ServiceStack REST API and CORS

Using the CorsFeature plugin

Enabling Global CORS support

We now have a CorsFeature which wraps CORS headers into the Plugin below to make it much easier to add CORS support to your ServiceStack services.

Commonly this is now all that’s needed:

Plugins.Add(new CorsFeature());

Which uses the default values:

CorsFeature(allowedOrigins:"*", 
    allowedMethods:"GET, POST, PUT, DELETE, OPTIONS", 
    allowedHeaders:"Content-Type", 
    allowCredentials:false);

You can leave out any of the values matching the default. E.g. if you just wanted to restrict the allowed methods to just GET and POST requests, you can just do:

Plugins.Add(CorsFeature(allowedMethods:"GET, POST"));

Globally enable CORS for all OPTION requests

Once the CorsFeature (or manual Global Headers) is registered, you can optionally choose to enable CORS for all OPTION requests by adding a PreRequest filter to emit all registered Global Headers (i.e. the Headers in CorsFeature) and short-circuit all OPTIONS requests with:

this.PreRequestFilters.Add((httpReq, httpRes) => {
    //Handles Request and closes Responses after emitting global HTTP Headers
    if (httpReq.Method == "OPTIONS") 
        httpRes.EndRequest(); //add a 'using ServiceStack;'
});

Enabling CORS per-service support

Instead of using the plugin above, ServiceStack also allows you to enable CORS on a per-service basis by using [EnableCors] Response Filter attribute which has the same defaults as above. E.g. You can enable just GET, POST as above with:

[EnableCors(allowedMethods:"GET,POST")]
public class MyService : Service { ... }

Manually enabling CORS

The beauty of ServiceStack is that it’s built on a highly flexible and simple core. We don’t try to build strong-typed APIs over everything, as it’s impossible to predict what new HTTP Headers / StatusCodes will exist in the future. So whilst we provide convenient behavior to accomplish common tasks, we also provide a flexible API that lets you configure any desired HTTP Output.

Setting Global HTTP Headers

This is how to globally enable Cross Origin Sharing in you AppHost config:

public override void Configure(Container container)
{
    //Permit modern browsers (e.g. Firefox) to allow sending of any REST HTTP Method
    base.SetConfig(new EndpointHostConfig
    {
        GlobalResponseHeaders = {
            { "Access-Control-Allow-Origin", "*" },
            { "Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS" },
            { "Access-Control-Allow-Headers", "Content-Type" },
        },
    });
}

Returning Custom HTTP Headers in a service

These headers will get sent on every request, alternatively you can also enable it for specific web services, i.e. take the Hello World Web Service for example:

public class Hello {
    public string Name { get; set; }
}

public class HelloResponse {
    public string Result { get; set; }
}

public class HelloService : IService 
{
    public object Any(Hello request)
    {
        var dto = new HelloResponse { Result = "Hello, " + request.Name };
        return new HttpResult(dto) {
            Headers = {
              { "Access-Control-Allow-Origin", "*" },
              { "Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS" } 
              { "Access-Control-Allow-Headers", "Content-Type" }, }
        };
    }
}

The above is all the C# code you need to develop a web service which is then automatically wired up for you on all HTTP Verbs (GET, POST, etc) and built-in endpoints, i.e. JSON, XML, JSV, HTML, CSV, SOAP 1.1/1.2 – for free, without any config or friction required. Checkout the live example of the above web service.

In addition to the above endpoints each service is available to be called by JSONP (another popular way to enable cross-domain service calls in Ajax apps) where each service can be called via JSONP by simply adding the ?callback=cb parameter to the querystring, e.g:

http://www.servicestack.net/ServiceStack.Hello/servicestack/hello/world?callback=cb

This is another example of the flexibility and productivity wins of using ServiceStack where you’re literally given friction-free flexibility and expressive freedom in your web service to literally return just about anything and it gets serialized as expected.

It’s not only easier to use than WCF (with more features out-of-the-box) but it’s also much faster where all its components are highly optimized for maximum performance.