HttpServletRequest get JSON POST data [duplicate]

Normaly you can GET and POST parameters in a servlet the same way:

request.getParameter("cmd");

But only if the POST data is encoded as key-value pairs of content type: "application/x-www-form-urlencoded" like when you use a standard HTML form.

If you use a different encoding schema for your post data, as in your case when you post a json data stream, you need to use a custom decoder that can process the raw datastream from:

BufferedReader reader = request.getReader();

Json post processing example (uses org.json package )

public void doPost(HttpServletRequest request, HttpServletResponse response)  throws ServletException, IOException {  StringBuffer jb = new StringBuffer();  String line = null;  try {    BufferedReader reader = request.getReader();    while ((line = reader.readLine()) != null)      jb.append(line);  } catch (Exception e) { /*report an error*/ }  try {    JSONObject jsonObject =  HTTP.toJSONObject(jb.toString());  } catch (JSONException e) {    // crash and burn    throw new IOException("Error parsing JSON request string");  }  // Work with the data using methods like...  // int someInt = jsonObject.getInt("intParamName");  // String someString = jsonObject.getString("stringParamName");  // JSONObject nestedObj = jsonObject.getJSONObject("nestedObjName");  // JSONArray arr = jsonObject.getJSONArray("arrayParamName");  // etc...}

Are you posting from a different source (so different port, or hostname)? If so, this very very recent topic I just answered might be helpful.

• Odd jQuery problem - Ajax request to a C program not quite working

The problem was the XHR Cross Domain Policy, and a useful tip on how to get around it by using a technique called JSONP. The big downside is that JSONP does not support POST requests.

I know in the original post there is no mention of JavaScript, however JSON is usually used for JavaScript so that's why I jumped to that conclusion