asp.net-mvc - 使用 Autofac 将依赖项注入(inject)自定义 Web API 操作过滤器属性

Question

我正在尝试解决我的自定义 AuthorizeAttribute 的依赖关系，我用它来装饰 MVC4 应用程序中的 API Controller 。问题是我在自定义过滤器中使用的服务依赖项上不断收到 NullReferenceException 。这是我的 Autofac 配置:

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        var builder = new ContainerBuilder();
        builder.RegisterApiControllers(Assembly.GetExecutingAssembly());
        builder.RegisterType<UnitOfWork>().As<IUnitOfWork>().InstancePerApiRequest();
        builder.RegisterType<DatabaseFactory>().As<IDatabaseFactory>().InstancePerApiRequest();
        builder.RegisterAssemblyTypes(typeof(UserProfileRepository).Assembly)
            .Where(t => t.Name.EndsWith("Repository"))
            .AsImplementedInterfaces().InstancePerApiRequest();

        builder.RegisterAssemblyTypes(typeof(IUserProfileMapper).Assembly)
            .Where(t => t.Name.EndsWith("Mapper"))
            .AsImplementedInterfaces().InstancePerApiRequest();

        builder.RegisterAssemblyTypes(typeof(UserProfileSvc).Assembly)
            .Where(t => t.Name.EndsWith("Svc"))
            .AsImplementedInterfaces().InstancePerApiRequest();

        builder.RegisterWebApiFilterProvider(config);
        var container = builder.Build();
        var resolver = new AutofacWebApiDependencyResolver(container);
        config.DependencyResolver = resolver;
    }
}

和我的自定义授权过滤器:

public class MyAuthorizeAttribute : AuthorizeAttribute
{
    public IAuthenticationSvc _authenticationSvc;
    protected override bool IsAuthorized(System.Web.Http.Controllers.HttpActionContext actionContext)
    {
        if (!base.IsAuthorized(actionContext))
        {
            return false;
        }
        var trueUserId = WebSecurity.CurrentUserId;

        if (_authenticationSvc.GetUsersRoles(trueUserId).Any(x => x == "Admin")) return true;
        // NullReferenceException on _authenticationSvc
     }
}

根据official docs所需要的只是:

var builder = new ContainerBuilder();
builder.RegisterWebApiFilterProvider(GlobalConfiguration.Configuration);

但这似乎也不起作用。感谢任何帮助。

Answer 1

我认为 Autofac 的文档为 WebApi 操作过滤器提供了更简单的解决方案。

public interface ServiceCallActionFilterAttribute : ActionFilterAttribute
{
  public override void OnActionExecuting(HttpActionContext actionContext)
  {
    // Get the request lifetime scope so you can resolve services.
    var requestScope = actionContext.Request.GetDependencyScope();

    // Resolve the service you want to use.
    var service = requestScope.GetService(typeof(IMyService)) as IMyService;

    // Do the rest of the work in the filter.
    service.DoWork();
  }
}

它不是“纯 DI”，因为它使用服务定位器，但它很简单并且适用于请求范围。您无需担心为每个 WebApi Controller 注册特定的操作过滤器。

来源: http://autofac.readthedocs.io/en/latest/integration/webapi.html#provide-filters-via-dependency-injection