使用 IMiddleware 时添加自定义中间件不起作用 [英] Adding custom middleware not working when using IMiddleware
问题描述
我正在尝试向管道添加自定义中间件(为了更容易,我将选择 .NET Core 文档示例).假设我们希望在调用 API 时设置西班牙文化.这是完美运行的代码:
I am trying to add a custom middleware to the pipeline (to be easier I will pick the .NET Core documentation example). Let's say we want to have the Spanish culture set whenever a call to API is fired. Here's the code which runs perfectly:
public class RequestCultureMiddleware
{
private readonly RequestDelegate _next;
public RequestCultureMiddleware(RequestDelegate next)
{
_next = next;
}
public async Task InvokeAsync(HttpContext context)
{
CultureInfo.CurrentCulture = new CultureInfo("es-ES");
CultureInfo.CurrentUICulture = new CultureInfo("es-ES");
// Call the next delegate/middleware in the pipeline
await _next(context);
}
}
public static class RequestCultureMiddlewareExtensions
{
public static IApplicationBuilder UseRequestCulture(
this IApplicationBuilder builder)
{
return builder.UseMiddleware<RequestCultureMiddleware>();
}
}
和启动类:
public class Startup
{
public Startup(IConfiguration configuration)
{
Configuration = configuration;
}
public IConfiguration Configuration { get; }
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
services.AddControllers();
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
//here is our custom middleware!
app.UseRequestCulture();
app.UseHttpsRedirection();
app.UseRouting();
app.UseAuthorization();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllers();
});
}
}
那很好,但是正如您所看到的,RequestCultureMiddleware 没有实现接口或基类/抽象类.您只需要记住在定义中间件以创建接收下一个中间件的构造函数时,您还需要创建一个专门名为InvokeAsync"的方法,并将HttpContext"作为参数.
That's fine, but as you can see, the RequestCultureMiddleware does not implement an interface or a base class/abstract class. You just need to remember when defining a middleware to create a constructor that receives the next middleware and also you need to create a method called specifically "InvokeAsync" with "HttpContext" as a parameter.
我试图找到一个契约……一个基类或一个接口,猜猜是什么,我们有IMiddleware",它是Microsoft.AspNetCore.Http"程序集的一部分.哇,这太完美了.让我们实施它.
I tried to find a contract... a base class or an interface and guess what, we have "IMiddleware" which is part of "Microsoft.AspNetCore.Http" assembly. Wow, that's perfect. Let's implement it.
界面如下:
namespace Microsoft.AspNetCore.Http
{
//
// Summary:
// Defines middleware that can be added to the application's request pipeline.
public interface IMiddleware
{
//
// Summary:
// Request handling method.
//
// Parameters:
// context:
// The Microsoft.AspNetCore.Http.HttpContext for the current request.
//
// next:
// The delegate representing the remaining middleware in the request pipeline.
//
// Returns:
// A System.Threading.Tasks.Task that represents the execution of this middleware.
Task InvokeAsync(HttpContext context, RequestDelegate next);
}
}
这是实现:
public class RequestCultureMiddleware : IMiddleware
{
public Task InvokeAsync(HttpContext context, RequestDelegate next)
{
CultureInfo.CurrentCulture = new CultureInfo("es-ES");
CultureInfo.CurrentUICulture = new CultureInfo("es-ES");
// Call the next delegate/middleware in the pipeline
return next(context);
}
}
public static class RequestCultureMiddlewareExtensions
{
public static IApplicationBuilder UseRequestCulture(
this IApplicationBuilder builder)
{
return builder.UseMiddleware<RequestCultureMiddleware>();
}
}
}
但是,在运行 API 时,我在运行时收到以下错误:
But, when running the API I am getting the following error at run-time:
System.InvalidOperationException: No service for type 'WebApplication1.RequestCultureMiddleware' has been registered.
at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
at Microsoft.AspNetCore.Http.MiddlewareFactory.Create(Type middlewareType)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.<>c__DisplayClass5_1.<<UseMiddlewareInterface>b__1>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
如果不使用扩展名UseMiddleware",我应该如何注册这个中间件?谢谢.
How exactly I am supposed to register this middleware if not by using the extension "UseMiddleware"? Thanks.
推荐答案
您正在使用 基于工厂的中间件.如这些文档中所述,您错过了一个重要步骤:
You're using factory-based middleware. As described in those docs, you've missed an important step:
... IMiddlewareFactory 实例在容器中注册用于解析IMiddleware 实现而不是使用基于约定的中间件激活逻辑.中间件注册为 应用的服务容器中的>作用域或临时服务.
... the IMiddlewareFactory instance registered in the container is used to resolve the IMiddleware implementation instead of using the convention-based middleware activation logic. The middleware is registered as a scoped or transient service in the app's service container.
在您的情况下,该注册看起来像这样:
In your case, that registration would look something like this:
public void ConfigureServices(IServiceCollection services)
{
// ...
services.AddTransient<RequestCultureMiddleware>();
}
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