How to forward request in struts 2.1.6?

[xnpeng]

from:

ServletActionContext.getServletContext().getRequestDispatcher("/post/message/"+id).forward(ServletActionContext.getRequest(),ServletActionContext.getResponse());

I want to forward request to http://localhost:8080/post/message/3166,

but it always throws out exception says requested resource not exist.

when replace the string with "/index.jsp",it can work correctly.

so, anyone who can help? I just want to forward request to an ACTION other than 
jsp file.

thanks.