Question

如何配置SimpleInjector来解析LogMiddleware的Invoke方法依赖，比如IMessageService？

据我所知，Asp.net核心使用HttpContext.RequestServices（IServiceProvider）来解析依赖关系，我将SimpleInjector容器设置为HttpContext.RequestServices属性但是没有用。我想动态更改ServiceProvider，因为每个租户都应该有一个容器。

public class LogMiddleware
{
    RequestDelegate next;
    private readonly ILogger log;

    public LogMiddleware(RequestDelegate next, ILoggerFactory loggerFactory)
    {
        this.next = next;
        this.log = loggerFactory.CreateLogger<LogMiddleware>();
    }

    public async Task Invoke(HttpContext context, IMessageService messageService)
    {
         await context.Response.WriteAsync(
                messageService.Format(context.Request.Host.Value));
    }
}

public interface IMessageService
{
    string Format(string message);
}

public class DefaultMessageService : IMessageService
{
  public string Format(string message)
  {
    return "Path:" + message;
  }
}

Answer 1

您可以按照以下方式使用LogMiddleware课程：

applicationBuilder.Use(async (context, next) => {
    var middleware = new LogMiddleware(
        request => next(),
        applicationBuilder.ApplicationServices.GetService<ILoggerFactory>());

    await middleware.Invoke(context, container.GetInstance<IMessageService>());
});

但是我建议你稍微改变你的中间件类。将运行时数据（next()委托）移出构造函数（自components should not require runtime data during construction起），并将IMessageService依赖项移动到构造函数中。并将ILoggerFactory替换为ILogger依赖项，因为注入构造函数应do no more than store its incoming dependencies（或将ILogger替换为your own application-specific logger abstraction instead）。

您的中间件类将如下所示：

public sealed class LogMiddleware
{
    private readonly IMessageService messageService;
    private readonly ILogger log;

    public LogMiddleware(IMessageService messageService, ILogger log) {
        this.messageService = messageService;
        this.log = log;
    }

    public async Task Invoke(HttpContext context, Func<Task> next) {
        await context.Response.WriteAsync(
            messageService.Format(context.Request.Host.Value));

        await next();
    }
}

这允许您按如下方式使用中间件：

var factory = applicationBuilder.ApplicationServices.GetService<ILoggerFactory>();

applicationBuilder.Use(async (context, next) => {
    var middleware = new LogMiddleware(
        container.GetInstance<IMessageService>(),
        factory.CreateLogger<LogMiddleware>());

    await middleware.Invoke(context, next);
});

或者，如果您在Simple Injector中注册了ILogger（或您的自定义日志记录抽象），您可以执行以下操作：

applicationBuilder.Use(async (context, next) => {
    var middleware = container.GetInstance<LogMiddleware>();
    await middleware.Invoke(context, next);
});

Answer 2

您的代码存在两个问题。

您的“DefaultMessageService”未实现“IMessageService”接口。它应该是这样的。

 public class DefaultMessageService : IMessageService
 {
 public string Format(string message)
{
   return "Path:" + message;
 }
}

您必须在Startup.cs中的ConfigureService中注册DefaultMessageService。

 public void ConfigureServices(IServiceCollection services)
        {
            // Add framework services.
            services.AddMvc();
            services.AddSingleton<IMessageService>(new DefaultMessageService());
        }

配置Simple Injector以支持解析ASP.NET Core中间件依赖项？

2 个答案: