MessageQueue.java

/**
 * The MIT License
 * Copyright (c) 2014 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package com.iluwatar.queue.load.leveling;

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 
 * MessageQueue class.
 * In this class we will create a Blocking Queue and 
 * submit/retrieve all the messages from it.
 */
public class MessageQueue {
  
  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
  
  private final BlockingQueue<Message> blkQueue;
  
  // Default constructor when called creates Blocking Queue object. 
  public MessageQueue() {
    this.blkQueue = new ArrayBlockingQueue<Message>(1024);
  }
  
  /**
   * All the TaskGenerator threads will call this method to insert the
   * Messages in to the Blocking Queue. 
   */
  public void submitMsg(Message msg) {
    try {
      if (null != msg) {
        blkQueue.add(msg);
      }
    } catch (Exception e) {
      LOGGER.error(e.getMessage());
    }
  }
  
  /**
   * All the messages will be retrieved by the ServiceExecutor by 
   * calling this method and process them.
   * Retrieves and removes the head of this queue, or returns null if this queue is empty.
   */
  public Message retrieveMsg() {
    Message retrievedMsg = null;
    try {
      retrievedMsg = blkQueue.poll();
    } catch (Exception e) {
      LOGGER.error(e.getMessage());
    }
    
    return retrievedMsg;
  }
}