前言

上次，我们介绍了如何《在业务层实现响应缓存》。

今天，我们同样使用IPipelineBehavior，介绍如何在业务层实现记录请求日志，用于跟踪每个请求执行的耗时。

Demo

创建ASP.NET Core Web API项目，引用Nuget包：

MediatR
MediatR.Extensions.Microsoft.DependencyInjection

1.实现IPipelineBehavior

创建LoggingBehavior，用于实现记录请求日志逻辑:

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){var stopwatch = new Stopwatch();stopwatch.Start();var response = await next();stopwatch.Stop();_logger.LogInformation($"{typeof(TRequest).Name}耗时:{stopwatch.ElapsedMilliseconds}");return response;}
}

2.注册IPipelineBehavior

修改Startup.cs：

services.AddMediatR(Assembly.GetExecutingAssembly());
services.AddTransient(typeof(IPipelineBehavior<,>), typeof(LoggingBehaviour<,>))

3.测试

修改WeatherForecastController，使用Mediator：

public class WeatherForecastController : ControllerBase
{private readonly IMediator _mediator;public WeatherForecastController(IMediator mediator){this._mediator = mediator;}[HttpGet]public async Task<IEnumerable<WeatherForecast>> Get(){return await this._mediator.Send(new GetWeatherForecastQuery());              }
}public class GetWeatherForecastQuery : IRequest<IEnumerable<WeatherForecast>>
{
}internal class GetWeatherForecastQueryHandler : IRequestHandler<GetWeatherForecastQuery, IEnumerable<WeatherForecast>>
{public async Task<IEnumerable<WeatherForecast>> Handle(GetWeatherForecastQuery request, CancellationToken cancellationToken){await Task.Delay(1000);var rng = new Random();return Enumerable.Range(1, 1).Select(index => new WeatherForecast{ TemperatureC = rng.Next(-20, 55),Summary = Summaries[rng.Next(Summaries.Length)]}).ToArray();}
}

为了体现效果，代码里故意加了等待时间。

运行程序，在控制台界面可以看到输出的日志。

结论

可以看到，在业务层实现记录请求日志功能，十分的简单！

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