How to get directory information in struts2 action?

[red phoenix]

I want to know how to get directory information in struts2 action,when I run
following action:
http://localhost:8080/struts2-blank-2.0.9/example/HelloWorld.action

I want to get the path value http://localhost:8080/struts2-blank-2.0.9 in
HelloWorld.action,such as:
   public String execute() throws Exception {
        String path=....//get path value
        return SUCCESS;
    }

how to do it?