library/src/test/java/org/apache/apex/malhar/lib/helper/SamplePubSubWebSocketServlet.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.apex.malhar.lib.helper;

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

import javax.servlet.http.HttpServletRequest;

import org.codehaus.jackson.map.ObjectMapper;
import org.eclipse.jetty.websocket.WebSocket;
import org.eclipse.jetty.websocket.WebSocketServlet;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.datatorrent.common.util.JacksonObjectMapperProvider;

/**
 *
 */
@SuppressWarnings("serial")
public class SamplePubSubWebSocketServlet extends WebSocketServlet
{
  private static final Logger LOG = LoggerFactory.getLogger(SamplePubSubWebSocketServlet.class);
  private ObjectMapper mapper = (new JacksonObjectMapperProvider()).getContext(null);
  private PubSubWebSocket subscriber;

  @Override
  public WebSocket doWebSocketConnect(HttpServletRequest hsr, String string)
  {
    return new PubSubWebSocket();
  }

  private class PubSubWebSocket implements WebSocket.OnTextMessage
  {
    private Connection connection;

    @SuppressWarnings("unchecked")
    @Override
    public void onMessage(String arg0)
    {
      // This parsing code will be handled by API in future in a manner that is transparent to the
      // user and should not be relied upon
      try {
        HashMap<String, Object> map = mapper.readValue(arg0, HashMap.class);
        String type = (String)map.get("type");
        String topic = (String)map.get("topic");
        if (type.equals("subscribe")) {
          if (topic != null) {
            subscriber = this;
          }
        } else if (type.equals("unsubscribe")) {
          subscriber = null;
        } else if (type.equals("publish")) {
          Object data = map.get("data");
          if (data != null) {
            if (subscriber != null) {
              sendData(subscriber, topic, data);
            }
          }
        }
      } catch (Exception ex) {
        LOG.warn("Data read error", ex);
      }
    }

    @Override
    public void onOpen(Connection cnctn)
    {
      this.connection = cnctn;
    }

    @Override
    public void onClose(int i, String string)
    {
      if (subscriber == this) {
        subscriber = null;
      }
    }

  }

  private synchronized void sendData(PubSubWebSocket webSocket, String topic, Object data)
  {
    // This composing code will be handled by API in future in a manner that is transparent to the
    // user and should not be relied upon
    HashMap<String, Object> map = new HashMap<String, Object>();
    map.put("type", "data");
    map.put("topic", topic);
    map.put("data", data);
    try {
      webSocket.connection.sendMessage(mapper.writeValueAsString(map));
    } catch (IOException ex) {
      LOG.warn("Connection send error", ex);
    }
  }

  public boolean hasSubscriber()
  {
    return subscriber != null;
  }

}