受到CQRS的影响,写了个EventBus,能实现发布订阅模式执行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:
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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 }
再来上发布代码:
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:
代码下载