| PortletRequest | Limited to request between the portal server and the portlet | object | getAttribute() setAttribute() removeAttribute() | Use a short term bucket for communication between portlet and JSP (ex: Portlet URI) |
| PortletSession | Limited to subsequent requests by the same user on the same concrete portlet instance | object | getAttribute() setAttribute() removeAttribute() | Use as an open line of communication between requests. (for example Shopping cart) |
| PortletSettings | Shared by all instances of the concrete portlet. Editable only in configure mode. | String | getAttribute() setAttribute() removeAttribute() | Use only for configuration information that is applicable to all instances (for example user ID) |
| PortletApplicationSettings | Shared by all concrete portlet instances deployed in the same concrete applicationd.itable only in configure mode. | String | getAttribute() setAttribute() removeAttribute() | Use only for configuration information that is applicable to all concrete portlet instances in the same application (for example server name ) |
| PortletData | Persistently available to a single concrete portlet instance. | object(serializable) | getAttribute() setAttribute() removeAttribute() | Use for information that needs life beyond a session (for example portlet preferences) |
| PortletURI | One request through to the actionPerformed method | String | addParameter() | Use to provide default parameter values in case the user does not enter a value in a form |
| PortletMessage | Only available to registered message listeners in the event processing phase | Object | Since each custom portlet message can be implemented uniquely, access is not pre-defined | Use to adequately capture all the information necessary to complete the message. There is no predictably regarding order of execution for listeners so do depend on this. |
| PortletConfig | Same config object is available to every concrete portlet instance derived from the same abstract portlet. | String | getInitParameter() | This vale can only be set during development or deployment. Since its scope is very broad, use carefully . |
| DefaultPortlet Action | Available as long as the PortletURI it is attached to is available. | object | setParameter() getParameters() | It is not recommended to store objects such as PortletResponse etc. Use sparingly. |
| PortletAdapter | Available to all instances of the concrete portlet. Value is not unique between users. | object | getVariable() setVariable() | Use this object to store attributes that are not unique to any one user, and can be lost if the server shuts down |
