import com.linecorp.armeria.client.ClientFactory;
import com.linecorp.armeria.client.WebClient;
import com.linecorp.armeria.common.*;
WebClient webClient = WebClient.of(uri);
RequestHeaders postJson = RequestHeaders.of(HttpMethod.POST, path, HttpHeaderNames.CONTENT_TYPE, "application/json; charset=UTF-8");
AggregatedHttpResponse response = webClient.execute(postJson, json).aggregate().join();
String msg = response.contentUtf8();
ssl 처리나 header, cookie 설정은 https://lloydkwon.tistory.com/entry/armeria-Webclient-post-Form 참고