Extending WebAssetHttpHandler

[Binu Thayamkery]

I am using SharedWebAssets to combine and compress all our JS script groups. I want to extend the WebAssetHttpHandler to  minify scripts before we compress the response. How do we do this? 
(I took an initial stab at this, but looks like there ProcessRequest() of the handler is using some internal methods, etc... so looking for pointers here)

Thanks!

[Edited: 12/21/2010]
I have figured out how to do this (think Reflection), I will post my complete finds for anyone who are interested soon.
 

[William Hurst]

Did you manage to complete this? I am looking to do the same thing.

[Binu Thayamkery]

Yes William. I created an extension to the AssetHttpHandler. Please note that my code does work only for SharedWebAssets. Also we found that there is a bit of issue with Caching. If you set your Asset Groups to cache, Asset Handler will be called only when this cache expires. So that means even if you have a new release, user's browser will not be requesting asset.axd. Workaround for this (as given by telerik support) is to have a file name change within each asset group, example: stick version to at least one file. Our solution was to add a versio0000.js and rename it with the build version as a post build event. We are currently testing this solution.

using Yahoo.Yui.Compressor;
:
:
public override void ProcessRequest(HttpContextBase context)

{

    var id = context.Request.QueryString[IdParameterName];

    var content = String.Empty;

    HttpResponseBase response = null;

    var minifyScripts = !bool.Parse(ConfigurationManager.AppSettings["DebugJavaScript"]);

 

    if (string.IsNullOrWhiteSpace(id)) return;

 

    var findScriptGroups = typeof(SharedWebAssets).GetMethod("FindScriptGroup",

                                                             BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static);

 

    var findStyleGroups = typeof(SharedWebAssets).GetMethod("FindStyleSheetGroup",

                                                            BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static);

 

 

    var group = findScriptGroups.Invoke(null, new object[]{id}) as WebAssetGroup

                ?? findStyleGroups.Invoke(null, new object[] { id }) as WebAssetGroup;

 

     

    if (group != null)

    {

        response = context.Response;

        // Set the content type

        response.ContentType = group.ContentType;

 

        var reader = typeof(WebAssetHttpHandler).GetField("reader", BindingFlags.NonPublic | BindingFlags.Instance);

        if (reader != null)

        {

            var assetGroupReader = reader.GetValue(this) as IWebAssetGroupReader;

            if (assetGroupReader != null)

                content = assetGroupReader.Read(group);

        }

 

        //Minify

        if (minifyScripts && response.ContentType.ToLower() == "text/javascript")

        {

            content = JavaScriptCompressor.Compress(content,

                                                    false, // Verbose Logging

                                                    true,  // Obfuscate JavaScript

                                                    true,  // Preserve all semi colons

                                                    false, // Disable Optimizations

                                                    -1,    // Line Break Position

                                                    Encoding.Default,

                                                    CultureInfo.CurrentCulture,

                                                    false // Ignore Eval

                                                    );

        }

    }

 

    if (string.IsNullOrWhiteSpace(content) || group == null) return;

 

    // Compress

    if (group.Compress && !context.IsMono())

    {

        var httpResponseCompressor = typeof (WebAssetHttpHandler).GetField("httpResponseCompressor",

                                                                           BindingFlags.NonPublic | BindingFlags.Instance);

 

        if (httpResponseCompressor != null)

        {

            var responseCompressor = httpResponseCompressor.GetValue(this) as IHttpResponseCompressor;

            if (responseCompressor != null)

                responseCompressor.Compress(context);

        }

    }

    // Write

    using (var sw = new StreamWriter((response.OutputStream)))

    {

        sw.Write(content);

    }

    // Cache

    if (!context.IsDebuggingEnabled)

    {

        var httpResponseCacher = typeof (WebAssetHttpHandler).GetField("httpResponseCacher",

                                                                       BindingFlags.NonPublic | BindingFlags.Instance);

 

        if (httpResponseCacher != null)

        {

            var responseCacher = httpResponseCacher.GetValue(this) as IHttpResponseCacher;

            if (responseCacher != null)

                responseCacher.Cache(context, TimeSpan.FromDays(group.CacheDurationInDays));

        }

    }

}

Good Luck!
[Edited 02/08] - In order to get caching to work, we ended up adding our build version to our asset group names. This way when we have a new release out, asset.axd url changes and it will invalidate browser cache.