JSR 168 missing Portlet Filters.

A portlet filter in Portlets is same as a servlet filter in Servlets. Hence a portlet filter is an object which intercepts or modify s the output to or from a portlet before it is aggregated to the portal page. I cant find anything in JSR 168 to achieve this feature but you can find vendor specific api's for it else you can use JSR 286 to work with it.