An error that happens when you try to use double quotes in the JSON that you send with cURL. The solution: https://stackoverflow.com/a/22597714/5432315

gistfile1.txt

C:\Users\Turek>curl -v -X POST localhost:8080/employees -H 'Content-Type:application/json' -d '{"name": "Samwise Gamgee", "role": "gardener"}' | python -mjson.tool
Note: Unnecessary use of -X or --request, POST is already inferred.
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0*   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 8080 (#0)
> POST /employees HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.55.1
> Accept: */*
> 'Content-Type:application/json'
> Content-Length: 7
> Content-Type: application/x-www-form-urlencoded
>
} [7 bytes data]
100     7    0     0  100     7      0      7  0:00:01 --:--:--  0:00:01   148* upload completely sent off: 7 out of 7 bytes
< HTTP/1.1 415
< Content-Type: application/json
< Transfer-Encoding: chunked
< Date: Fri, 08 May 2020 07:20:13 GMT
<
{ [205 bytes data]
100   206    0   199  100     7    199      7  0:00:01 --:--:--  0:00:01   628
* Connection #0 to host localhost left intact
Note: Unnecessary use of -X or --request, POST is already inferred.
* Rebuilt URL to: Samwise Gamgee,/
* Could not resolve host: Samwise Gamgee,
* Closing connection 1
curl: (6) Could not resolve host: Samwise Gamgee,
Note: Unnecessary use of -X or --request, POST is already inferred.
* Rebuilt URL to: role:/
  0     0    0     0    0     0      0      0 --:--:--  0:00:01 --:--:--     0* Could not resolve host: role
* Closing connection 2
curl: (6) Could not resolve host: role
curl: (3) [globbing] unmatched close brace/bracket in column 9
{
    "timestamp": "2020-05-08T07:20:13.315+0000",
    "status": 415,
    "error": "Unsupported Media Type",
    "message": "Content type 'application/x-www-form-urlencoded;charset=UTF-8' not supported",
    "path": "/employees"
}