Apache Struts 2 Documentation
Why does FreeMarker complain that there's an error in my user-directive when I used JSP Tag
To use JSP Tags with our FreeMarker templates, the jspSupportServlet needs to be loaded through the web.xml.
web.xml
<servlet>
<servlet-name>jspSupportServlet</servlet-name>
<servlet-class>org.apache.struts2.views.JspSupportServlet</servlet-class>
<load-on-startup>10</load-on-startup>
</servlet>
The servlet element registers the JspSupportServlet and loads it on startup. FreeMarker obtains the information it needs to render JSP tags from the servlet instance.