JAVA HTTP POST请求(请求参数格式为json)

public static String JsonSMS(String postData, String postUrl) {
    try {
        //发送POST请求
        URL url = new URL(postUrl);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("POST");
        conn.setRequestProperty("Content-Type", "application/json");
        conn.setRequestProperty("Connection", "Keep-Alive");
        conn.setUseCaches(false);
        conn.setDoOutput(true);
        conn.setRequestProperty("Content-Length", "" + postData.length());
        OutputStreamWriter out = new OutputStreamWriter(conn.getOutputStream(), "UTF-8");
        out.write(postData);
        out.flush();
        out.close();
        //获取响应状态
        if (conn.getResponseCode() != HttpURLConnection.HTTP_OK) {
            System.out.println("connect failed!");
            return "";
        }
        //获取响应内容体
        String line, result = "";
        BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "utf-8"));
        while ((line = in.readLine()) != null) {
            result += line + "\n";
        }
        in.close();
        return result;
    } catch (IOException e) {
        e.printStackTrace(System.out);
    }
    return "";
}