[领域驱动设计] [Architect] Abp 框架原理解析(2) EventBus

本节目录
原理介绍 Abp源码分析代码实现原理介绍
事件总线大致原理：
（1）       在事件总线内部维护着一个事件与事件处理程序相映射的字典。
（2）       利用反射，事件总线会将实现了IEventHandler的处理程序与相应事件关联到一起，相当于实现了事件处理程序对事件的订阅。
（3）       当发布事件时，事件总线会从字典中找出相应的事件处理程序，然后利用反射去调用事件处理程序中的方法。
Abp源码分析
1.AbpKernelModule的Initialize方法

2.EventBusInstaller的Install方法

3.Kernel_ComponentRegistered

以上将事件注册完成了.
剩下就需要如何触发了.
触发实际上是写在代码里的,最终调用的其实还是EventBus.Trigger()

代码实现
看完Abp的实现,关键点还是反射以及IoC注册对象事件的拦截.
先上实现效果:

    interface IPerson
    {
        void Say();
    }
    class Person : IPerson
    {
        public IEventBus EventBus { get; set; }
        public void Say()
        {
            var str = "Say";
            Console.WriteLine(str);
            EventBus.Trigger(typeof(SayEventData), this, new SayEventData() { Content = str });
        }
    }

定义上面需要的EventData,实际这是事件基类.

    [Serializable]
    public abstract class EventData : IEventData
    {
        public DateTime EventTime { get; set; }

        /// <summary>
        /// The object which triggers the event (optional).
        /// </summary>
        public object EventSource { get; set; }

        protected EventData()
        {
            EventTime = DateTime.Now;
        }
    }

    public interface IEventData
    {
        DateTime EventTime { get; set; }

        object EventSource { get; set; }
    }

自定义事件,继承事件基类,可以添加事件需要传递的数据.

    public class SayEventData : EventData
    {
        public string Content { get; set; }
    }

定义IEventHandle,实际这是事件处理程序,一个事件一般对应多个事件处理程序.

　　public interface IEventHandler
    {

    }
    public interface IEventHandler<in TEventData> : IEventHandler
    {
        /// <summary>
        /// Handler handles the event by implementing this method.
        /// </summary>
        /// <param name="eventData">Event data</param>
        void HandleEvent(TEventData eventData);
    }

自定义的EventHandle,各种事件订阅器.

    public class SayEvent : IEventHandler<SayEventData>
    {
        public void HandleEvent(SayEventData eventData)
        {
            Console.WriteLine("进入事件啦：" + eventData.Content);
        }
    }

事件总线EventBus,管理事件的中心.可以细化接口.

    public interface IEventBus
    {
        void Register(Type eventType, IEventHandler handler);

        void Trigger(Type eventType, object eventSource, IEventData eventData);
    }

EventBus实现,核心是反射调用事件处理程序.

    public class EventBus : IEventBus
    {
        public static EventBus Default { get { return DefaultInstance; } }
        private static readonly EventBus DefaultInstance = new EventBus();
        private readonly Dictionary<Type, List<IEventHandler>> _eventHandlers;
        public EventBus()
        {
            _eventHandlers = new Dictionary<Type, List<IEventHandler>>();
        }
        public void Register(Type eventType, IEventHandler handler)
        {
            GetOrCreateHandlerFactories(eventType).Add(handler);
        }
        private List<IEventHandler> GetOrCreateHandlerFactories(Type eventType)
        {
            List<IEventHandler> handlers;
            if (!_eventHandlers.TryGetValue(eventType, out handlers))
            {
                _eventHandlers[eventType] = handlers = new List<IEventHandler>();
            }
            return handlers;
        }
        public void Trigger(Type eventType, object eventSource, IEventData eventData)
        {
            eventData.EventSource = eventSource;
            var handles = GetOrCreateHandlerFactories(eventType);
            if (handles.Count > 0)
            {
                foreach (var eventHandler in handles)
                {
                    if (eventHandler == null)
                    {
                        throw new Exception("Registered event handler for event type " + eventType.Name + " does not implement IEventHandler<" + eventType.Name + "> interface!");
                    }
                    //eventHandler.
                    var handlerType = typeof(IEventHandler<>).MakeGenericType(eventType);

                    handlerType
                        .GetMethod("HandleEvent", BindingFlags.Public | BindingFlags.Instance, null, new[] { eventType }, null)
                        .Invoke(eventHandler, new object[] { eventData });
                }
            }
        }
    }

执行,来测试是否通了.

        private static IEventBus _eventBus;
        static void Main(string[] args)
        {
            var container = IocManager.Instance.IocContainer;
            container.Register(Component.For<IEventBus>().Instance(EventBus.Default));
            _eventBus = container.Resolve<IEventBus>();
            container.Kernel.ComponentRegistered += Kernel_ComponentRegistered;

            //在Abp中,由于注册了所有ITransientDependency,所以这2个不需要手动注册
            container.Register(Component.For<Person, IPerson>());
            container.Register(Component.For<IEventHandler<SayEventData>, SayEvent>());

            container.Resolve<IPerson>().Say();
            Console.ReadKey();
        }

　　
注册事件的绑定

private static void Kernel_ComponentRegistered(string key, IHandler handler)
        {
            if (!typeof(IEventHandler).IsAssignableFrom(handler.ComponentModel.Implementation))
            {
                return;
            }

            var interfaces = handler.ComponentModel.Implementation.GetInterfaces();
            foreach (var @interface in interfaces)
            {
                if (!typeof(IEventHandler).IsAssignableFrom(@interface))
                {
                    continue;
                }

                var genericArgs = @interface.GetGenericArguments();
                if (genericArgs.Length == 1)
                {
                    //_eventBus.Register(genericArgs[0], handler.ComponentModel.Implementation.CreateInstance<IEventHandler>());
                    _eventBus.Register(genericArgs[0], (IEventHandler)IocManager.Instance.IocContainer.Resolve(handler.ComponentModel.Implementation));
                }
            }
        }

至此,事件成功执行

本文地址:http://www.cnblogs.com/neverc/p/5254859.html

[领域驱动设计][Architect] Abp 框架原理解析(2) EventBus