Post request with only query parameters using RestTemplate POST method - spring-boot

Question

I am trying to call an API using POST method. There is no body in it and all parameters in the URL only.
This is how I am building request to call via okHttpClient version :
Request requestToken = new Request.Builder()
.url(TOKEN_GEN_API_URL + ConfigConstants.TOKEN_CLIENT_ID_PARAM
+ TOKEN_CLIENT_ID_PARAM_VALUE + ConfigConstants.TOKEN_CLINET_SECRET_PARAM
+ TOKEN_CLIENT_SECRET_PARAM_VALUE + ConfigConstants.TOKEN_GRANT_TYPE_PARAM
+ TOKEN_GRANT_TYPE_PARAM_VALUE)
.post(requestBody)
.addHeader("Content-Type", "application/json")
.addHeader("cache-control", "no-cache")
.build();
ConfigConstants Class :
public class ConfigConstants {
public static final String TOKEN_CLIENT_ID_PARAM = "?client_id=";
public static final String TOKEN_CLINET_SECRET_PARAM = "&client_secret=";
public static final String TOKEN_GRANT_TYPE_PARAM = "&grant_type=";
}
This would create URL something like this :
<endpoint>?client_id=...&client_secret=..&grant_type=..
Now, I am trying call this via RestTemplate, I think it would less complicated in that. But, I am not sure how to build this request without any body.
#RestController
public class TokenRestAPI {
#Autowired
RestTemplate restTemplate;
private static final Logger logger = LogManager.getLogger(TokenRestAPI.class);
#Value("${TOKEN_CLIENT_SEC_PARAM_VALUE}")
private String TOKEN_CLIENT_SECRET_PARAM_VALUE;
#Value("${TOKEN_CLIENT_ID_PARAM_VALUE}")
private String TOKEN_CLIENT_ID_PARAM_VALUE;
#Value("${TOKEN_GRANT_TYPE_PARAM_VALUE}")
private String TOKEN_GRANT_TYPE_PARAM_VALUE;
#Value("${TOKEN_GEN_API_URL}")
private String TOKEN_GEN_API_URL;
#PostMapping("/")
public void getAuthToken() {
ResponseEntity<TokenPOJO> response = restTemplate.postForEntity(TOKEN_GEN_API_URL, request, TokenPOJO.class);
}
}

Answer 1

If you don't want to send a body, just pass null as the request object:
ResponseEntity<TokenPOJO> response = restTemplate.postForEntity(TOKEN_GEN_API_URL, null, TokenPOJO.class);
you will still have to either build up the URL or use the parameters. The last you can do by putting variables in your url string like:
String url = "http://example.com?foo={bar}"
and pass a map with the variable name as key and the parameter value as the value.