Only allow Nancy to return json or Xml and 406 when accept header is html - http

Question

I'm writing a Nancy endpoint and I want to do something that I think should be really simple. I want to support returning the content in either json or xml but when html or any other type is requested to return a 406 Not supported. I can easily force either XML or JSON only, and I guess I could do and if (accept is html) return 406 but I would assume that there is some support for this in the content Negotiation support.
Can anybody shed any light?

Answer 1

Implement your own IResponseProcessor, Nancy will pick it up and hook in the engine.
public sealed class NoJsonOrXmlProcessor : IResponseProcessor
{
public ProcessorMatch CanProcess(MediaRange requestedMediaRange, dynamic model, NancyContext context)
{
if (requestedMediaRange.Matches("application/json") || requestedMediaRange.Matches("aaplication/xml"))
{
//pass on, so the real processors can handle
return new ProcessorMatch{ModelResult = MatchResult.NoMatch, RequestedContentTypeResult = MatchResult.NoMatch};
}
return new ProcessorMatch{ModelResult = MatchResult.ExactMatch, RequestedContentTypeResult = MatchResult.ExactMatch};
}
public Response Process(MediaRange requestedMediaRange, dynamic model, NancyContext context)
{
return new Response{StatusCode = HttpStatusCode.NotAcceptable};
}
public IEnumerable<Tuple<string, MediaRange>> ExtensionMappings { get; private set; }
}

Answer 2

We avoided the use of ResponseProcessor for the whole reason that the request was still being run all the way through our authentication layer, domain layer, etc. We wanted a way to quickly kill the request as soon as possible.
What we ended up doing was performing the check inside our own Boostrapper
public class Boostrapper : DefaultNancyBootstrapper
{
protected override void RequestStartup(TinyIoCContainer requestContainer, IPipelines pipelines, NancyContext context)
{
base.RequestStartup(requestContainer, pipelines, context);
pipelines.BeforeRequest += nancyContext =>
{
RequestHeaders headers = nancyContext.Request.Headers
if (!IsAcceptHeadersAllowed(headers.Accept))
{
return new Response() {StatusCode = HttpStatusCode.NotAcceptable};
}
return null;
}
}
private bool IsAcceptHeadersAllowed(IEnumerable<Tuple<string, decimal>> acceptTypes)
{
return acceptTypes.Any(tuple =>
{
var accept = new MediaRange(tuple.Item1);
return accept.Matches("application/json") || accept.Matches("application/xml");
});
}
}