从 ASP.NET 到 .NET Core 的 DelegateHandler

在一个旧的 asp.net 项目中，我有一个类实现DelegatingHandler我为每条路线设置的：

public class AdminSecurityMessageHandler : DelegatingHandler
{
    private readonly HttpConfiguration _config;

    public AdminSecurityMessageHandler(HttpConfiguration config)
    {
        if (config == null)
        {
            throw new ArgumentNullException("config");
        }
        _config = config;
    }

    protected override Task<HttpResponseMessage> SendAsync(
        HttpRequestMessage request, CancellationToken cancellationToken)
    {
        var repository = (IUserRepository)_config.DependencyResolver.GetService(typeof(IUserRepository));
        var accessTokener = (IAccessTokener)_config.DependencyResolver.GetService(typeof(IAccessTokener));

        if (!request.Headers.Contains(AccessTokener.CallerId))
        {
            return Unauthorized(String.Empty);
        }

        var guid = request.Headers.GetValues(AccessTokener.CallerId).FirstOrDefault();
        var user = repository.GetByGuid(guid);

        if (user == null)
        {
            return Unauthorized(String.Empty);
        }

        var result = accessTokener.CheckAccessTokenHash(user.Guid, request.Headers.Authorization.Parameter);
        switch (result)
        {
            case AccessTokenCheckerResult.Invalid:
                return Unauthorized(String.Empty);
            case AccessTokenCheckerResult.Expired:
                return Unauthorized("AccessToken.Expired");
        }

        if (!user.IsAdmin)
        {
            return Unauthorized("No admin rights");
        }

        var claims = new List<Claim>();
        claims.Add(new Claim(ClaimTypes.Name, user.Id.ToString()));
        var identity = new ClaimsIdentity(claims, "custom");
        var principal = new UserPrincipal(identity, user);
        request.GetRequestContext().Principal = principal;

        return base.SendAsync(request, cancellationToken);
    }

我需要将项目移动到.NET Core，并且在尝试注册它们时遇到一些麻烦。 我可以注册这样的简单路线：

app.UseMvc(routes => { routes.MapWebApiRoute("DefaultApi", "api/{controller}/{id?}"); });

所以问题是我应该如何实施和设置类似的东西DelegatingHandler当我在 .NET Core 中注册路由时，来自 ASP.NET？ （为每条路线设置不同的处理程序）

它在 ASP.NET 中的工作原理： 注册方法在WebApiConfig class.

public static void RegisterRoutes(HttpConfiguration config, HttpMessageHandler routeHandlers, HttpMessageHandler adminRouteHandlers)
{
    .......................

    config.Routes.MapHttpRoute(
        name: "FriendsAPI",
        routeTemplate: "api/users/{id}/friends/{friendId}",
        defaults: new { controller = "Friends", friendId = RouteParameter.Optional },
        constraints: null,
        handler: routeHandlers
    );


    config.Routes.MapHttpRoute(
        name: "AdminUserBlocksApi",
        routeTemplate:
            "api/admin/user-blocks/{userId}",
        defaults: new { controller = "AdminUserBlocks", userId = RouteParameter.Optional },
        constraints: null,
        handler: adminRouteHandlers
    .......................
    );
}

既然没有DelegateHandlers in Asp.Net Core你可以尝试创建一个自定义的middleware。请参阅简化版middleware您可以使用它来满足您的要求：

public class AdminSecurityMiddleware
{
    private readonly RequestDelegate _next;
    IUserRepository userRepository; // IUserRepository should be registered for dependency injection in Startup.ConfigureServices

    public AdminSecurityMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task Invoke(HttpContext context)
    {
        bool isAdminUserBlocksApiRoute; 
        //check for route here. As I know there is no elegant way to get name of the route since context.GetRouteData() returns null until mvc middleware is called.
        // probably you can check like this context.Request.Path.StartsWithSegments("/api/admin")

        if (isAdminUserBlocksApiRoute)
        {
            _userRepository = context.RequestServices.GetService<IUserRepository>();
            bool isUserAuthorized;
            // check here for Authorization
            if (!isUserAuthorized)
            {
                context.Response.Clear();
                context.Response.StatusCode = (int)System.Net.HttpStatusCode.Unauthorized;
                await context.Response.WriteAsync("Unauthorized");
                return;
            }

            // adding custom claims
            var identity = new ClaimsIdentity(new GenericIdentity("user.Id"), new[] { new Claim("user_id", "id") });
            context.User.AddIdentity(identity);
        }
        await _next.Invoke(context);
    }
}

然后将其添加到之前的管道中mvc middleware in Startup:

app.UseMiddleware<AdminSecurityMiddleware>();
app.UseMvc(routes =>
{
    ...
}

阅读有关中间件的更多信息here https://docs.asp.net/en/latest/fundamentals/middleware.html#writing-middleware