使用ASP.NET MVC 4 Web API的授权过滤器依赖注入

Question

我正在尝试在MVC 4 Web Api授权过滤器上实现依赖注入。我创建了一个继承自ActionDescriptorFilterProvider的FilterProvider：

public class UnityWebApiFilterAttributeFilterProvider : ActionDescriptorFilterProvider, System.Web.Http.Filters.IFilterProvider
{
    private readonly IUnityContainer _container;

    public UnityWebApiFilterAttributeFilterProvider(IUnityContainer container)
    {
        _container = container;
    }

    public IEnumerable<FilterInfo> GetFilters(HttpConfiguration configuration, HttpActionDescriptor actionDescriptor)
    {
        var filters = base.GetFilters(configuration, actionDescriptor);

        this.BuildUpAttributes(filters);

        return filters;
    }

    private void BuildUpAttributes(IEnumerable filterInfo)
    {
        foreach (FilterInfo filter in filterInfo)
        {
            object o = _container.BuildUp(filter.GetType(), filter);
        }
    }
}

我在Global.asax文件中设置了这个提供程序为默认提供程序：

var providers = GlobalConfiguration.Configuration.Services.GetFilterProviders().ToList();
        //Remove the default provider
        var defaultprovider = providers.Single(i => i is ActionDescriptorFilterProvider);
        GlobalConfiguration.Configuration.Services.Remove(typeof(System.Web.Http.Filters.IFilterProvider), defaultprovider);
        //Add our custom provider
        GlobalConfiguration.Configuration.Services.Add(typeof(System.Web.Http.Filters.IFilterProvider), new UnityWebApiFilterAttributeFilterProvider(new UnityContainer()));

我还在AuthorizationFilter中添加了一个依赖项：

public class WebApplicationApiAuthorizeAttribute : System.Web.Http.AuthorizeAttribute
{

    [Dependency]
    public IAuthorizationHelper AuthorizationHelper { get; set; }

    #region OnAuthorization
    public override void OnAuthorization(System.Web.Http.Controllers.HttpActionContext actionContext)
{
    //Authorization code, which uses the AuthorizationHelper lives here
}   

}

我在Unity配置文件中设置了映射:

container.RegisterType<WebApplicationApiAuthorizeAttribute>(new InjectionMember[]
            {
                new InjectionProperty("AuthorizationHelper", new ResolvedParameter<IAuthorizationHelper>())
            });

        container.RegisterType<IAuthorizationHelper, WebAuthorizationHelper>(new InjectionMember[]
            {
                new InjectionProperty("Cache", new ResolvedParameter<ICache>(cacheType)),
                new InjectionProperty("UserSessionManager", new ResolvedParameter<IUserSessionManager>()),
                new InjectionProperty("AuthorizationPermissionManager", new ResolvedParameter<IAuthorizationPermissionManager>()),
                new InjectionProperty("ExceptionLogger", new ResolvedParameter<IExceptionLogger>()),
            });

我能看到UnityWebApiFilterAttributeFilterProvider类中的“BuildUpAttributes”方法被执行，并且过滤器被传递到_container.BuildUp(...)方法中，但是WebApplicationApiAuthorizeAttribute中的“IAuthorizationHelper”依赖项没有被解析。当我调试WebApplicationApiAuthorizeAttribute时，它是null。

那么为什么这个依赖关系没有被解析呢？

- Agreene

---

有没有人知道是否有一种方法可以检索与类级别关联而不是方法级别的过滤器？在UnityWebApiFilterAttributeFilterProvider中的GetFilters方法似乎只作用于方法级别的过滤器。 - Agreene

Answer 1

您的代码中有两个错误。

1. You're building up the FilterInfo object instead of its Instance:

   foreach (FilterInfo filter in filterInfo)
   {
       object o = _container.BuildUp(filter.GetType(), filter);
   }
   

   But this is the correct code:

   foreach (FilterInfo filter in filterInfo)
   {
       _container.BuildUp(filter.Instance.GetType(), filter.Instance);
   }
   

2. Your custom UnityWebApiFilterAttributeFilterProvider gets a new and empty container:

   GlobalConfiguration.Configuration.Services.Add(
       typeof(System.Web.Http.Filters.IFilterProvider), 
       new UnityWebApiFilterAttributeFilterProvider(new UnityContainer()));
   

   But you should pass on the application's configured container:

   GlobalConfiguration.Configuration.Services.Add(
       typeof(System.Web.Http.Filters.IFilterProvider), 
       new UnityWebApiFilterAttributeFilterProvider(container));
   

- Steven

---

我正在尝试解决相同的问题，不得不从_container.BuildUp(filter.GetType(), filter.Instance)改为_container.BuildUp(filter.Instance.GetType(), filter.Instance)的一部分。 - Tim Sneed

@TimSneed：你说得对。谢谢。我已经更新了我的答案。 - Steven

@TimSneed 我也不得不这样做。谢谢你们两个。 - Agreene