AvroJsonConverter.java

/*
 * Copyright 2014-2016 CyberVision, Inc.
 *
 * Licensed 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.kaaproject.kaa.common.avro;

import org.apache.avro.Schema;
import org.apache.avro.io.DecoderFactory;
import org.apache.avro.io.EncoderFactory;
import org.apache.avro.io.JsonDecoder;
import org.apache.avro.io.JsonEncoder;
import org.apache.avro.specific.SpecificDatumReader;
import org.apache.avro.specific.SpecificDatumWriter;
import org.apache.avro.specific.SpecificRecordBase;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.charset.Charset;

/**
 * The Class AvroJsonConverter is used to convert {#link org.apache.avro.specific.SpecificRecordBase
 * specific Avro records} to/from json. NOT Thread safe.
 *
 * @param <T> the generic type that extends SpecificRecordBase
 * @author Igor Kulikov
 */
public class AvroJsonConverter<T extends SpecificRecordBase> {

  private static final Charset UTF8 = Charset.forName("UTF-8");

  Schema schema;
  SpecificDatumReader<T> avroReader;
  SpecificDatumWriter<T> avroWriter;
  JsonDecoder jsonDecoder;
  JsonEncoder jsonEncoder;

  /**
   * Instantiates a new Avro json converter based on class.
   *
   * @param schema             the schema
   * @param typeParameterClass the type parameter class
   */
  public AvroJsonConverter(Schema schema, Class<T> typeParameterClass) {
    super();
    this.schema = schema;
    avroReader = new SpecificDatumReader<T>(typeParameterClass);
    avroWriter = new SpecificDatumWriter<T>(typeParameterClass);
  }

  /**
   * Decode json data.
   *
   * @param data the data
   * @return the decoded object
   * @throws IOException Signals that an I/O exception has occurred.
   */
  public T decodeJson(String data) throws IOException {
    return decodeJson(data, null);
  }

  /**
   * Decode json data.
   *
   * @param data the data
   * @return the decoded object
   * @throws IOException Signals that an I/O exception has occurred.
   */
  public T decodeJson(byte[] data) throws IOException {
    return decodeJson(new String(data, UTF8), null);
  }

  /**
   * Decode json data.
   *
   * @param data  the data
   * @param reuse the reuse
   * @return the decoded object
   * @throws IOException Signals that an I/O exception has occurred.
   */
  public T decodeJson(String data, T reuse) throws IOException {
    jsonDecoder = DecoderFactory.get().jsonDecoder(this.schema, data, true);
    return avroReader.read(null, jsonDecoder);
  }

  /**
   * Encode record to Json String.
   *
   * @param record the object to encode
   * @return the string
   * @throws IOException Signals that an I/O exception has occurred.
   */
  public String endcodeToJson(T record) throws IOException {
    return new String(encodeToJsonBytes(record), UTF8);
  }

  /**
   * Encode record to Json and then convert to byte array.
   *
   * @param record the object to encode
   * @return the byte[]
   * @throws IOException Signals that an I/O exception has occurred.
   */
  public byte[] encodeToJsonBytes(T record) throws IOException {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    jsonEncoder = EncoderFactory.get().jsonEncoder(this.schema, baos, true);
    avroWriter.write(record, jsonEncoder);
    jsonEncoder.flush();
    baos.flush();
    return baos.toByteArray();
  }

}