MASA Framework -- EventBus入门与设计( 二 ) _生活百科

自定义中间件根据需要我们可以自定义中间件，并注册到EventBus的请求管道中，比如通过增加FluentValidation, 将参数验证从业务代码中剥离开来，从而使得处理程序更专注于业务

注册FluentValidation, 修改Program.cs

builder.Services.AddValidatorsFromAssembly(Assembly.GetEntryAssembly());

自定义验证中间件ValidatorMiddleware.cs ，用于验证参数

public class ValidatorMiddleware<TEvent> : Middleware<TEvent> where TEvent : IEvent{ private readonly ILogger<ValidatorMiddleware<TEvent>>? _logger; private readonly IEnumerable<IValidator<TEvent>> _validators; public ValidatorMiddleware(IEnumerable<IValidator<TEvent>> validators, ILogger<ValidatorMiddleware<TEvent>>? logger = null) { _validators = validators; _logger = logger; } public override async Task HandleAsync(TEvent @event, EventHandlerDelegate next) { var typeName = @event.GetType().FullName; _logger?.LogDebug("----- Validating command {CommandType}", typeName); var failures = _validators .Select(v => v.Validate(@event)) .SelectMany(result => result.Errors) .Where(error => error != null) .ToList(); if (failures.Any()) { _logger?.LogError("Validation errors - {CommandType} - Event: {@Command} - Errors: {@ValidationErrors}", typeName, @event, failures); throw new ValidationException("Validation exception", failures); } await next(); }}

注册EventBus并使用验证中间件ValidatorMiddleware

builder.Services.AddEventBus(eventBusBuilder=>eventBusBuilder.UseMiddleware(typeof(ValidatorMiddleware<>)));

添加注册用户验证类RegisterUserEventValidator.cs

public class RegisterUserEventValidator : AbstractValidator<RegisterUserEvent>{ public RegisterUserEventValidator() { RuleFor(e => e.Account).NotNull().WithMessage("用户名不能为空"); RuleFor(e => e.Email).NotNull().WithMessage("邮箱不能为空"); RuleFor(e => e.Password) .NotNull().WithMessage("密码不能为空") .MinimumLength(6) .WithMessage("密码必须大于6位") .MaximumLength(20) .WithMessage("密码必须小于20位"); }}编排EventBus 支持事件编排，它们可以用来处理一些对执行顺序有要求的业务，比如: 注册用户必须成功之后才可以发送注册邮件通知，发送奖励等等，那我们可以这样做
将注册用户业务拆分为三个Handler，并通过指定Order的值来对执行事件排序
public class UserHandler{ private readonly ILogger<UserHandler>? _logger; public UserHandler(ILogger<UserHandler>? logger = null) { _logger = logger; } [EventHandler(1)] public void RegisterUser(RegisterUserEvent @event) { _logger?.LogDebug("-----------{Message}-----------", "检测用户是否存在并注册用户"); //todo: 编写注册用户业务 } [EventHandler(2)] public void SendAwardByRegister(RegisterUserEvent @event) { _logger?.LogDebug("-----------{Account} 注册成功 {Message}-----------", @event.Account, "发送注册奖励"); //todo: 编写发送奖励等 } [EventHandler(3)] public void SendNoticeByRegister(RegisterUserEvent @event) { _logger?.LogDebug("-----------{Account} 注册成功 {Message}-----------", @event.Account, "发送注册成功邮件"); //todo: 编写发送注册通知等 }}