httpclient4 post 以json方式传参数

public static String sendSetHeaderGetRequestByPostForJson(String url,Map<String,String> map,Map<String,Object> psotMap/*String appUid,String listMsgIds*/ ) throws Exception{BufferedReader buffer=null;String result="";try {      CloseableHttpClient httpclient = HttpClients.createDefault();              RequestConfig requestConfig = RequestConfig.custom().setSocketTimeout(3000).setConnectTimeout(3000).build();//设置请求和传输超时时间      HttpPost httpPost = new HttpPost(url);      httpPost.setConfig(requestConfig);                      httpPost.addHeader(HTTP.CONTENT_TYPE, "application/json");      httpPost.addHeader(HTTP.CONTENT_TYPE,  "text/json");      httpPost.setHeader("appKey", map.get("appKey"));      httpPost.setHeader("nonce", map.get("nonce"));      httpPost.setHeader("timestamp", map.get("timestamp"));      httpPost.setHeader("signature", map.get("signature"));      JSONObject obj=JSONObject.fromObject(psotMap);       StringEntity se = new StringEntity(obj.toString());       se.setContentEncoding(new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));       httpPost.setEntity(se);       CloseableHttpResponse  response= httpclient.execute(httpPost);       buffer=new BufferedReader(new InputStreamReader(response.getEntity().getContent(),"utf-8"));       result =buffer.readLine();       return result;} catch (Exception e) {e.printStackTrace();}finally{buffer.close();}    return null;  }