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
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 : 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
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 : 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！
