微服務實戰(七)：落地微服務架構到直銷系統(實現命令與命令處理器)

咱們先來看看CQRS架構，你對下圖的架構還有印象嗎？每一個組件的功能都還清楚嗎？若是有疑問，請查考文章《微服務實戰(五)：落地微服務架構到直銷系統(構建高性能大併發系統)》。

前一篇文章已經實現了Event Store的基礎功能部分，本篇文章咱們經過C端的標準方式，實現一個下單的高併發命令端，來看看須要實現的具體流程：

1.前端用戶調用一個下單Command WebApi，傳遞下單命令；下單Command WebApi接受到下單命令後，將下單命令數據投遞到一個命令隊列中，向前端用戶返回一個信息。

2.下單Command Handler WebApi偵聽命令隊列中的下單命令，而後調用領域對象邏輯，將執行的結果也就是Order對象的當前狀態持久化到Event Store中。

3.下單Command Handler WebApi將下單相關信息經過事件的方式發佈到一個事件隊列中。(用戶事件處理器最終將訂單信息更新到業務庫中)

下面經過代碼簡單體現下過程：

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;
    }
}
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2.訂單 Command WebApi接受前端用戶傳遞的訂單命令：

[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);
            //發佈命令到命令總線
            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;
    }
}
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固然須要定義要注入的命令總線：

public void ConfigureServices(IServiceCollection services)
    {
        services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
        //定義要發佈命令的命令總線
        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));
    }
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3.訂單Command Handler Web Api偵聽訂單命令，並訂閱須要處理訂單的訂單命令處理器：

//偵聽訂單建立命令隊列裏的消息
        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>();
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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存儲
        try
        {
            new DomainAndEventStorage().SaveEvent(ordercreateevent);
            var eventbuss = iserviceprovider.GetServices(typeof(IEventBus))
                as IEnumerable<IEventBus>;
            var eventbusls = eventbuss.ToList();
            var eventbus = eventbusls[1];
            //發佈到事件隊列，用於將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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