Event Bus & DomainNotification

Christ3D.Domain.Core/Bus/IMediatorHandler.cs

@@ -1,6 +1,6 @@
 using System.Threading.Tasks;
 using Christ3D.Domain.Core.Commands;
-
+using Christ3D.Domain.Core.Events;
 
 namespace Christ3D.Domain.Core.Bus
 {
@@ -18,5 +18,15 @@ public interface IMediatorHandler
         /// <param name="command"> 命令模型，比如RegisterStudentCommand </param>
         /// <returns></returns>
         Task SendCommand<T>(T command) where T : Command;
+
+
+        /// <summary>
+        /// 引发事件，通过总线，发布事件
+        /// </summary>
+        /// <typeparam name="T"> 泛型 继承 Event：INotification</typeparam>
+        /// <param name="event"> 事件模型，比如StudentRegisteredEvent，</param>
+        /// 请注意一个细节：这个命名方法和Command不一样，一个是RegisterStudentCommand注册学生命令之前,一个是StudentRegisteredEvent学生被注册事件之后
+        /// <returns></returns>
+        Task RaiseEvent<T>(T @event) where T : Event;
     }
 }

Christ3D.Domain.Core/Christ3D.Domain.Core.csproj

@@ -4,10 +4,6 @@
     <TargetFramework>netcoreapp2.1</TargetFramework>
   </PropertyGroup>
 
-  <ItemGroup>
-    <Folder Include="Events\" />
-  </ItemGroup>
-
   <ItemGroup>
     <PackageReference Include="FluentValidation" Version="8.1.0-preview1" />
     <PackageReference Include="MediatR" Version="5.1.0" />

Christ3D.Domain.Core/Events/Event.cs

@@ -0,0 +1,21 @@
+using System;
+using MediatR;
+
+namespace Christ3D.Domain.Core.Events
+{
+    /// <summary>
+    /// 事件模型 抽象基类，继承 INotification
+    /// 也就是说，拥有中介者模式中的 发布/订阅模式
+    /// </summary>
+    public abstract class Event : INotification
+    {
+        // 时间戳
+        public DateTime Timestamp { get; private set; }
+
+        // 每一个事件都是有状态的
+        protected Event()
+        {
+            Timestamp = DateTime.Now;
+        }
+    }
+}

Christ3D.Domain.Core/Notifications/DomainNotification.cs

@@ -0,0 +1,30 @@
+using System;
+using Christ3D.Domain.Core.Events;
+
+namespace Christ3D.Domain.Core.Notifications
+{
+    /// <summary>
+    /// 领域通知模型，用来获取当前总线中出现的通知信息
+    /// 继承自领域事件和 INotification（也就意味着可以拥有中介的发布/订阅模式）
+    /// </summary>
+    public class DomainNotification : Event
+    {
+        // 标识
+        public Guid DomainNotificationId { get; private set; }
+        // 键（可以根据这个key，获取当前key下的全部通知信息）
+        // 这个我们在事件源和事件回溯的时候会用到，伏笔
+        public string Key { get; private set; }
+        // 值（与key对应）
+        public string Value { get; private set; }
+        // 版本信息
+        public int Version { get; private set; }
+
+        public DomainNotification(string key, string value)
+        {
+            DomainNotificationId = Guid.NewGuid();
+            Version = 1;
+            Key = key;
+            Value = value;
+        }
+    }
+}

Christ3D.Domain.Core/Notifications/DomainNotificationHandler.cs

@@ -0,0 +1,49 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using MediatR;
+
+namespace Christ3D.Domain.Core.Notifications
+{
+    /// <summary>
+    /// 领域通知处理程序，把所有的通知信息放到事件总线中
+    /// 继承 INotificationHandler<T>
+    /// </summary>
+    public class DomainNotificationHandler : INotificationHandler<DomainNotification>
+    {
+        // 通知信息列表
+        private List<DomainNotification> _notifications;
+
+        // 每次访问该处理程序的时候，实例化一个空集合
+        public DomainNotificationHandler()
+        {
+            _notifications = new List<DomainNotification>();
+        }
+
+        // 处理方法，把全部的通知信息，添加到内存里
+        public Task Handle(DomainNotification message, CancellationToken cancellationToken)
+        {
+            _notifications.Add(message);
+            return Task.CompletedTask;
+        }
+
+        // 获取当前生命周期内的全部通知信息
+        public virtual List<DomainNotification> GetNotifications()
+        {
+            return _notifications;
+        }
+
+        // 判断在当前总线对象周期中，是否存在通知信息
+        public virtual bool HasNotifications()
+        {
+            return GetNotifications().Any();
+        }
+
+        // 手动回收（清空通知）
+        public void Dispose()
+        {
+            _notifications = new List<DomainNotification>();
+        }
+    }
+}

Christ3D.Domain/CommandHandlers/CommandHandler.cs

@@ -1,5 +1,6 @@
 using Christ3D.Domain.Core.Bus;
 using Christ3D.Domain.Core.Commands;
+using Christ3D.Domain.Core.Notifications;
 using Christ3D.Domain.Interfaces;
 using Microsoft.Extensions.Caching.Memory;
 using System;
@@ -33,20 +34,25 @@ public CommandHandler(IUnitOfWork uow, IMediatorHandler bus, IMemoryCache cache)
             _cache = cache;
         }
 
+
         //将领域命令中的验证错误信息收集
         //目前用的是缓存方法（以后通过领域通知替换）
         protected void NotifyValidationErrors(Command message)
         {
             List<string> errorInfo = new List<string>();
             foreach (var error in message.ValidationResult.Errors)
             {
-                errorInfo.Add(error.ErrorMessage);
+                //errorInfo.Add(error.ErrorMessage);
 
+                //将错误信息提交到事件总线，派发出去
+                _bus.RaiseEvent(new DomainNotification("", error.ErrorMessage));
             }
-            //将错误信息收集
-            _cache.Set("ErrorData", errorInfo);
+
+            //将错误信息收集一：缓存方法（错误示范）
+            //_cache.Set("ErrorData", errorInfo);
         }
 
+
         //工作单元提交
         //如果有错误，下一步会在这里添加领域通知
         public bool Commit()

Christ3D.Domain/CommandHandlers/StudentCommandHandler.cs

@@ -4,6 +4,8 @@
 using System.Threading.Tasks;
 using Christ3D.Domain.Commands;
 using Christ3D.Domain.Core.Bus;
+using Christ3D.Domain.Core.Notifications;
+using Christ3D.Domain.Events;
 using Christ3D.Domain.Interfaces;
 using Christ3D.Domain.Models;
 using MediatR;
@@ -63,14 +65,17 @@ public Task<Unit> Handle(RegisterStudentCommand message, CancellationToken cance
             // 实例化领域模型，这里才真正的用到了领域模型
             // 注意这里是通过构造函数方法实现
             var customer = new Student(Guid.NewGuid(), message.Name, message.Email, message.Phone, message.BirthDate);
-            
+
             // 判断邮箱是否存在
             // 这些业务逻辑，当然要在领域层中（领域命令处理程序中）进行处理
             if (_studentRepository.GetByEmail(customer.Email) != null)
             {
-                //这里对错误信息进行发布，目前采用缓存形式
-                List<string> errorInfo = new List<string>() { "The customer e-mail has already been taken." };
-                Cache.Set("ErrorData", errorInfo);
+                ////这里对错误信息进行发布，目前采用缓存形式
+                //List<string> errorInfo = new List<string>() { "该邮箱已经被使用！" };
+                //Cache.Set("ErrorData", errorInfo);
+
+                //引发错误事件
+                Bus.RaiseEvent(new DomainNotification("", "该邮箱已经被使用！"));
                 return Task.FromResult(new Unit());
             }
 
@@ -83,7 +88,7 @@ public Task<Unit> Handle(RegisterStudentCommand message, CancellationToken cance
                 // 提交成功后，这里需要发布领域事件
                 // 比如欢迎用户注册邮件呀，短信呀等
 
-                // waiting....
+                Bus.RaiseEvent(new StudentRegisteredEvent(customer.Id, customer.Name, customer.Email, customer.BirthDate, customer.Phone));
             }
 
             return Task.FromResult(new Unit());
@@ -95,6 +100,7 @@ public Task<Unit> Handle(UpdateStudentCommand message, CancellationToken cancell
         {
             if (!message.IsValid())
             {
+                NotifyValidationErrors(message);
                 return Task.FromResult(new Unit());
 
             }
@@ -107,6 +113,7 @@ public Task<Unit> Handle(UpdateStudentCommand message, CancellationToken cancell
                 if (!existingCustomer.Equals(customer))
                 {
 
+                    Bus.RaiseEvent(new DomainNotification("", "该邮箱已经被使用！"));
                     return Task.FromResult(new Unit());
 
                 }
@@ -117,6 +124,7 @@ public Task<Unit> Handle(UpdateStudentCommand message, CancellationToken cancell
             if (Commit())
             {
 
+                Bus.RaiseEvent(new StudentUpdatedEvent(customer.Id, customer.Name, customer.Email, customer.BirthDate, customer.Phone));
             }
 
             return Task.FromResult(new Unit());
@@ -128,6 +136,7 @@ public Task<Unit> Handle(RemoveStudentCommand message, CancellationToken cancell
         {
             if (!message.IsValid())
             {
+                NotifyValidationErrors(message);
                 return Task.FromResult(new Unit());
 
             }
@@ -136,6 +145,7 @@ public Task<Unit> Handle(RemoveStudentCommand message, CancellationToken cancell
 
             if (Commit())
             {
+                Bus.RaiseEvent(new StudentRemovedEvent(message.Id));
             }
 
             return Task.FromResult(new Unit());

Christ3D.Domain/EventHandlers/StudentEventHandler.cs

@@ -0,0 +1,37 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Christ3D.Domain.Events;
+using MediatR;
+
+namespace Christ3D.Domain.EventHandlers
+{
+    public class StudentEventHandler :
+        INotificationHandler<StudentRegisteredEvent>,
+        INotificationHandler<StudentUpdatedEvent>,
+        INotificationHandler<StudentRemovedEvent>
+    {
+        // 学习被注册成功后的事件处理方法
+        public Task Handle(StudentRegisteredEvent message, CancellationToken cancellationToken)
+        {
+            // 恭喜您，注册成功，欢迎加入我们。
+
+            return Task.CompletedTask;
+        }
+
+        // 学生被修改成功后的事件处理方法
+        public Task Handle(StudentUpdatedEvent message, CancellationToken cancellationToken)
+        {
+            // 恭喜您，更新成功，请牢记修改后的信息。
+
+            return Task.CompletedTask;
+        }
+
+        // 学习被删除后的事件处理方法
+        public Task Handle(StudentRemovedEvent message, CancellationToken cancellationToken)
+        {
+            // 您已经删除成功啦，记得以后常来看看。
+
+            return Task.CompletedTask;
+        }
+    }
+}

Christ3D.Domain/Events/Student/StudentRegisteredEvent.cs

@@ -0,0 +1,26 @@
+using System;
+using Christ3D.Domain.Core.Events;
+
+namespace Christ3D.Domain.Events
+{
+    public class StudentRegisteredEvent : Event
+    {
+        public StudentRegisteredEvent(Guid id, string name, string email, DateTime birthDate, string phone)
+        {
+            Id = id;
+            Name = name;
+            Email = email;
+            BirthDate = birthDate;
+            Phone = phone;
+        }
+        public Guid Id { get; set; }
+
+        public string Name { get; private set; }
+
+        public string Email { get; private set; }
+
+        public DateTime BirthDate { get; private set; }
+
+        public string Phone { get; private set; }
+    }
+}

Christ3D.Domain/Events/Student/StudentRemovedEvent.cs

@@ -0,0 +1,15 @@
+using System;
+using Christ3D.Domain.Core.Events;
+
+namespace Christ3D.Domain.Events
+{
+    public class StudentRemovedEvent : Event
+    {
+        public StudentRemovedEvent(Guid id)
+        {
+            Id = id;
+        }
+
+        public Guid Id { get; set; }
+    }
+}

Christ3D.Domain/Events/Student/StudentUpdatedEvent.cs

@@ -0,0 +1,26 @@
+using System;
+using Christ3D.Domain.Core.Events;
+
+namespace Christ3D.Domain.Events
+{
+    public class StudentUpdatedEvent : Event
+    {
+        public StudentUpdatedEvent(Guid id, string name, string email, DateTime birthDate,string phone)
+        {
+            Id = id;
+            Name = name;
+            Email = email;
+            BirthDate = birthDate;
+            Phone = phone;
+        }
+        public Guid Id { get; set; }
+
+        public string Name { get; private set; }
+
+        public string Email { get; private set; }
+
+        public DateTime BirthDate { get; private set; }
+
+        public string Phone { get; private set; }
+    }
+}