WCF Rest 4.0、动态路由和 OutputCache

Question

我在让 OutputCaching 与 WCF 4.0 WebHttp 服务的 HttpContext.RewritePath 配合使用时遇到问题。

我的服务是本地化的。这个想法是，您可以像这样调用 URL：

/languageCode/ServiceName/Method
e.g.
/en/MyService/GetItems

它将返回本地化为正确语言的结果。

我的方案基于这篇文章。这个想法是创建 RouteBase 的衍生产品，创建通往真实服务的独特的“私有”路由。当用户发出请求时，将从 URL 中解压缩语言代码并将其设置为当前线程的区域性，然后使用 HttpContext.RewritePath 加载实际的服务。

对于我的一生，我无法弄清楚如何将 OutputCaching 融入其中。我已经用 AspNetCacheProfile 装饰了我的服务方法，并且看到我自己的 VaryByCustom 重写被调用。然而，尽管从 VaryByCustom 收到重复的结果，.NET 仍然继续进入我的服务方法。

下面有很多代码，抱歉转储，但我怀疑它们都是相关的。

---

如何在 Global.asax.cs 中添加路由

RouteTable.Routes.Add(new CulturedServiceRoute(
    "devices", 
    new StructureMapServiceHostFactory(), 
    typeof(DeviceService)));

VaryByCustom 覆盖 Global.asax.cs 中的：

public override string GetVaryByCustomString(
    HttpContext context, string custom)
{

    // This method gets called twice: Once for the initial request, then a 
    // second time for the rewritten URL. I only want it to be called once!

    if (custom == "XmlDataFreshness")
    {
        var outputString = String.Format("{0}|{1}|{2}", 
            XmlDataLoader.LastUpdatedTicks, 
            context.Request.RawUrl, 
            context.Request.HttpMethod);
        return outputString;
    }

    return base.GetVaryByCustomString(context, custom);
}

这是动态服务路由类。

public class CulturedServiceRoute : RouteBase, IRouteHandler
{
    private readonly string _virtualPath = null;
    private readonly ServiceRoute _innerServiceRoute = null;
    private readonly Route _innerRoute = null;

    public CulturedServiceRoute(
        string pathPrefix, 
        ServiceHostFactoryBase serviceHostFactory, 
        Type serviceType)
    {
        if (pathPrefix.IndexOf("{") >= 0)
        {
            throw new ArgumentException(
                "Path prefix cannot include route parameters.", 
                "pathPrefix");
        }
        if (!pathPrefix.StartsWith("/")) pathPrefix = "/" + pathPrefix;
        pathPrefix = "{culture}" + pathPrefix;

        _virtualPath = String.Format("Cultured/{0}/", serviceType.FullName);
        _innerServiceRoute = new ServiceRoute(
            _virtualPath, serviceHostFactory, serviceType);
        _innerRoute = new Route(pathPrefix, this);
    }

    public override RouteData GetRouteData(
        HttpContextBase httpContext)
    {
        return _innerRoute.GetRouteData(httpContext);
    }

    public override VirtualPathData GetVirtualPath(
        RequestContext requestContext, RouteValueDictionary values)
    {
        return null;
    }

    public IHttpHandler GetHttpHandler(RequestContext requestContext)
    {
        // This method is called even if VaryByCustom 
        // returns a duplicate response!

        var culture = requestContext.RouteData.Values["culture"].ToString();
        var ci = new CultureInfo(culture);
        Thread.CurrentThread.CurrentUICulture = ci;
        Thread.CurrentThread.CurrentCulture = 
            CultureInfo.CreateSpecificCulture(ci.Name);

        requestContext.HttpContext.RewritePath("~/" + _virtualPath, true);
        return _innerServiceRoute.RouteHandler.GetHttpHandler(requestContext);
    }
}

最后，服务本身的相关部分：

[ServiceContract]
[AspNetCompatibilityRequirements(
    RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
public class DeviceService
{
    [AspNetCacheProfile("MyCacheProfile")]
    [WebGet(UriTemplate = "")]
    public IEnumerable<DeviceListItemModel> GetDevices()
    {
        // This is called AFTER the first VaryByCustom override is called.
        // I'd expect it not to be called unless VaryByCustom changes!

        var devices =
            from d in _deviceRepository.GetAll()
            where d.ReleaseDate < DateTime.Now
            orderby d.Id descending
            select new DeviceListItemModel(d);

        return devices;
    }

更新：我的缓存配置文件：

<caching>
  <outputCacheSettings>
    <outputCacheProfiles>
      <add name="MyCacheProfile" varyByCustom="XmlDataFreshness"
           varyByHeader="accept" varyByParam="*" location="Server"
           duration="3600" />
    </outputCacheProfiles>
  </outputCacheSettings>
</caching>

Answer 1

嗯，对我来说似乎是一个有效的方法。缓存配置文件配置是否正确？当缓存不需要更新时，varyByCustom是否被多次调用并且一定会返回相同的结果？