事件总线EventBus实现邮件推送

基于事件总线EventBus实现邮件推送功能

   有时候，有人给我的网站留了言，但是我必须要打开我的网站（https://www.xiandanplay.com/）才知道，所以我便决定给网站增加一个邮件推送的功能，好让我第一时间知道。于是乎，按照我自己的思路，同时为了去学习了解rabbitmq以及EventBus概念，我便设计了一套邮件推送的功能，这里分享出来，可能方案不是很好，大家不喜勿喷。

什么是事件总线   

    事件总线是对发布-订阅模式的一种实现。它是一种集中式事件处理机制，允许不同的组件之间进行彼此通信而又不需要相互依赖，达到一种解耦的目的。

    关于这个概念，网上有很多讲解的，这里我推荐一个讲的比较好的（事件总线知多少）

什么是RabbitMQ

   RabbitMQ这个就不用说了，想必到家都知道。

粗糙流程图

简单来解释就是：

      1、定义一个事件抽象类

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public abstract class EventData     {         /// <summary>         /// 唯一标识         /// </summary>         public string Unique { get; set; }         /// <summary>         /// 是否成功         /// </summary>         public bool Success { get; set; }         /// <summary>         /// 结果         /// </summary>         public string Result { get; set; }     }

　2、定义一个事件处理抽象类，以及对应的一个队列消息执行的一个记录

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public abstract class EventHandler<T> where T : EventData     {         public async Task Handler(T eventData)         {             await BeginHandler(eventData.Unique);             eventData = await ProcessingHandler(eventData);             if (eventData.Success)                 await FinishHandler(eventData);         }         /// <summary>         ///  开始处理         /// </summary>         /// <param name="unique"></param>         /// <returns></returns>         protected abstract Task BeginHandler(string unique);         /// <summary>         /// 处理中         /// </summary>         /// <param name="eventData"></param>         /// <returns></returns>         protected abstract Task<T> ProcessingHandler(T eventData);         /// <summary>         /// 处理完成         /// </summary>         /// <param name="eventData"></param>         /// <returns></returns>         protected abstract Task FinishHandler(T eventData);     }         [Table("Sys_TaskRecord")]     public class TaskRecord : Entity<long>     {         /// <summary>         /// 任务类型         /// </summary>         public TaskRecordType TaskType { get; set; }         /// <summary>         /// 任务状态         /// </summary>         public int TaskStatu { get; set; }         /// <summary>         /// 任务值         /// </summary>         public string TaskValue { get; set; }         /// <summary>         /// 任务结果         /// </summary>         public string TaskResult { get; set; }         /// <summary>         /// 任务开始时间         /// </summary>         public DateTime TaskStartTime { get; set; }         /// <summary>         /// 任务完成时间         /// </summary>         public DateTime? TaskFinishTime { get; set; }         /// <summary>         /// 任务最后更新时间         /// </summary>         public DateTime? LastUpdateTime { get; set; }         /// <summary>         /// 任务名称         /// </summary>         public string TaskName { get; set; }         /// <summary>         /// 附加数据         /// </summary>         public string AdditionalData { get; set; }     }

　　 3、定义一个邮件事件消息类，继承自EventData，以及一个邮件处理的Hanler继承自EventHandler

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public class EmailEventData:EventData    {        /// <summary>        /// 邮件内容        /// </summary>        public string Body { get; set; }        /// <summary>        /// 接收者        /// </summary>        public string Reciver { get; set; }    }   public class CreateEmailHandler<T> : Core.EventBus.EventHandler<T> where T : EventData    {        private IEmailService emailService;        private IUnitOfWork unitOfWork;        private ITaskRecordService taskRecordService;        public CreateEmailHandler(IEmailService emailService, IUnitOfWork unitOfWork, ITaskRecordService taskRecordService)        {            this.emailService = emailService;            this.unitOfWork = unitOfWork;            this.taskRecordService = taskRecordService;        }        protected override async Task BeginHandler(string unique)        {            await taskRecordService.UpdateRecordStatu(Convert.ToInt64(unique), (int)MqMessageStatu.Processing);            await unitOfWork.CommitAsync();        }          protected override async Task<T> ProcessingHandler(T eventData)        {            try            {                EmailEventData emailEventData = eventData as EmailEventData;                await emailService.SendEmail(emailEventData.Reciver, emailEventData.Reciver, emailEventData.Body, "[闲蛋]收到一条留言");                eventData.Success = true;            }            catch (Exception ex)            {                await taskRecordService.UpdateRecordFailStatu(Convert.ToInt64(eventData.Unique), (int)MqMessageStatu.Fail,ex.Message);                await unitOfWork.CommitAsync();                eventData.Success = false;            }            return eventData;          }          protected override async Task FinishHandler(T eventData)        {            await taskRecordService.UpdateRecordSuccessStatu(Convert.ToInt64(eventData.Unique), (int)MqMessageStatu.Finish,"");            await unitOfWork.CommitAsync();        }

　　 4、接着就是如何把事件消息和事件Hanler关联起来，那么我这里思路就是把EmailEventData的类型和CreateEmailHandler的类型先注册到字典里面，这样我就可以根据EmailEventData找到对应的处理程序了，找类型还不够，如何创建实例呢，这里就还需要把CreateEmailHandler注册到DI容器里面，这样就可以根据容器获取对象了，如下

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public void AddSub<T, TH>()              where T : EventData              where TH : EventHandler<T>         {             Type eventDataType = typeof(T);             Type handlerType = typeof(TH);             if (!eventhandlers.ContainsKey(typeof(T)))                 eventhandlers.TryAdd(eventDataType, handlerType);             _serviceDescriptors.AddScoped(handlerType);         } -------------------------------------------------------------------------------------------------------------------  public Type FindEventType(string eventName)         {             if (!eventTypes.ContainsKey(eventName))                 throw new ArgumentException(string.Format("eventTypes不存在类名{0}的key", eventName));             return eventTypes[eventName];         } ------------------------------------------------------------------------------------------------------------------------------------------------------------   public object FindHandlerType(Type eventDataType)         {             if (!eventhandlers.ContainsKey(eventDataType))                 throw new ArgumentException(string.Format("eventhandlers不存在类型{0}的key", eventDataType.FullName));             var obj = _buildServiceProvider(_serviceDescriptors).GetService(eventhandlers[eventDataType]);             return obj;         } ----------------------------------------------------------------------------------------------------------------------------------  private static IServiceCollection AddEventBusService(this IServiceCollection services)         {             string exchangeName = ConfigureProvider.configuration.GetSection("EventBusOption:ExchangeName").Value;             services.AddEventBus(Assembly.Load("XianDan.Application").GetTypes())                 .AddSubscribe<EmailEventData, CreateEmailHandler<EmailEventData>>(exchangeName, ExchangeType.Direct, BizKey.EmailQueueName);             return services;         }

　　 5、发送消息，这里代码简单，就是简单的发送消息，这里用eventData.GetType().Name作为消息的RoutingKey，这样消费这就可以根据这个key调用FindEventType，然后找到对应的处理程序了

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using (IModel channel = connection.CreateModel()) {      string routeKey = eventData.GetType().Name;      string message = JsonConvert.SerializeObject(eventData);      byte[] body = Encoding.UTF8.GetBytes(message);      channel.ExchangeDeclare(exchangeName, exchangeType, true, false, null);      channel.QueueDeclare(queueName, true, false, false, null);      channel.BasicPublish(exchangeName, routeKey, null, body); }

　　

6、订阅消息，核心的是这一段

  Type eventType = _eventBusManager.FindEventType(eventName);
  var eventData = (T)JsonConvert.DeserializeObject(body, eventType);
  EventHandler<T> eventHandler = _eventBusManager.FindHandlerType(eventType)  as       EventHandler<T>;

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public void Subscribe<T, TH>(string exchangeName, string exchangeType, string queueName)            where T : EventData            where TH : EventHandler<T>        {            try            {                _eventBusManager.AddSub<T, TH>();                IModel channel = connection.CreateModel();                channel.QueueDeclare(queueName, true, false, false, null);                channel.ExchangeDeclare(exchangeName, exchangeType, true, false, null);                channel.QueueBind(queueName, exchangeName, typeof(T).Name, null);                var consumer = new EventingBasicConsumer(channel);                consumer.Received += async (model, ea) =>                {                    string eventName = ea.RoutingKey;                    byte[] resp = ea.Body.ToArray();                    string body = Encoding.UTF8.GetString(resp);                    try                    {                        Type eventType = _eventBusManager.FindEventType(eventName);                        var eventData = (T)JsonConvert.DeserializeObject(body, eventType);                        EventHandler<T> eventHandler = _eventBusManager.FindHandlerType(eventType) as EventHandler<T>;                        await eventHandler.Handler(eventData);                    }                    catch (Exception ex)                    {                        LogUtils.LogError(ex, "EventBusRabbitMQ", ex.Message);                    }                    finally                    {                        channel.BasicAck(ea.DeliveryTag, false);                    }                                     };                channel.BasicConsume(queueName, autoAck: false, consumer: consumer);            }            catch (Exception ex)            {                LogUtils.LogError(ex, "EventBusRabbitMQ.Subscribe", ex.Message);            }          }

　　  注意，这里我使用的时候有个小坑，就是最开始是用using包裹这个IModel channel = connection.CreateModel();导致最后程序启动后无法收到消息，然后去rabbitmq的管理界面发现没有channel连接，队列也没有消费者，最后发现可能是using执行完后就释放掉了，把using去掉就好了。

   好了，到此，我的思路大概讲完了，现在我的网站留言也可以收到邮件了，那么多测试邮件，哈哈哈哈哈

 

  大家感兴趣的话可以去我的网站（https://www.xiandanplay.com/）踩一踩，互加友链也可以的，谢谢大家，不喜勿喷喽！