WCF中使用观察者模式实现事件通知
看了一些WCF的例子,实现事件通知使用的是多播委托的特性,有点复杂,操作起来也不是很直观,看到一堆委托和事件我一般头就晕了。下面介绍一种使用观察者模式实现事件通知的简单方法。没别的,就是简单,简单最美。
工程代码如下:https://files.cnblogs.com/dyj057/WcfEvent.rar
1.定义接口
为了简单举了一个写日志的例子, Write(string logMsg)就是写入日志的方法,参数logMsg是需要写入的日志信息。当客户单没有调用RegisterListener()订阅事件的时候,是不会收到写日志的事件通知的,相应的要获得写日志的事件通知,就需要调用RegisterListener()方法。如果要取消订阅就调用UnregisterListener()方法。写日志的功能和事件的订阅功能是分开的。
2.服务实现
3.客户端访问
定义回调的客户端:
然后在程序中使用它:
需要注意的问题:
A. 因为客户也要监听端口,所以确保防火墙没有对它进行阻止。
B. 这里使用的是单实例的服务,所以需要进行多进程访问的保护,才能实际使用。
工程代码如下:https://files.cnblogs.com/dyj057/WcfEvent.rar
1.定义接口
[ServiceContract(SessionMode = SessionMode.Required, CallbackContract = typeof(IWriteLogCallback))]
public interface ILogService
{
[OperationContract(IsInitiating = true, IsTerminating = false)]
void Write(string logMsg);
[OperationContract(IsInitiating = true, IsTerminating = false)]
void RegisterListener();
[OperationContract(IsInitiating = false, IsTerminating = false)]
void UnregisterListener();
}
[ServiceContract]
public interface IWriteLogCallback
{
[OperationContract(IsOneWay = true)]
void OnWriteLog(string logMsg);
}
public interface ILogService
{
[OperationContract(IsInitiating = true, IsTerminating = false)]
void Write(string logMsg);
[OperationContract(IsInitiating = true, IsTerminating = false)]
void RegisterListener();
[OperationContract(IsInitiating = false, IsTerminating = false)]
void UnregisterListener();
}
[ServiceContract]
public interface IWriteLogCallback
{
[OperationContract(IsOneWay = true)]
void OnWriteLog(string logMsg);
}
为了简单举了一个写日志的例子, Write(string logMsg)就是写入日志的方法,参数logMsg是需要写入的日志信息。当客户单没有调用RegisterListener()订阅事件的时候,是不会收到写日志的事件通知的,相应的要获得写日志的事件通知,就需要调用RegisterListener()方法。如果要取消订阅就调用UnregisterListener()方法。写日志的功能和事件的订阅功能是分开的。
2.服务实现
[ServiceBehavior(
IncludeExceptionDetailInFaults = true,
InstanceContextMode = InstanceContextMode.Single,
ConcurrencyMode = ConcurrencyMode.Multiple)]
class LogService:ILogService
{
public LogService()
{
Trace.WriteLine("Create LogService Instance.");
}
Dictionary<string, OperationContext> listeners = new Dictionary<string, OperationContext>();
private void BroadCast(string logMsg)
{
List<string> errorClints = new List<string>();
foreach (KeyValuePair<string, OperationContext> listener in listeners)
{
try
{
listener.Value.GetCallbackChannel<IWriteLogCallback>().OnWriteLog(logMsg);
}
catch (System.Exception e)
{
errorClints.Add(listener.Key);
Trace.WriteLine("BROAD EVENT ERROR:" + e.Message);
}
}
foreach (string id in errorClints)
{
listeners.Remove(id);
}
}
#region ILogService 成员
public void Write(string logMsg)
{
Trace.WriteLine("Write LOG:"+logMsg);
BroadCast(logMsg);
}
public void RegisterListener()
{
listeners.Add(OperationContext.Current.SessionId, OperationContext.Current);
Trace.WriteLine("SessionID:" + OperationContext.Current.SessionId);
Trace.WriteLine("Register listener. Client Count:" + listeners.Count.ToString());
}
public void UnregisterListener()
{
listeners.Remove(OperationContext.Current.SessionId);
Trace.WriteLine("SessionID:" + OperationContext.Current.SessionId);
Trace.WriteLine("Unregister listener. Client Count:" + listeners.Count.ToString());
}
#endregion
}
Dictionary<string, OperationContext> listeners包含了所有的事件订阅者。发布事件的时候,如果调用订阅者的回调函数失败,就把该订阅者从listeners移除。代码很简单,就不多说了。IncludeExceptionDetailInFaults = true,
InstanceContextMode = InstanceContextMode.Single,
ConcurrencyMode = ConcurrencyMode.Multiple)]
class LogService:ILogService
{
public LogService()
{
Trace.WriteLine("Create LogService Instance.");
}
Dictionary<string, OperationContext> listeners = new Dictionary<string, OperationContext>();
private void BroadCast(string logMsg)
{
List<string> errorClints = new List<string>();
foreach (KeyValuePair<string, OperationContext> listener in listeners)
{
try
{
listener.Value.GetCallbackChannel<IWriteLogCallback>().OnWriteLog(logMsg);
}
catch (System.Exception e)
{
errorClints.Add(listener.Key);
Trace.WriteLine("BROAD EVENT ERROR:" + e.Message);
}
}
foreach (string id in errorClints)
{
listeners.Remove(id);
}
}
#region ILogService 成员
public void Write(string logMsg)
{
Trace.WriteLine("Write LOG:"+logMsg);
BroadCast(logMsg);
}
public void RegisterListener()
{
listeners.Add(OperationContext.Current.SessionId, OperationContext.Current);
Trace.WriteLine("SessionID:" + OperationContext.Current.SessionId);
Trace.WriteLine("Register listener. Client Count:" + listeners.Count.ToString());
}
public void UnregisterListener()
{
listeners.Remove(OperationContext.Current.SessionId);
Trace.WriteLine("SessionID:" + OperationContext.Current.SessionId);
Trace.WriteLine("Unregister listener. Client Count:" + listeners.Count.ToString());
}
#endregion
}
3.客户端访问
定义回调的客户端:
class LogClient:IWriteLogCallback
{
#region IWriteLogCallback 成员
public void OnWriteLog(string logMsg)
{
Trace.WriteLine("RECV LOG EVENT:" + logMsg);
}
#endregion
}
{
#region IWriteLogCallback 成员
public void OnWriteLog(string logMsg)
{
Trace.WriteLine("RECV LOG EVENT:" + logMsg);
}
#endregion
}
然后在程序中使用它:
class Program
{
static void Main(string[] args)
{
Trace.Listeners.Add(new ConsoleTraceListener());
LogClient client = new LogClient();
ILogService service = DuplexChannelFactory<ILogService>.CreateChannel(client,
new WSDualHttpBinding(), new EndpointAddress("http://localhost:8888/log"));
//订阅消息
service.RegisterListener();
service.Write("Client start");
Console.WriteLine("Press enter key to exit.");
Console.ReadLine();
service.UnregisterListener();
}
{
static void Main(string[] args)
{
Trace.Listeners.Add(new ConsoleTraceListener());
LogClient client = new LogClient();
ILogService service = DuplexChannelFactory<ILogService>.CreateChannel(client,
new WSDualHttpBinding(), new EndpointAddress("http://localhost:8888/log"));
//订阅消息
service.RegisterListener();
service.Write("Client start");
Console.WriteLine("Press enter key to exit.");
Console.ReadLine();
service.UnregisterListener();
}
需要注意的问题:
A. 因为客户也要监听端口,所以确保防火墙没有对它进行阻止。
B. 这里使用的是单实例的服务,所以需要进行多进程访问的保护,才能实际使用。