springmvc的form:form标签中不能用JSP表达式？

我这么写（一个普通的form标签）可以解析
form action="<%=request.getContextPath() %>/index.html">
这么写就不对，
form:form action="<%=request.getContextPath() %>/student/studentModifyFinished.act">

这你最好用base标签：String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";