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@darrelmiller
Created September 11, 2012 13:07
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Some Web API techniques
using System;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using System.Web.Http.SelfHost;
namespace WebApiSelfHost
{
class Program
{
static void Main(string[] args)
{
var baseAddress = new Uri("http://localhost:8080/");
var configuration = new HttpSelfHostConfiguration(baseAddress);
configuration.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
var host = new HttpSelfHostServer(configuration);
host.OpenAsync().Wait();
Console.WriteLine("Host open. Hit enter to exit...");
Console.Read();
host.CloseAsync().Wait();
}
}
public class Foo
{
public string A { get; set; }
public string B { get; set; }
}
public class Error
{
public string Code { get; set; }
public string Message { get; set; }
}
// Helper class to allow actions that return HttpResponseMessage to easily embed CLR types
public class HttpResponseMessage<T> : HttpResponseMessage
{
public HttpResponseMessage(HttpRequestMessage request, T value)
{
var config = request.GetConfiguration();
var contentNegotiator = config.Services.GetContentNegotiator();
var connegResult = contentNegotiator.Negotiate(
typeof(T), request, config.Formatters
);
request.CreateResponse(HttpStatusCode.Accepted, value);
Content = new ObjectContent<T>(value, connegResult.Formatter);
}
}
// Return a HttpResponseMessage that has a strongly typed payload
public class FooController : ApiController
{
public HttpResponseMessage Get()
{
var value = new Foo()
{
A = "Hello",
B = "World"
};
return new HttpResponseMessage<Foo>(Request, value);
}
}
// Return an error message along with a status code
public class BarController : ApiController
{
public HttpResponseMessage Get()
{
return new HttpResponseMessage(HttpStatusCode.BadRequest) { ReasonPhrase = "You have failed"};
}
}
// Return error message by throwing an exception
public class BazController : ApiController
{
public Foo Get()
{
throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.BadRequest ) {ReasonPhrase= "You have failed"}) ;
}
}
// Return an error message body by throwing an exception
public class BlahController : ApiController
{
public Foo Get()
{
throw new HttpResponseException(new HttpResponseMessage<Error>(Request,new Error() {Code = "911", Message="You failed"}) {StatusCode = HttpStatusCode.BadRequest} );
}
}
}
@mythz
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mythz commented Sep 11, 2012

That's ok, by comparison different ways to do error handling in ServiceStack:

 public class BlahService : RestServiceBase<Foo>
 {
     public override object OnGet(Foo request)
     {
         //StatusCode = 400, StatusDesciption = You failed
         throw new ArgumentException("You failed"); 

         //StatusCode = 911, StatusDesciption = You failed
         throw new HttpError { Status = 911, StatusDescription = "You failed" };
    }
 }

Also if you have a FooResponse DTO you also get typed, structured error handling back in the client: https://github.com/ServiceStack/ServiceStack/wiki/Validation e.g:

try 
{
    var client = new JsonServiceClient(BaseUri);
    var response = client.Send<UserResponse>(new User());
} 
catch (WebServiceException webEx) 
{
    /*
      webEx.StatusCode  = 400
      webEx.ErrorCode   = ArgumentNullException
      webEx.Message     = Value cannot be null. Parameter name: Name
      webEx.StackTrace  = (your Server Exception StackTrace - if DebugMode is enabled)
      webEx.ResponseDto = (your populated Response DTO)
      webEx.ResponseStatus   = (your populated Response Status DTO)
      webEx.GetFieldErrors() = (individual errors for each field if any)
    */
}

The error is just a serialized JSON / XML FooResponse DTO so can easily be read by dynamic clients as well.

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