ServiceStack default format

Question

I would like to set ServiceStack's default format to JSON, as opposed to the HTML formatted response it normally returns when a service is accessed from a browser. I know this can be specified on each request by sending a ?format=json parameter or setting the Accept header to application/json. Is there a way to change this without having to rely on these hints from the request?

Answer 1

In addition to specifying it on the QueryString with ?format=json, by appending the format .ext to the end of the route, e.g: /rockstars.json, or by specifying the HTTP Header (in your HttpClient): Accept: application/json.

Otherwise if your HttpClient doesn't send an Accept header you can specify JSON as the default content type in your AppHost with:

SetConfig(new HostConfig {
     DefaultContentType = MimeTypes.Json 
});

All Configuration options in ServiceStack are set here.

The issue when calling web services from a web browser is that they typically ask for Accept: text/html and not JSON which by contract ServiceStack obliges by returning back HTML if it is enabled.

To ensure JSON is returned you may also want to disable the HTML feature with:

SetConfig(new HostConfig {
    EnableFeatures = Feature.All.Remove(Feature.Html),
});

Different ways to specify the Response Content Type

Otherwise if you want to override the Accept header you can force your service to always return json with any of these ways to Customize the HTTP Response, e.g:

Using a filter (AddHeader is built-in):

[AddHeader(ContentType=MimeTypes.Json)]
public object Any(Request request) { ... }

Setting the Response in the service:

public object Any(Request request) 
{ 
    base.Response.ContentType = MimeTypes.Json;
    return dto;
}

Returning a decorated response:

return new HttpResult(dto, MimeTypes.Json);

Answer 2

I use the PreRequestFilter to force JSON responses to a browser. You still see the ?format=json on the querystring, but it's useful if you've disabled html & xml.

this.PreRequestFilters.Add( (req, res) =>
    {
        const string queryString = "format=json"; 
        var jsonAccepted = req.AcceptTypes.Any(t => t.Equals(ContentType.Json, StringComparison.InvariantCultureIgnoreCase));
        var jsonSpecifiedOnQuerystring = !string.IsNullOrEmpty(req.QueryString["format"]) && req.QueryString["format"].Equals("json", StringComparison.InvariantCultureIgnoreCase);
        if (!jsonAccepted && !jsonSpecifiedOnQuerystring)
        {
            var sb = new StringBuilder(req.AbsoluteUri);
            sb.Append(req.AbsoluteUri.Contains("?") ? "&" : "?");
            sb.Append(queryString);
            res.RedirectToUrl(sb.ToString(), HttpStatusCode.SeeOther);
            res.Close();
        }
    });

Answer 3

Late to the question, but since I couldn't find the answer anywhere, I finally figured it out from ServiceStack's source code :)

The simplest way I found to default to Json instead of Html from the browser was this:

HttpRequestExtensions.PreferredContentTypes = new[] { MimeTypes.Json, MimeTypes.Xml };

Call this at the startup of your app, and it will override default's ServiceStack mime types and start with json (which will work with your browser's requests since / will match it).

Note that you should still disable Html and make Json the default mime type:

SetConfig(new HostConfig {
     DefaultContentType = MimeTypes.Json 
     EnableFeatures = Feature.All.Remove(Feature.Html),
});

---

For the curious: ServiceStack uses internally HttpRequestExtensions.GetResponseContentType (see HttpRequestExtensions.cs), which loops through preferred content types. Because it contains MimeTypes.Html, it will catch the first accept type from the browser (text/html) and ignore whatever is coming after. By overriding this, text/html is not seen as a preferred content type, and it then skips to */* which defaults to json as expected.