Java原生使用HttpURLConnection实现POSTJson的例子

前面介绍了Java原生无依赖使用HttpURLConnection实现Get的例子，有时候需要是POST，所以给出POST的例子（内容Payload是JSON String）

 /**
 * 
 * @param url 请求地址
 * @param headers 请求头，多个用key，value的形式存储，key为header的名称，value为header的值，可以为null
 * @param json 请求体，json格式的字符串
 * @return 服务器返回值
 */
public static String httpPostJson(String url, HashMap<String, String> headers, String json) throws IOException {
    HttpURLConnection connection = null;
    try {
        connection = (HttpURLConnection) new URL(url).openConnection();
        connection.setRequestMethod("POST");
        connection.setRequestProperty("Content-Type", "application/json");
        connection.setRequestProperty("Accept", "application/json");
        if (headers != null) {
            for (Map.Entry<String, String> entry : headers.entrySet()) {
                connection.setRequestProperty(entry.getKey(), entry.getValue());
            }
        }
        connection.setDoOutput(true);

        OutputStream os = connection.getOutputStream();
        byte[] input = json.getBytes(StandardCharsets.UTF_8);
        os.write(input, 0, input.length);

        int responseCode = connection.getResponseCode();
        if (responseCode != 200) {
            throw new IOException("http post error return code: " + responseCode + ", url: " + url);
        }

        BufferedReader br = new BufferedReader(
                new InputStreamReader(connection.getInputStream(), StandardCharsets.UTF_8));
        StringBuilder response = new StringBuilder();
        String responseLine;
        while ((responseLine = br.readLine()) != null) {
            response.append(responseLine.trim()).append("\n");
        }
        return response.toString();
    } catch (IOException e) {
        throw new RuntimeException(e);
    } finally {
        if (connection != null) {
            connection.disconnect();
        }
    }
}

如果要发送form，那么只要Content-Type设置为：application/x-www-form-urlencoded