Question

serverlet中，使用 request.getRequestDispatcher发送数据到jsp页面中处理失败

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String num1 = request.getParameter("num1");
String num2 = request.getParameter("num2");
String oper = request.getParameter("oper");

int res = Operation.getResult(num1, num2, oper);

request.setAttribute("num1", num1);
request.setAttribute("num2", num2);
request.setAttribute("oper", oper);
request.setAttribute("result", num1);
System.out.println(res);

request.getRequestDispatcher("/view/result.jsp").forward(request, response);
}
result.jsp:
<%
String num1=request.getParameter("num1");
String num2=request.getParameter("num2");
String oper=request.getParameter("oper");
String result=request.getParameter("result");
System.out.println(result);
%>
第一个数：<%=num1 %><br>
第二个数：<%=num2 %><br>
运算符：<%=oper %><br>
结果：<%=result %>
结果4个数都没能够取到值，num1,num2,oper可以显示，但应该是最初的那个页面发过来的值，result显示为null

Answer 1

<%
String num1=request.getParameter("num1");
String num2=request.getParameter("num2");
String oper=request.getParameter("oper");
String result=request.getParameter("result");
System.out.println(result);
%>
这个地方应该改为
<%
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);
%>