感谢大佬daichangxia
原文：https://blog.csdn.net/daichangxia/article/details/72853267

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;

import com.google.gson.JsonObject;
public static String getJsonData(JsonObject jsonParam, String urls) {
StringBuffer sb=new StringBuffer();
try {
;
// 创建url资源
URL url = new URL(urls);
// 建立http连接
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
// 设置允许输出
conn.setDoOutput(true);
// 设置允许输入
conn.setDoInput(true);
// 设置不用缓存
conn.setUseCaches(false);
// 设置传递方式
conn.setRequestMethod(“POST”);
// 设置维持长连接
conn.setRequestProperty(“Connection”, “Keep-Alive”);
// 设置文件字符集:
conn.setRequestProperty(“Charset”, “UTF-8”);
// 转换为字节数组
byte[] data = (jsonParam.toString()).getBytes();
// 设置文件长度
conn.setRequestProperty(“Content-Length”, String.valueOf(data.length));
// 设置文件类型:
conn.setRequestProperty(“content-Type”, “application/json”);
// 开始连接请求
conn.connect();
OutputStream out = new DataOutputStream(conn.getOutputStream()) ;
// 写入请求的字符串
out.write((jsonParam.toString()).getBytes());
out.flush();
out.close();

        System.out.println(conn.getResponseCode());

        // 请求返回的状态
        if (HttpURLConnection.HTTP_OK == conn.getResponseCode()){
            System.out.println("连接成功");
            // 请求返回的数据
            InputStream in1 = conn.getInputStream();
            try {
                String readLine=new String();
                BufferedReader responseReader=new BufferedReader(new InputStreamReader(in1,"UTF-8"));
                while((readLine=responseReader.readLine())!=null){
                    sb.append(readLine).append("\n");
                }
                responseReader.close();
                System.out.println(sb.toString());

            } catch (Exception e1) {
                e1.printStackTrace();
            }
        } else {
            System.out.println("error++");

        }

    } catch (Exception e) {

    }

    return sb.toString();

}