What are Portlet Events

Portlet events are intended to allow portlets to react to actions or state changes not directly related to an interaction of the user with the portlet. Events could be either portal or portlet container generated or the result of a user interaction with other portlets. The portlet event model is a loosely coupled, brokered model that allows creating portlets as stand-alone portlets that can be wired together with other portlets at runtime. In response to an event a portlet may publish new events that should be delivered to other portlets and thus may trigger state changes on these other portlets.

In order to receive events the portlet must implement the EventPortlet interface in the javax.portlet package. The portlet container will call the processEvent method for each event targeted to the portlet with an EventRequest and EventResponse object. Events are targeted by the portal / portlet container to a specific portlet window in the current client request.

Events are a life cycle operation that occurs before the rendering phase. The portlet may issue events via the setEvent method during the action processing which will be processed by the portlet container after the action processing has finished. As a result of issuing an event the portlet may optionally receive events from other portlets or container events. A portlet that is not target of a user action may optionally receive container events, e.g. a portlet mode changed event, or events from other portlets, e.g. an item was added to the shopping cart event.

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