api-caller 之 MediatR

MediatR

地址

• github repository

• 个人demo

使用到的模式

• Notification
  通知模式，如发布订阅模式，需是实现一个通知接口(INotification) 及 一个或者多个handler(INotificationHandler<T>) ,
  调用方式 ： await mediator.Publish(new Notification()) , 无任何返回值。

    public class SendMessageNotification : INotification
    {
        public string Message { get; set; }
    }

    public class MessageLogHandler : INotificationHandler<SendMessageNotification>
    {
        public Task Handle(SendMessageNotification notification, CancellationToken cancellationToken)
        {
            Console.WriteLine($"log : {notification.Message}");
            return Task.CompletedTask;
        }
    }

    public class MessageEmailHandler : INotificationHandler<SendMessageNotification>
    {
        public Task Handle(SendMessageNotification notification, CancellationToken cancellationToken)
        {
            Console.WriteLine($"email : {notification.Message}");
            return Task.CompletedTask;
        }
    }

    public class MessageSmsHandler : INotificationHandler<SendMessageNotification>
    {
        public Task Handle(SendMessageNotification notification, CancellationToken cancellationToken)
        {
            Console.WriteLine($"sms : {notification.Message}");
            return Task.CompletedTask;
        }
    }

• Request
  发送命令，需要实现一个命令结构定义(IRequest) 以及一个命令handler(IRequestHandler<in TRequest, TResponse>) , 请保证 结构和handler的TResponse一致。调用方式：await mediator.Send(new Request()); ,返回值类型为 TResponse

   public class AddUserRequest: User,IRequest<bool>
    {
    }

    public class AddUserHandler : IRequestHandler<AddUserRequest, bool>
    {
        private readonly DataContext _dataContext;

        public AddUserHandler(DataContext dataContext)
        {
            this._dataContext = dataContext;
        }

        public Task<bool> Handle(AddUserRequest request, CancellationToken cancellationToken)
        {
            _dataContext.Users.Add(request);

            return Task.FromResult(true);
        }
    }

• PipelineBehavior
  管道，aop的一种实现，类似于aspnet中的filter。我是在看eshop项目时发现的，eshop中使用它实现了Command(CQRS模式，使用MediatR Request实现)运行的监视(日志)，数据库事务(除了查询都用Commond)，数据模型验证(结合了FluentValidation)。

  

  本人直接copy了Command监控代码

  public class LoggingBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
  {
      private readonly ILogger<LoggingBehavior<TRequest, TResponse>> _logger;
      public LoggingBehavior(ILogger<LoggingBehavior<TRequest, TResponse>> logger) => _logger = logger;
      public async Task<TResponse> Handle(TRequest request, CancellationToken cancellationToken, RequestHandlerDelegate<TResponse> next)
      {
          _logger.LogInformation("----- Handling command {CommandName} ({@Command})", request?.GetType().Name, request);
          var response = await next();
          _logger.LogInformation("----- Command {CommandName} handled - response: {@Response}", request?.GetType().Name, response);
        
          return response;
      }
  }

那如何生效呢，直接依赖注入即可 services.AddScoped(typeof(IPipelineBehavior<,>), typeof(LoggingBehavior<,>));

目前本人就了解了这么点儿，如果有更多使用技巧，欢迎指教