Java中發送POST請求并傳輸JSON結構體的方法如下：

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;
public class HttpPostJsonUtil {
public static String sendPostJson(String json, String url) throws Exception {
// 創建連接
URL obj = new URL(url);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
// 設置請求頭
con.setRequestProperty("Content-Type", "application/json;charset=UTF-8");
con.setRequestProperty("Accept", "application/json;charset=UTF-8");
// 設置POST請求
con.setRequestMethod("POST");
con.setDoOutput(true);
// 發送POST請求傳輸JSON數據
con.getOutputStream().write(json.getBytes(StandardCharsets.UTF_8));
// 獲取響應結果
String response = "";
BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
String inputLine;
while ((inputLine = in.readLine()) != null) {
response += inputLine;
}
in.close();
return response;
}
}

其中，通過URL對象創建連接，并設置請求頭為application/json;charset=UTF-8，Accept為application/json;charset=UTF-8，指定請求方法為POST，開啟doOutput并傳輸JSON數據。最后通過連接對象的getInputStream方法獲取響應結果，并通過BufferedReader讀取數據。