SpringBoot: HttpClientErrorException$BadRequest: 400: [no body] when calling restTemplate.postforEntity or restTemplate.exchange - spring

Question

I am trying to hit a restful endpoint from my springboot application using restTemplate.exchange and restTemplate.postForEntity and I am getting 400 Bad request [no body] exception.
I tried every possible solution to figure out the issue. From the same code I used HttpURLConnection to hit the endpoint and it works fine. I am able to get valid response. I also tried hitting the endpoint from Postman and it works fine
Below is endpoint code
#RestController
#RequestMapping("auth")
#Slf4j
public class AuthController {
#PostMapping(value = "/as/resourceOwner",
consumes = MediaType.APPLICATION_FORM_URLENCODED_VALUE,
produces = MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<Token> getToken(#RequestParam(required = false)MultiValuedMap<?, ?> params) {
log.info("token endpoint");
return new ResponseEntity<>(new Token(), HttpStatus.OK);
}
}
The below code with HttpURLConnection class works fine
public class Test {
public static void main(String[] args) {
try {
URL url = new URL("http://localhost:8080/fc-services-mock-auth/fmrco/as/resourceOwner");
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setDoOutput(true);
urlConnection.setRequestMethod("POST");
urlConnection.setRequestProperty("Content-Type", MediaType.APPLICATION_FORM_URLENCODED_VALUE);
OutputStream writer = urlConnection.getOutputStream();
writer.write("a=a&b=b".getBytes(StandardCharsets.UTF_8));
writer.flush();
writer.close();
BufferedReader reader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
String line = null;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
} catch (Exception e) {
System.out.println(e);
}
}
}
But the below code with restTemplate does not work
try {
HttpEntity httpEntity = new HttpEntity<>(createBody(), createHeaders());
ResponseEntity<String> response = restTemplate.exchange(new URI(endpointConfig.getTokenServiceUrl()),
HttpMethod.POST, httpEntity, String.class);
HttpEntity<MultiValueMap<String, String>> request =
new HttpEntity<>(createBody(), createHeaders());
ResponseEntity<TokenResponse> tokenResponse = restTemplate.postForEntity(
new URI(endpointConfig.getTokenServiceUrl()),
request,
TokenResponse.class);
logger.debug(" token process completed");
return tokenResponse.getBody();
} catch (Exception e) {
throw new TokenException(" token error: ", e);
}
private HttpHeaders createHeaders() {
HttpHeaders headers = new HttpHeaders();
headers.add("Content-Type", MediaType.APPLICATION_FORM_URLENCODED_VALUE);
return headers;
}
private MultiValueMap createBody() {
MultiValueMap<String, String> map = new LinkedMultiValueMap<>();
map.add("client_id", applicationConfig.getTokenClientId());
map.add("client_secret", applicationConfig.getTokenClientSecret());
map.add("grant_type", "password");
map.add("username", applicationConfig.getTokenUsername());
map.add("password", applicationConfig.getTokenPassword());
return map;
}
Can anyone please tell me what is wrong here?
Additionally I have written another GET restful endpoint like below and while hitting the endpoint using exchange I still get the same error.
#GetMapping(value = "test", produces = MediaType.TEXT_PLAIN_VALUE)
public ResponseEntity<String> test() {
return new ResponseEntity<>("Hello", HttpStatus.OK);
}
try {
HttpHeaders headers = new HttpHeaders();
headers.setAccept(Arrays.asList(MediaType.TEXT_PLAIN));
HttpEntity<MultiValueMap<String, String>> entity =
new HttpEntity<>(null, headers);
ResponseEntity<String> response = restTemplate.exchange(
"http://localhost:8080/context/path",
HttpMethod.GET, entity, String.class);
} catch (Exception e) {
System.out.println(e);
}
Also, intentionally I tried making a POST call to the get endpoint to see if it returns 405 Method not allowed. But to my wonder it still returned 400 Bad Request no body.

Answer 1

I finally figured it out. The restTemplate is configured to use a proxy. I removed the proxy and it is working fine now.

Answer 2

You can try something like:-
public void fetchAuthenticationToken() {
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
headers.setAccept(List.of(MediaType.APPLICATION_JSON));
MultiValueMap<String, String> map = new LinkedMultiValueMap<>();
map.add("client_id", applicationConfig.getTokenClientId());
map.add("client_secret", applicationConfig.getTokenClientSecret());
map.add("grant_type", "client_credentials");
map.add("username", applicationConfig.getTokenUsername());
map.add("password", applicationConfig.getTokenPassword());
HttpEntity<MultiValueMap<String, String>> entity = new HttpEntity<>(map, headers);
String tokenEndPoint = "{your endpoints URL}";
ResponseEntity<TokenResponse> responseEntity = testRestTemplate.exchange(tokenEndPoint,
HttpMethod.POST, entity, TokenResponse.class, new HashMap<String, String>());
assertThat(responseEntity.getStatusCode()).isEqualTo(HttpStatus.OK);
TokenResponse token = responseEntity.getBody();
assertThat(token).isNotNull();
System.out.println("Auth Token value is "+ token)
}