org.apache.jasper.JasperException: /frame.jsp(3,64) equal symbol expected

<%@page import="com.demo.servlet.ServLogin"%>
<%
    String dir = (String)session.getAttribute("dir");
%>
<jsp:forward page="/WEB-INF/<%=dir %>/frame.jsp"></jsp:forward>

上面代码报错信息：org.apache.jasper.JasperException: /frame.jsp(3,64) equal symbol expected

改为下面这样，问题就解决了。

<%@page import="com.demo.servlet.ServLogin"%>
<%
    String dir = "/WEB-INF/"+session.getAttribute("dir")+"/frame.jsp";
%>
<jsp:forward page="<%=dir %>"></jsp:forward>