src/main/csharp/MessageConsumer.cs

using System;
using System.Messaging;
using System.Threading;
/*
 * 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.
 */
using Apache.NMS.Util;

namespace Apache.NMS.MSMQ
{
	/// <summary>
	/// An object capable of receiving messages from some destination
	/// </summary>
	public class MessageConsumer : IMessageConsumer
	{
		protected TimeSpan zeroTimeout = new TimeSpan(0);

		private readonly Session session;
		private readonly AcknowledgementMode acknowledgementMode;
		private MessageQueue messageQueue;
		private event MessageListener listener;
		private AtomicBoolean asyncDelivery = new AtomicBoolean(false);

		public MessageConsumer(Session session, AcknowledgementMode acknowledgementMode, MessageQueue messageQueue)
		{
			this.session = session;
			this.acknowledgementMode = acknowledgementMode;
			this.messageQueue = messageQueue;
		}

		public event MessageListener Listener
		{
			add
			{
				listener += value;
				StartAsyncDelivery();
			}
			remove
			{
				listener -= value;
			}
		}

		public IMessage Receive()
		{
			Message message = messageQueue.Receive();
			return ToNmsMessage(message);
		}

		public IMessage Receive(TimeSpan timeout)
		{
			Message message = messageQueue.Receive(timeout);
			return ToNmsMessage(message);
		}

		public IMessage ReceiveNoWait()
		{
			Message message = messageQueue.Receive(zeroTimeout);
			return ToNmsMessage(message);
		}

		public void Dispose()
		{
			throw new NotImplementedException();
		}

		public void Close()
		{
			StopAsyncDelivery();
			Dispose();
		}

		public void StopAsyncDelivery()
		{
			asyncDelivery.Value = false;
		}

		protected virtual void StartAsyncDelivery()
		{
			if(asyncDelivery.CompareAndSet(false, true))
			{
				Thread thread = new Thread(new ThreadStart(DispatchLoop));
				thread.IsBackground = true;
				thread.Start();
			}
		}

		protected virtual void DispatchLoop()
		{
			Tracer.Info("Starting dispatcher thread consumer: " + this);
			while(asyncDelivery.Value)
			{
				IMessage message = Receive();
				if(message != null)
				{
					try
					{
						listener(message);
					}
					catch(Exception e)
					{
						HandleAsyncException(e);
					}
				}
			}
			Tracer.Info("Stopping dispatcher thread consumer: " + this);
		}

		protected virtual void HandleAsyncException(Exception e)
		{
			session.Connection.HandleException(e);
		}

		protected virtual IMessage ToNmsMessage(Message message)
		{
			if(message == null)
			{
				return null;
			}
			return session.MessageConverter.ToNmsMessage(message);
		}
	}
}