Portlet 2 features: actions, shared parameters

I’m newbie with portlets, and even more with portlets 2.0. I’ve seen the example VaadinInterPortletEventPortlet. Simple, and I’ve get it work.

The question is about actions and shared parameters (that class adds a shared parameter). Using Vaadin 6.2.0 I think there is no need to create actions as Vaadin handles all for you. Events are great for IPC and shared parameters are not needed. You can set in the event definition the class of the event payload. You can pass anything to the event receiver. So, IPC between portlets 2.0 doesn’t need shared parameters or actions.

A different case is if portlets cannot use IPC, then another techniques like url parameters must be used. it seems that is not a clean interface, and portlet documentation must specify which actions and parameters are supported.

I have a doubt about them. Actions and shared parameters seem to be added to the url. Therefore all portlets see all those parameters, and side effects are impredectible. The doubt is who removes those parameters? are they kept forever? even when navigation goes to another page in the portal? What happens when the former page is navigated to from another page? Does that mean url is used to keep the session state?


I have found a very good page
A Comprehensive article about jsr-286

The main outcomes are:

  • events and shared render parameters are limited to the current page, unless these properties are set in portal-ext.proterties (for Liferay)


  • if parameters are only for the same page, they remain there until navigation to another page. When navigate back, they are not set
  • shared parameters are a lightweight way to IPC as they involve less workload than events. If you see the article, both definitions are very similar. Parameters are limited to string values.