request.getParameter() returns null but data can read from request.getInputStream() for huge data in http post method

Question

I am having an issue where calling request.getParameter() returns null when large amounts of data are passed to the page. The header Content-Type is application/x-www-form-urlencoded. And the setting for maximum POST size is set to 12,582,912 bytes (i.e. maxPostSize=12582912) in server.xml.

Client Code

 public class Send
    {
    public static int readTimeout = 30000;
    public static int connectionTimeout = 10000;

    public static void main(String[] args) throws IOException, JSONException
    {
        sendFile(1000,1);
    }

    public static void sendFile(int n,int m) throws IOException, JSONException
    {
        String urlStr = "http://localhost:8080/sendChange";
        URL url = new URL(urlStr);
        HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
        httpConn.setConnectTimeout(connectionTimeout);
        httpConn.setReadTimeout(readTimeout);
        httpConn.setRequestMethod("POST");
        httpConn.setDoOutput(true);
        httpConn.setDoInput(true);
        httpConn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
        JSONArray list;
        StringBuilder stringBuilder = new StringBuilder();
        for (int i = 0; i < m; i++)
        {
            list = new JSONArray();
            for (int j = 0; j < n; j++)
            {
                list.put(getChange());
            }
            if(i==0)
            {
                stringBuilder.append("bulk=");
            }
            else
            {
                stringBuilder.append("&bulk_").append(i).append("=");
            }
            stringBuilder.append(list.toString());
        }
        int length = stringBuilder.toString().getBytes().length;
        System.out.println(length);
        httpConn.setRequestProperty("Content-Length", Integer.toString(stringBuilder.toString().getBytes().length));
        DataOutputStream printout = new DataOutputStream(httpConn.getOutputStream());
        printout.write(stringBuilder.toString().getBytes());
        printout.close();
        int responseCode = httpConn.getResponseCode();
        System.out.println(responseCode);
    }

Server Code

import org.json.JSONArray;
import org.json.JSONException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * Created by mohan-4019 on 12/28/16.
 */
@WebServlet(name = "CollectorServlet")
public class CollectorServlet extends HttpServlet
{
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
    {
        doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException
    {

        String bulk = request.getParameter("bulk");
        try
        {
            JSONArray bulkJSON = new JSONArray(bulk);
            int length = bulkJSON.length();
        }
        catch (JSONException e)
        {
            System.out.println(e);
        }
    }
}

The call to getChange() returns a JSONObject, which has size 7kb. It works perfectly for data with small size. Large data can read from request.getInputStream().