Question

我是Java的新手，并尝试了一些我用于学习的财务分析java文件。当我在bean本身内创建一个main方法时，我得到了它。但是，当我尝试通过jsp表单传递所需的值并使用servlet doPost方法通过实例化bean中的方法来进行计算时，没有任何反应，我得到一个NullPointerException。我假设BlackScholes.java作为bean应该工作，并且问题在所提供的代码中。非常感谢帮助。

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);
    }
  }
}

用于创建表单数据的jsp文件：

<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

您正在使用getParameters读取的某个操作参数未填充。这可能会导致您正在解析的后续调用中出现Null Pointer异常。

使用Servlet doPost方法

1 个答案: