Question

我的Mediatr正在使用SyncContinueOnException publish strategy，在传播开始之前，有什么方法可以运行一些验证吗？

示例：

_mediatr.Publish(new MyNotification());

public class MyValidationHandler :
    INotificationHandler<MyValidationHandler>
{
    Task INotificationHandler<MyValidationHandler>.Handle(MyValidationHandler notification, CancellationToken cancellationToken)
    {
        // STOP propagation if some condition is false
    }
}

public class FirstHandlers :
    INotificationHandler<MyNotification>
{
    Task INotificationHandler<MyNotification>.Handle(MyNotification notification, CancellationToken cancellationToken)
    {
        Console.WriteLine("x");
        return Task.CompletedTask;
    }
}

public class SecondHandlers :
    INotificationHandler<MyNotification>
{
    Task INotificationHandler<MyNotification>.Handle(MyNotification notification, CancellationToken cancellationToken)
    {
        Console.WriteLine("x");
        return Task.CompletedTask;
    }
}

Answer 1

更新抱歉，原来是看错了！

包装MediatR Publish行为的一种方法是手动装饰IMediator实例本身，或使用Scrutor之类的库。您可以添加一个标记接口，以标识应通过验证逻辑传递的通知，而其他任何事件都将直接传递给MediatR。

public class MediatorDecorator : IMediator
{
    private readonly IMediator _mediator;

    public MediatorDecorator(IMediator mediator)
    {
        _mediator = mediator;
    }

    public Task Publish<TNotification>(TNotification notification, CancellationToken cancellationToken = default) where TNotification : INotification
    {
        if (notification is IValidatableNotification)
        {
            // Your validation behavior here
            return Task.CompletedTask; // if the validation fails, respond as you'd like ...
        }
        return _mediator.Publish(notification, cancellationToken);
    }

    // ...
}

在启动中，在MediatR注册之后，使用Scrutor的Decorate：

services.AddMediatR(typeof(Startup));
services.Decorate<IMediator, MediatorDecorator>();

MediatR取消发布后续消息

1 个答案: