Java HttpClient:无法读取post请求中的json数据

这里我使用HttpClient发布JSON数据。但我无法读取其他应用程序上的数据。当我执行

request.getParameter（“用户名”）

时，它返回null。我的两个应用程序都部署在同一台服务器上。请告诉我我做错了什么。多谢各位

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        DefaultHttpClient httpClient = new DefaultHttpClient();

        HttpPost postRequest = new HttpPost("http://localhost:8080/AuthenticationService/UserIdentificationServlet");
        postRequest.setHeader("Content-type", "application/json");

        StringEntity input = new StringEntity("{\"username\":\""+username+"\"}");
        input.setContentType("application/json");
        postRequest.setEntity(input);

        HttpResponse postResponse = httpClient.execute(postRequest);

        BufferedReader br = new BufferedReader(new InputStreamReader((postResponse.getEntity().getContent())));
        String output;
        System.out.println("Output from Server .... \n");
        while ((output = br.readLine()) != null) {
            System.out.println(output);
        }

        httpClient.getConnectionManager().shutdown();
    }

---

如果要使用request.getParameter，则必须以URL编码的格式发布数据

//this example from apache httpcomponents doc
List<NameValuePair> formparams = new ArrayList<NameValuePair>();
formparams.add(new BasicNameValuePair("param1", "value1"));
formparams.add(new BasicNameValuePair("param2", "value2"));
UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, "UTF-8");
HttpPost httppost = new HttpPost("http://localhost/handler.do");
httppost.setEntity(entity);

//此示例来自ApacheHttpComponents文档
List formparams=new ArrayList（）；
formparams.add（新的BasicNameValuePair（“param1”、“value1”）；
formparams.add（新的BasicNameValuePair（“param2”、“value2”）；
UrlEncodedFormEntity实体=新的UrlEncodedFormEntity（formparams，“UTF-8”）；
HttpPost HttpPost=新的HttpPost（“http://localhost/handler.do");
httppost.setEntity（实体）；

您需要了解ie表单请求参数（

HttpServletRequest#getParameter（）

）和请求主体为

json

（

HttpServletRequest#getInputStream（）

）的

应用程序/json

之间的区别。