common/src/main/java/com/datatorrent/common/util/PubSubMessageCodec.java

/**
 * Copyright (C) 2015 DataTorrent, 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 com.datatorrent.common.util;

import java.io.IOException;
import java.util.HashMap;

import org.codehaus.jackson.map.ObjectMapper;

import com.datatorrent.common.util.PubSubMessage.PubSubMessageType;

/**
 * <p>PubSubMessageCodec class.</p>
 *
 * @param <T>
 * @since 0.3.5
 */
public class PubSubMessageCodec<T>
{

  private final ObjectMapper mapper;

  public PubSubMessageCodec(ObjectMapper mapper) {
    this.mapper = mapper;
  }

  public String formatMessage(PubSubMessage<T> pubSubMessage) throws IOException {
    HashMap<String, Object> map = new HashMap<String, Object>();
    map.put(PubSubMessage.TYPE_KEY, pubSubMessage.getType().getIdentifier());
    map.put(PubSubMessage.TOPIC_KEY, pubSubMessage.getTopic());
    T data = pubSubMessage.getData();
    if (data != null) {
      map.put(PubSubMessage.DATA_KEY, data);
    }

    return mapper.writeValueAsString(map);
  }

  /**
   *
   * @param message
   * @return a {@link PubSubMessage} message.
   * @throws IOException
   */
  @SuppressWarnings({"unchecked"})
  public PubSubMessage<T> parseMessage(String message) throws IOException {
    HashMap<String, Object> map = mapper.readValue(message, HashMap.class);
    PubSubMessage<T> pubSubMessage = new PubSubMessage<T>();
    pubSubMessage.setType(PubSubMessageType.getPubSubMessageType((String)map.get(PubSubMessage.TYPE_KEY)));
    pubSubMessage.setTopic((String)map.get(PubSubMessage.TOPIC_KEY));
    pubSubMessage.setData((T)map.get(PubSubMessage.DATA_KEY));
    return pubSubMessage;
  }
}