受到CQRS的影响,写了个EventBus,能实现订阅模式执行event,在DDD模型中,可以使用如下代码触发事件:
EventBus bus = EventBus.Instance();
bus.Publish(new OrderAddedEvent());
解决方案结构图如下,很简单易懂:
xml事件配置代码sample如下(1个event可以定义多个订阅者,如下):
<?xml version="1.0" encoding="utf-8" ?>
<Events>
<Event>
<PublishEvent>ConsoleApplication2.code.Events.OrderAddedEvent</PublishEvent>
<SubscribedEvents>
<SubscribedEvent>ConsoleApplication2.code.EventHandlers.OrderAddedEventHandler_CachePrepare</SubscribedEvent>
<SubscribedEvent>ConsoleApplication2.code.EventHandlers.OrderAddedEventHandler_PDFGenerate</SubscribedEvent>
</SubscribedEvents>
</Event>
<Event>
<PublishEvent>ConsoleApplication2.code.Events.OrderDeletedEvent</PublishEvent>
<SubscribedEvents>
<SubscribedEvent>ConsoleApplication2.code.EventHandlers.OrderDeletedEventHandler_NotifyClient</SubscribedEvent>
<SubscribedEvent>ConsoleApplication2.code.EventHandlers.OrderDeletedEventHandler_RemovCache</SubscribedEvent>
</SubscribedEvents>
</Event>
</Events>
我们先来定义Event:
public class BaseEvent //空的,不需要实现其他方法
{
}
public class OrderAddedEvent : BaseEvent //订单已经加入,触发的event
{
}
public class OrderDeletedEvent : BaseEvent //订单已经删除,触发的event
{
public Guid OrderId { get; set; }
public OrderDeletedEvent(Guid orderId)
{
this.OrderId = orderId;
}
}
定义事件的处理程序:
public interface IEventHandler<T>
where T : BaseEvent
{
void Handle(T evt);
}
public class OrderDeletedEventHandler_NotifyClient : IEventHandler<OrderDeletedEvent>
{
public void Handle(OrderDeletedEvent evt)
{
Console.WriteLine("[Order deleted] Notified.");
}
}
上面2个步骤很简单,只是简单的定义事件、事件处理程序,要怎样才能触发事件处理程序并且做成可配置的方式呢?请看下面代码即可:
private static Dictionary<Type, List<Type>> eventMapping = new Dictionary<Type, List<Type>>();
XElement root=XElement.Load(System.IO.Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "EventBus.xml")); //这个xml文件需要设置为一直拷贝到程序目录中
foreach (var evt in root.Elements("Event"))
{
List<Type> eventHandlers = new List<Type>();
Type publishEventType = Type.GetType(evt.Element("PublishEvent").Value);
foreach (var subscritedEvt in evt.Elements("SubscribedEvents"))
foreach (var concreteEvt in subscritedEvt.Elements("SubscribedEvent"))
eventHandlers.Add(Type.GetType(concreteEvt.Value));
eventMapping[publishEventType] = eventHandlers; //加入Dictionary中
}
再来上代码:
public void Publish(BaseEvent evt)
{
var result = from tb in eventMapping
where tb.Key.Equals(evt.GetType())
select tb;
foreach (KeyValuePair<Type, List<Type>> t in result.ToList())
{
foreach (Type tt in t.Value)
{
Type targetType = tt;
MethodInfo mi=targetType.GetMethod("Handle"); //这个Handle文本字符串,必须和IEventHandler<T>中定义的方法一致
if(mi==null)
continue;
object o = Activator.CreateInstance(targetType); //new实例
mi.Invoke(o, new object[] { evt }); //调用方法,并且传入事件参数
}
}
}
运行效果图如下: