package surc.test;

import java.io.IOException;
import java.io.PrintWriter;

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 org.json.JSONObject;

/**
 * Servlet implementation class NewComment
 */
@WebServlet("/newComment")
public class NewComment extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public NewComment() {
		super();
		// TODO Auto-generated constructor stub
	}

	/**
	 * @see HttpServlet#service(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void service(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("application/json; charset=UTF-8");

		PrintWriter out = response.getWriter();
		JSONObject obj = new JSONObject();
		obj.put("status", "ok");
		out.println(obj);
	}
}

package surc.test;

import java.io.IOException;
import java.io.PrintWriter;

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

/**
 * Servlet implementation class NewComment
 */
@WebServlet("/newComment")
public class NewComment extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public NewComment() {
		super();
		// TODO Auto-generated constructor stub
	}

	/**
	 * @see HttpServlet#service(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void service(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("application/json; charset=UTF-8");

		// To submit the comment, you need to load the comment content by a
		// parameter name "comment" first. Additionally, you need to add all the
		// files into database as well, which still remain in session.

		PrintWriter out = response.getWriter();
		out.println("{\"status\":\"ok\"}");
	}
}

Update Example - Submit New Comment