java - 结果不显示在jsp中

Question

在网页界面中。当我输入提交时，应该期待正确的结果 但是当我点击提交时没有任何反应。想知道计算后为什么没有显示结果变量。

在index.jsp中：

<form action="/index.jsp" method="post">
        <label for="principalamount">Principal Amount:</label><br>
        <input type="number" id="principalamount" name="principalamount" min ="1000" required> <br>

        <label for="interestrate">Interest Rate:</label><br>
        <input type="number" id="interestrate" name="interestrate" min="0" step=".01" required ><br><br>

        <label for="Time">Time:</label><br>
        <input type="number" id="Time" name="Time" min="0" step=".01" required ><br><br>

        <label for="Frequency">Frequency:</label><br>
        <input type="number" id="Frequency" name="Frequency" min="0" step=".01" required ><br><br>

        <button type="submit">Calculate</button>
        <p> results: ${result}</p>
    </form>

HelloServelet.java：

@WebServlet(name = "helloServlet", urlPatterns = {""})
public class HelloServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
        getServletContext().getRequestDispatcher("/index.jsp").forward(request, response); }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
        String principalamount0 = request.getParameter("principalamount");
        String interestrate0 = request.getParameter("interestrate");
        String Time0 = request.getParameter("Time");
        String Frequency0 = request.getParameter("Frequency");
        double result = interestCalculateCompound.calculate(Double.parseDouble(principalamount0), Double.parseDouble(interestrate0), Double.parseDouble(Frequency0), Double.parseDouble(Time0));
        //Send the result as an attribute to be displayed in the JSP
        request.setAttribute("principalamount", principalamount0);
        request.setAttribute("interestrate", interestrate0);
        request.setAttribute("Time", Time0);
        request.setAttribute("Frequency", Frequency0);
        request.setAttribute("result", result);
        getServletContext().getRequestDispatcher("/index.jsp").forward(request, response);
    }
}

标签： javajspservlets