Access HTTP specific features in services

ServiceStack is based on http handlers, but ServiceStack provides a clean, dependency-free IService to implement your Web Services logic in. The philosophy behind this approach is that the less dependencies you have on your environment and its request context, the more testable and re-usable your services become.

Accessing the IHttpRequest and IHttpResponse in filters and Services

Request Filters

The Request Filters are applied before the service gets called and accepts: (IHttpRequest, IHttpResponse, RequestDto) e.g:

//Add a request filter to check if the user has a session initialized
this.RequestFilters.Add((httpReq, httpResponse, requestDto) =>
{
    httpReq.Headers["HttpHeader"];
    httpReq.QueryString["queryParam"];
    httpReq.Form["htmlFormParam"];
    httpReq.GetParam("aParamInAnyOfTheAbove");

    httpReq.Cookies["requestCookie"];
    httpReq.AbsoluteUri;
    httpReq.Items["requestData"] = "Share data between Filters and Services";

     //Access underlying Request in ASP.NET hosts
    var aspNetRequest = httpResponse.OriginalRequest as HttpRequest;
     //Access underlying Request in HttpListener hosts
    var listenerRequest = httpResponse.OriginalRequest as HttpListenerRequest;
});

Services

When inheriting from Service you can access them via base.Request and base.Response:

public class MyService : Service
{
    public object Any(Request request)
    {
        var value = base.Request.GetParam("aParamInAnyHeadersFormOrQueryString");
        base.Response.AddHeader("X-CustomHeader", "Modify HTTP Response in Service");
    }
}

Accessing the Request and Response from the RequestContext

The HttpRequest and HttpResponse is also accessible from a RequestContext with:

var httpReq = requestContext.Get<IHttpRequest>();
var httpRes = requestContext.Get<IHttpResponse>();

Response Filters

The Response Filters are applied after your service is called and accepts: (IHttpRequest, IHttpResponse, ResponseDto) e.g Add a response filter to add a 'Content-Disposition' header so browsers treat it as a native .csv file:

this.ResponseFilters.Add((req, res, responseDto) => 
{
    if (req.ResponseContentType == ContentType.Csv)
    {
        res.AddHeader(HttpHeaders.ContentDisposition,
            "attachment;filename={0}.csv".Fmt(req.OperationName));
    }

    //Access underlying Response in ASP.NET hosts
    var aspNetResponse = httpResponse.OriginalResponse as HttpResponse;
    //Access underlying Response in HttpListener hosts
    var listenerResponse = httpResponse.OriginalResponse as HttpListenerResponse;
});

Communicating throughout the Request Pipeline

The recommended way to pass additional metadata about the request is to use the IHttpRequest.Items collection. E.g. you can change what Razor View template the response DTO gets rendered in with:

httpReq.Items["Template"] = "_CustomLayout";

...

var preferredLayout = httpReq.Items["Template"];

Advantages for having dependency-free services

If you don't need to access the HTTP specific features your services can be called by any non-HTTP endpoint, like from a message queue.

Injecting the IRequestContext into your Service

Although working in a clean-room can be ideal from re-usability and testability point of view, you stand the chance of missing out a lot of the features present in HTTP.

Just like using built-in Funq IOC container, the way to tell ServiceStack to inject the request context is by implementing the IRequiresRequestContext interface which will get the IRequestContext injected before each request.

public interface IRequestContext : IDisposable
{
    T Get<T>() where T : class;
    string IpAddress { get; }
    string GetHeader(string headerName);
    IDictionary<string, Cookie> Cookies { get; }
    EndpointAttributes EndpointAttributes { get; }
    IRequestAttributes RequestAttributes { get; }
    string ContentType { get; }
    string ResponseContentType { get; }
    string CompressionType { get; }
    string AbsoluteUri { get; }
    string PathInfo { get; }
    IFile[] Files { get; }
}

Note: ServiceStack's Service base class already implements IRequiresRequestContext which allows you to access the IRequestContext with base.RequestContext and the HTTP Request and Response with base.Request and base.Response.

Note: To return a customized HTTP Response, e.g. set Response Cookies or Headers, return the HttpResult object.