Spring RestTemplate POST Request with URL encoded data

I think the problem is that when you try to send data to server didn't set the content type header which should be one of the two: "application/json" or "application/x-www-form-urlencoded" . In your case is: "application/x-www-form-urlencoded" based on your sample params (name and color). This header means "what type of data my client sends to server".

RestTemplate restTemplate = new RestTemplate();HttpHeaders headers = new HttpHeaders();headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);headers.add("PRIVATE-TOKEN", "xyz");MultiValueMap<String, String> map = new LinkedMultiValueMap<>();map.add("name","feature");map.add("color","#5843AD");HttpEntity<MultiValueMap<String, String>> entity = new HttpEntity<>(map, headers);ResponseEntity<LabelCreationResponse> response =    restTemplate.exchange("https://foo/api/v3/projects/1/labels",                          HttpMethod.POST,                          entity,                          LabelCreationResponse.class);

You need to set the Content-Type to application/json. Content-Type has to be set in the request. Below is the modified code to set the Content-Type

final String uri = "https://someserver.com/api/v3/projects/1/labels";String input = "US";HttpHeaders headers = new HttpHeaders();headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);headers.add("PRIVATE-TOKEN", "xyz");HttpEntity<String> request = new HttpEntity<String>(input, headers);ResponseEntity<LabelCreationResponse> response = restTemplate.postForObject(uri, request,  LabelCreationResponse.class);

Here, HttpEntity is constructed with your input i.e "US" and with headers. Let me know if this works, if not then please share the exception.Cheers!

It may be a Header issue check if the header is a Valid header, are u referring to "BasicAuth" header?

HttpHeaders headers = new HttpHeaders();headers.add("Content-Type", MediaType.APPLICATION_FORM_URLENCODED.toString());headers.add("Accept", MediaType.APPLICATION_JSON.toString()); //Optional in case server sends back JSON data    MultiValueMap<String, String> requestBody = new LinkedMultiValueMap<String, String>();requestBody.add("name", "feature");requestBody.add("color", "#5843AD");    HttpEntity formEntity = new HttpEntity<MultiValueMap<String, String>>(requestBody, headers);    ResponseEntity<LabelCreationResponse> response =    restTemplate.exchange("https://example.com/api/request", HttpMethod.POST, formEntity, LabelCreationResponse.class);