<p>Is there a way to substring in JSP files, using struts2 technologies? I mean, struts2 has its own taglib and also uses ognl. How can I get a substring from a stacked value or bean value?</p>

http://java.sun.com/products/jsp/jstl/1.1/docs/tlddocs/index.html
Look for fn:substring and its variants.
I've used Struts 1, but not 2.