Rest – Fiddler POST Invalid Header Name

fiddlerrestwcf

I am sending a POST request to a WCF Web service using fiddler, and the service responds with HTTP 400: The request has an invalid header name.
The post request looks like this:

User-Agent: Fiddler
Host: localhost:49392
Content-Type: application/json
Content-Length: 0
{  "clientFirstName" : "John"}

My endpoint is defined as follows:

 [OperationContract]
 [System.ServiceModel.Web.WebInvoke
       (Method = "POST",
       RequestFormat = WebMessageFormat.Json,
       ResponseFormat = System.ServiceModel.Web.WebMessageFormat.Json,
       BodyStyle = System.ServiceModel.Web.WebMessageBodyStyle.Wrapped,
       UriTemplate = "MakeReservation")]
 String MakeReservation(Stream reservationStream);

MORE

First of all, the JSON was in the wrong pane. I moved it to the Request Body pane.

I changed the prototype of the function to take a String instead of Stream as the input parameter. The service now accepts my call and returns 200, but in the debugger I see that the input parameter String is null. When I change it back to Stream, I get 400 again.

YET MORE

Enable tracing gives me at trace file with the following message:

Incoming message for operation 'MakeReservation' (contract 'ITalLimoService' with namespace 
'http://tempuri.org/') contains an unrecognized http body format value 'Json'. The expected body 
format value is 'Raw'. This can be because a WebContentTypeMapper has not been configured on the 
binding. See the documentation of WebContentTypeMapper for more details.

As noted int the WebInvoke definitiuon, both the RequestFormat and ResponseFormat are set to WebMessageFormate.Json. Why is IIS complaining about this?

Best Answer

I don't know why this works, but for some reason removing the following line from the fiddler Composer did the trick:

Content-Type: application/json

And that is that. I would give points for an explanation.

Related Solutions

Rest – the difference between POST and PUT in HTTP

Overall:

Both PUT and POST can be used for creating.

You have to ask, "what are you performing the action upon?", to distinguish what you should be using. Let's assume you're designing an API for asking questions. If you want to use POST, then you would do that to a list of questions. If you want to use PUT, then you would do that to a particular question.

Great, both can be used, so which one should I use in my RESTful design:

You do not need to support both PUT and POST.

Which you use is up to you. But just remember to use the right one depending on what object you are referencing in the request.

Some considerations:

Do you name the URL objects you create explicitly, or let the server decide? If you name them then use PUT. If you let the server decide then use POST.
PUT is defined to assume idempotency, so if you PUT an object twice, it should have no additional effect. This is a nice property, so I would use PUT when possible. Just make sure that the PUT-idempotency actually is implemented correctly in the server.
You can update or create a resource with PUT with the same object URL
With POST you can have 2 requests coming in at the same time making modifications to a URL, and they may update different parts of the object.

An example:

I wrote the following as part of another answer on SO regarding this:

POST:

Used to modify and update a resource
POST /questions/<existing_question> HTTP/1.1
Host: www.example.com/
Note that the following is an error:
POST /questions/<new_question> HTTP/1.1
Host: www.example.com/
If the URL is not yet created, you should not be using POST to create it while specifying the name. This should result in a 'resource not found' error because <new_question> does not exist yet. You should PUT the <new_question> resource on the server first.

You could though do something like this to create a resources using POST:
POST /questions HTTP/1.1
Host: www.example.com/
Note that in this case the resource name is not specified, the new objects URL path would be returned to you.

PUT:

Used to create a resource, or overwrite it. While you specify the resources new URL.

For a new resource:
PUT /questions/<new_question> HTTP/1.1
Host: www.example.com/
To overwrite an existing resource:
PUT /questions/<existing_question> HTTP/1.1
Host: www.example.com/

Additionally, and a bit more concisely, RFC 7231 Section 4.3.4 PUT states (emphasis added),

4.3.4. PUT

The PUT method requests that the state of the target resource be created or replaced with the state defined by the representation enclosed in the request message payload.

Json – How to POST JSON data with cURL

You need to set your content-type to application/json. But -d (or --data) sends the Content-Type application/x-www-form-urlencoded, which is not accepted on Spring's side.

Looking at the curl man page, I think you can use -H (or --header):

-H "Content-Type: application/json"

Full example:

curl --header "Content-Type: application/json" \
  --request POST \
  --data '{"username":"xyz","password":"xyz"}' \
  http://localhost:3000/api/login

(-H is short for --header, -d for --data)

Note that -request POST is optional if you use -d, as the -d flag implies a POST request.

On Windows, things are slightly different. See the comment thread.

Best Answer

Related Solutions

Rest – the difference between POST and PUT in HTTP

Json – How to POST JSON data with cURL

Related Topic