jsr 168 (portlet specification) don't allow you to pass values from ActionRequest to RenderRequest using get/setAttibute.
You have to use get/setParameter from PortletRequest (superclass of ActionRequest and RenderRequest)...
but i found i problem with it (probably a bug in jbp 2.2.1RC2). Parameter should be associated only to the current Request (see portlet specification), instead parameters in jbp are stored and maintened over all next requests.
So i used to put attribute in the portlet session (pay attenction to remove the attribute from the session if it isn't useful after read it)
Hope this help
I tried get/set parameter also but as you found, it did not work for me in 2.2.1 RC2.
But the set/get attribute did work in the previous versions of JBP. I found this when I migrated my code to use 2.2.1 RC2 from 2.0, if I remember correct.
So was curious to know if there was a bug in the new release.
And on using the session set/get attribute I guess now that is the only way to pass parameters from processAction to render.
Any word from the developer community ? Is what I see a expected