serverlet中，使用 request.getRequestDispatcher發送數據到jsp頁面中處理失敗

String num1=request.getParameter("num1");

String num2=request.getParameter("num2");

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

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

System.out.println(result);

%>

這個地方應該改為

<%

String num1=(String)request.getAttribute("num1");

String num2=(String)request.getAttribute("num2");

String oper=(String)request.getAttribute("oper");

String result=(String)request.getAttribute("result");

System.out.println(result);

%>