我可以在ASP.NET MVC中使用[CompressFilter]而不破坏甜甜圈缓存

Question

我试图让[ CompressFilter ]使用甜甜圈缓存并遇到问题。

会发生什么是整个页面被缓存而不仅仅是甜甜圈。 我正在使用的CompressFilter的源代码如下。 我将其从原始源更改为使用OnResultExecuted而不是OnActionExecuting()因为我需要访问结果的类型以避免缓存某些ActionResult子类。

看看OutputCacheAttribute的实际MVC v1源代码看起来它也使用OnResultExecuted() ，但我不认为这个事实直接导致了冲突。

我不太清楚替换缓存是如何工作的，以了解其行为方式。 我认为值得注意的是，这并不会导致任何类型的损坏显示。 它只是表现得没有甜甜圈！

它看起来像我将不得不使用某种IIs'插件'来处理缓存，我真的想避免这样做，但它看起来我也需要甜甜圈缓存。

我现在更感兴趣的是知道它为什么会产生这种效果，但如果可能的话，解决方案也会很棒。

public class CompressFilter : ActionFilterAttribute
{
    public override void OnResultExecuted(ResultExecutedContext filterContext)
    {
        HttpRequestBase request = filterContext.HttpContext.Request;

        // dont encode images!
        if (filterContext.Result is ImageResult)
        {
            return;
        }

        string acceptEncoding = request.Headers["Accept-Encoding"];

        if (string.IsNullOrEmpty(acceptEncoding)) return;

        acceptEncoding = acceptEncoding.ToUpperInvariant();

        HttpResponseBase response = filterContext.HttpContext.Response;

        if (acceptEncoding.Contains("GZIP"))
        {
            response.AppendHeader("Content-encoding", "gzip");
            response.Filter = new GZipStream(response.Filter, CompressionMode.Compress);
        }
        else if (acceptEncoding.Contains("DEFLATE"))
        {
            response.AppendHeader("Content-encoding", "deflate");
            response.Filter = new DeflateStream(response.Filter, CompressionMode.Compress);
        }
    }
}

Answer 1

这是CompressFilter类的糟糕实现。

请阅读： 在C＃中查找首选接受编码

我写了自己的，将遵循基于上述文章的AcceptEncoding ::

public class CompressFilter : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        HttpRequestBase request = filterContext.HttpContext.Request;

        string[] supported = new string[] { "gzip", "deflate" };

        IEnumerable<string> preferredOrder = new AcceptList(request.Headers["Accept-Encoding"], supported);

        string preferred = preferredOrder.FirstOrDefault();

        HttpResponseBase response = filterContext.HttpContext.Response;

        switch (preferred)
        {
            case "gzip":
                response.AppendHeader("Content-Encoding", "gzip");
                response.Filter = new GZipStream(response.Filter, CompressionMode.Compress);
                break;

            case "deflate":
                response.AppendHeader("Content-Encoding", "deflate");
                response.Filter = new DeflateStream(response.Filter, CompressionMode.Compress);
                break;

            case "identity":
            default:
                break;
        }
    }
}

public class AcceptList : IEnumerable<string>
{
    Regex parser = new Regex(@"(?<name>[^;,\r\n]+)(?:;q=(?<value>[\d.]+))?", RegexOptions.Compiled);

    IEnumerable<string> encodings;

    public AcceptList(string acceptHeaderValue, IEnumerable<string> supportedEncodings)
    {
        List<KeyValuePair<string, float>> accepts = new List<KeyValuePair<string, float>>();

        if (!string.IsNullOrEmpty(acceptHeaderValue))
        {
            MatchCollection matches = parser.Matches(acceptHeaderValue);

            var values = from Match v in matches
                         where v.Success
                         select new
                         {
                             Name = v.Groups["name"].Value,
                             Value = v.Groups["value"].Value
                         };

            foreach (var value in values)
            {
                if (value.Name == "*")
                {
                    foreach (string encoding in supportedEncodings)
                    {
                        if (!accepts.Where(a => a.Key.ToUpperInvariant() == encoding.ToUpperInvariant()).Any())
                        {
                            accepts.Add(new KeyValuePair<string, float>(encoding, 1.0f));
                        }
                    }

                    continue;
                }

                float desired = 1.0f;
                if (!string.IsNullOrEmpty(value.Value))
                {
                    float.TryParse(value.Value, out desired);
                }

                if (desired == 0.0f)
                {
                    continue;
                }

                accepts.Add(new KeyValuePair<string, float>(value.Name, desired));
            }
        }

        this.encodings = from a in accepts
                         where supportedEncodings.Where(se => se.ToUpperInvariant() == a.Key.ToUpperInvariant()).Any() || a.Key.ToUpperInvariant() == "IDENTITY"
                         orderby a.Value descending
                         select a.Key;
    }

    IEnumerator<string> IEnumerable<string>.GetEnumerator()
    {
        return this.encodings.GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return ((IEnumerable)this.encodings).GetEnumerator();
    }
}

Answer 2

我重写OnResultExecuting方法。 在呈现ActionResult之前调用它。 在检查客户端是否接受压缩之前，我会检查我尝试呈现的Result类型。 如果它不是ViewResult，我不应用任何类型的压缩。

为此，您的Actions必须显式调用View（）或PartialView（）。

以下是CompressOutputAttrtibute的样子：

public class CompressOutputAttribute : ActionFilterAttribute
{
    public override void OnResultExecuting(ResultExecutingContext filterContext) 
    {
        var result = filterContext.Result;
        if (!(result is ViewResult))
            return;

        HttpRequestBase request = filterContext.HttpContext.Request;
        string acceptEncoding = request.Headers["Accept-Encoding"];
        if (string.IsNullOrEmpty(acceptEncoding))
            return;

        acceptEncoding = acceptEncoding.ToUpperInvariant();

        HttpResponseBase response = filterContext.HttpContext.Response;
        if (acceptEncoding.Contains("GZIP"))
        {        
            // we want to use gzip 1st
            response.AppendHeader("Content-encoding", "gzip");
            //Add DeflateStream to the pipeline in order to compress response on the fly 
            response.Filter = new GZipStream(response.Filter, CompressionMode.Compress);
        }
        else if (acceptEncoding.Contains("DEFLATE"))
        {
            //If client accepts deflate, we'll always return compressed content 
            response.AppendHeader("Content-encoding", "deflate");
            //Add DeflateStream to the pipeline in order to compress response on the fly 
            response.Filter = new DeflateStream(response.Filter, CompressionMode.Compress);
        }
    }
}

控制器内部：

[CompressOutput]
public class ArticleController : Controller

    public PartialViewResult MostPopular()
    {
        var viewModel = ArticleMostPopularViewModel();
        viewModel.Articles = CmsService.GetMostPopularArticles();
        return PartialView(viewModel);
    }

    public ViewResult Show(int id)
    {
        var viewModel = ArticleShowViewModel();
        viewModel.Article = CmsService.GetArticle(id);
        return View(viewModel);
    }
}