如何使用servlet中的隐藏按钮传递变量的值

Question

i am working on servlet when i trying the below code it produce NumberFormatException,i have initialize all the variable but when i click the button it assign null value in variable which cause the Exeption

public class page1 extends HttpServlet 
{
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();
    int q=0,mq=0,umq=0;
    String qno="0";
   if(request.getParameter("Bt")!=null)
    {
        qno=request.getParameter("Bt");
        q=Integer.parseInt(qno);
    }
   if(request.getParameter("markBt")!=null)
    {
        qno=request.getParameter("markBt");
        q=Integer.parseInt(qno);
        mq=q;
        q++;
    }
   if(request.getParameter("unmarkBt")!=null)
    {
        qno=request.getParameter("unmarkBt");
        q=Integer.parseInt(qno);
        umq=q;
    }
   if(request.getParameter("saveBt")!=null)
    {
        qno=request.getParameter("saveBt");
        q=Integer.parseInt(qno);
        mq=q;
        q++;
    }
    qno=""+q;

    try
    {
        out.println("<script src=\"myScript.js\"></script>");

        out.println("<form action=\"page1\" method=\"POST\">");

        out.println("<input type=\"hidden\" name=\"markBt\" />");
        out.println("<label>");
        out.println("<br /><input type=\"submit\" name=\"button\" value=\"Marks For Review & Next\" id=\"mark\" onclick=\"setColor(b"+qno+",'#fff200');this.form.markBt.value="+qno+";this.form.action='page1?flag=1&act=1';this.form.submit();\" />");
        out.println("</label>");

        out.println("<input type=\"hidden\" name=\"unmarkBt\" />");
        out.println("<label>");
        out.println(" <input type=\"submit\" name=\"button\" value=\"Unmarks For Review & Next\" id=\"unmark\" onclick=\"setColor(b"+qno+",'#fff200');this.form.unmarkBt.value="+qno+";this.form.action='page1?flag=1&act=1';this.form.submit();\" />");
        out.println("</label>");

        out.println("<input type=\"hidden\" name=\"saveBt\" />");
        out.println("<label>");
        out.println(" <input type=\"reset\" value=\"Clear Response\" /> <input type=\"submit\" name=\"button\" value=\"Save & Next\" id=\"save\" onclick=\"this.form.saveBt.value="+qno+";this.form.action='page1?flag=1&act=1';this.form.submit();\" />");
        out.println("</label>");

        out.println("</form>");

    out.println("<h1>qno="+q+"</h1>");
        out.println("<h1>qno="+mq+"</h1>");
        out.println("<h1>qno="+umq+"</h1>");
    out.println("<h1>qno="+qno+"</h1>");

        out.println(" </body>");
        out.println("</html>");

    }
    finally
    {

    }
  }
 }

what to do to pass the value of variable can anyone help please,thanks in advance

Answer 1

尝试比较空字符串（“”），如果它不起作用，请提供#number格式异常的堆栈跟踪示例：-！“”。equals（var）

Answer 2

您应该编写单独的html代码，在jsp中编写html代码以及在servlet中编写逻辑。然后，您将无法获得NumberFormatException。