How to send and catch parameter from JavaScript (AJAX request) to Servlet

Question

I created InformationServlet that whenever I need some details I can send it what I want (with AJAX) and it will return me the information.

I searched how to do it on Ajax and according to: How to send parameter to a servlet using Ajax Call

I used: url: "InformationServlet?param=numberOfPlayers"

But on the servlet the request's attributes doesn't contain the parameter I sent so I suppose I am not doing it correctly:

you can see that the attributes size is zero

Servlet:

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {
            Gson gson = new Gson();
            Engine engine = (Engine)getServletContext().getAttribute("engine");
            String responseJson = "";

            if(request.getAttribute("numberOfPlayers") != null)
            {
                String numberOfPlayers = "";
                numberOfPlayers = gson.toJson(String.valueOf(engine.GetNumOfPlayers()));
                responseJson = numberOfPlayers;
            }

            out.print(responseJson);

        } finally {
            out.close();
        }
    }

JavaScript (AJAX request):

function getNumberOfPlayersAndPrintSoldiers()
{
      $.ajax({
        url: "InformationServlet?param=numberOfPlayers",
        timeout: 2000,

        error: function() {
            console.log("Failed to send ajax");
        },
        success: function(numberOfPlayers) {
            var r = numberOfPlayers;

        }
    });
}

Answer 1

Edit:

you probably want to use getParameter and not getAttribute

Moreover, please pay attention to the order of parameter name and his value:

request.getParameter("param");

instad of:

request.getParameter("numberOfPlayers");

because the url form contains parameter name first and then the parameter value. for example:

myurl.html?param=17

and if more parameters needed then use the separator & sign

myurl.html?firstName=bob&age=5