how to send application/x-www-form-urlencoded in Spring 6 RestClient

Question

I use spring-web 6.1.1. Below is working for RestTemplate

RestTemplate restTemplate = new RestTemplate();
String url = "https://dev-test.com/token";

HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);

MultiValueMap<String, String> map= new LinkedMultiValueMap<String, String>();
map.add("username", "aaa");
map.add("password", "bbc");
map.add("grant_type", "password");

HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<MultiValueMap<String, String>>(map, headers);

ResponseEntity<String> response = restTemplate.postForEntity( url, request, String.class );

When using new RestClient, I got the error:

RestClient test = RestClient.builder()
                .baseUrl("https://dev-test.com/")
                .build();

        ResponseEntity responseLicenseCheck = test.post()
                .uri("/token")
                .body(request)
                .retrieve()
                .toEntity(String.class);

--

Exception in thread "main" org.springframework.web.client.HttpClientErrorException$BadRequest: 400 Bad Request: "{"error":"unsupported_grant_type"}"
    at org.springframework.web.client.HttpClientErrorException.create(HttpClientErrorException.java:103)

Answer 1

restClient is different with restTemplate on body() method, you need to pass data object to it instead of requestEntity, and declare headers separately. In your example:

ResponseEntity responseLicenseCheck = test.post()
            .uri("/token")
            .body(map)
            .contentType(MediaType.APPLICATION_FORM_URLENCODED)
            .retrieve()
            .toEntity(String.class);

or

ResponseEntity responseLicenseCheck = test.post()
            .uri("/token")
            .body(map)
            .headers(headers->headers.addAll(xxxxList))
            .retrieve()
            .toEntity(String.class);