf.setStrings("io.serializations", serializations.toArray(new String[0]));
      }
    }
  
    /**
     * Sets the writer schema of the AvroKey datum that is being
     * serialized/deserialized.
     *
     * @param conf   The configuration.
     * @param schema The Avro key schema.
     */
    public static void setKeyWriterSchema(Configuration conf, Schema schema) {
      if (null == schema) {
        throw new IllegalArgumentException("Writer schema may not be null");
      }
      conf.set(CONF_KEY_WRITER_SCHEMA, schema.toString());
    }
  
    /**
     * Sets the reader schema of the AvroKey datum that is being
     * serialized/deserialized.
     *
     * @param conf   The configuration.
     * @param schema The Avro key schema.
     */
    public static void setKeyReaderSchema(Configuration conf, Schema schema) {
      conf.set(CONF_KEY_READER_SCHEMA, schema.toString());
    }
  
    /**
     * Sets the writer schema of the AvroValue datum that is being
     * serialized/deserialized.
     *
     * @param conf   The configuration.
     * @param schema The Avro value schema.
     */
    public static void setValueWriterSchema(Configuration conf, Schema schema) {
      if (null == schema) {
        throw new IllegalArgumentException("Writer schema may not be null");
      }
      conf.set(CONF_VALUE_WRITER_SCHEMA, schema.toString());
    }
  
    /**
     * Sets the reader schema of the AvroValue datum that is being
     * serialized/deserialized.
     *
     * @param conf   The configuration.
     * @param schema The Avro value schema.
     */
    public static void setValueReaderSchema(Configuration conf, Schema schema) {
      conf.set(CONF_VALUE_READER_SCHEMA, schema.toString());
    }
  
    /**
     * Sets the data model class for de/serialization.
     *
     * @param conf       The configuration.
     * @param modelClass The data model class.
     */
    public static void setDataModelClass(Configuration conf, Class<? extends GenericData> modelClass) {
      conf.setClass(CONF_DATA_MODEL, modelClass, GenericData.class);
    }
  
    /**
     * Gets the writer schema of the AvroKey datum that is being
     * serialized/deserialized.
     *
     * @param conf The configuration.
     * @return The Avro key writer schema, or null if none was set.
     */
    public static Schema getKeyWriterSchema(Configuration conf) {
      String json = conf.get(CONF_KEY_WRITER_SCHEMA);
      return null == json ? null : new Schema.Parser().parse(json);
    }
  
    /**
     * Gets the reader schema of the AvroKey datum that is being
     * serialized/deserialized.
     *
     * @param conf The configuration.
     * @return The Avro key reader schema, or null if none was set.
     */
    public static Schema getKeyReaderSchema(Configuration conf) {
      String json = conf.get(CONF_KEY_READER_SCHEMA);
      return null == json ? null : new Schema.Parser().parse(json);
    }
  
    /**
     * Gets the writer schema of the AvroValue datum that is being
     * serialized/deserialized.
     *
     * @param conf The configuration.
     * @return The Avro value writer schema, or null if none was set.
     */
    public static Schema getValueWriterSchema(Configuration conf) {
      String json = conf.get(CONF_VALUE_WRITER_SCHEMA);
      return null == json ? null : new Schema.Parser().parse(json);
    }
  
    /**
     * Gets the reader schema of the AvroValue datum that is being
     * serialized/deserialized.
     *
     * @param conf The configuration.
     * @return The Avro value reader schema, or null if none was set.
     */
    public static Schema getValueReaderSchema(Configuration conf) {
      String json = conf.get(CONF_VALUE_READER_SCHEMA);
      return null == json ? null : new Schema.Parser().parse(json);
    }
  
    /**
     * Gets the data model class for de/serialization.
     *
     * @param conf The configuration.
     */
    public static Class<? extends GenericData> getDataModelClass(Configuration conf) {
      return conf.getClass(CONF_DATA_MODEL, ReflectData.class, GenericData.class);
    }
  
    private static GenericData newDataModelInstance(Class<? extends GenericData> modelClass, Configuration conf) {
      GenericData dataModel;
      try {
        Constructor<? extends GenericData> ctor = modelClass.getDeclaredConstructor(ClassLoader.class);
        ctor.setAccessible(true);
        dataModel = ctor.newInstance(conf.getClassLoader());
      } catch (Exception e) {
        throw new RuntimeException(e);
      }
      ReflectionUtils.setConf(dataModel, conf);
      return dataModel;
    }
  
    /**
     * Gets an instance of data model implementation, defaulting to
     * {@link ReflectData} if not explicitly specified.
     *
     * @param conf The job configuration.
     * @return Instance of the job data model implementation.
     */
    public static GenericData createDataModel(Configuration conf) {
      Class<? extends GenericData> modelClass = getDataModelClass(conf);
      return newDataModelInstance(modelClass, conf);
    }
  }
  