/// <summary>
/// As a <see cref="IResourceFilter"/>, this filter looks at the request and rejects it before going ahead if
/// 1. The format in the request does not match any format in the map.
/// 2. If there is a conflicting producesFilter.
/// </summary>
/// <param name="context">The <see cref="ResourceExecutingContext"/>.</param>
public void OnResourceExecuting(ResourceExecutingContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
var format = GetFormat(context);
if (format == null)
{
// no format specified by user, so the filter is muted
return;
}
var contentType = _options.FormatterMappings.GetMediaTypeMappingForFormat(format);
if (contentType == null)
{
_logger.UnsupportedFormatFilterContentType(format);
// no contentType exists for the format, return 404
context.Result = new NotFoundResult();
return;
}
// Determine media types this action supports.
var responseTypeFilters = context.Filters.OfType <IApiResponseMetadataProvider>();
var supportedMediaTypes = new MediaTypeCollection();
foreach (var filter in responseTypeFilters)
{
filter.SetContentTypes(supportedMediaTypes);
}
// Check if support is adequate for requested media type.
if (supportedMediaTypes.Count == 0)
{
_logger.ActionDoesNotExplicitlySpecifyContentTypes();
return;
}
// We need to check if the action can generate the content type the user asked for. That is, treat the
// request's format and IApiResponseMetadataProvider-provided content types similarly to an Accept
// header and an output formatter's SupportedMediaTypes: Confirm action supports a more specific media
// type than requested e.g. OK if "text/*" requested and action supports "text/plain".
if (!IsSuperSetOfAnySupportedMediaType(contentType, supportedMediaTypes))
{
_logger.ActionDoesNotSupportFormatFilterContentType(contentType, supportedMediaTypes);
context.Result = new NotFoundResult();
}
}