Servlet handling requests

TradingEngineServlet-doGet.java

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    String path = req.getServletPath();
    LOGGER.debug("received command: '" + path + "'");

    String who = req.getParameter("userId");
    String productId = req.getParameter("productId");
    TradingEngineThread engine = kids.get(productId);
    int quantity = Integer.parseInt(req.getParameter("quantity"));
    int id = ID.getAndIncrement();

    // e.g. /buy?productId=1&quantity=10&userId=ant
    if (path.equals("/buy")) {
        PurchaseOrder po = engine.addPurchaseOrder(who, productId, quantity, id);
        resp.getWriter().write("\"id\":" + id + ", " + String.valueOf(po));
    } else if (path.equals("/sell")) {