OGNL - Calling Static Methods and Fields - struts 2

Most of the time, we have used to declare system constants as static fields
of a class, and some time static methods are being involved. If we want to access this kind of field from a JSP page with struts 2 taglibs, we have tow methods. I have tow classes 'SystemConstants' and 'Utils' in my own application.

public class SystemConstants{
// ............
public static final SESSION_DATA = "sessionData";
// .........
}

Also I have a separate class called "SessionData" to keep the data needed for the entire session. Useful information needed to keep through out the session are stored in the "SessionData".

public class SessionData{

private User user ;

public setUser(User user){
this.user = user;
}

public User getUser(){
return this.user;
}

}
I have stored the SessionData object in the session object from an "Action" class of struts 2.
SessionData sd = new SessionData();
getServletRequest().getSession()
.setAttribute(SystemConstants.SESSION_DATA, sd);

Now, I want to access the session object and the "SESSION_DATA" static field from the jsp page. This is where the point comes. For this, we have tow methods.


Method one:
To access the static field ,
<s:set name="sdKey"
value="@com.axiohelix.pda.utils.SystemConstants@SESSION_DATA"></s:set>

Then to access the session object from the "ActionContext",
<s:set name="objSd" value="#session[#sdKey]"/>

Then we can access the fields and methods declared in the SessionData object.
<s:property value="#objSd.user.userName"/>

This is how, we access static methods
@com.axiohelix.utils.Utils@getSessionId()

If our field or method will resole in the 'ValueStack' in advance, we can use the fallowing syntax to access relevants
Method tow:
@vs@SESSION_DATA
@vs@getSessionId()

The SESSION_DATA static field is declared in the class 'SystemConstants' packaged at 'com.axiohelix.utils' and getSessionId() function is implemented within the Utils class packaged at 'com.axiohelix.utils'