How to get token from a REST service with Spring - spring

Question

The service provider supplies me with the header data: grant_type, Content-Type. And the body data: grant_type, username and password. Which I use in Postman where it generates OK token. But in the Spring application it generates an error HttpClientErrorException $ BadRequest: 400 Bad Request.
I have the class to set the body data:
public class BodyToken {
private String grant_type = "password";//set body data
private String username = "User";//set body data
private String password = "123";//set body data
private String access_token;
#JsonGetter("access_token")
public String getAccess_token() {
return access_token;
}
public void setAccess_token(String access_token) {
this.access_token = access_token;
}
#JsonGetter("grant_type")
public String getGrant_type() {
return grant_type;
}
#JsonGetter("username")
public String getUsername() {
return username;
}
#JsonGetter("password")
public String getPassword() {
return password;
}
}
This is the controller where the header data is set:
#PostMapping("/TokenGeneration")
#ResponseBody
public BodyToken TokenGeneration() throws IOException {
RestTemplate restTemplate = new RestTemplate();
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
headers.set("grant_type", "password");//set header data
headers.set("Content-Type", "application/x-www-form-urlencoded");//set header data
HttpEntity request = new HttpEntity(headers);
headers.add("User-Agent", "Spring's RestTemplate" );
ResponseEntity<BodyToken> response = restTemplate.exchange(
"https://sw/token",
HttpMethod.POST,
request,
BodyToken.class
);
try {
return response.getBody();
} catch (Exception e) {
BodyToken body = new BodyToken();
log.info(e.getMessage());
return body;
}
}

Answer 1

OK was solved with using the Class MultiValueMap and LinkedMultiValueMap. The credentials are added to this new object and it is sent together with the request:
#PostMapping("/TokenGeneration")
#ResponseBody
public BodyToken TokenGeneration() throws IOException {
RestTemplate restTemplate = new RestTemplate();
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
headers.set("grant_type", "password");//set header data
headers.set("Content-Type", "application/x-www-form-urlencoded");//set header data
MultiValueMap<String, String> body = new LinkedMultiValueMap<String, String>();//line solution
body.add("grant_type", "password");//line solution
body.add("username", "user");//line solution
body.add("password", "123");//line solution
HttpEntity request = new HttpEntity(body, headers);//and I add this body to HttpEntity
headers.add("User-Agent", "Spring's RestTemplate" );
ResponseEntity<BodyToken> response = restTemplate.exchange(
"https://sw/token",
HttpMethod.POST,
request,
BodyToken.class
);
try {
return response.getBody();
} catch (Exception e) {
BodyToken body = new BodyToken();
log.info(e.getMessage());
return body;
}
}