import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.web.client.RestTemplate;

public static String hanlelPost(String url, String body){
   RestTemplate restTemplate = new RestTemplate();
   HttpHeaders headers = new HttpHeaders();
   HttpEntity<String> formEntity = new HttpEntity<>(body, headers);
   String json = restTemplate.postForEntity(url, formEntity, String.class).getBody();
   return json;
}

RestTemplate、HttpHeaders、HttpEntity<String>