java中請求post類型的接口，參數使用json

如果編碼格式不是utf-8可以換成別的，或者提出來一個參數也行

/**
 * 
 * @param urlstr 請求的地址
 * @param json json格式的參數
 * @param headerMap 需要傳入的header信息，如果沒有可以爲空
 * @return
 */
public static String doPostJson(String urlstr, String json, Map<String, ?> headerMap) {
    try {
        URL url = new URL(urlstr);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setDoOutput(true);
        connection.setDoInput(true);
        connection.setRequestMethod("POST");
        connection.setUseCaches(false);
        connection.setInstanceFollowRedirects(true);
        connection.setRequestProperty("Content-Type", "application/json");
        if(headerMap!=null){
            Iterator<String> keys = headerMap.keySet().iterator();
            while (keys.hasNext()) {
                String key = keys.next();
                Object val = headerMap.get(key);
                List tmpList = new ArrayList();
                tmpList.add(val.toString());
                connection.addRequestProperty(key, val.toString());
            }
        }
        connection.connect();
        DataOutputStream out = new DataOutputStream(connection.getOutputStream());
        JSONObject obj = JSONObject.parseObject(json);

        out.writeBytes(obj.toString());
        out.flush();
        out.close();

        //讀取響應
        BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
        String lines;
        StringBuffer sb = new StringBuffer("");
        while ((lines = reader.readLine()) != null) {
            lines = new String(lines.getBytes(), "utf-8");
            sb.append(lines);
        }
        reader.close();
        connection.disconnect();
        return sb.toString();
        // 斷開連接
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return "";
}