微服务实战(七)：落地微服务架构到直销系统(实现命令与命令处理器)

我们先来看看CQRS架构，你对下图的架构还有印象吗？每个组件的功能都还清楚吗？如果有疑问，请查考文章《微服务实战(五)：落地微服务架构到直销系统(构建高性能大并发系统)》。

前一篇文章已经实现了Event Store的基础功能部分，本篇文章我们通过C端的标准方式，实现一个下单的高并发命令端，来看看需要实现的具体流程：

1.前端用户调用一个下单Command WebApi，传递下单命令；下单Command WebApi接受到下单命令后，将下单命令数据投递到一个命令队列中，向前端用户返回一个信息。

2.下单Command Handler WebApi侦听命令队列中的下单命令，然后调用领域对象逻辑，将执行的结果也就是Order对象的当前状态持久化到Event Store中。

3.下单Command Handler WebApi将下单相关信息通过事件的方式发布到一个事件队列中。(用户事件处理器最终将订单信息更新到业务库中)

下面通过代码简单体现下过程：

1.定义创建订单命令：

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;
        }
    }

2.订单 Command WebApi接受前端用户传递的订单命令：

[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);
                //发布命令到命令总线
                commandbus.Publish(createordercommand);
                result.IsSuccess = true;
                result.Msg = "下单处理中!";
            }
            catch(Exception error)
            {
                result.ErrorCode = 200;
                result.Msg = error.Message;
            }
            return result;
        }
    }

当然需要定义要注入的命令总线：

public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
            //定义要发布命令的命令总线
            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));
        }

3.订单Command Handler Web Api侦听订单命令，并订阅需要处理订单的订单命令处理器：

//侦听订单创建命令队列里的消息
            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));

//订阅创建订单命令
            var commandbuss = app.ApplicationServices.GetServices<IEventBus>();
            var commandbus = commandbuss.ToList()[0];
            commandbus.Subscribe<CreateOrderCommand, OrderCreateCommandHandler>();

4.实现订单命令处理器：

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;
            //完成业务逻辑
            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;
            //对创建订单事件持久化事件存储
            try
            {
                new DomainAndEventStorage().SaveEvent(ordercreateevent);
                var eventbuss = iserviceprovider.GetServices(typeof(IEventBus))
                    as IEnumerable<IEventBus>;
                var eventbusls = eventbuss.ToList();
                var eventbus = eventbusls[1];
                //发布到事件队列，用于未来持久化到业务库中
                eventbus.Publish(ordercreateevent);
            }
            catch(Exception error)
            {
                throw error;
            }
            return Task.FromResult(true);
        }
    }

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来源：oschina

链接：https://my.oschina.net/u/4291709/blog/3279433

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commandbus