我們先來看看CQRS架構，你對下圖的架構還有印象嗎？每個元件的功能都還清楚嗎？如果有疑問，請查考文章《微服務實戰(五)：落地微服務架構到直銷系統(構建高效能大併發系統)》。
1.前端使用者呼叫一個下單Command WebApi，傳遞下單命令；下單Command WebApi接受到下單命令後，將下單命令資料投遞到一個命令佇列中，向前端使用者返回一個資訊。
2.下單Command Handler WebApi偵聽命令佇列中的下單命令，然後呼叫領域物件邏輯，將執行的結果也就是Order物件的當前狀態持久化到Event Store中。
3.下單Command Handler WebApi將下單相關資訊通過事件的方式釋出到一個事件佇列中。(使用者事件處理器最終將訂單資訊更新到業務庫中)
下面通過程式碼簡單體現下過程：
1.定義建立訂單命令：
public class CreateOrderCommand:BaseEvent
{
public OrderDTO orderdto { get; set; }
public CreateOrderCommand() { }
public CreateOrderCommand(OrderDTO orderdto)
{
this.orderdto = orderdto;
this.AggregationRootId = Guid.NewGuid();
this.AssemblyQualifiedAggreateRooType = typeof(Orders).AssemblyQualifiedName;
this.AssemblyQualifiedCommandAndEventType = this.GetType().AssemblyQualifiedName;
}
}
複製程式碼2.訂單 Command WebApi接受前端使用者傳遞的訂單命令：
[Produces("application/json")]
[Route("api/Order")]
public class OrderController : Controller
{
private readonly IEventBus commandbus;
public OrderController(IEventBus commandbus)
{
this.commandbus = commandbus;
}
[HttpPost]
[Route("CreateOrderCmd")]
public ResultEntity<bool> CreateOrderCmd([FromBody] OrderDTO orderdto)
{
var result = new ResultEntity<bool>();
try
{
var createordercommand = new CreateOrderCommand(orderdto);
//釋出命令到命令匯流排
commandbus.Publish(createordercommand);
result.IsSuccess = true;
result.Msg = "下單處理中!";
}
catch(Exception error)
{
result.ErrorCode = 200;
result.Msg = error.Message;
}
return result;
}
}
複製程式碼當然需要定義要注入的命令匯流排：
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
//定義要釋出命令的命令匯流排
services.AddSingleton<IEventHandlerExecutionContext>(new EventHandlerExecutionContext(services));
var connectionFactory = new ConnectionFactory { HostName = "localhost" };
services.AddSingleton<IEventBus>(sp => new RabbitMqEB(connectionFactory,
sp.GetRequiredService<IEventHandlerExecutionContext>(), "exchange1", "direct", "ordercreatecommandqueue", 1));
}
複製程式碼3.訂單Command Handler Web Api偵聽訂單命令，並訂閱需要處理訂單的訂單命令處理器：
//偵聽訂單建立命令佇列裡的訊息
services.AddSingleton<IEventHandlerExecutionContext>(new EventHandlerExecutionContext(services));
var connectionFactory = new ConnectionFactory { HostName = "localhost" };
services.AddSingleton<IEventBus>(sp => new RabbitMqEB(connectionFactory,
sp.GetRequiredService<IEventHandlerExecutionContext>(), "exchange1", "direct", "ordercreatecommandqueue", 2));
//訂閱建立訂單命令
var commandbuss = app.ApplicationServices.GetServices<IEventBus>();
var commandbus = commandbuss.ToList()[0];
commandbus.Subscribe<CreateOrderCommand, OrderCreateCommandHandler>();
複製程式碼4.實現訂單命令處理器：
public class OrderCreateCommandHandler : IEventHandler
{
private readonly IServiceProvider iserviceprovider;
public OrderCreateCommandHandler()
{
var iwebhost = FindIWebHost.GetWwebHost("OrderCommandHandler.WebApi");
iserviceprovider = iwebhost.Services;
}
public Task<bool> HandleAsync<TEvent>(TEvent @event) where TEvent : IEvent
{
var orderdtocommand = @event as CreateOrderCommand;
var orderdto = orderdtocommand.orderdto;
var orderid = orderdtocommand.AggregationRootId;
Orders order = new Orders();
var productskus = new List<ProductSKU>();
for (int i = 0; i < orderdto.ProductSPUNames.Count; i++)
{
var productsku = new ProductSKU();
productsku.ProductSPUName = orderdto.ProductSPUNames[i];
productsku.DealerPrice = orderdto.ProductDealerPrices[i];
productsku.PV = orderdto.ProductPVS[i];
productsku.Id = orderdto.ProductSKUIds[i];
productsku.Spec = orderdto.ProductSepcs[i];
productskus.Add(productsku);
}
var contact = new Contact();
contact.ContactName = orderdto.ContactName;
contact.ContactTel = orderdto.ContactTel;
contact.Province = orderdto.Privence;
contact.City = orderdto.City;
contact.Zero = orderdto.Zero;
contact.Street = orderdto.Street;
//完成業務邏輯
var orders = order.CreateOrders(orderid, orderdto.DealerId, productskus, orderdto.Counts,
contact);
var ordercreateevent = new OrderCreateEvent();
ordercreateevent.AggregationRootId = orders.Id;
ordercreateevent.AssemblyQualifiedAggreateRooType = orderdtocommand.AssemblyQualifiedAggreateRooType;
ordercreateevent.AssemblyQualifiedCommandAndEventType = orderdtocommand.AssemblyQualifiedCommandAndEventType;
ordercreateevent.CreateDate = orders.OrderDateTime;
ordercreateevent.Id = orders.Id;
ordercreateevent.OrderDateTime = orders.OrderDateTime;
ordercreateevent.OrderDealerId = orders.OrderDealerId;
ordercreateevent.OrderItems = orders.OrderItems;
ordercreateevent.OrderStreet = orders.OrderStreet;
ordercreateevent.OrderTotalPrice = orders.OrderTotalPrice;
ordercreateevent.OrderTotalPV = orders.OrderTotalPV;
ordercreateevent.Code = orders.Code;
ordercreateevent.Telephone = orders.Telephone;
ordercreateevent.Version = 0;
//對建立訂單事件持久化事件儲存
try
{
new DomainAndEventStorage().SaveEvent(ordercreateevent);
var eventbuss = iserviceprovider.GetServices(typeof(IEventBus))
as IEnumerable<IEventBus>;
var eventbusls = eventbuss.ToList();
var eventbus = eventbusls[1];
//釋出到事件佇列，用於未來持久化到業務庫中
eventbus.Publish(ordercreateevent);
}
catch(Exception error)
{
throw error;
}
return Task.FromResult(true);
}
}
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