基于事件总线EventBus实现邮件推送功能

本文主要是介绍基于事件总线EventBus实现邮件推送功能，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

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

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、

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

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

  public void AddSub<T, TH>()where T : EventDatawhere 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

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>;

public void Subscribe<T, TH>(string exchangeName, string exchangeType, string queueName)where T : EventDatawhere 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