HttpServletRequest get JSON POST data

Question

How do I get the POST data (jsondata) from HttpServletRequest?

If I enumerate the request params, I can only see one param, which is "cmd", not the POST data.

Answer 1

Normally 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...
}

Comments

if i put your code in a spring boot application, in a post controller, it will not work, it will fail at getReader() time

---

be correct with the imports

Answer 2

request object from Python standard library. In the lastest requests package, you can use json parameter in requests. post() method to send a json dict, and the Content-Type in header will be set to application/json . There is no need to specify header explicitly.

Answer 3

Configure the action as given below:

1. Method: Since we need to post data, select 'POST' action from the dropdown list.
2. URL: Enter the URL to which you wish to post data.
3. Header: Enter 'Content-Type' as the header name.
4. Value: Enter 'application/json' as the value for the specified header.