【IT168技术文档】
上篇讲到WinCe下的MSMQ安装 ，这篇讲述一下MSMQ在.NET Compact Framework下的开发。
所谓MQ就是Message Queue，消息队列。消息队列可以作为不同应用程序之间，甚至不同机器之间通信的渠道。在消息队列下进行通信的内容称为消息（Message），在C#程序下Message就是对象。
MSMQ就是Microsoft公司提供的MQ服务程序。MQ服务程序负责管理消息队列，保证消息在消息队列这一渠道下能无误的发送到对端，MQ支持离线交易，有时候消息会缓存在MQ服务程序中，当接收方再线时候在提取消息。这一特性使得MQ可以广泛使用在移动领域，因为移动应用的网络不能保证7×24的长连接。
生成队列
在CF.net下开发MQ，需要引用System.Messaging库。
using System.Messaging;
public class MQService
{
private const string mMachinePrefix = @".\";
private const string mPrivateQueueNamePrefix = mMachinePrefix + @"Private$\";
private const string mServiceQueuePath = mPrivateQueueNamePrefix + "MQServiceQueue$";
private MessageQueue mServiceQueue;
private void InitServiceQueue()
{
// create the message queue
try
{
// check to make sure the message queue does not exist already
if (!MessageQueue.Exists(mServiceQueuePath))
{
// create the new message queue and make it transactional
mServiceQueue = MessageQueue.Create(mServiceQueuePath);
mServiceQueue.Close();
}
else
{
mServiceQueue = new MessageQueue(mServiceQueuePath);
}
Type[] types = new Type[1];
types[0] = typeof(string);
mServiceQueue.Formatter = new XmlMessageFormatter(types);
mServiceQueue.ReceiveCompleted += new ReceiveCompletedEventHandler(MessageListenerEventHandler);
// Begin the asynchronous receive operation.
mServiceQueue.BeginReceive();
mServiceQueue.Close();
}
// show message if we used an invalid message queue name;
catch (MessageQueueException MQException)
{
Console.WriteLine(MQException.Message);
}
return;
}
}
在建立Q之前先检查该Q是否存在，如果存在就生成Q的处理对象，如果不存在就先在队列管理器建立这个Q。建立Q的时候，输入参数为一个string，这个string可以为path（路径），FormatName或者Label。使用path的相对广泛，在例子中使用path作为输入参数。Path由MachineName and QueueName组成，建立的Q可以分为Public，Private，Journal和DeadLetter。使用广泛的是Public和Private，Public的Q由MachineName and QueueName组成，格式如MachineName\QueueName，而Private的Q的格式为MachineName\Private$\QueueName，比Public的Q多了一个标识Private$，在例子中使用了Private的Q。路径“.\”指的是本地机器。
Property Formatter十分重要，他定义了消息体的格式，所谓消息体的格式就是通过这个Q通信的消息的数据类型，一个Q可以传递多个不同的数据类型，需要在Type进行定义然后赋值给Formatter。
Event ReceiveCompleted用来注册接收处理函数，当Q接收到消息后，使用注册的函数进行处理。使用ReceiveCompleted注册处理函数以后，必须调用BeginReceive让这个Q进入异步接收状态。
下面讲述MQ应用中两种常见的应用模式，第一种为请求回应模式，第二种为注册广播模式。
请求回应模式
public class MQService
{
private const string mMachinePrefix = @".\";
private const string mPrivateQueueNamePrefix = mMachinePrefix + @"Private$\";
private const string mServiceQueuePath = mPrivateQueueNamePrefix + "MQServiceQueue$";
private System.Messaging.MessageQueue mServiceQueue;
private void InitServiceQueue()
{
// create the message queue
try
{
// check to make sure the message queue does not exist already
if (!System.Messaging.MessageQueue.Exists(mServiceQueuePath))
{
// create the new message queue and make it transactional
mServiceQueue = System.Messaging.MessageQueue.Create(mServiceQueuePath);
mServiceQueue.Close();
}
else
{
mServiceQueue = new System.Messaging.MessageQueue(mServiceQueuePath);
}
Type[] types = new Type[1];
types[0] = typeof(string);
mServiceQueue.Formatter = new System.Messaging.XmlMessageFormatter(types);
mServiceQueue.ReceiveCompleted += new System.Messaging.ReceiveCompletedEventHandler(MessageListenerEventHandler);
// Begin the asynchronous receive operation.
mServiceQueue.BeginReceive();
mServiceQueue.Close();
}
// show message if we used an invalid message queue name;
catch (System.Messaging.MessageQueueException MQException)
{
Console.WriteLine(MQException.Message);
}
return;
}
private void MessageListenerEventHandler(object sender, System.Messaging.ReceiveCompletedEventArgs e)
{
try
{
// Connect to the queue.
System.Messaging.MessageQueue mq = (System.Messaging.MessageQueue)sender;
// End the asynchronous receive operation.
System.Messaging.Message msg = mq.EndReceive(e.AsyncResult);
if (msg.Body.ToString() == "mq_reques_1")
{
msg.ResponseQueue.Send("mq_respond_1");
}
else if (msg.Body.ToString() == "mq_reques_2")
{
msg.ResponseQueue.Send(true);
}
// Restart the asynchronous receive operation.
mq.BeginReceive();
}
catch (System.Messaging.MessageQueueException ex)
{
// Handle sources of MessageQueueException.
Console.WriteLine(ex.Message);
}
return;
}
}
public class MQClient
{
private const string mMachinePrefix = @".\";
private const string mPrivateQueueNamePrefix = mMachinePrefix + @"Private$\";
private const string mServiceQueuePath = mPrivateQueueNamePrefix + "MQServiceQueue$";
private const string mClientQueuePath = mPrivateQueueNamePrefix + "MQClientQueue$";
private System.Messaging.MessageQueue mServiceQueue;
private System.Messaging.MessageQueue mClientQueue;
public void InitQueues()
{
// create the message queue
try
{
mServiceQueue = new System.Messaging.MessageQueue(mServiceQueuePath);
// check to make sure the message queue does not exist already
if (!System.Messaging.MessageQueue.Exists(mClientQueuePath))
{
// create the new message queue and make it transactional
mClientQueue = System.Messaging.MessageQueue.Create(mClientQueuePath);
mClientQueue.Close();
}
else
{
mClientQueue = new System.Messaging.MessageQueue(mClientQueuePath);
}
Type[] types = new Type[2];
types[0] = typeof(string);
types[1] = typeof(bool);
mClientQueue.Formatter = new System.Messaging.XmlMessageFormatter(types);
mClientQueue.Close();
}
// show message if we used an invalid message queue name;
catch (System.Messaging.MessageQueueException MQException)
{
Console.WriteLine(MQException.Message);
}
return;
}
private void SendRequest()
{
try
{
System.Messaging.Message message = new System.Messaging.Message("mq_reques_1");
message.ResponseQueue = mClientQueue;
mClientQueue.Purge();
mServiceQueue.Send(message);
System.Messaging.Message msg = mClientQueue.Receive(new TimeSpan(0, 0, 4));
//handle the result.
Console.WriteLine(msg.Body.ToString());
}
// show message if we used an invalid message queue name;
catch (System.Messaging.MessageQueueException MQException)
{
Console.WriteLine(MQException.Message);
}
}
}
MQService是服务程序，负责服务队列".\Private$\MQServiceQueue$"的建立和管理，当有新消息发送到该服务队列时MessageListenerEventHandler函数就会callback，取出消息进行分析处理和发送返回，返回是通过client原先建立的Q进行返回，不是通过原服务Q返回，因为MQ的队列是单向的。MQClient负责客户端队列".\Private$\MQClientQueue$"的建立，在发送请求的时候把客户端队列赋值到properties ResponseQueue里，让服务程序可以返回到这个客户端的队列里面，同时在等待返回的时候有超时控制。
注册广播模式
注册广播模式是Observer模式的一种应用，Observer模式可见实用设计模式之一--Observer模式。
客户端可以往服务端注册关心的消息，服务端通过MQ自动广播消息到客户端。
public class MQService
{
private const string mMachinePrefix = @".\";
private const string mPrivateQueueNamePrefix = mMachinePrefix + @"Private$\";
private const string mServiceQueuePath = mPrivateQueueNamePrefix + "MQServiceQueue$";
private System.Messaging.MessageQueue mServiceQueue;
private Dictionary<string, MessageQueue> mmClientQueues = new Dictionary<string, MessageQueue>();
private void InitServiceQueue()
{
// create the message queue
try
{
// check to make sure the message queue does not exist already
if (!System.Messaging.MessageQueue.Exists(mServiceQueuePath))
{
// create the new message queue and make it transactional
mServiceQueue = System.Messaging.MessageQueue.Create(mServiceQueuePath);
mServiceQueue.Close();
}
else
{
mServiceQueue = new System.Messaging.MessageQueue(mServiceQueuePath);
}
Type[] types = new Type[1];
types[0] = typeof(string);
mServiceQueue.Formatter = new System.Messaging.XmlMessageFormatter(types);
mServiceQueue.ReceiveCompleted += new System.Messaging.ReceiveCompletedEventHandler(MessageListenerEventHandler);
// Begin the asynchronous receive operation.
mServiceQueue.BeginReceive();
mServiceQueue.Close();
}
// show message if we used an invalid message queue name;
catch (System.Messaging.MessageQueueException MQException)
{
Console.WriteLine(MQException.Message);
}
return;
}
private void MessageListenerEventHandler(object sender, System.Messaging.ReceiveCompletedEventArgs e)
{
try
{
// Connect to the queue.
System.Messaging.MessageQueue mq = (System.Messaging.MessageQueue)sender;
// End the asynchronous receive operation.
System.Messaging.Message msg = mq.EndReceive(e.AsyncResult);
if(msg.Body.ToString() == "mq_register_1")
{
mmClientQueues.Add(msg.Label, msg.ResponseQueue);
}
else if(msg.Body.ToString() == "mq_unregister_1")
{
mmClientQueues[msg.Label].Purge();
mmClientQueues.Remove(msg.Label);
}
// Restart the asynchronous receive operation.
mq.BeginReceive();
}
catch (System.Messaging.MessageQueueException ex)
{
// Handle sources of MessageQueueException.
Console.WriteLine(ex.Message);
}
return;
}
private void Notify(string str)
{
if (mmClientQueues.Count > 0)
{
foreach(MessageQueue mq in mmClientQueues.Values)
{
mq.Send(str);
}
}
}
}
public class MQClient
{
private const string mMachinePrefix = @".\";
private const string mPrivateQueueNamePrefix = mMachinePrefix + @"Private$\";
private const string mServiceQueuePath = mPrivateQueueNamePrefix + "MQServiceQueue$";
private const string mClientQueuePath = mPrivateQueueNamePrefix + "MQClientQueue$";
private System.Messaging.MessageQueue mServiceQueue;
private System.Messaging.MessageQueue mClientQueue;
public void InitQueues()
{
// create the message queue
try
{
mServiceQueue = new System.Messaging.MessageQueue(mServiceQueuePath);
// check to make sure the message queue does not exist already
if (!System.Messaging.MessageQueue.Exists(mClientQueuePath))
{
// create the new message queue and make it transactional
mClientQueue = System.Messaging.MessageQueue.Create(mClientQueuePath);
mClientQueue.Close();
}
else
{
mClientQueue = new System.Messaging.MessageQueue(mClientQueuePath);
}
Type[] types = new Type[2];
types[0] = typeof(string);
types[1] = typeof(bool);
mClientQueue.Formatter = new System.Messaging.XmlMessageFormatter(types);
//Initiate the asynchronous receive operation by telling the Message
// Queue to begin receiving messages and notify the event handler
// when finished
mClientQueue.ReceiveCompleted +=
new System.Messaging.ReceiveCompletedEventHandler(ClientQueueReceiveCompleted);
mClientQueue.BeginReceive();
mClientQueue.Close();
}
// show message if we used an invalid message queue name;
catch (System.Messaging.MessageQueueException MQException)
{
Console.WriteLine(MQException.Message);
}
return;
}
private void RegisterService()
{
try
{
System.Messaging.Message message = new System.Messaging.Message("mq_register_1");
message.Label = "client1";
message.ResponseQueue = mClientQueue;
mServiceQueue.Send(message);
}
// show message if we used an invalid message queue name;
catch (System.Messaging.MessageQueueException MQException)
{
Console.WriteLine(MQException.Message);
}
}
private void UnregisterService()
{
try
{
System.Messaging.Message message = new System.Messaging.Message("mq_unregister_1");
message.Label = "client1";
mServiceQueue.Send(message);
Thread.Sleep(500);
mClientQueue.Purge();
}
// show message if we used an invalid message queue name;
catch (System.Messaging.MessageQueueException MQException)
{
Console.WriteLine(MQException.Message);
}
}
private void ClientQueueReceiveCompleted(Object source,
ReceiveCompletedEventArgs asyncResult)
{
try
{
// End the Asynchronous Receive Operation
Message message =
mClientQueue.EndReceive(asyncResult.AsyncResult);
if (message.Body is string)
{
Console.WriteLine(message.Body.ToString());
}
}
catch (MessageQueueException e)
{
Console.WriteLine
(String.Format(System.Globalization.CultureInfo.CurrentCulture,
"Failed to receive Message: {0} ", e.ToString()));
}
//Begin the next Asynchronous Receive Operation
mClientQueue.BeginReceive();
}
}
和请求回应模式相比MQService使用容器保存所有注册的客户端的Q，当需要notify的时候遍历所有客户端Q进行广播。MQClient建立广播Q，然后注册函数ClientQueueReceiveCompleted处理广播事件。MQ的应用能把Oberver模式应用跨进程和跨系统，消息订阅广播机制可以借助MQ和observer模式来实现。
