In a recent post, we discussed using content negotiation to control the format of data returned by an API, using the Accept header as set by the client.

In all the examples, the requests were GET requests.

If you use a POST request instead, you may get the following response:

JSONClientResponse

The logs will show the following:

JSONException

The culprit here is the request:

JSONClientPostRequest

The payload is the following:

{
 "RequestDate": "2024-09-01T12:45:00Z"
}

The problem here is that the Content-Type header is missing - Content-Type: application/json

When making a POST request, make sure you specify the Content-Type header.

TLDR

When making a POST request with a payload, the Content-Type header is mandatory.

Happy hacking!