It is possible to have them span two HTTP requests. JSF portlet bridge implementations have this built-in as a feature.
At the end of the ACTION_PHASE, save a uniqueId as a render parameter: http://portals.apache.org/pluto/portlet-2.0-apidocs/javax/portlet/StateAwareResponse.html#setRenderParameter(java.lang.String, java.lang.String)
At the beginning of the RENDER_PHASE, get the value of the uniquieId from the render parameter: http://portals.apache.org/pluto/portlet-2.0-apidocs/javax/portlet/PortletRequest.html#getParameter(java.lang.String)
It is possible to have them span two HTTP requests. JSF portlet bridge implementations have this built-in as a feature.
At the end of the ACTION_PHASE, save a uniqueId as a render parameter:
http://portals.apache.org/pluto/portlet-2.0-apidocs/javax/portlet/StateAwareResponse.html#setRenderParameter(java.lang.String, java.lang.String)
At the beginning of the RENDER_PHASE, get the value of the uniquieId from the render parameter:
http://portals.apache.org/pluto/portlet-2.0-apidocs/javax/portlet/PortletRequest.html#getParameter(java.lang.String)