how to create tabs with the framework of struts2....?

Many of the Liferay supplied portlets are based on Struts and use tabs. All of them have the source code available, so that should help you get started....

We are using struts 2 too. For tabs, we do them manually using some jquery plugins.

Perahps you should try this http://code.google.com/p/struts2-jquery/wiki/TabbedPanelTag but we have not tested them in a portlet context