使用Servlet的doPost方法

Question

Im new to Java and trying out some financial analysis java file I'm using for my studies. I got it to work when I created a main method within the bean itself. However when I try to pass the values needed through a jsp form and using a servlet doPost method to do the calculations by instantiating the methods from the bean nothing happens I get a NullPointerException. Im assuming the BlackScholes.java works as a bean should and that the issue is within the code presented. Help here would be greatly appreciated.

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

    String action = request.getParameter("action");

    if (action != null) {
        try {
            String spotPrice = request.getParameter("sprice");
            String strikePrice = request.getParameter("strike");
            String interestRate = request.getParameter("rate");
            String timeTo = request.getParameter("time");
            String vol = request.getParameter("volatility");

            double sprice = Double.parseDouble(spotPrice);
            double strike = Double.parseDouble(strikePrice);
            double rate = Double.parseDouble(interestRate);
            double time = Double.parseDouble(timeTo);
            double volatility = Double.parseDouble(vol);
            double carryrate = rate;

            request.setAttribute("sprice", sprice);
            request.setAttribute("strike", strike);
            request.setAttribute("rate", rate);
            request.setAttribute("time", time);
            request.setAttribute("volatility", volatility);

            BlackScholes BS = new BlackScholes(carryrate);
            BS.bscholEprice(sprice, strike, volatility, time, rate);
            double currentpriceC = BS.getCalle();
            request.setAttribute("validation1", currentpriceC);
        } catch (NullPointerException e) {
            return;
        }
    } else {
        request.getRequestDispatcher("/index.jsp").forward(request,
                response);
    }
  }
}

The jsp file used to creat the form data:

<form action="${pageContext.request.contextPath}/OptionsController"
    method="post">
    <input type="hidden" name="action" value="docalculate" /> 

    Spot Price: <input type="text" name="sprice" /> <br />
    <p />
    Strike Price: <input type="text" name="strike" /> <br />
    <p />
    Risk Free Rate: <input type="text" name="rate" /> <br />
    <p />
    Months To Expire: <input type="text" name="time" /> <br />
    <p />
    Volatility: <input type="text" name="volatility" /> <br />
    <p />

    <input type="submit" value="Submit" /><br />
    <p />
    One call options costs: <input type="text" name="validation1"
        readonly="readonly"
        value="<%if (request.getAttribute("validation1") != null) {
            out.print(request.getAttribute("validation1"));
        }%>">
</form>

Answer 1

Potentially one of your action parameters, which you are reading using getParameters is not filled. This could lead to a Null Pointer exception in the subsequent calls where you are parsing.