public AssetDispatcher(ResourceStreamer streamer,
    ClasspathAssetAliasManager aliasManager,
    ResourceCache resourceCache) 
{
        this.streamer = streamer;
        this.aliasManager = aliasManager;
        this.resourceCache = resourceCache;
}

 public boolean dispatch(Request request,
    Response response) throws IOException 
{
        String path = request.getPath();
        // Remember that the request path does not include the context path, so we can simply start
        // looking for the asset path prefix right off the bat.
        if (!path.startsWith(RequestConstants.ASSET_PATH_PREFIX)) return false;
        // ClassLoaders like their paths to start with a leading slash.
        String resourcePath = aliasManager.toResourcePath(path);
        Resource resource = findResourceAndValidateDigest(response, resourcePath);
        if (resource == null) return true;
        if (!resource.exists())
        {
            response.sendError(HttpServletResponse.SC_NOT_FOUND, ServicesMessages
                    .assetDoesNotExist(resource));
            return true;
        }
        long ifModifiedSince = 0;
        try
        {
            ifModifiedSince = request.getDateHeader(IF_MODIFIED_SINCE_HEADER);
        }
        catch (IllegalArgumentException ex)
        {
            // Simulate the header being missing if it is poorly formatted.
            ifModifiedSince = -1;
        }
        if (ifModifiedSince  > 0)
        {
            long modified = resourceCache.getTimeModified(resource);
            if (ifModifiedSince  >= modified)
            {
                response.sendError(HttpServletResponse.SC_NOT_MODIFIED, "");
                return true;
            }
        }
        streamer.streamResource(resource);
        return true;
}