Q:

How to determine css-class-wrapper programmatically in Liferay?

liferay-portlet.xml file allows <css-class-wrapper> tag inside <portlet> tag. 
Is it possible to determine it's content programmatically in portlet class or JSP?

A:

You can get it by code below
Portlet portlet = (Portlet)request.getAttribute(WebKeys.RENDER_PORTLET);
String cssClassWrapper=portlet.getCssClassWrapper();

