java - 无法显示隐含的 EL（表达式语言）范围对象

Question

我创建了 servlet 'SetAttributes' 作为，

request.setAttribute("a1","v1");
HttpSession session=request.getSession();
session.setAttribute("a2","v2");
ServletContext application=getServletContext();
application.setAttribute("a3","v3");
request.setAttribute("c","request");
session.setAttribute("c","session");
application.setAttribute("c","application");

RequestDispatcher rd=request.getRequestDispatcher("Process.jsp");
rd.forward(request, response);

现在Process.jsp如下，

a1, a2, a3 can be directly accessed as: ${a1} ${a2} ${a3}<br />

        Each attribute can also be accessed as: ${requestScope.a1} ${sessionScope.a2} ${applicationScope.a3}<br />

        Accessing the repeated attribute directly then the value will be for: ${c}<br />
        Common attribute can also be accessed as: ${requestScope.c} ${sessionScope.c} ${applicationScope.c}<br />

        Trying to access out of scope attribute we get: ${applicationScope.a1}

属性的值，即“a1”、“a2”和“a3”应该显示在我的网页上，但我得到一个空白值。

下面是我对 Process.jsp 的输出，

a1, a2, a3 can be directly accessed as: 
Each attribute can also be accessed as: 
Accessing the repeated attribute directly then the value will be for: Common attribute can also be accessed as: 
Trying to access out of scope attribute we get:

任何帮助表示赞赏。

Answer 1

您直接访问 JSP，而无需通过设置所有属性的 servlet。所以很明显，当JSP被执行时，所有的属性都是空的。

地址栏中的 URL 必须是 servlet 的 URL，而不是 JSP 的 URL。