String url = "";

  HttpPost httpPost = new HttpPost(url);

  List<NameValuePair> params = new ArrayList<>();

  params.add(new BasicNameValuePair("username", "root"));

  params.add(new BasicNameValuePair("password", "123456"));

  UrlEncodedFormEntity uefEntity = new UrlEncodedFormEntity(params, "utf-8");

  httpPost.setHeader("Content-Type", "application/x-www-form-urlencoded;charset=UTF-8");

  httpPost.setEntity(uefEntity);

 String url = "";

 String json = ""; // 请求参数，json格式

 HttpPost httpPost = new HttpPost(url);

 StringEntity entity = new StringEntity(json, "UTF-8");

 httpPost.setHeader("Content-Type", "application/json");

 httpPost.setEntity(entity);

 String url = "";

 String xml = ""; // 请求参数，xml格式

 HttpPost httpPost = new HttpPost(url);

 StringEntity entity = new StringEntity(xml, "UTF-8");

 httpPost.setHeader("Content-Type", "text/xml");

 httpPost.setEntity(entity);